WO2015168838A1

WO2015168838A1 - Aligning disparity vector for advanced residual prediction and inter-view motion prediction in3d-hevc

Info

Publication number: WO2015168838A1
Application number: PCT/CN2014/076777
Authority: WO
Inventors: Hongbin Liu; Ying Chen
Original assignee: Qualcomm Incorporated
Priority date: 2014-05-05
Filing date: 2014-05-05
Publication date: 2015-11-12

Abstract

A video coding device may include a video coder configured to,for a first block of video data, determine a disparity vector based on neighboring blocks; perform inter- view motion prediction using the disparity vector; and, perform advanced residual prediction(ARP)using the disparity vector.

Description

ALIGNING DISPARITY VECTOR FOR ADVANCED RESIDUAL PREDICTION AND INTER- VIEW MOTION PREDICTION IN 3D-HEVC

TECHNICAL FIELD

[0001] This disclosure relates to video encoding and decoding.

BACKGROUND

[0002] Digital video capabilities can be incorporated into a wide range of devices, including digital televisions, digital direct broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, digital cameras, digital recording devices, digital media players, video gaming devices, video game consoles, cellular or satellite radio telephones, video teleconferencing devices, and the like. Digital video devices implement video compression techniques, such as those described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T

H.264/MPEG-4, Part 10, Advanced Video Coding (AVC), the High Efficiency Video Coding (HEVC) standard presently under development, and extensions of such standards, to transmit, receive and store digital video information more efficiently.

[0003] Extensions of some of the aforementioned standards, including H.264/AVC, may provide techniques for multiview video coding in order to produce stereo or three- dimensional ("3D") video. In particular, techniques for multiview coding have been proposed for use in AVC, with the scalable video coding (SVC) standard (which is the scalable extension to H.264/AVC), and the multi-view video coding (MVC) standard (which has become the multiview extension to H.264/ AVC).

[0004] Typically, stereo video is achieved using two views, e.g., a left view and a right view. A picture of the left view can be displayed substantially simultaneously with a picture of the right view to achieve a three-dimensional video effect. For example, a user may wear polarized, passive glasses that filter the left view from the right view. Alternatively, the pictures of the two views may be shown in rapid succession, and the user may wear active glasses that rapidly shutter the left and right eyes at the same frequency, but with a 90 degree shift in phase. SUMMARY

[0005] In general, this disclosure describes techniques for 3D video coding. In particular, this disclosure is related to techniques for advanced residual prediction (ARP) and inter-view motion prediction in 3D-HEVC.

[0006] In one example, a method of decoding video data includes, for a first block of the video data, determining a disparity vector based on neighboring blocks; performing inter-view motion prediction using the disparity vector; performing advanced residual prediction (ARP) using the disparity vector; and, based on the inter-view motion prediction and the ARP, generating a predictive block.

[0007] In another example, a method of encoding video data includes, for a first block, of the video data, determining a disparity vector based on neighboring blocks;

performing inter-view motion prediction using the disparity vector; performing advanced residual prediction (ARP) using the disparity vector; and, generating for inclusion in an encoded bitstream, syntax information for decoding the first block.

[0008] In another example, a video coding device includes a video coder configured to, for a first block of video data, determine a disparity vector based on neighboring blocks; perform inter- view motion prediction using the disparity vector; and, perform advanced residual prediction (ARP) using the disparity vector.

[0009] In another example, a device for coding video data includes means for determining a disparity vector based on neighboring blocks for a first block of video data; means for performing inter-view motion prediction using the disparity vector; and, means for performing advanced residual prediction (ARP) using the disparity vector.

[0010] In another a computer-readable medium stores instructions that when executed by one or more processors cause the one or more processors to, for a first block of video data, determine a disparity vector based on neighboring blocks; perform inter- view motion prediction using the disparity vector; and, perform advanced residual prediction (ARP) using the disparity vector.

[0011] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0012] FIG. 1 is a block diagram illustrating an example video encoding and decoding system that may utilize the techniques described in this disclosure.

[0013] FIG. 2 is a conceptual diagram illustrating an example multiview decoding order.

[0014] FIG. 3 is a conceptual diagram illustrating an example prediction structure for multiview coding.

[0015] FIG. 4 shows an example of spatial neighboring blocks relative to a coding unit.

[0016] FIG. 5 is a conceptual diagram illustrating techniques related to backward view synthesis prediction (BVSP) using neighboring blocks.

[0017] FIG. 6 shows an example relationship between a current block, reference block, and a motion compensated block in multi-view video coding.

[0018] FIG. 7 shows an example prediction structure for sub-PU level inter-view motion prediction.

[0019] FIG. 8 shows an example prediction structure for advanced residual prediction (ARP) in 3D-HEVC.

[0020] FIG. 9 shows an example relationship between a current block, reference block, and a motion compensated block in multi-view video coding.

[0021] FIG. 10 shows an example of ARP for inter-view residual data.

[0022] FIG. 11 shows an example of a video encoder configured to implement techniques described in this disclosure.

[0023] FIG. 12 shows an example of a video decoder configured to implement techniques described in this disclosure.

[0024] FIG. 13 is a flow diagram illustrating a technique that may be performed by an encoder or a decoder, e.g., as part of an encoding process or a decoding process.

DETAILED DESCRIPTION

[0025] This disclosure describes techniques related to advanced residual prediction (ARP) for 3D-HEVC. The techniques of this disclosure may be performed by a video coder, such as a video encoder or a video decoder. In ARP, a video coder generates a residual predictor based on a difference between already coded images. The video coder then adds this residual predictor to an original predictive block to generate a final predictive block. The final predictive block, which includes the residual predictor, is potentially a better predictor, i.e. more closely resembles the block being predicted, than the original predictor.

[0026] There are at least two different types of ARP, referred to in this disclosure as temporal ARP and inter- view ARP. In temporal ARP, for a current block in a first view, a video coder locates a corresponding block in a second view using a disparity vector for the current block. In this disclosure, this corresponding block in the second view will be referred to as a base block. Using a temporal motion vector of the current block, a video coder locates a reference block of the current block in a different picture of the first view. In this disclosure, this block is referred to as a current reference block.

Using the same temporal motion vector used to identify the current reference block, a video coder locates a reference block of the base block in a picture of the second view. In this disclosure, this block will be referred to as a reference base block. The difference between the base block and the base reference block can be calculated as a residual predictor. The video coder then adds the residual predictor, possibly with a weighting factor, to the current reference block to determine a final predictor.

[0027] In inter- view ARP, for a current block in a first view, a video coder locates a corresponding block in a second view using a disparity motion vector for the current block. Using a temporal motion vector of the base block, the video coder locates a reference base block of the base block in a different picture of the second view. Using the same temporal motion vector used to identify the base reference block, the video coder identifies a current reference block of the current block in a picture of the first view. The video coder calculates the difference between the current reference block and the base reference block and used calculated difference as a residual predictor. The video coder then adds this residual predictor, possibly with a weighting factor, to the base block to determine a final predictor.

[0028] As explained above, when performing temporal ARP, a video coder determines a disparity vector. As will be explained in greater detail below, the video coder may also determine a disparity vector as part of performing inter-view motion prediction techniques. Moreover, there are many ways in which the video coder may determine the disparity vector for use in inter- view motion prediction. This disclosure describes techniques that align the determination of a disparity vector for interview motion prediction with the determination of a disparity vector for ARP such that, in some coding scenarios, the video coder may use the same disparity vector for both. Using the same disparity vector for both ARP and inter-view motion prediction for some coding scenarios may reduce overall coding complexity.

[0029] FIG. 1 is a block diagram illustrating an example video encoding and decoding system 10 that may be configured to perform the ARP techniques and inter- view motion prediction techniques described in this disclosure. As shown in FIG. 1, system 10 includes a source device 12 that generates encoded video data to be decoded at a later time by a destination device 14. Source device 12 and destination device 14 may comprise any of a wide range of devices, including desktop computers, notebook (i.e., laptop) computers, tablet computers, set-top boxes, telephone handsets such as so-called "smart" phones, so-called "smart" pads, televisions, cameras, display devices, digital media players, video gaming consoles, video streaming devices, or the like. In some cases, source device 12 and destination device 14 may be equipped for wireless communication.

[0030] System 10 may operate in accordance with different video coding standards, a proprietary standard, or any other way of multiview coding. The following describes a few examples of video coding standards, and should not be considered limiting. Video coding standards include ITU-T H.261, ISO/IEC MPEG-1 Visual, ITU-T H.262 or ISO/IEC MPEG-2 Visual, ITU-T H.263, ISO/IEC MPEG-4 Visual and ITU-T H.264 (also known as ISO/IEC MPEG-4 AVC), including its Scalable Video Coding (SVC) and Multiview Video Coding (MVC) extensions. The latest joint draft of MVC is described in "Advanced video coding for generic audiovisual services," ITU-T

Recommendation H.264, Mar 2010, the entire content of which is incorporated herein by reference. Another joint draft of the MVC is described in "Advanced video coding for generic audiovisual services," ITU-T Recommendation H.264, June 2011, the entire content of which is incorporated herein by reference. Some additional video coding standards include the MVC+D and 3D- AVC, which are based on AVC. In addition, a new video coding standard, namely the High-Efficiency Video Coding (HEVC), has been developed by the Joint Collaboration Team on Video Coding (JCT-VC) of ITU-T Video Coding Experts Group (VCEG) and ISO/IEC Motion Picture Experts Group (MPEG).

[0031] For purposes of illustration only, some of the techniques described in this disclosure are described with examples in accordance with the 3D-HEVC video coding standard. However, the techniques described in this disclosure should not be considered limited to these example standards, and may be extendable to other video coding standards for multiview coding or 3D video coding (e.g., 3D-AVC), or to techniques related to multiview coding or 3D video coding that are not necessarily based on a particular video coding standard. For example, the techniques described in this disclosure are implemented by video encoders/decoders (codecs) for multiview coding, where multiview coding includes coding of two or more views.

[0032] Destination device 14 may receive the encoded video data to be decoded via a link 16. Link 16 may comprise any type of medium or device capable of moving the encoded video data from source device 12 to destination device 14. In one example, link 16 may comprise a communication medium to enable source device 12 to transmit encoded video data directly to destination device 14 in real-time. The encoded video data may be modulated according to a communication standard, such as a wireless communication protocol, and transmitted to destination device 14. The communication medium may comprise any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The

communication medium may form part of a packet-based network, such as a local area network, a wide-area network, or a global network such as the Internet. The

communication medium may include routers, switches, base stations, or any other equipment that may be useful to facilitate communication from source device 12 to destination device 14.

[0033] Alternatively, encoded data may be output from output interface 22 to a storage device 34. Similarly, encoded data may be accessed from storage device 34 by input interface. Storage device 34 may include any of a variety of distributed or locally accessed data storage media such as a hard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage media for storing encoded video data. In a further example, storage device 34 may correspond to a file server or another intermediate storage device that may hold the encoded video generated by source device 12. Destination device 14 may access stored video data from storage device 34 via streaming or download. The file server may be any type of server capable of storing encoded video data and transmitting that encoded video data to the destination device 14. Example file servers include a web server (e.g., for a website), an FTP server, network attached storage (NAS) devices, or a local disk drive. Destination device 14 may access the encoded video data through any standard data connection, including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., DSL, cable modem, etc.), or a combination of both that is suitable for accessing encoded video data stored on a file server. The transmission of encoded video data from storage device 34 may be a streaming transmission, a download transmission, or a combination of both.

[0034] The techniques of this disclosure for ARP are not necessarily limited to wireless applications or settings. The techniques may be applied to video coding in support of any of a variety of multimedia applications, such as over-the-air television broadcasts, cable television transmissions, satellite television transmissions, streaming video transmissions, e.g., via the Internet, encoding of digital video for storage on a data storage medium, decoding of digital video stored on a data storage medium, or other applications. In some examples, system 10 may be configured to support one-way or two-way video transmission to support applications such as video streaming, video playback, video broadcasting, and/or video telephony.

[0035] In the example of FIG. 1, source device 12 includes a video source 18, video encoder 20 and an output interface 22. As will be explained in greater detail below, video encoder 20 may be configured to perform the ARP techniques described in this disclosure. In some cases, output interface 22 may include a modulator/demodulator (modem) and/or a transmitter. In source device 12, video source 18 may include a source such as a video capture device, e.g., a video camera, a video archive containing previously captured video, a video feed interface to receive video from a video content provider, and/or a computer graphics system for generating computer graphics data as the source video, or a combination of such sources. As one example, if video source 18 is a video camera, source device 12 and destination device 14 may form so-called camera phones or video phones. However, the techniques described in this disclosure may be applicable to video coding in general, and may be applied to wireless and/or wired applications.

[0036] The captured, pre-captured, or computer-generated video may be encoded by video encoder 20. The encoded video data may be transmitted directly to destination device 14 via output interface 22 of source device 12. The encoded video data may also (or alternatively) be stored onto storage device 34 for later access by destination device 14 or other devices, for decoding and/or playback.

[0037] Destination device 14 includes an input interface 28, a video decoder 30, and a display device 32. As will be explained in greater detail below, video decoder 30 may be configured to perform the ARP techniques described in this disclosure. In some cases, input interface 28 may include a receiver and/or a modem. Input interface 28 of destination device 14 receives the encoded video data over link 16. The encoded video data communicated over link 16, or provided on storage device 34, may include a variety of syntax elements generated by video encoder 20 for use by a video decoder, such as video decoder 30, in decoding the video data. Such syntax elements may be included with the encoded video data transmitted on a communication medium, stored on a storage medium, or stored a file server.

[0038] Display device 32 may be integrated with, or external to, destination device 14. In some examples, destination device 14 may include an integrated display device and also be configured to interface with an external display device. In other examples, destination device 14 may be a display device. In general, display device 32 displays the decoded video data to a user, and may comprise any of a variety of display devices such as a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

[0039] Although not shown in FIG. 1, in some aspects, video decoder 30 may each be integrated with an audio encoder and decoder, and may include appropriate MUX- DEMUX units, or other hardware and software, to handle encoding of both audio and video in a common data stream or separate data streams. If applicable, in some examples, MUX-DEMUX units may conform to the ITU H.223 multiplexer protocol, or other protocols such as the user datagram protocol (UDP).

