JP2018056957A - Encoding device, decoding device, encoding method, and decoding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a time required for encoding a frame.SOLUTION: An encoding device 10 comprises: an acquisition part 101 for acquiring an encoding object frame from a memory; a blocking filter 102 for applying filter-processing to a boundary of a block that is a processing unit included in the encoding object frame acquired by the acquisition part 101; a conversion part 103 for applying conversion-processing including frequency conversion or order conversion to the filter-processed encoding object frame for each block; a difference part 104 for acquiring a reference frame from the memory, and calculating a difference between the acquired reference frame and the conversion-processed encoding object frame; a quantization part 105 for quantizing the difference frame calculated by the difference part 104; and an encoding part 106 for encoding the difference frame quantized by the quantization part 105 and generating encoding data.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an encoding device, a decoding device, an encoding method, and a decoding method.

  When moving image content is transferred through a network, a compression technique that reduces the amount of communication in the network is used. In the compression technique, a transmission device compresses and encodes a frame constituting the content, transmits the frame to a network, and the reception device receives and decodes the compressed and encoded data to restore the content.

  There are differential encoding schemes that improve the compression rate in compression techniques. In the differential encoding method, intra-frame encoding is performed using a part of the frame included in the content as a key frame. Further, the remaining part excluding the part of the frame included in the content is set as a difference frame, and the difference from the key frame is encoded, that is, inter-frame encoded.

  Japanese Patent Laid-Open No. 2004-228688 suppresses a rapid increase in the coding processing amount of a key frame in a compression coding technique, and also shows a difference that appears during reproduction between an intra-frame coded frame and an inter-frame coded frame. Disclosed is a technique for making the size smaller.

JP 2002-171527 A

  Although the technique disclosed in Patent Document 1 is expected to have an effect of suppressing a rapid increase in the amount of encoding processing of key frames, there is a problem that the time required for encoding can be increased. Specifically, in the above technique, a process of re-encoding a once-encoded frame in order to reduce a difference that appears during reproduction between an intra-frame encoded frame and an inter-frame encoded frame. By performing (in other words, re-encoding process), a predetermined time is required for the frame encoding process.

  The present invention has been made to solve the above problem, and an object thereof is to provide an encoding device or the like that reduces the time required for encoding a frame.

  In order to solve the above problems, an encoding apparatus according to an aspect of the present invention includes an acquisition unit that acquires an encoding target frame from a memory, and a processing unit included in the encoding target frame acquired by the acquisition unit. A filter unit that performs a filtering process on a boundary of a block, a conversion unit that performs a conversion process including a frequency conversion or an order conversion for each block on the encoding target frame after the filter process, and for reference A frame is acquired from the memory, a difference unit that calculates a difference between the acquired reference frame and the encoding target frame after the conversion process as a difference frame, and the difference frame calculated by the difference unit A quantization unit that performs quantization; and an encoding unit that encodes the difference frame quantized by the quantization unit to generate encoded data.

  According to this, the encoding apparatus performs memory access at two points of time when the acquisition unit acquires the encoding target frame and when the difference unit acquires the reference frame. Considering the order of processing by the encoding device, after the memory access by the acquisition unit, the processing by the filter unit and the conversion unit is performed, and then the memory access by the difference unit is performed. Therefore, the timing at which the two memory accesses are performed is not simultaneous (or substantially simultaneous). For this reason, if two memory accesses are performed substantially simultaneously, a waiting time that may occur can be avoided. As described above, the encoding apparatus can reduce the time required for encoding a frame.

  Further, when the encoding target frame is a key frame, the quantization unit quantizes the encoding target frame after the conversion processing by the conversion unit, and the encoding device further includes the difference When the frame is a key frame, the frame includes a dequantization unit that dequantizes and stores the difference frame after quantization by the quantization unit in a memory, and the difference unit is configured to store the memory by the dequantization unit. The difference may be calculated using the key frame stored in the reference frame as the reference frame.

  According to this, the difference unit uses a frame (for example, a frequency coefficient) generated only by dequantizing a quantized frame (that is, a quantization coefficient) as a reference frame, and uses it for the process of calculating the difference. . Therefore, it is possible to generate the reference frame in a shorter time than when the reference frame is generated by performing a larger number of processes than the above. Therefore, the encoding device can reduce the time required for encoding the frame.

  Further, the encoding device further determines whether to encode a new encoding target frame within a frame or between frames based on a data size of encoded data generated by the encoding unit. You may provide the control part to control.