[0040] Video decoder 30 each may be implemented as any of a variety of suitable encoder circuitry, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays

(FPGAs), discrete logic, software, hardware, firmware or any combinations thereof. For example, the techniques described in this disclosure may be described from the perspective of an apparatus or a device. As one example, the apparatus or device may include video decoder 30 (e.g., destination device 14 as part of a wireless

communication device), and video decoder 30 may include one or more processors configured to implement techniques described in this disclosure (e.g., decode video data in accordance with techniques described in this disclosure). As another example, the apparatus or device may include a micro-processor or an integrated circuit (IC) that includes video decoder 30, and the micro-processor or IC may be part of destination device 14 or another type of device. The same may apply for video encoder 20 (i.e., an apparatus or device like source device 12 and/or a micro-controller or IC includes video encoder 20, where video encoder 20 is configured to encode video data in accordance with techniques described in this disclosure).

[0041] When the techniques are implemented partially in software, a device may store instructions for the software in a suitable, non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Each of video encoder 20 and video decoder 30 may be included in one or more encoders or decoders, either of which may be integrated as part of a combined encoder/decoder (CODEC) in a respective device.

[0042] A video sequence typically includes a series of video pictures from a view. A group of pictures (GOP) generally comprises a series of one or more video pictures. A GOP may include syntax data in a header of the GOP, a header of one or more pictures of the GOP, or elsewhere, that describes a number of pictures included in the GOP. Each picture may include picture syntax data that describes an encoding mode for the respective picture. Video encoder 20 typically operates on video blocks within individual video pictures in order to encode the video data. A video block may correspond to a macroblock, a partition of a macroblock, and possibly a sub-block of a partition, as defined in the H.264 standard. The video blocks may have fixed or varying sizes, and may differ in size according to a specified coding standard. Each video picture may include a plurality of slices. Each slice may include a plurality of blocks.

[0043] As an example, the ITU-T H.264 standard supports intra-prediction in various block sizes, such as 16 by 16, 8 by 8, or 4 by 4 for luma components, and 8x8 for chroma components, as well as inter-prediction in various block sizes, such as 16x16, 16x8, 8x16, 8x8, 8x4, 4x8 and 4x4 for luma components and corresponding scaled sizes for chroma components. In this disclosure, "NxN" and "N by N" may be used interchangeably to refer to the pixel dimensions of the block in terms of vertical and horizontal dimensions (e.g., 16x16 pixels or 16 by 16 pixels). In general, a 16x16 block has 16 pixels in a vertical direction (y = 16) and 16 pixels in a horizontal direction (x = 16). Likewise, an NxN block generally has N pixels in a vertical direction and N pixels in a horizontal direction, where N represents a nonnegative integer value. The pixels in a block may be arranged in rows and columns. Moreover, blocks need not necessarily have the same number of pixels in the horizontal direction as in the vertical direction. For example, blocks may comprise NxM pixels, where M is not necessarily equal to N.

[0044] When the block is intra-mode encoded (e.g., intra-predicted), the block may include data describing an intra-prediction mode for the block. As another example, when the block is inter-mode encoded (e.g., inter-predicted), the block may include information defining a motion vector for the block. This motion vector refers to a reference picture in the same view (e.g., a temporal motion vector), or refers to a reference picture in another view (e.g., a disparity motion vector). The data defining the motion vector for a block describes, for example, a horizontal component of the motion vector, a vertical component of the motion vector, a resolution for the motion vector (e.g., one-quarter pixel precision or one-eighth pixel precision). In addition, when inter- predicted, the block may include reference index information such as a reference picture to which the motion vector points, and/or a reference picture list (e.g., RefPicListO or RefPicListl) for the motion vector.

[0045] In the H.264 standard, following intra-predictive or inter-predictive coding, video encoder 20 calculates residual data for the macroblocks. The residual data may correspond to pixel differences between pixels of the unencoded picture and prediction values for the macroblock in H.264.

[0046] Following any transforms to produce transform coefficients, video encoder 20 performs quantization of the transform coefficients, in some examples. Quantization generally refers to a process in which transform coefficients are quantized to possibly reduce the amount of data used to represent the coefficients, providing further compression. The quantization process reduces the bit depth associated with some or all of the coefficients. For example, an n-bit value is rounded down to an m-bit value during quantization, where n is greater than m.

[0047] In some examples, video encoder 20 utilizes a predefined scan order to scan the quantized transform coefficients to produce a serialized vector that can be entropy encoded. In other examples, video encoder 20 performs an adaptive scan. After scanning the quantized transform coefficients to form a one-dimensional vector, in some examples, video encoder 20 entropy encodes the one-dimensional vector according to context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), Probability Interval Partitioning Entropy (PIPE) coding or another entropy encoding methodology, as a few examples. Video encoder 20 also entropy encodes syntax elements associated with the encoded video data for use by video decoder 30 in decoding the video data.

[0048] To perform CABAC, video encoder 20 may assign a context within a context model to a symbol to be transmitted. The context may relate to, for example, whether neighboring values of the symbol are non-zero or not. To perform CAVLC, video encoder 20 may select a variable length code for a symbol to be transmitted.

Codewords in VLC may be constructed such that relatively shorter codes correspond to more probable symbols, while longer codes correspond to less probable symbols. In this way, the use of VLC may achieve a bit savings over, for example, using equal- length codewords for each symbol to be transmitted. The probability determination may be based on a context assigned to the symbol.

[0049] Video decoder 30 implements the inverse of the techniques of video encoder 20. For example, video decoder 30 decodes the encoded video bitstream and determines the residual blocks by inverse quantization and inverse transform. Video decoder 30 sums the residual blocks with blocks of previously decoded pictures to determine the pixel values for the blocks within the picture.

[0050] Certain techniques described in this disclosure may be performed by both video encoder 20 and video decoder 30. As one example, video encoder 20 may perform ARP as part of determining how to encode a block of video data and/or may perform ARP as part of a decoding loop in the video encoder. Video decoder 30 may perform the same ARP techniques performed by video encoder 20 as part of decoding the video block. This disclosure may at times refer to video decoder 30 performing certain ARP techniques described in this disclosure. It should be understood, however, that unless stated otherwise, such techniques may also be performed by video encoder 20.

[0051] As described above, the techniques described in this disclosure are directed to 3D video coding. To better understand the techniques, the following describes some H.264/AVC coding techniques, multiview video coding from the perspective of

H.264/MVC extension and the High Efficiency Video Coding (HEVC) standard, and 3D-AVC techniques.

[0052] For H.264/ Advance Video Coding (AVC), video encoding or decoding (e.g., coding) is implemented on macroblocks, where a macroblock represents a portion of a frame which are inter-predicted or intra-predicted (i.e., inter-prediction encoded or decoded or intra-prediction encoded or decoded). For instance, in H.264/AVC, each inter Macroblock (MB) (e.g., inter-predicted macroblock) may be partitioned in four different ways: one 16x16 MB partition, two 16x8 MB partitions, two 8x16 MB partitions, or four 8x8 MB partitions. Different MB partitions in one MB may have different reference index values for each direction (i.e., RefPicListO or RefPicListl). When a MB is not partitioned into multiple (more than 1) MB partitions, it has only one motion vector for the whole MB partition in each direction.

[0053] As part of video coding (encoding or decoding), video encoder 20 and video decoder 30 may be configured to construct one or two reference picture lists, referred to as RefPicListO and RefPicListl. The reference picture list(s) identify reference pictures that can be used to inter-predict macroblocks of a frame or a slice. For instance, video encoder 20 may signal a reference index and a reference picture list identifier. Video decoder 30 may receive the reference index and the reference picture list identifier and determine the reference picture that is to be used for inter-prediction decoding the current macroblock from the reference index and the reference picture list identifier.

[0054] When a MB is partitioned into four 8x8 MB partitions, each 8x8 MB partition can be further partitioned into sub-blocks. There are four different ways to get sub- blocks from an 8x8 MB partition: one 8x8 sub-block, two 8x4 sub-blocks, two 4x8 sub- blocks, or four 4x4 sub-blocks. Each sub-block can have a different motion vector in each direction, but shares the same reference picture index for each direction. The manner in which an 8x8 MB partition is partitioned into sub-blocks is named sub-block partition.

[0055] This disclosure will generally use the term block to refer to any block of video data. For example, in the context of H.264 coding and its extensions, a block may refer to any of macroblocks, macroblock partitions, sub-blocks, or any other types of blocks. In the context of HEVC and its extensions, a block may refer to any of PUs, TUs, CUs, or any other types of blocks. A sub-block as used in this disclosure generally refers to any portion of a larger block. A sub-block may also itself be referred to simply as a block.

[0056] For multiview video coding there are multiple different video coding standards. To avoid confusion, when this disclosure describes multiview video coding generically, this disclosure uses the phrase "multiview video coding." In general, in multiview video coding, there is a base view and one or more non-base or dependent views. The base view is fully decodable without reference to any of the dependent views (i.e., the base view is only inter-predicted with temporal motion vectors). This allows a codec that is not configured for multiview video coding to still receive at least one view that is fully decodable (i.e., the base view can be extracted out and the other views discarded, allowing a decoder not configured for multiview video coding to still decode the video content albeit without 3D experience). The one or more dependent views may be inter- predicted with respect to the base view or with respect to another dependent view (i.e., disparity compensation predicted), or with respect to other pictures in the same view (i.e., motion compensated predicted).

[0057] Whereas "multiview video coding" is used generically, the acronym MVC is associated with an extension of H.264/AVC. Accordingly, when the disclosure uses the acronym MVC, the disclosure is referring specifically to the extension to H.264/AVC video coding standard. The MVC extension of H.264/AVC relies upon disparity motion vectors as another type of motion vector in addition to temporal motion vectors.

Another video coding standard, referred to as MVC plus depth (MVC+D), has also been developed by JCT-3V and MPEG. MVC+D applies the same low-level coding tools as those of MVC for both texture and depth, with the decoding of depth being independent to the decoding of texture and vice-versa. For instance, in MVC, a frame is represented only by one view component, referred to as a texture view component, or simply texture. In MVC+D, there are two view components: texture view component and depth view component, or simply texture and depth. For example, in MVC+D, each view includes a texture view and a depth view, where the view includes a plurality of view

components, the texture view includes a plurality of texture view components, and the depth view includes a plurality of depth view components.

[0058] Each texture view component is associated with a depth view component to form a view component of a view. The depth view component represents relative depth of the objects in the texture view component. In MVC+D, the depth view component and the texture view component are separately decodable. For example, video decoder 30 may implement two instances of an MVC codec, in which a first codec decodes the texture view components and a second codec decodes the depth view components.

These two codecs can execute independent of one another because the texture view components and the depth view components are separately encoded.

[0059] In MVC+D, a depth view component is always immediately following the associated (e.g., corresponding) texture view component. In this manner, MVC+D supports texture-first coding, where the texture view component is decoded prior to the depth view component.

[0060] A texture view component and its associated (e.g., corresponding) depth view component may include the same picture order count (POC) value and view_id (i.e., the POC value and view_id of a texture view component and its associated depth view component is the same). The POC value indicates the display order of the texture view component and the view_id indicates the view to which the texture view component and depth view component belong.

[0061] FIG. 2 shows a typical MVC decoding order (i.e. bitstream order). The decoding order arrangement is referred as time-first coding. Note that the decoding order of access units may not be identical to the output or display order. In FIG. 2, S0- S7 each refers to different views of the multiview video. T0-T8 each represents one output time instance. An access unit may include the coded pictures of all the views for one output time instance. For example, a first access unit may include all of the views S0-S7 for time instance TO, a second access unit may include all of the views S0-S7 for time instance Tl, and so forth.

[0062] For purposes of brevity, the disclosure may use the following definitions:

view component: A coded representation of a view in a single access unit.

When a view includes both coded texture and depth representations, a view component may include a texture view component and a depth view component.

texture view component: A coded representation of the texture of a view in a single access unit.

depth view component: A coded representation of the depth of a view in a single access unit.

[0063] As discussed above, in the context of this disclosure, the view component, texture view component, and depth vide component may be generally referred to as a layer. In FIG. 2, each of the views includes sets of pictures. For example, view SO includes set of pictures 0, 8, 16, 24, 32, 40, 48, 56, and 64, view S I includes set of pictures 1, 9, 17, 25, 33, 41, 49, 57, and 65, and so forth. Each set includes two pictures: one picture is referred to as a texture view component, and the other picture is referred to as a depth view component. The texture view component and the depth view component within a set of pictures of a view may be considered as corresponding to one another. For example, the texture view component within a set of pictures of a view is considered as corresponding to the depth view component within the set of the pictures of the view, and vice- versa (i.e., the depth view component corresponds to its texture view component in the set, and vice- versa). As used in this disclosure, a texture view component that corresponds to a depth view component may be considered as the texture view component and the depth view component being part of a same view of a single access unit. [0064] The texture view component includes the actual image content that is displayed. For example, the texture view component may include luma (Y) and chroma (Cb and Cr) components. The depth view component may indicate relative depths of the pixels in its corresponding texture view component. As one example analogy, the depth view component is like a gray scale image that includes only luma values. In other words, the depth view component may not convey any image content, but rather provide a measure of the relative depths of the pixels in the texture view component.

[0065] For example, a purely white pixel in the depth view component indicates that its corresponding pixel or pixels in the corresponding texture view component is closer from the perspective of the viewer, and a purely black pixel in the depth view

component indicates that its corresponding pixel or pixels in the corresponding texture view component is further away from the perspective of the viewer. The various shades of gray in between black and white indicate different depth levels. For instance, a very gray pixel in the depth view component indicates that its corresponding pixel in the texture view component is further away than a slightly gray pixel in the depth view component. Because only gray scale is needed to identify the depth of pixels, the depth view component need not include chroma components, as color values for the depth view component may not serve any purpose. The above explanation is intended to be an analogy for purposes of relating depth images to texture images. The depth values in a depth image do not in fact represent shades of gray, but in fact, represent 8-bit, or other bit size, depth values.

[0066] The depth view component using only luma values (e.g., intensity values) to identify depth is provided for illustration purposes and should not be considered limiting. In other examples, any technique may be utilized to indicate relative depths of the pixels in the texture view component.

[0067] FIG. 3 shows a typical MVC prediction structure (including both inter-picture prediction within each view and inter- view prediction between views) for multi-view video coding. Prediction directions are indicated by arrows, the pointed-to object using the pointed-from object as the prediction reference. In MVC, inter- view prediction is supported by disparity motion compensation, which uses the syntax of the H.264/AVC motion compensation, but allows a picture in a different view to be used as a reference picture.

[0068] In the example of FIG. 3, eight views (having view IDs "SO" through "S7") are illustrated, and twelve temporal locations ("TO" through "Ti l") are illustrated for each view. That is, each row in FIG. 3 corresponds to a view, while each column indicates a temporal location.

[0069] Although MVC has a so-called base view, which is decodable by H.264/AVC decoders, and stereo view pairs may also be supported by MVC, the advantage of MVC is that it could support an example that uses more than two views as a 3D video input and decodes this 3D video represented by the multiple views. A renderer of a client having an MVC decoder may expect 3D video content with multiple views.

[0070] Pictures in FIG. 3 are indicated at the intersection of each row and each column. The H.264/AVC standard may use the term frame to represent a portion of the video. This disclosure may use the term picture and frame interchangeably.

[0071] The pictures in FIG. 3 are illustrated using a block including a letter, the letter designating whether the corresponding picture is intra-coded (that is, an I-picture), or inter-coded in one direction (that is, as a P-picture) or in multiple directions (that is, as a B-picture). In general, predictions are indicated by arrows, where the pointed-to pictures use the pointed-from picture for prediction reference. For example, the P- picture of view S2 at temporal location TO is predicted from the I-picture of view SO at temporal location TO.

[0072] As with single view video encoding, pictures of a multiview video coding video sequence may be predictively encoded with respect to pictures at different temporal locations. For example, the b-picture of view SO at temporal location Tl has an arrow pointed to it from the I-picture of view SO at temporal location TO, indicating that the b- picture is predicted from the I-picture. Additionally, however, in the context of multiview video encoding, pictures may be inter-view predicted. That is, a view component can use the view components in other views for reference. In MVC, for example, inter-view prediction is realized as if the view component in another view is an inter-prediction reference. The potential inter-view references are signaled in the Sequence Parameter Set (SPS) MVC extension and can be modified by the reference picture list construction process, which enables flexible ordering of the inter-prediction or inter-view prediction references. Inter-view prediction is also a feature of proposed multiview extension of HEVC, including 3D-HEVC (multiview plus depth).

[0073] FIG. 3 provides various examples of inter- view prediction. Pictures of view S I, in the example of FIG. 3, are illustrated as being predicted from pictures at different temporal locations of view S I, as well as inter-view predicted from pictures of views SO and S2 at the same temporal locations. For example, the b-picture of view S I at temporal location Tl is predicted from each of the B -pictures of view S I at temporal locations TO and T2, as well as the b-pictures of views SO and S2 at temporal location Tl.

[0074] In some examples, FIG. 3 may be viewed as illustrating the texture view components. For example, the I-, P-, B-, and b-pictures illustrated in FIG. 2 may be considered as texture view components for each of the views. In accordance with the techniques described in this disclosure, for each of the texture view components illustrated in FIG. 3 there is a corresponding depth view component. In some examples, the depth view components may be predicted in a manner similar to that illustrated in FIG. 3 for the corresponding texture view components.

[0075] Coding of two views may also be supported by MVC. One of the advantages of MVC is that an MVC encoder may take more than two views as a 3D video input and an MVC decoder may decode such a multiview representation. As such, any renderer with an MVC decoder may decode 3D video content with more than two views.

[0076] As discussed above, in MVC, inter-view prediction is allowed among pictures in the same access unit (meaning, in some instances, with the same time instance). When coding a picture in one of the non-base views, a picture may be added into a reference picture list, if it is in a different view but within a same time instance. An inter- view prediction reference picture may be put in any position of a reference picture list, just like any inter-prediction reference picture. As shown in FIG. 3, a view component can use the view components in other views for reference. In MVC, interview prediction is realized as if the view component in another view was an inter- prediction reference.

[0077] In MVC, inter-view prediction is allowed among pictures in the same access unit (i.e., with the same time instance). When coding a picture in one of the non-base views, a picture may be added into a reference picture list, if it is in a different view but with a same time instance. An inter-view prediction reference picture can be put in any position of a reference picture list, just like any inter prediction reference picture.

[0078] As shown in FIG. 3, a view component can use the view components in other views for reference. This is called inter-view prediction. In MVC, inter-view prediction is realized as if the view component in another view was an inter prediction reference.

[0079] In the context of multiview video coding, there are at least two different types of motion vectors. One type of motion vector is a normal motion vector (which may be referred to as a temporal motion vector) pointing to temporal reference pictures. The corresponding temporal inter prediction is motion-compensated prediction (MCP). The other type of motion vector is a disparity motion vector pointing to pictures in a different view (i.e., inter-view reference pictures). The corresponding inter prediction is disparity-compensated prediction (DCP).

[0080] Video decoder 30 may decode video using multiple HEVC inter coding modes. In HEVC standard, there are two inter prediction modes, named merge mode (skip mode is generally considered as a special case of merge) and advanced motion vector prediction (AM VP) mode respectively for a prediction unit (PU). In either AM VP or merge mode, video decoder 30 maintains a motion vector (MV) candidate list for multiple motion vector predictors. The motion vector(s), as well as reference indices in the merge mode, of the current PU may be generated by taking one candidate from the MV candidate list.

[0081] The MV candidate list contains, for example, up to five candidates for the merge mode and only two candidates for the AMVP mode. A merge candidate may contain a set of motion information, e.g., motion vectors corresponding to both reference picture lists (list 0 and list 1) and the reference indices. If a merge candidate is identified by a merge index, the reference pictures are used for the prediction of the current blocks, as well as the associated motion vectors are determined. However, under AMVP mode for each potential prediction direction from either list 0 or list 1, a reference index needs to be explicitly signaled, together with an MVP index to the MV candidate list since the AMVP candidate contains only a motion vector. In AMVP mode, motion vector difference between selected motion vector and motion vector predictor corresponding to the MVP index is further signaled. As can be seen above, a merge candidate corresponds to a full set of motion information while an AMVP candidate contains just one motion vector for a specific prediction direction and reference index.

[0082] As described above, video decoder 30 may decode video that was coded according to the HEVC-based 3D video coding standard. Currently, a Joint

Collaboration Team on 3D Video Coding (JCT-3C) of VCEG and MPEG is developing a 3DV standard based on HEVC, for which part of the standardization efforts includes the standardization of the multiview video codec based on HEVC (MV-HEVC) and the standardization of the 3D video codec based on HEVC (3D-HEVC). For 3D-HEVC, new coding tools, including tools for CU/PU level coding, for both texture and depth views may be included and supported. The latest software 3D-HTM for 3D-HEVC can be, as of 2 May 2014, downloaded from the following link:

[3D-HTM version 9. Or 1]:

https://hevc.hhi.fraunhofer.de/svn/svn_3DVCSoftware/tags/HTM-9.0rl/.

[0083] The latest reference software description is available as follows:

Li Zhang, Gerhard Tech, Krzysztof Wegner, Sehoon Yea, "Test Model 6 of 3D-HEVC and MV-HEVC," JCT3V-F1005, Joint Collaborative Team on 3D Video Coding

Extension Development of ITU-T SG 16 WP 3 and ISO/IEC JTC 1/SC 29/WG 11, 6th

Meeting: Geneva, CH, Nov. 2013. It may be downloaded, as of 2 May 2014, from the following link:

http ://phenix .it- sudparis .eu/jct2/doc_end_user/current_document.php?id= 1636.

[0084] The latest working draft of 3D-HEVC is available as follows:

Gerhard Tech, Krzysztof Wegner, Ying Chen, Sehoon Yea, "3D-HEVC Draft Text 2," JCT3V-F1001, Joint Collaborative Team on 3D Video Coding Extension Development of ITU-T SG 16 WP 3 and ISO/IEC JTC 1/SC 29/WG 11, 6th Meeting: Geneva, CH, Nov. 2013. It could be downloaded from the following link:

http://phenix.it-sudparis.eu/jct2/doc_end_user/documents/6_Geneva/wgl l/JCT3V- F1001-v4.zip

[0085] Video decoder 30 may be configured to determine implicit disparity vectors (IDVs). Video decoder 30 generates an IDV when a PU employs inter- view motion vector prediction, or in other words, when the candidate for AMVP or merge modes is derived from a corresponding block in the other view with the help of a disparity vector. Such a disparity vector is called an IDV. Video decoder 30 stores the IDV for the PU for the purpose of disparity vector derivation.

[0086] Video decoder 30 may be configured to implement various disparity vector derivation processes. An example of one such process is called Neighboring Blocks based Disparity Vector (NBDV), which is used in current 3D-HTM. NBDV utilizes disparity motion vectors from spatial and temporal neighboring blocks. In NBDV, video decoder 30 checks the motion vectors of spatial or temporal neighboring blocks in a fixed checking order. Once video decoder 30 identifies a disparity motion vector or an IDV, video decoder 30 terminates the checking process, and the identified disparity motion vector is returned and converted to the disparity vector and may be used in interview motion prediction and potentially inter-view residual prediction. If no such disparity vector is found after checking all the pre-defined neighboring blocks, video decoder 30 may use a zero disparity vector for the inter- view motion prediction while inter-view residual prediction is disabled for the corresponding PU.

[0087] As introduced above, when implementing NBDV, video decoder 30 may check spatial and temporal neighboring blocks using a specified checking order. In some implementations of NBDV, video decoder 30 uses two spatial neighboring blocks for the disparity vector derivation. Those two blocks are the left and above neighboring blocks of the current PU, denoted by Ai and Bi, as defined in Figure 8-3 of HEVC specification. Video decoder 30 may check up to two reference pictures from the current view (e.g. the co-located picture and the random-access picture or the reference picture with the smallest POC difference and smallest temporal ID) for temporal block checks. In one example, video decoder 30 may first check the random- access picture, followed by the co-located picture. For each candidate picture, video decoder 30 checks the center block, which corresponds to the center 4x4 block of the co-located region of the current PU, as shown by 'Pos. A' in FIG. 4.

[0088] FIG. 4 is a conceptual diagram illustrating temporal neighboring blocks for neighboring blocks disparity vector derivation. In the example of FIG. 4, video decoder 30 may check two candidate blocks for each candidate picture:

a) Center block (CR): The center 4x4 block of the co-located region of the current PU, see 'Pos. A' in FIG. 4.

b) Bottom Right block (BR): Bottom-right 4x4 block of co-located region of the current PU, see 'Pos. B' in FIG. 4.

[0089] Video decoder 30 may check the neighboring blocks using a specified checking order. Video decoder 30 first checks to determine whether DMVs are used for all the temporal/spatial neighboring blocks, followed by IDVs. In one implementation, temporal neighboring blocks may be checked first, followed by spatial neighboring blocks.

• For each of the temporal candidate reference picture (up to two), video decoder 30 may check CR to determine if it uses a DMV. If it uses a DMV, then video decoder 30 may terminate the checking process and use the corresponding DMV as the final disparity vector.

• Video decoder 30 may check two spatial neighboring blocks in the order of Ai, Bi. If one of them uses a DMV, then video decoder 30 may terminate the checking process and use the corresponding DMV as the final disparity vector. • Video decoder 30 may check two spatial neighboring blocks in the order of Ai, Bi to determine if one of them uses an IDV and it is coded as skip mode. If one of blocks Ai or Bi uses the IDV and is coded in a skip mode, then video decoder 30 may terminate the checking process and use the corresponding IDV as the final disparity vector.

[0090] Video decoder 30 may also refine the determined disparity vector, in some examples. For example, video decoder 30 may refine the disparity vector generated using NBDV using the information in the coded depth map. That is, video decoder 30 may enhance the accuracy of the disparity vector by using the information coded in the base view depth map. As part of the refinement process, video decoder 30 may first locate a corresponding depth block by the derived disparity vector in the previously coded reference depth view, such as the base view. The size of the corresponding depth block may be the same as that of current PU. Video decoder 30 may then calculate a disparity vector from the collocated depth block, e.g. from the maximum value of the four corner depth values. Video decoder 30 may set the horizontal component of the disparity vector to this calculated value, while the vertical component of the disparity vector is set to 0.

[0091] This new disparity vector is called a depth oriented neighboring block based disparity vector (DoNBDV). In some instances, video decoder 30 may utilize the disparity vector found using DoNBDV instead of the disparity vector found using NBDV for inter-view candidate derivation for the AMVP and merge modes. Video decoder 30 may, however, use the unrefined disparity vector for inter- view residual prediction. Additionally, video decoder 30 may store the refined disparity vector as the motion vector of one PU if it is coded with backward VSP mode.

[0092] DoNBDV may be enabled/disabled by the flag depth_refinement_flag[ layerld ] signaled in a parameter set, such as a video parameter set (VPS). When

depth_refinement_flag[ layerld ] is equal to 0, DoNBDV is disabled, and video decoder 30 may use NBDV for finding the IDV. Otherwise, when

depth_refinement_flag[ layerld ] is equal to 1, video decoder 30 may use DoNBDV for finding the IDV.

[0093] FIG. 5 is a conceptual diagram illustrating techniques related to backward view synthesis prediction (BVSP) using neighboring blocks. BVSP has been proposed, and adopted, as a technique for 3D-HEVC. The backward-warping VSP approach as proposed in JCT3V-C0152 was adopted in the 3rd JCT-3V meeting. The basic idea of this backward-warping VSP is the same as the block-based VSP in 3D-AVC. Both of these two techniques use the backward-warping and block-based VSP to avoid transmitting the motion vector differences and use more precise motion vectors.

Implementation details are different due to different platforms. This disclosure generally uses the initialism BVSP to refer to backward view synthesis prediction in 3D-HEVC, although BVSP may also refer to block-based view synthesis prediction of 3D-AVC.

[0094] In 3D-HTM, texture first coding is applied in common test conditions.

Therefore, the corresponding non-base depth view is unavailable when decoding one non-base texture view. Therefore, the depth information is estimated and used to perform BVSP. In order to estimate the depth information for a block, it was proposed to first derive a disparity vector from the neighboring blocks, and then use the derived disparity vector to obtain a depth block from a reference view.

[0095] As already introduced above, in the HTM 5.1 test model, there exists a process to derive a disparity vector predictor, known as NBDV Let (dvx, dvy) denote the disparity vector identified from the NBDV function, and the current block position is (blockx, blocky). It was proposed to fetch a depth block at (blockx+dvx, blocky+dvy) in the depth image of the reference view. The fetched depth block would have the same size of the current prediction unit (PU), and it would then be used to do backward warping for the current PU. FIG. 5 illustrates the steps for locating a depth block from the reference view and then using the depth block for BVSP prediction.

[0096] In the example of FIG. 5, depth picture 150 and texture picture 154 correspond to the same view, while texture picture 152 corresponds to a different view. In particular, texture picture 152 includes current block 160 being coded relative to texture picture 154, acting as a reference picture. A video coder may refer to neighboring block 162, which neighbors current block 160. Neighboring block 162 includes a previously determined disparity vector 166. Disparity vector 166 may be derived as a disparity vector 164 for current block 160. Thus, disparity vector 164 refers to depth block 156 in depth picture 150 of the reference view.

[0097] The video coder may then use pixels (that is, depth values) of depth block 156 to determine disparity values 168 for pixels (that is, texture values) of current block 160, for performing backward warping. The video coder may then synthesize values for a predicted block (i.e., a BVSP reference block) for current block 160 from the pixels identified by disparity values 168. The video coder may then predict current block 160 using this predicted block. For instance, during video encoding by video encoder 20, video encoder 20 may calculate pixel-by-pixel differences between the predicted block and current block 160 to produce a residual value, which video encoder 20 may then transform, quantize, and entropy encode. On the other hand, during video decoding by video decoder 30, video decoder 30 may entropy decode, inverse quantize, and inverse transform residual data, then combine the residual data (on a pixel-by-pixel basis) with the predicted block to reproduce current block 160.

[0098] JCT3V-C0152 proposed changes to the BVSP techniques of 3D-HEVC, as described below. In particular, italicized text represents text added to 3D-HEVC, while bracketed text preceded by "removed:" represents deletions from 3D-HEVC:

If BVSP is enabled in the sequence, the NBDV process for inter- view motion prediction is changed and the differences are highlighted in the following paragraphs:

• For each of the temporal neighboring blocks, if it uses a disparity motion vector, the disparity motion vector is returned as the disparity vector and it is further refined with the method described in Section 1.6.1.3 of 3D-HEVC.

• For each of the spatial neighboring blocks, the following apply:

o For reference picture list 0 and reference picture list 1 in order:

^■ If it uses a disparity motion vector, the disparity motion vector is returned as the disparity vector and it is further refined with the method described in Section 1.6.1.3.

^■ Otherwise, if it uses BVSP mode, the associated motion vector is returned as the disparity vector. It is further refined in a similar way as described in Section 1.6.1.3. However, the maximum depth value is selected from all pixels of the corresponding depth block rather than four corner pixels and the vertical component of the refined disparity vector is set to 0.

• For each of the spatial neighboring blocks, if it uses an IDV, the IDV is returned as the disparity vector and it is further refined with the method described in Section 1.6.1.3.

[0099] The introduced BVSP mode is treated as a special inter-coded mode, and a flag indicating the usage of BVSP mode may be maintained for each PU. Rather than signalling the flag in the bitstream, a new merging candidate (BVSP merging candidate) was added to the merge candidate list. The flag is dependent on whether the decoded merge candidate index corresponds to a BVSP merging candidate. The BVSP merging candidate is defined, per JCT3V-C0152, as follows:

• Reference picture index for each reference picture list: -1

• Motion vector for each reference picture list: the refined disparity vector

[00100] In JCT3V-C0152, the inserted position of the BVSP merging candidate is dependent on the spatial neighboring blocks, as discussed below:

• If any of the five spatial neighboring blocks (AO, Al, B0, B l, or B2, shown in FIG. 8-3 of the HEVC specification) is coded with the BVSP mode, i.e., the maintained flag of the neighboring block is equal to 1, BVSP merging candidate is treated as the corresponding spatial merging candidate and inserted to the merge candidate list. BVSP merging candidate may only be inserted to the merge candidate list once.

• Otherwise (none of the five spatial neighboring blocks are coded with the BVSP mode), the BVSP merging candidate is inserted to the merge candidate list just before the temporal merging candidates.

[00101] It is noted that during the combined bi-predictive merging candidate derivation process, additional conditions may be checked to avoid including the BVSP merging candidate.

[00102] As described above, video decoder 30 may perform an inter-view candidate derivation process for skip and merge modes. Based on the disparity vector derived from DoNBDV or NBDV, a new motion vector candidate, Inter-view Predicted Motion Vector Candidate (IPMVC), if available, may be added by video decoder 30 to the skip or merge modes. The inter- view predicted motion vector, if available, is a temporal motion vector. As skip mode has the same motion vector derivation process as merge mode, all techniques described in this disclosure with respect to merge may also be considered applicable to skip mode.

[00103] For the merge/skip mode, video decoder 30 derives the inter- view predicted motion vector by performing several steps. First, video decoder 30 locates a

corresponding block of a current PU/CU in a reference view of the same access unit using the disparity vector. If the corresponding block is not intra-coded and not interview predicted and its reference picture has a POC value equal to that of one entry in the same reference picture list of current PU/CU, then video decoder 30 derives its motion information (prediction direction, reference pictures, and motion vectors), after converting the reference index based on POC is derived to be the inter-view predicted motion vector.

[00104] Video decoder 30 identifies the corresponding block as follows:

Denote a luma location (xP, yP) of the top-left luma sample of the current prediction unit relative to the top-left luma sample of the current picture, nPSW and nPSH denote the width and height of the current prediction unit, respectively, reference view order index refViewIdx, and a disparity vector mvDisp, the reference layer luma location (xRef, yRef) is derived by:

xRef = Clip3( 0, PicWidthInSamples_L - 1, xP + ( nPSW » 1 ) + ( ( mvDisp[ 0 ] + 2 ) » 2 ) )

yRef = Clip3( 0, PicHeightInSamples_L - 1, yP + ( nPSH » 1 ) + ( ( mvDisp[ 1 ] + 2 ) » 2 ) )

The corresponding block is set to the prediction unit that covers the luma location ( xRef, yRef ) in the view component with Viewldx equal to refViewIdx.

[00105] FIG. 6 shows an example of the derivation process of the inter-view predicted motion vector candidate. For current block 120 in a first view (VI), video decoder 30 locates a corresponding block 121 in a different view (V0). Video decoder 30 may reuse the motion information of reference block 121 to derive motion information for current block 120. For example, if video decoder 30 used motion vector 124B to predict reference block 121, then video decoder 30 may use motion vector 124A to predict current block 120. Motion vector 124 A and motion vector 124B are intended to represent two different instances of the same motion vector.

[00106] Video decoder 30 may convert disparity vector 124A to an inter-view disparity motion vector, which is added into merge candidate list in a different position from IPMVC. Either IPMVC or Inter-view Disparity Motion Vector Candidate (IDMVC) may be referred to as an 'inter-view candidate' in this context.

[00107] In the merge/skip mode, video decoder 30 may insert the IPMVC, if available, before all spatial and temporal merge candidates into the merge candidate list. Video decoder 30 may insert the IDMVC before the spatial merge candidate derived from Ao.

[00108] Video decoder 30 may also derive a shifted inter-view candidate for skip/merge mode. In addition to the IPMVC, video decoder 30 may also add a shifted inter-view predicted motion vector candidate (SIPMVC), if available, to the skip/merge modes. Similar derivation process with IPMVC (described in subclause 1.8.5.3.2.11 of the 3D- HEVC standard with the title "Derivation process for a temporal inter-view motion vector candidate") is used to derive SIPMVC. The difference in derivation of IPMVC and SPEVIVC are the used reference layer luma location.

[00109] In SIPMVC, the reference layer luma location ( xRef, yRef ) is derived as: xRef = Clip3( 0, PicWidthInSamples_L - 1, xP + ( nPSW » 1 ) +( ( mvDisp[ 0 ] + nPbW *2 + 4 + 2 ) » 2 ) )

yRef = Clip3( 0, PicHeightInSamples_L - 1, yP + ( nPSH » 1 ) +( ( mvDisp[ 1 ] + nPbH *2 + 4 + 2 ) » 2 ) )

[00110] Video decoder 30 may shift the disparity vector derived in DoNBDV/NBDV by a constant, e.g., (+4, 0) and convert it to a Shifted Inter-view Disparity Motion Vector (SIDMVC).

[00111] FIG. 7 shows an example of sub-PU level inter-view motion prediction.

FIG. 7 shows a current view, referred to as VI, and a reference view, referred to as V0. Current PU 190 includes four sub-PUs A-D. Video decoder 30 may use disparity vectors of each of the four sub-PUs A-D to locate reference blocks 191, which includes four reference blocks A_R - D_R. The disparity vectors of sub-PUs A-D are shown in FIG. 7 as DV[i], where i corresponds to A-D. As each of the four sub-PUs has a unique disparity vector, the location of sub-PUs A-D relative to one another may differ than the location of reference blocks A_R-D_R relative to one another. In sub-PU level interview motion prediction, video decoder 30 may use the motion vector of a reference block to predict a sub-PU. The motion vectors of reference blocks A_R-D_R are shown in FIG. 7 as MV[i], where i corresponds to A-D. Thus, as one example, for sub-PU A, video decoder 30 may use DV[A] to locate reference block A_R, determine reference block A_R was coded using MV[A], and use MV[A] to locate a predictive block for sub-PU A.

[00112] Video decoder 30 may be configured to perform sub-PU level inter-view motion prediction as introduced above with respect to FIG. 7. Aspects of inter- view motion prediction are described above, where only the motion information of the reference block is used for the current PU in the dependent view. However, the current PU may correspond to a reference area (with the same size as current PU identified by the disparity vector) in the reference view and the reference are may have plentiful motion information. Sub-PU level inter- view motion prediction (SPIVMP) as shown in FIG. 7 can use plentiful motion information in the reference area. SPrVMP may only apply for partition mode 2Nx2N. [00113] Denote coordination of top left sample of current PU relative to top left sample of the depth picture by (xP, yP). Denote the assigned sub-PU size by NxN. The SPIVMP merge candidate is derived as follows:

- First, divide the current PU into multiple sub-PUs with a smaller size. Denote the size of current PU by nPSW x nPSH and size of sub-PU by nPSWsub x nPSHSub. nPSWsub = min(N, nPSW)

nPSHSub = min(N, nPSH)

- Second, set default motion vector tmvLX and refLX equal to motion vector and reference index of the reference block associated with the center sub-PU, for each reference picture list.

o Obtain a reference sample location (xRefCSub, yRefCSub) by:

xRefCSub = Clip3( 0, PicWidthlnSamplesL - 1,

(xP/nPSWsub/2)*nPSWsub + nPSWsub/2 + ( ( mvDisp[ 0 ] + 2 ) » 2 ) ) yRefCSub = Clip3( 0, PicHeightlnSamplesL - 1,

(yP/nPSWsub/2)*nPSHsub + nPSHSub 12 + ( ( mvDisp[ 1 ] + 2 ) » 2 ) ) o Identify a block in the reference view that covers (xRefSub, yRefSub). o For the identified reference block,

- if it is coded using temporal motion vectors, tmvLX and refLX are set equal to the motion vectors and reference index of the identified reference block.

- Otherwise (the reference block is intra coded), SPIVMP is considered as unavailable and derivation process of SPIVMP terminates.

- For each sub-PU in the raster scan order (denote coordination of its top left sample relative to top left sample of the depth picture by (xPsub, yPsub)), the following applies:

o add the DV to the middle position of current sub-PU to obtain a reference sample location (xRefSub, yRefSub) by:

xRefSub = Clip3( 0, PicWidthlnSamplesL - 1, xPSub + nPSWsub/2 + ( ( mvDisp[ 0 ] + 2 ) » 2 ) )

yRefSub = Clip3( 0, PicHeightlnSamplesL - 1, yPSub + nPSHSub 12 + ( ( mvDisp[ 1 ] + 2 ) » 2 ) )

a block in the reference view that covers (xRefSub, yRefSub) is used as the reference block for current sub-PU.

o For the identified reference block, - if it is coded using temporal motion vectors, the associated motion parameters are used as candidate motion parameters for the current sub-PU.

- Otherwise (the reference block is intra coded), the motion

information of current sub-PU is set equal to tmvLX and refLX.

[00114] Different sub-PU block size may be applied, for example, 4x4, 8x8, and 16x16.

[00115] A syntax element is present in VPS indicating for each layer the sub-PU size. If the sub-PU size is large enough, e.g., larger than the current PU, the whole PU does not use sub-PU inter- view prediction.

[00116] Detailed semantics of such syntax element is as follows.

log2_sub_pb_size_minus3[ layerld ] specifies the value of the variable

SubPbSize[ layerld ] that is used in the decoding of prediction units using the inter- view merge candidate. The value of log2_sub_pb_size_minus3 shall be in the range of ( MinCbLog2SizeY - 3 ) to ( CtbLog2SizeY - 3 ), inclusive.

[00117] Video decoder 30 may be configured to construct a merge candidate list for texture coding in 3D-HEVC. Video decoder 30 may first derive a disparity vector using either DoNBDV or NBDV. With the disparity vector, the merge candidate list construction process in 3D-HEVC can be defined in a series of ordered steps. First, video decoder 30 may derive spatial merge candidates Ai, Bi, Bo, Ao, and B₂ (as shown in FIG. 8-3 of the HEVC specification), one or more temporal merge candidates, and bi- predictive merge candidates. Video decoder 30 may, for example, derive the spatial merge candidates, one or more temporal merge candidates, and bi-predictive merge candidates using the techniques of sub-clause 8.5.3.2.1 in the HEVC specification.

[00118] Next, video decoder 30 may insert an SPIVMP or IPMVC candidate into the list. Video decoder 30 may derive and insert into the merge list the SPIVMP or IPMVC candidate if is available. For example, if partition mode of the PU is equal to 2Nx2N, video decoder 30 may invoke the above-described SPIVMP derivation process. If SPIVMP is available, video decoder 30 may insert it into the merge list. Otherwise, if partition mode of the PU is not equal to 2Nx2N, video decoder 30 may invoke the above-described IPMVC derivation process. If an IPMVC candidate is available, video decoder 30 may insert into the merge list.

[00119] Next, video decoder 30 may insert spatial merge candidates, BVSP candidates, and IDMVC candidates. Video decoder 30 may check the motion information of spatial neighboring PUs in the order of Ai, Bi, Bo, Ao, or B₂. Video decoder 30 may perform constrained pruning using the following procedures:

- If Ai and SPIVMP (or IPMVC) have the same motion vectors and the same reference indices, Ai is not inserted into the candidate list;

otherwise it is inserted into the list.

- If B i and Ai/SPIVMP (or IPMVC) have the same motion vectors and the same reference indices, Bi is not inserted into the candidate list;

otherwise it is inserted into the list.

- If Bo is available, it is added to the candidate list.

- If IDMVC is available and it is different from the candidates derived from Ai and Bi, it is inserted to the candidate list.

- If BVSP is enabled for the whole picture or for the current slice, then the BVSP merge candidate is inserted to the merge candidate list.

- If Ao is available, it is added to the candidate list.

- If B₂ is available, it is added to the candidate list.

[00120] Next, video decoder 30 may insert a shifted inter-view merge candidate into the list. Video decoder 30 may check an SIPMVC, a disparity motion vector in the partially constructed merge list, and an SIDMVC in the following order.

- If SIPMVC and SPIVMP (or IPMVC) have the same motion vectors and the same reference indices, SIPMVC is not inserted into the candidate list; otherwise it is inserted into the list. If SIPMVC is inserted into the candidate list, the checking process terminates and following steps are skipped.

- If SIPMVC is not available, following derivation process applies:

i. If there is at least one disparity motion vector in the partially constructed merge list, identify the first disparity motion vector and shift it by a constant number, e.g., (+4, 0), and insert it into the merge list.

ii. Otherwise, if there is no disparity motion vector in the partially constructed merge list, insert SIDMVC into the merge list.

[00121] Next, video decoder 30 may insert a temporal merge candidate and bi- predictive merge candidates into the merge list. If the total number of candidates derived from the above steps is less than the maximum number of candidates, video decoder 30 may insert a temporal merge candidate and bi-predictive merge candidates into the merge list in order.

[00122] Next, video decoder 30 may insert zero motion vector merge candidates into the merge list. If the total number of candidates derived from the above steps is less than the maximum number of candidates, video decoder 30 may insert zero motion vector merge candidates into the merge list.

[00123] Video decoder 30 may also be configured to perform ARP, which is a coding tool that exploits the residual correlation between views. In ARP, a residual predictor is produced by aligning the motion information at the current view for motion

compensation in the reference view. In addition, weighting factors are introduced to compensate the quality differences between views. When ARP is enabled for one block, the difference between current residual and the residual predictor is signaled. Currently, ARP could only be applied to inter-coded CUs with partition mode equal to

Part_2Nx2N. ARP is applied for both the luma (Y) component and the chroma (Cb and Cr) component. In the following description, operation (such as sum, subtraction) on one block (or pixel) means operation on each component (Y, Cb and Cr) of each pixel in the block (or pixel). When there is a need to distinguish the process for luma and chroma components, the process for luma component is called luma ARP (sub-PU ARP) and the process for chroma components is called chroma ARP (sub-PU ARP).

[00124] FIG. 8 shows an example prediction structure for temporal ARP in 3D-

HEVC, which was adopted in the 4^th JCT3V meeting, as proposed in JCT3V-D0177. FIG. 8 illustrates the prediction structure of ARP for temporal residual (i.e., current reference picture in one reference picture list is a temporal reference picture) in multiview video coding.

[00125] As shown in FIG. 8, video decoder 30 identifies the following blocks in the prediction of the current block being coded. The current block is shown in FIG. 8 as Curr 150. Base 151 represents a reference block in a reference/base view derived by the disparity vector (DV 152A). CurrTRef 153 represents a block in the same view as block Curr 150 derived by a temporal motion vector (TMV 154 A) of the current block. BaseTRef 155 represents a block in the same view as block Base 151 derived by the temporal motion vector of the current block (TMV 154B). Thus, TMV 154A and TMV 154B correspond to the same motion vector, meaning they identify the same amount of displacement along the x-axis and y-axis. The difference in relative location between BaseTRef 155 and Curr 150 can be expressed with a vector of TMV+DV. The difference in relative location between CurrTRef 153 and BaseTRef 155 can be expressed by the disparity vector DV 152B. TMV+DV and DV 152B are provided in FIG. 8 to show the relationship between the various blocks and do not necessarily correspond to vectors that are derived or used by video decoder 30.

[00126] When performing temporal ARP, video decoder 30 may calculate the residual predictor as BaseTRef-Base, where the subtraction operation applies to each pixel of the denoted pixel arrays. Video decoder 30 may multiply the residual predictor by a weighting factor (w). Therefore, the final predictor of the current block determined by video decoder 30 is denoted as CurrTRef w*(Base-BaseTRef).

[00127] The example of FIG. 8 shows the case of uni-directional prediction.

When extending to the case of bi-directional prediction, video decoder 30 may apply the above steps for each reference picture list. Thus, for bi-directional prediction, video decoder 30 may determine two residual predictors for two different predictive blocks.

[00128] FIG. 9 shows an example relationship between a current block 160, a corresponding block 161, and motion compensated block 162. Video decoder 30 may perform ARP by first obtaining a disparity vector (DV 163) pointing to a target reference view (Vo). Video decoder 30 may obtain DV 163 using, for example, any of the techniques specified in the current 3D-HEVC. In the picture of reference view Vo within the same access unit, video decoder 30 may locate the corresponding block 161 using DV 163. Video decoder 30 may re-use the motion information of reference block 161 to derive motion information for current block 160. For example, if video decoder 30 used motion vector 164B to predict reference block 161, then video decoder 30 may use motion vector 164A to predict current block 160. Motion vector 164A and motion vector 164B are intended to represent two different instances of the same motion vector.

[00129] Video decoder 30 may apply motion compensation for current block 160 based on the same motion vector used to code corresponding block 161 and derived reference picture in the reference view for the reference block, to derive a residue block. Video decoder 30 selects the reference picture in the reference view (Vo) which has the same POC value as the reference picture of the current view (V_m) as the reference picture of the corresponding block. Video decoder 30 applies the weighting factor to the residue block to get a weighted residue block and adds the values of the weighted residue block to the predicted samples.

[00130] Video decoder 30 may also be configured to perform inter-view ARP.

Similar to temporal ARP, when a current prediction unit uses an inter- view reference picture, prediction of inter-view residual is enabled. First, the inter-view residual within a different access unit is calculated, then the calculated residual information may be used to predict the inter-view residual of the current block. This technique was proposed in JCT3V-F0123_and has been adopted into 3D-HEVC.

[00131] FIG. 10 shows an example prediction structure for inter-view ARP. As shown in FIG.10, for inter-view ARP, video decoder 30 identifies three related blocks for current block 170. Base 171 represents the reference block in the reference view located by the disparity motion vector (DMV 172A) of current block 170. BaseRef 173 represents the reference block of Base 171 in the reference view located by the temporal motion vector mvLX 174A and reference index, if available, contained by Base 171. CurrRef 175 represent a reference block in current view identified by reusing the temporal motion information from Base 171. Thus, video decoder 30 may locate CurrRef 175 using mvLX 174B, where mvLX 174A and mvLX 174B represent two instances of the same motion vector. DMV 172B is equal to DMV 172A as included in FIG. 10 to illustrate that the disparity between Curr 170 and Base 171 is equal to the disparity between CurrRef 175 and BaseRef 173. DMV 172B may not actually correspond to a disparity motion vector used or generated by video decoder 30.

[00132] With the identified three blocks, video decoder 30 may calculate the residual predictor of the residual signal for current PU (i.e. Curr 170) as the difference between CurrRef and BaseRef. Furthermore, the inter-view predictor may be multiplied by a weighting factor (w). Therefore, the final predictor of the current block (Curr 170) determined by video decoder 30 is denoted as Base+ w*(CurrRef-BaseRef).

[00133] Video decoder 30 may use bi-linear filtering to generate the three relative blocks as in some known designs of ARP for temporal residual prediction. Furthermore, when the temporal motion vector contained by Base 171 points to a reference picture that is in a different access unit of the first available temporal reference picture of current PU, video decoder 30 may scale the temporal motion vector to the first available temporal reference picture and the scaled motion vector may be used to locate two blocks in a different access unit.

[00134] When ARP is applied for inter-view residual, the current PU is using inter-view ARP, when ARP is applied for temporal residual, the current PU is using temporal ARP.

[00135] In the following description, if the corresponding reference for one reference picture list is a temporal reference picture and ARP is applied, it is denoted as temporal ARP. Otherwise, if the corresponding reference for one reference picture list is an inter-view reference picture and ARP is applied, it is denoted as inter-view ARP.

[00136] As introduced above, video decoder 30 may multiply the residual predictor by a weighting factor. Three weighting factors are typically used in ARP (i.e., 0, 0.5, and 1) although more or fewer weighting factors as well as different weighting factors may also be used. Video encoder 20 may, for example, select the weighting factor leading to minimal rate-distortion cost for the current CU as the final weighting factor and signal the corresponding weighting factor index (0, 1 and 2 which correspond to weighting factor 0, 1, and 0.5, respectively) in the bitstream at the CU level. All PU predictions in one CU may share the same weighting factor. When the weighting factor is equal to 0, ARP is not used for the current CU.

[00137] Video decoder 30 may be configured to perform reference picture selection via motion vector scaling. In JCT3V-C0049, the reference pictures of prediction units coded with non-zero weighting factors may be different from block to block. Therefore, different pictures from the reference view may need to be accessed to generate the motion-compensated block (i.e., BaseTRef in FIG. 8) of the corresponding block. When the weighting factor is unequal to 0, for temporal residual, the motion vectors of the current PU is scaled towards a fixed picture before performing motion compensation for both residual and residual predictor generation processes. When ARP is applied to inter-view residual, the temporal motion vectors of the reference block (i.e., Base in FIG. 10) is scaled towards a fixed picture before performing motion

compensation for both residual and residual predictor generation processes.

[00138] For both cases (i.e, temporal residual or inter-view residual), the fixed picture is defined as the first available temporal reference picture of each reference picture list. When the decoded motion vector does not point to the fixed picture, it is firstly scaled and then used to identify CurrTRef and BaseTRef.

[00139] Such a reference picture used for ARP is called target ARP reference picture. Note when current slice is a B slice, the target ARP reference picture is associated with the reference picture list. Therefore, two target ARP reference pictures may be utilized.

[00140] Video decoder 30 may perform an availability check of target ARP reference pictures. The target ARP reference picture associated with one reference picture list X (with X being 0 or 1) may be denoted by RpRefPicLX, and the picture in the view with view order index equal to the one derived from NBDV process and with the same POC value of RpRefPicLX may be denoted by RefPicInRefViewLX. When one of the following conditions is false, video decoder 30 may disable ARP disabled for reference picture list X: (1) RpRefPicLX is unavailable, (2) RefPicInRefViewLX is not stored in decoded picture buffer, (3) RefPicInRefViewLX is not included in any of the reference picture lists of the corresponding block (i.e, Base in FIG. 5 and FIG. 7) located by the DV from NBDV process or DMV associated with current block, ARP may be disabled for this reference picture list.

[00141] When ARP is applied, video decoder 30 may use a bi-linear filter when generating the residual and residual predictor. That is, the three blocks exclude current block involved in the ARP process may be generated using bi-linear filter.

[00142] Existing ARP techniques may have certain problems. For example, in

3D-HEVC, different reference blocks (in a reference view) are identified in inter-view motion prediction and advanced residual prediction for a current block. In inter- view motion prediction, a disparity vector generated using a DoNBDV process is used to identify a reference block of a current block. In other words, in derivation processes for inter- view predicted motion vector candidates, shifted inter-view predicted motion vector candidates, and sub-PU level inter-view motion prediction a DoNBDV process is used. For identifying a reference block of a current block in temporal residual prediction, however, a disparity vector is generated using an NBDV process.

[00143] The misalignment of the disparity vectors for ARP and inter- view motion prediction may cause some potential problems. As one example, the reference blocks in the base/reference view used for inter- view motion prediction and ARP are found using different processes. As will be described in this disclosure, the techniques of this disclosure may improve performance of a video coder because, in some coding scenarios, only one disparity vector needs to be derived instead of two. Additionally, using two different processes for inter-view prediction and ARM may necessitate accessing pixel samples and motion information from different reference blocks and, thus, may lead to additional and/or misaligned memory access.

[00144] This disclosure introduces techniques that may address some of the problems discussed above with respect to ARP. According to one technique of this disclosure, when ARP is used for a current block, video decdoer 30 may be configured to use one single disparity vector to identify the reference block (e.g. in a reference view) of the current block in both inter-view motion prediction and temporal residual prediction. In other words, video decoder 30 may use one single disparity vector in the derivation process of an inter-view predicted motion vector candidate, shifted inter-view predicted motion vector candidate, sub-PU level inter-view motion prediction, and temporal residual prediction. Here the ARP can be the temporal ARP (uni-directional or bidirectional) or the inter-view ARP (uni-directional or bi-directional) or both temporal ARP and inter-view ARP (temporal ARP in one prediction direction and inter- view ARP in another prediction direction).

[00145] In one example, video decoder 30 may set the single disparity vector equal to the disparity vector generated in an NBDV process. In this example, when ARP is used for the current CU/PU, the merge candidate list generation process of each PU(s) of the current CU/PU may always utilize the disparity vector that is derived from NBDV, and therefore, there may be no need to perform DoNBDV for the currrent CU even when accessing depth view is allowed for texture coding of the current slice. In another example, video decoder 30 may set the single disparity vector equal to the disparity vector generated in an DoNBDV process.

[00146] ARP may be considered to be used for the current block when the ARP weighting factor of the current block is not equal to zero. In other words, when the weighting factor is 0, video decoder 30 may perform NBDV or DoNBDV for inter- view motion prediction, but when the weighting factor does not equal zero, video decoder 30 may select NBDV or DoNBDV in such a way that it aligns with the disparity vector used for ARP.

[00147] Alternatively or additionally, ARP is considered to be used for a current block when both the ARP weighting factor is unequal to zero and the following conditions are also true in any prediction direction X, where X = 0 or 1. According to the first condition, there is at least one temporal reference picture in reference picture list X. Denote the temporal reference picture (in reference picture list X) with smallest POC difference from current slice as RpRefPicLX. According to the second condition, denote targetRefViewIdx as the view order index derived in NBDV process, and denote RefPicInRefViewLX as the texture picture with view order index equal to

targetRefViewIdx and POC value equal to POC of RpRefPicLX. RefPicInRefViewLX shall be stored in the decoded picture buffer and marked as "used for reference".

[00148] According to another example of this disclosure, alternatively or additional, when the current block is coded with ARP but each of the prediction directions, if ARP is used, utilizes just inter-view ARP, the disparity vector used in inter-view motion prediction, (i.e., the disparity vector used in derivation process of inter-view predicted motion vector candidate, shifted inter- view predicted motion vector candidate and sub- PU level inter-view motion prediction) may be not aligned with the disparity vector used in ARP. In these instances, video decoder 30 may generate separate disparity vectors for inter- view motion prediction and ARP.

[00149] According to another example of this disclosure, alternatively or additionally, when ARP is used for a current block and the current block is bi-directionally predicted from both a temporal reference picture and and inter- view reference picture with signalled temporal motion vector and disparity motion vector, the signaled disparity motion vector is used to identify a reference block of currernt block in temporal ARP. Video decoder 30 may use the dispairty vector generated by NBDV to identify the reference block of the current block in the derivation process of inter- view predicted motion vector candidate, shifted inter-view predicted motion vector candidate, sub-PU level inter-view motion prediction and any other processes that require a disparity vector. Alternatively, video decoder 30 may use the disparity vector generated by DoNBDV to identify a reference block of the current block in the derivation processes of inter- view predicted motion vector canddiate, shifted inter-view predicted motion vector candidate, sub-PU level inter- view motion prediction and any other processes that require a disparity vector.

[00150] Implementation of the various techniques discussed above with respect to 3D- HEVC will now be discussed. Newly added parts proposed by this disclosure are underlined and deleted parts are marked as strikethrough.

[00151] In this example, disparity vector generated in NBDV derivation process is used to to identify the reference block of current block in derivation process of inter- view predicted motion vector candidate, shifted inter- view predicted motion vector candidate, sub-PU level inter- view motion prediction and temporal residual prediction. ARP is considered to be used for current block when ARP weighting factor of current block is not equal to zero

[00152] H.8.5.3.2.10 Derivation process for inter-view merge candidates - This process is not invoked when iv_mv_pred_flag[ nuh_layer_id ] is equal to 0 and

mpi_flag[ nuh_layer_id ] is equal to 0.

Inputs to this process are:

- a luma location ( xPb, yPb ) of the top-left sample of the current luma prediction block relative to the top-left luma sample of the current picture,

- two variables nPbW and nPbH specifying the width and the height of the current luma prediction block,

Outputs of this process are (with X being 0 or 1, respectively)

- the availability flags availableFlaglvMC, availableFlaglvMCShift and

availableFlaglvDC specifying whether the inter- view merge candidates are available,

- the reference indices refldxLXIvMC, refldxLXIvMCShift and refldxLXIvDC,

- the prediction list utilization flags predFlagLXIvMC, predFlagLXIvMCShift and predFlagLXIvDC,

- the motion vectors mvLXIvMC, mvLXIvMCShift and mvLXIvDC.

The availability flags availableFlaglvMC, availableFlaglvMCShift and

availableFlaglvDC are set equal to 0, and for X in the range of 0 to 1, inclusive, the variables predFlagLXIvMC, predFlagLXIvMCShift, predFlagLXIvDC are set equal to 0, the variables refldxLXIvMC, refldxLXIvMCShift and refldxLXIvDC are set equal to -1, and both components of mvLXIvMC, mvLXIvMCShift and mvLXIvDC are set equal to 0.

The temporal inter-view motion vector merging candidate is derived by the following ordered steps.

1. Depending on PartMode, the following applies:

- If PartMode is equal to PART_2Nx2N, the derivation process for inter layer predicted sub prediction block motion vector candidates as specified in subclause 1.8.5.3.2.16 is invoked with the luma location ( xPb, yPb ), the variables nPbW and nPbH, the view order index RefViewIdx[ xPb ][ yPb ] and the disparity vector ( iv res pred weight idx != 0 ) ?

MvDispr xPb 1Γ yPb 1 : MvRefinedDisp[ xPb ][ yPb ] as inputs, and the outputs are, with X being in the range of 0 to 1, inclusive, the flag availableFlagLXIvMC, the motion vector mvLXIvMC and the reference index refldxLXIvMC.

- Otherwise (PartMode is not equal to PART_2Nx2N), the derivation process for a temporal inter-view motion vector candidate as specified in subclause 1.8.5.3.2.11 is invoked with the luma location ( xPb, yPb ), the variables nPbW and nPbH, the prediction list indication X, the view order index RefViewIdx[ xPb ][ yPb ], and the disparity vector

( iv res pred weight idx != 0 ) ? MvDispT xPb 1Γ yPb 1 :

MvRefinedDisp[ xPb ][ yPb ] as inputs, and the outputs are the flag availableFlagLXIvMC, the motion vector mvLXIvMC and the reference index refldxLXIvMC.

2. The availability flag availableFlaglvMC, and the prediction utilization flags predFlagLOIvMC and predFlagLUvMC are derived by

availableFlaglvMC = availableFlagLOIvMC 1 1 availableFlagLUvMC (1-134) predFlagLOIvMC = availableFlagLOIvMC (1-135) predFlagLUvMC = availableFlagLUvMC (1-136) When DepthFlag is equal to 0, the shifted temporal inter-view motion vector merging candidate is derived by the following ordered steps.

1. For the prediction list indication X being 0 and 1 the following applies:

- The derivation process for a temporal inter-view motion vector candidate as specified in subclause 1.8.5.3.2.11 is invoked with the luma location ( xPb, yPb ), the variables nPbW and nPbH, the prediction list indication X, the view order index RefYiewIdx[ xPb ][ yPb ], and the disparity vector ( ( iv_res_pred_weight_idx != 0 ) ? MvDisp[ xPb ][ yPb ] :

MvRefinedDisp[ xPb ][ yPb ] ) + ( nPbW *2 + 4, nPbH *2 + 4 ) as inputs, and the outputs are the flag availableFlagLXIvMCShift, the motion vector mvLXIvMCShift and the reference index refldxLXIvMCShift.

2. The availability flag availableFlaglvMCShift, and the prediction utilization flags predFlagLOIvMCShift and predFlagLUvMCShift are derived by

availableFlaglvMCShift = availableFlagLOIvMCShift 1 1 availableFlagLUvM

CShift (1-137) predFlagLOIvMCShift = availableFlagLOIvMCShift (1-138) predFlagLUvMCShift = availableFlagLUvMCShift (1-139)

When DepthFlag is equal to 0, the disparity inter-view motion vector merging candidate is derived by the following ordered steps.

1. For the prediction list indication X being 0 and 1 the following applies:

- The derivation process for a disparity inter-view motion vector candidate as specified in subclause 1.8.5.3.2.12 is invoked with the luma location ( xPb, yPb ), the variables nPbW and nPbH, the view order index RefYiewIdx[ xPb ][ yPb ], the disparity vector MvRefinedDisp[ xPb ][ yPb ], and the prediction list indication X, as inputs, and the outputs are the flag availableFlagLXIvDC, the motion vector mvLXIvDC, and the reference index refldxLXIvDC. 2. The availability flag availableFlaglvDC, and the prediction utilization flags predFlagLOIvDC and predFlagLUvDC are derived by

availableFlaglvDC = availableFlagLOIvDC 1 1 availableFlagLUvDC (1-140) predFlagLOIvDC = availableFlagLOIvDC (1-141) predFlagLUvDC = availableFlagLUvDC (1-142)

[00153] Alternatively, ARP is considered to be used for current block when ARP weighting factor of current block is not equal to zero and following conditions are true in any prediction direction X, X = 0 or 1 :

1. There is at least one temporal reference picture in reference picture list X.

Denote the temporal reference picture (in reference picture list X) with smallest POC difference from current slice as RpRefPicLX.

2. Denote targetRefViewIdx as the view order index derived in NBDV process, and denote RefPicInRefViewLX as the texture picture with view order index equal to targetRefViewIdx and POC value equal to POC of RpRefPicLX. RefPicInRefViewLX shall be stored in the decoded picture buffer and marked as "used for reference".

H.8.5.3.2.10 Derivation process for inter-view merge candidates

This process is not invoked when iv_mv_pred_flag[ nuh_layer_id ] is equal to 0 and mpi_flag[ nuh_layer_id ] is equal to 0.

Inputs to this process are:

Outputs of this process are (with X being 0 or 1, respectively)

- the availability flags availableFlaglvMC, availableFlaglvMCShift and

- the reference indices refldxLXIvMC, refldxLXIvMCShift and refldxLXIvDC,

- the motion vectors mvLXIvMC, mvLXIvMCShift and mvLXIvDC.

The availability flags availableFlaglvMC, availableFlaglvMCShift and

For X in the range of 0 to 1, the variable resPredFlagX is derived as specified in the following:

resPredFlagX = ( iv res pred weight idx != 0 ) &&

RpRefPicAvailFlagLX &&

RefRpRefAvailFlagLXr RefViewIdxr xP 1Γ vP 1 1 (I-xxx) The variable resPredFlagX is derived as ( resPredFlagO 1 1 resPredFlagl ).

The temporal inter- view motion vector merging candidate is derived by the following ordered steps.

3. Depending on PartMode, the following applies:

- If PartMode is equal to PART_2Nx2N, the derivation process for inter layer predicted sub prediction block motion vector candidates as specified in subclause 1.8.5.3.2.16 is invoked with the luma location ( xPb, yPb ), the variables nPbW and nPbH, the view order index RefViewIdx[ xPb ][ yPb ] and the disparity vector ( resPredFlag != 0 ) ? MvDispT xPb 1Γ yPb 1 :

MvRefinedDisp[ xPb ][ yPb ] as inputs, and the outputs are, with X being in the range of 0 to 1, inclusive, the flag availableFlagLXIvMC, the motion vector mvLXIvMC and the reference index refldxLXIvMC.

- Otherwise (PartMode is not equal to PART_2Nx2N), the derivation process for a temporal inter-view motion vector candidate as specified in subclause 1.8.5.3.2.11 is invoked with the luma location ( xPb, yPb ), the variables nPbW and nPbH, the prediction list indication X, the view order index RefViewIdx[ xPb ][ yPb ], and the disparity vector ( resPredFlag != 0 ) ? MvDispr xPb 1Γ yPb 1 : MvRefinedDisp[ xPb ][ yPb ] as inputs, and the outputs are the flag availableFlagLXIvMC, the motion vector mvLXIvMC and the reference index refldxLXIvMC.

4. The availability flag availableFlaglvMC, and the prediction utilization flags predFlagLOIvMC and predFlagLUvMC are derived by

availableFlaglvMC = availableFlagLOIvMC I I availableFlagLUvMC (1-134) predFlagLOIvMC = availableFlagLOIvMC (1-135) predFlagLUvMC = availableFlagLUvMC (1-136) When DepthFlag is equal to 0, the shifted temporal inter-view motion vector merging candidate is derived by the following ordered steps.

5. For the prediction list indication X being 0 and 1 the following applies:

- The derivation process for a temporal inter-view motion vector candidate as specified in subclause 1.8.5.3.2.11 is invoked with the luma location

( xPb, yPb ), the variables nPbW and nPbH, the prediction list indication X, the view order index RefViewIdx[ xPb ][ yPb ], and the disparity vector ( ( resPredFlag != 0 ) ? MvDisp[ xPb 1Γ vPb 1 :

6. The availability flag availableFlaglvMCShift, and the prediction utilization flags predFlagLOIvMCShift and predFlagLUvMCShift are derived by

availableFlaglvMCShift = availableFlagLOIvMCShift 1 1 availableFlagLUvM CShift (1-137) predFlagLOIvMCShift = availableFlagLOIvMCShift (1-138) predFlagLUvMCShift = availableFlagLUvMCShift (1-139)

7. For the prediction list indication X being 0 and 1 the following applies:

- The derivation process for a disparity inter-view motion vector candidate as specified in subclause 1.8.5.3.2.12 is invoked with the luma location

( xPb, yPb ), the variables nPbW and nPbH, the view order index RefViewIdx[ xPb ][ yPb ], the disparity vector MvRefinedDisp[ xPb ][ yPb ], and the prediction list indication X, as inputs, and the outputs are the flag availableFlagLXIvDC, the motion vector mvLXIvDC, and the reference index refldxLXIvDC.

8. The availability flag availableFlaglvDC, and the prediction utilization flags

predFlagLOIvDC and predFlagLUvDC are derived by

[00154] FIG. 11 is a block diagram illustrating an example of a video encoder that may implement the ARP and inter-view prediction techniques described in this disclosure. For example, FIG. 11 illustrates video encoder 20 which may represent either a 3D- AVC compliant or a 3D-HEVC compliant video encoder. Video encoder 20 will be described using certain HEVC terminology such as PUs, TUs, and CUs, but it should be understood that the techniques described with reference to video encoder 20 may also be performed with video coded according to the H.264 standard.

[00155] Video encoder 20 may perform intra- and inter-coding of video blocks within video slices. For example, video encoder 20 may perform inter-prediction encoding or intra-prediction encoding. Intra-coding relies on spatial prediction to reduce or remove spatial redundancy in video within a given video frame or picture. Inter-coding relies on temporal prediction or inter- view prediction to reduce or remove temporal redundancy within adjacent frames or pictures of a video sequence or redundancy between pictures in different views. Intra-mode (I mode) may refer to any of several spatial based compression modes. Inter- modes, such as uni-directional prediction (P mode) or bi-prediction (B mode), may refer to any of several temporal-based compression modes.

[00156] In the example of FIG. 11, video encoder 20 includes video data memory 40, prediction processing unit 42, reference picture memory 64, summer 50, transform processing unit 52, quantization processing unit 54, and entropy encoding unit 56. Prediction processing unit 42 includes motion and disparity estimation unit 44, motion and disparity compensation unit 46, and intra-prediction unit 48. For video block reconstruction, video encoder 20 also includes inverse quantization processing unit 58, inverse transform processing unit 60, and summer 62. A deblocking filter (not shown in FIG. 11) may also be included to filter block boundaries to remove blockiness artifacts from reconstructed video. If desired, the deblocking filter would typically filter the output of summer 62. Additional loop filters (in loop or post loop) may also be used in addition to the deblocking filter.

[00157] Video data memory 40 may store video data to be encoded by the components of video encoder 20. The video data stored in video data memory 40 may be obtained, for example, from video source 18. Reference picture memory 64 is one example of a decoding picture buffer (DPB that stores reference video data for use in encoding video data by video encoder 20 (e.g., in intra- or inter-coding modes, also referred to as intra- or inter-prediction coding modes). Video data memory 40 and reference picture memory 64 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory 40 and reference picture memory 64 may be provided by the same memory device or separate memory devices. In various examples, video data memory 40 may be on-chip with other components of video encoder 20, or off-chip relative to those components.

[00158] Video encoder 20 receives video data, and a partitioning unit (not shown) partitions the data into video blocks. This partitioning may also include partitioning into slices, tiles, or other larger units, as wells as video block partitioning (e.g., macroblock partitions and sub-blocks of partitions). Video encoder 20 generally illustrates the components that encode video blocks within a video slice to be encoded. The slice may be divided into multiple video blocks (and possibly into sets of video blocks referred to as tiles). Prediction processing unit 42 may select one of a plurality of possible coding modes, such as one of a plurality of intra coding modes (intra- prediction coding modes) or one of a plurality of inter coding modes (inter-prediction coding modes), for the current video block based on error results (e.g., coding rate and the level of distortion). Prediction processing unit 42 may provide the resulting intra- or inter-coded block to summer 50 to generate residual block data and to summer 62 to reconstruct the encoded block for use as a reference picture.

[00159] Intra prediction unit 48 within prediction processing unit 42 may perform intra- predictive coding of the current video block relative to one or more neighboring blocks in the same frame or slice as the current block to be coded to provide spatial

compression. Motion and disparity estimation unit 44 and motion and disparity compensation unit 46 within prediction processing unit 42 perform inter-predictive coding of the current video block relative to one or more predictive blocks in one or more reference pictures to provide temporal compression.

[00160] Motion and disparity estimation unit 44 may be configured to determine the inter-prediction mode for a video slice according to a predetermined pattern for a video sequence. The predetermined pattern may designate video slices in the sequence as P slices or B slices. Motion and disparity estimation unit 44 and motion and disparity compensation unit 46 may be highly integrated, but are illustrated separately for conceptual purposes. Motion estimation, performed by motion and disparity estimation unit 44, is the process of generating motion vectors, which estimate motion for video blocks. A motion vector, for example, may indicate the displacement of a video block within a current video frame or picture relative to a predictive block within a reference picture.

[00161] A predictive block is a block that is found to closely match the video block to be coded in terms of pixel difference, which may be determined by sum of absolute difference (SAD), sum of square difference (SSD), or other difference metrics. In some examples, video encoder 20 may calculate values for sub-integer pixel positions of reference pictures stored in reference picture memory 64. For example, video encoder 20 may interpolate values of one-quarter pixel positions, one-eighth pixel positions, or other fractional pixel positions of the reference picture. Therefore, motion and disparity estimation unit 44 may perform a motion search relative to the full pixel positions and fractional pixel positions and output a motion vector with fractional pixel precision.

[00162] Motion and disparity estimation unit 44 calculates a motion vector for a video block in an inter-coded (inter-prediction coded) slice by comparing the position of the video block to the position of a predictive block of a reference picture. The reference picture may be selected from a first reference picture list (RefPicListO) or a second reference picture list (RefPicListl), each of which identify one or more reference pictures stored in reference picture memory 64. Motion and disparity estimation unit 44 sends the calculated motion vector to entropy encoding unit 56 and motion and disparity compensation unit 46.

[00163] Motion compensation, performed by motion and disparity compensation unit 46, may involve fetching or generating the predictive block based on the motion vector determined by motion estimation, possibly performing interpolations to sub-pixel precision. Upon receiving the motion vector for the current video block, motion and disparity compensation unit 46 may locate the predictive block to which the motion vector points in one of the reference picture lists. Video encoder 20 forms a residual video block by subtracting pixel values of the predictive block from the pixel values of the current video block being coded, forming pixel difference values. The pixel difference values form residual data for the block, and may include both luma and chroma difference components. Summer 50 represents the component or components that perform this subtraction operation. Motion and disparity compensation unit 46 may also generate syntax elements associated with the video blocks and the video slice for use by video decoder 30 in decoding the video blocks of the video slice.

[00164] Intra-prediction unit 48 may intra-predict a current block, as an alternative to the inter-prediction performed by motion and disparity estimation unit 44 and motion and disparity compensation unit 46, as described above. In particular, intra-prediction unit 48 may determine an intra-prediction mode to use to encode a current block. In some examples, intra-prediction unit 48 may encode a current block using various intra- prediction modes, e.g., during separate encoding passes, and intra-prediction unit 48 (or a mode select unit, in some examples) may select an appropriate intra-prediction mode to use from the tested modes. For example, intra-prediction unit 48 may calculate rate- distortion values using a rate-distortion analysis for the various tested intra-prediction modes, and select the intra-prediction mode having the best rate-distortion

characteristics among the tested modes. Rate-distortion analysis generally determines an amount of distortion (or error) between an encoded block and an original, unencoded block that was encoded to produce the encoded block, as well as a bit rate (that is, a number of bits) used to produce the encoded block. Intra-prediction unit 48 may calculate ratios from the distortions and rates for the various encoded blocks to determine which intra-prediction mode exhibits the best rate-distortion value for the block.

[00165] In any case, after selecting an intra-prediction mode for a block, intra-prediction unit 48 may provide information indicative of the selected intra-prediction mode for the block to entropy encoding unit 56. Entropy encoding unit 56 may encode the information indicating the selected intra-prediction mode in accordance with the techniques of this disclosure. Video encoder 20 may include in the transmitted bitstream configuration data, which may include a plurality of intra-prediction mode index tables and a plurality of modified intra-prediction mode index tables (also referred to as codeword mapping tables), definitions of encoding contexts for various blocks, and indications of a most probable intra-prediction mode, an intra-prediction mode index table, and a modified intra-prediction mode index table to use for each of the contexts.

[00166] After prediction processing unit 42 generates the predictive block for the current video block via either inter-prediction or intra-prediction, video encoder 20 forms a residual video block by subtracting the predictive block from the current video block. The residual video data in the residual block may be applied to transform processing unit 52. Transform processing unit 52 transforms the residual video data into residual transform coefficients using a transform, such as a discrete cosine transform (DCT) or a conceptually similar transform. Transform processing unit 52 may convert the residual video data from a pixel domain to a transform domain, such as a frequency domain.

[00167] Transform processing unit 52 may send the resulting transform coefficients to quantization processing unit 54. Quantization processing unit 54 quantizes the transform coefficients to further reduce bit rate. The quantization process may reduce the bit depth associated with some or all of the coefficients. The degree of quantization may be modified by adjusting a quantization parameter. In some examples, quantization processing unit 54 may then perform a scan of the matrix including the quantized transform coefficients. Alternatively, entropy encoding unit 56 may perform the scan.

[00168] Following quantization, entropy encoding unit 56 entropy encodes the quantized transform coefficients. For example, entropy encoding unit 56 may perform context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding or another entropy encoding methodology or technique. Following the entropy encoding by entropy encoding unit 56, the encoded bitstream may be transmitted to video decoder 30, or archived for later transmission or retrieval by video decoder 30. Entropy encoding unit 56 may also entropy encode the motion vectors and the other syntax elements for the current video slice being coded.

[00169] Inverse quantization processing unit 58 and inverse transform processing unit 60 apply inverse quantization and inverse transformation, respectively, to reconstruct the residual block in the pixel domain for later use as a reference block of a reference picture. Motion and disparity compensation unit 46 may calculate a reference block by adding the residual block to a predictive block of one of the reference pictures within one of the reference picture lists. Motion and disparity compensation unit 46 may also apply one or more interpolation filters to the reconstructed residual block to calculate sub-integer pixel values for use in motion estimation. Summer 62 adds the

reconstructed residual block to the motion compensated prediction block produced by motion and disparity compensation unit 46 to produce a reference block for storage in reference picture memory 64. The reference block may be used by motion and disparity estimation unit 44 and motion and disparity compensation unit 46 as a reference block to inter-predict a block in a subsequent video frame or picture. [00170] In this manner, video encoder 20 is an example of a video encoder that may be configured to implement one or more example techniques described in this disclosure. For example, video data memory 40 stores video data. The video data may include a texture video component of a dependent view and a depth view component that corresponds to the texture view component, each of which video encoder 20 is to encode in a 3D-AVC compliant or 3D-HEVC compliant video coding process.

[00171] In the techniques described in this disclosure, video encoder 20 may include one or more processors that are configured to encode, in a 3D-AVC compliant or 3D- HEVC compliant video coding process, a texture view component of a dependent view of the video data. As described above, each view in a 3D-AVC includes a texture view component and depth view component. There is one base view and one or more enhancement or dependent views in 3D-AVC, where texture view components of the one or more enhancement or dependent views may be inter-view predicted.

[00172] To encode the texture view component, video encoder 20 may be configured to evaluate motion information of one or more neighboring blocks of a current block in the texture view component to determine whether at least one neighboring block is interview predicted with a disparity motion vector that refers to an inter-view reference picture in a view other than the dependent view. Video encoder 20 may derive a disparity vector for the current block based on the disparity motion vector for one of the neighboring blocks. For texture-first coding, video encoder 20 may encode a depth view component, of the video data, that corresponds to the texture view component subsequent to encoding the texture view component.

[00173] In some examples, prediction processing unit 42 of video encoder 20 may be one example of a processor configured to implement the examples described in this disclosure. In some examples, a unit (e.g., one or more processors) other than prediction processing unit 42 may implement the examples described above. In some examples, prediction processing unit 42 in conjunction with one or more other units of video encoder 20 may implement the examples described above. In some examples, a processor of video encoder 20 (not shown in FIG. 11) may, alone or in conjunction with other processors of video encoder 20, implement the examples described above.

[00174] FIG. 12 is a block diagram illustrating an example of a video decoder that may implement the ARP and inter-view prediction techniques described in this disclosure. FIG. 12 is a block diagram illustrating an example of a video decoder that may implement the techniques described in this disclosure. For example, FIG. 12 illustrates video decoder 30 which may represent either a 3D-AVC compliant or a 3D-HEVC compliant video decoder. Video decoder 30 will be described using certain HEVC terminology such as PUs, TUs, and CUs, but it should be understood that the techniques described with reference to video decoder 30 may also be performed with video coded according to the H.264 standard.

[00175] Video decoder 30 may perform inter-prediction decoding or intra-prediction decoding. FIG. 12 illustrates video decoder 30. In the example of FIG. 12, video decoder 30 includes video data memory 69, entropy decoding unit 70, prediction processing unit 71, inverse quantization processing unit 76, inverse transform

processing unit 78, summer 80, and reference picture memory 82. Prediction processing unit 71 includes motion and disparity compensation unit 72 and intra-prediction unit 74. Video decoder 30 may, in some examples, perform a decoding pass generally reciprocal to the encoding pass described with respect to video encoder 20 from FIG. 11.

[00176] Video data memory 69 may store video data, such as an encoded video bitstream, to be decoded by the components of video decoder 30. The video data stored in video data memory 69 may be obtained, for example, from storage device 34, from a local video source, such as a camera, via wired or wireless network communication of video data, or by accessing physical data storage media. Video data memory 69 may form a coded picture buffer (CPB) that stores encoded video data from an encoded video bitstream.

[00177] Reference picture memory 82 is one example of a decoded picture buffer (DPB) that stores reference video data for use in decoding video data by video decoder 30 (e.g., in intra- or inter-coding modes). Video data memory 69 and reference picture memory 82 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory 69 and reference picture memory 82 may be provided by the same memory device or separate memory devices. In various examples, video data memory 69 may be on-chip with other components of video decoder 30, or off-chip relative to those components.

[00178] During the decoding process, video decoder 30 receives an encoded video bitstream that represents video blocks of an encoded video slice and associated syntax elements from video encoder 20. Entropy decoding unit 70 of video decoder 30 entropy decodes the bitstream to generate quantized coefficients, motion vectors, and other syntax elements. Entropy decoding unit 70 forwards the motion vectors and other syntax elements to prediction processing unit 71. Video decoder 30 may receive the syntax elements at the video slice level and/or the video block level.

[00179] When the video slice is coded as an intra-coded (I) slice, intra-prediction unit 74 of prediction processing unit 71 may generate prediction data for a video block of the current video slice based on a signaled intra-prediction mode and data from previously decoded blocks of the current frame or picture. When the video frame is coded as an inter-coded (i.e., B or P) slice, motion and disparity compensation unit 72 of prediction processing unit 71 produces predictive blocks for a video block of the current video slice based on the motion vectors and other syntax elements received from entropy decoding unit 70. The predictive blocks may be produced from one of the reference pictures within one of the reference picture lists. Video decoder 30 may construct the reference picture lists (RefPicListO and RefPicListl) using default construction techniques based on reference pictures stored in reference picture memory 82.

[00180] Motion and disparity compensation unit 72 determines prediction information for a video block of the current video slice by parsing the motion vectors and other syntax elements, and uses the prediction information to produce the predictive blocks for the current video block being decoded. For example, motion and disparity compensation unit 72 uses some of the received syntax elements to determine a prediction mode (e.g., intra- or inter-prediction) used to code the video blocks of the video slice, an inter-prediction slice type (e.g., B slice or P slice), construction information for one or more of the reference picture lists for the slice, motion vectors for each inter-encoded video block of the slice, inter-prediction status for each inter- coded video block of the slice, and other information to decode the video blocks in the current video slice.

[00181] Motion and disparity compensation unit 72 may be configured to perform the ARP techniques described in this disclosure. As one example, for a bi-directionally predicted current block coded using ARP, motion and disparity compensation unit 72 may determine a first disparity motion vector for the current block and, using the first disparity motion vector, locate a first corresponding block of the current block in a second view. Motion and disparity compensation unit 72 may also determine a second disparity motion vector for the current block and, using the second disparity motion vector, locate a second corresponding block of the current block in a third view. From motion information of the first corresponding block and the second corresponding block, motion and disparity compensation unit 72 may determine a single motion vector. Motion and disparity compensation unit 72 may use this single motion vector to determine a reference block of the current block, a reference block of the first corresponding block, and a reference block of the second corresponding block. Motion and disparity compensation unit 72 may generate a first predictive block based on the first corresponding block, the reference block of the current block, and the reference block of the first corresponding block and generate a second predictive block based on the second corresponding block, the reference block of the current block, and the reference block of the second corresponding block.

[00182] Motion and disparity compensation unit 72 may further be configured to For example, motion and disparity compensation unit 72 may determine a current block of a first view is coded using an advanced residual prediction (ARP) mode and that the current block is bi-directionally predicted. For a luma block of the current block, motion and disparity compensation unit 72 may perform ARP for a first prediction direction to determine a first predictive block of the luma block and perform ARP for a second prediction direction to determine a second predictive block of the luma block. For a chroma block of the current block, motion and disparity compensation unit 72 may perform ARP for only one of the first prediction direction or the second prediction direction to determine a first predictive block of the chroma block.

[00183] Motion and disparity compensation unit 72 may further be configured to perform the ARP and inter-view motion prediction techniques of this disclosure. For example, in some coding scenarios, for a first block, motion and disparity compensation unit 72 may determine a disparity vector based on neighboring blocks and perform both inter-view motion prediction and ARP using that determined disparity vector as part of decoding the first block. In other coding scenarios, motion and disparity compensation unit 72 may use different disparity vectors for inter- view motion prediction and ARP.

[00184] Motion and disparity compensation unit 72 may also perform interpolation based on interpolation filters. Motion and disparity compensation unit 72 may use interpolation filters as used by video encoder 20 during encoding of the video blocks to calculate interpolated values for sub-integer pixels of reference blocks. In this case, motion and disparity compensation unit 72 may determine the interpolation filters used by video encoder 20 from the received syntax elements and use the interpolation filters to produce predictive blocks. [00185] Inverse quantization processing unit 76 inverse quantizes (i.e., de-quantizes), the quantized transform coefficients provided in the bitstream and decoded by entropy decoding unit 70. The inverse quantization process may include use of a quantization parameter calculated by video encoder 20 for each video block in the video slice to determine a degree of quantization and, likewise, a degree of inverse quantization that should be applied. Inverse transform processing unit 78 applies an inverse transform (e.g., an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process), to the transform coefficients in order to produce residual blocks in the pixel domain.

[00186] After motion and disparity compensation unit 72 generates the predictive block for the current video block based on the motion vectors and other syntax elements, video decoder 30 forms a decoded video block by summing the residual blocks from inverse transform processing unit 78 with the corresponding predictive blocks generated by motion and disparity compensation unit 72. Summer 80 represents the component or components that perform this summation operation. If desired, a deblocking filter may also be applied to filter the decoded blocks in order to remove blocking artifacts. Other loop filters (either in the coding loop or after the coding loop) may also be used to smooth pixel transitions, or otherwise improve the video quality. The decoded video blocks in a given picture are then stored in reference picture memory 82, which stores reference pictures used for subsequent motion compensation. Reference picture memory 82 also stores decoded video for later presentation on a display device, such as display device 32 of FIG. 1.

[00187] In this manner, video decoder 30 is an example of a video decoder that may be configured to implement one or more example techniques described in this disclosure. For example, video data memory 69 stores video data. The video data may include information from which video decoder 30 can decode a texture video component of a dependent view and a depth view component that corresponds to the texture view component, each of which video encoder 20 is encoded in a 3D-AVC compliant or 3D- HEVC compliant video coding process.

[00188] In the techniques described in this disclosure, video decoder 30 may include one or more processors that are configured to decode, in a 3D-AVC compliant or 3D- HEVC compliant video coding process, a texture view component of a dependent view of the video data. To decode the texture view component, video decoder 30 may be configured to evaluate motion information of one or more neighboring blocks of a current block in the texture view component to determine whether at least one neighboring block is inter- view predicted with a disparity motion vector that refers to an inter-view reference picture in a view other than the dependent view. Video decoder 30 may derive a disparity vector for the current block based on the disparity motion vector for one of the neighboring blocks. For texture-first coding, video decoder 30 may decode a depth view component, of the video data, that corresponds to the texture view component subsequent to decoding the texture view component.

[00189] In some examples, prediction processing unit 71 of video decoder 30 may be one example of a processor configured to implement the examples described in this disclosure. In some examples, a unit (e.g., one or more processors) other than prediction processing unit 71 may implement the examples described above. In some examples, prediction processing unit 71 in conjunction with one or more other units of video decoder 30 may implement the examples described above. In yet some other examples, a processor of video decoder 30 (not shown in FIG. 12) may, alone or in conjunction with other processors of video decoder 30, implement the examples described above.

[00190] FIG. 13 is a flow chart showing an example process in accordance with the techniques of this disclosure. The techniques of FIG. 13 will be described with respect to a generic video coder, which may, for example, correspond to either video encoder 20 or video decoder 30. The techniques of FIG. 13, however, are not limited to any one particular type of video encoder or decoder.

[00191] The video coder may, for a first block, determine a disparity vector based on neighboring blocks (202). The video coder may perform inter-view motion prediction using the disparity vector (204). The video coder may perform ARP using the disparity vector. Thus, the video coder may, for some coding scenarios reduce coding complexity by using the same disparity vector for both inter- view motion prediction and ARP. In other video coding scenarios, the video coder may not use the same disparity vector for both inter-view motion prediction and ARP. Examples of the types of ARP the video coder may perform include both temporal ARP and inter- view ARP.

Examples of the types of inter-view motion prediction the video coder may perform include, but are not limited to, NDBDV, DoNBDV, using the disparity vector to determine a sub-PU level inter-view predicted motion vector candidate, using the disparity vector to determine a shifted inter- view predicted motion vector candidate, and/or using the disparity vector to determine an inter-view predicted motion vector candidate.

[00192] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over, as one or more instructions or code, a computer-readable medium and executed by a hardware-based processing unit.

Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer- readable media generally may correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[00193] By way of example, and not limitation, such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but are instead directed to non-transient, tangible storage media. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. [00194] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor," as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and/or software modules configured for encoding and decoding, or incorporated in a combined codec. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[00195] The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC) or a set of ICs (e.g., a chip set). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, various units may be combined in a codec hardware unit or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware.

[00196] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method of decoding video data, the method comprising:

for a first block of the video data, determining a disparity vector based on

neighboring blocks;

performing inter-view motion prediction using the disparity vector;

performing advanced residual prediction (ARP) using the disparity vector; based on the inter- view motion prediction and the ARP, generating a predictive block.

2. A method of encoding video data, the method comprising:

for a first block of the video data, determining a disparity vector based on

neighboring blocks;

performing inter-view motion prediction using the disparity vector;

performing advanced residual prediction (ARP) using the disparity vector; and, generating for inclusion in an encoded bitstream, syntax information for

decoding the first block.

3. The method of claim 1 or 2 , wherein determining the disparity vector comprises performing a neighboring block based disparity vector (NDBDV) process.

4. The method of claim 1 or 2, wherein determining the disparity vector comprises performing a depth oriented neighboring block based disparity vector (DoNBDV) process.

5. The method of any of claims 1-4, wherein performing inter- view motion vector prediction comprises using the disparity vector to determine an inter-view predicted motion vector candidate.

6. The method of any of claims 1-4, wherein performing inter-view motion vector prediction comprises using the disparity vector to determine a shifted inter-view predicted motion vector candidate.

7. The method of any of claims 1-4, wherein performing inter-view motion vector prediction comprises using the disparity vector to determine a sub-PU level inter- view predicted motion vector candidate.

8. The method of any of claims 1-7, wherein performing ARP using the disparity vector comprises performing temporal ARP.

9. The method of any of claims 1-7, wherein performing ARP using the disparity vector comprises performing inter- view ARP.

10. The method of any of claims 1-9, further comprising:

performing the ARP using the disparity vector in response to an ARP weighting factor for the block being not equal to 0.

11. The method of claim 10, wherein the first block is predicted using a reference picture from a reference picture list, and the method further comprises:

performing the ARP in response to there being at least one temporal reference picture in the reference picture list and a reference picture being stored in a decoded picture buffer and being marked as used for reference, wherein the reference picture corresponds to a texture picture with a view order index equal to a view order for a target reference view derived using NBDV and a POC value equal to a temporal reference picture in the reference picture list with a smallest POC difference from a current slice.

12. The method of any of claims 1-11, further comprising:

for a second block coded with ARP, wherein each prediction direction for the second block utilizes inter- view ARP, determining a first disparity vector for inter- view motion prediction and determining a second disparity vector for ARP, wherein the first disparity vector for inter- view motion prediction is different than the second disparity vector for ARP.

13. The method of any of claims 1-11, further comprising:

for a third block coded with ARP, wherein the third block is bi-directionally predicted using temporal reference pictures and inter-view reference pictures with a signalled temporal motion vector and a disparity motion vector, identifying a reference block of the third block using the signaled disparity motion vector of the currernt block for temporal ARP.

14. The method of claim 13, further comprising:

using the disparity vector to identify a reference block of the third block in an inter- view motion prediction process.

15. The method of claim 1, wherein the method of decoding the video data is performed as part of a video encoding process.

16. A computer-readable medium storing instructions that when executed by one or more processors cause the one or more processors to perform the method of any combination of claims 1-15.

17. A video coding device comprising:

a video coder configured to, for a first block of video data, determine a disparity vector based on neighboring blocks; perform inter-view motion prediction using the disparity vector; and, perform advanced residual prediction (ARP) using the disparity vector.

18. The video coding device of claim 17, wherein the video coder is further configured to determine the disparity vector comprises performing a neighboring block based disparity vector (NDBDV) process.

19. The video coding device of claim 17, wherein the video coder is further configured to determine the disparity vector comprises performing a depth oriented neighboring block based disparity vector (DoNBDV) process.

20. The video coding device of any of claims 17-19, wherein the video coder performs inter- view motion vector prediction comprises using the disparity vector to determine an inter-view predicted motion vector candidate.

21. The video coding device of any of claims 17-19, wherein the video coder performs inter- view motion vector prediction comprises using the disparity vector to determine a shifted inter- view predicted motion vector candidate.

22. The video coding device of any of claims 17-19, wherein the video coder performs inter- view motion vector prediction comprises using the disparity vector to determine a sub-PU level inter-view predicted motion vector candidate.

23. The video coding device of any of claims 17-22, wherein the video coder performs ARP using the disparity vector comprises performing temporal ARP.

24. The video coding device of any of claims 17-22, wherein the video coder performs ARP using the disparity vector comprises performing inter- view ARP.

25. The video coding device of any of claims 17-24, wherein the video coder is further configured to:

perform the ARP using the disparity vector in response to an ARP weighting factor for the block being not equal to 0.

26. The video coding device of any of claims 25, wherein the first block is predicted using a reference picture from a reference picture list, and wherein the video coder is further configured to perform the ARP in response to there being at least one temporal reference picture in the reference picture list and a reference picture being stored in a decoded picture buffer and being marked as used for reference, wherein the reference picture corresponds to a texture picture with a view order index equal to a view order for a target reference view derived using NBDV and a POC value equal to a temporal reference picture in the reference picture list with a smallest POC difference from a current slice.

27. The video coding device of any of claims 17-26, wherein the video coder is further configured to, for a second block coded with ARP, wherein each prediction direction for the second block utilizes inter- view ARP, determining a first disparity vector for inter- view motion prediction and determining a second disparity vector for ARP, wherein the first disparity vector for inter- view motion prediction is different than the second disparity vector for ARP.

28. The video coding device of any of claims 17-26, wherein the video coder is configured to, for a third block coded with ARP, wherein the third block is bi- directionally predicted using temporal reference pictures and inter-view reference pictures with a signalled temporal motion vector and a disparity motion vector, identifying a reference block of the third block using the signaled disparity motion vector of the currernt block for temporal ARP.

29. The video coding device of any of claims 28, wherein the video coder is further configured to use the disparity vector to identify a reference block of the third block in an inter-view motion prediction process.

30. The video coding device of any of claims 17-29, wherein the video coder comprises a video encoder, and wherein the video encoder is configured to:

generate for inclusion in an encoded bitstream, syntax information for decoding the block.

31. The video coding device of any of claims 17-29, wherein the video coder comprises a video decoder, and wherein the video decoder is further configured:

decode the first block.

32. The device of any of claims 17-31, wherein the device comprises at least one of:

an integrated circuit;

a microprocessor; and,

a wireless communication device that includes the video coder. A device for coding video data, the device comprising:

means for determining a disparity vector based on neighboring blocks for a first block of video data;

means for performing inter-view motion prediction using the disparity vector; means for performing advanced residual prediction (ARP) using the disparity vector.