  According to this, the control unit controls whether the next frame is intra-frame encoded or inter-frame encoded based on the data size of the encoded data generated by the actual encoding. To do. Therefore, the encoding device can more appropriately control the encoding of the next frame based on the actual encoding result, and avoid an increase in processing time that occurs if the encoding is performed again. it can.

  Further, the control unit determines whether or not a data size of the encoded data generated by the encoding unit performing inter-frame encoding is equal to or larger than a threshold value, and (a) the data size is equal to or larger than the threshold value. If so, control is performed so that the new encoding target frame is intra-frame encoded, and (b) control is performed so that the new encoding target frame is inter-frame encoded when the data size is less than the threshold. May be.

  According to this, the control unit determines whether the effect of performing differential encoding (interframe encoding) according to the size of the data size is appropriately exhibited, and if it is not properly demonstrated, a new It is possible to perform control so as to exert the effect of differential encoding by performing intra-frame encoding on a specific encoding target frame.

  The control unit may perform control so that a new encoding target frame is inter-frame encoded when the encoding unit generates the encoded data by performing intra-frame encoding.

  According to this, the control unit can perform control so as to exhibit the effect of differential encoding by performing inter-frame encoding after intra-frame encoding.

  Further, the decoding device according to one aspect of the present invention includes: an adder that acquires a reference frame from a memory, adds the acquired reference frame and encoded data, and generates an added frame; and the adder An inverse quantization unit that performs inverse quantization on the addition frame generated by the inverse quantization unit, and an inverse frequency transform or an inverse order transform for each block that is a processing unit included in the addition frame inversely quantized by the inverse quantization unit. An inverse transform unit that performs an inverse transform process including: a filter unit that performs a filter process on a boundary of the block in the addition frame after the inverse transform process; and a frame based on the addition frame after the filter process. A generating unit for generating.

  According to this, the encoded data encoded by the encoding device can be appropriately decoded.

  The encoding method according to one aspect of the present invention includes an acquisition step of acquiring an encoding target frame from a memory, and a block boundary that is a processing unit included in the encoding target frame acquired in the acquisition step. A filtering step for performing filtering processing, a conversion step for performing conversion processing including frequency conversion or order conversion for each block on the encoding target frame after the filtering processing, and obtaining a reference frame from the memory A difference step of calculating a difference between the acquired reference frame and the encoding target frame after the conversion process as a difference frame, and a quantization step of quantizing the difference frame calculated in the difference step And encoding the difference frame quantized in the quantization step to generate encoded data And a Goka step.

  Thereby, there exists an effect similar to the said encoding apparatus.

  The decoding method according to one aspect of the present invention includes an addition step of acquiring a reference frame from a memory, adding the acquired reference frame and encoded data to generate an addition frame, and the addition step Inverse quantization step for inverse quantization with respect to the addition frame generated in step 1, and inverse frequency transformation or inverse order transformation for each block which is a processing unit included in the addition frame inversely quantized in the inverse quantization step. An inverse transform step for performing an inverse transform process, a filter step for performing a filter process on a boundary of the block in the added frame after the inverse transform process, and a frame based on the added frame after the filter process. Generating step.

  Thereby, there exists an effect similar to the said decoding apparatus.

  The encoding device according to the present invention can reduce the time required for encoding a frame.

FIG. 1 is a configuration diagram showing a configuration of a content reproduction system according to an embodiment. FIG. 2 is a block diagram illustrating a hardware configuration of the encoding apparatus according to the embodiment. FIG. 3 is a block diagram showing a configuration of the encoding apparatus according to the embodiment. FIG. 4 is a flowchart showing processing of the encoding apparatus according to the embodiment. FIG. 5 is a block diagram showing a configuration of the decoding apparatus according to the embodiment. FIG. 6 is a flowchart showing processing of the decoding apparatus according to the embodiment. FIG. 7 is a block diagram showing a configuration of an encoding apparatus according to related technology. FIG. 8 is a block diagram illustrating a configuration of a decoding device according to related technology. FIG. 9 is a block diagram showing a configuration of an encoding apparatus according to a modification of the embodiment. FIG. 10 is a flowchart showing processing of the encoding device according to the modification of the embodiment.

  Hereinafter, embodiments will be specifically described with reference to the drawings.

  Each of the embodiments described below shows a preferred specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connecting forms of the constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept of the present invention are described as optional constituent elements that constitute a more preferable embodiment. In addition, the same code | symbol is attached | subjected to the same component and description may be abbreviate | omitted.

(Embodiment)
In the present embodiment, an encoding device, a decoding device, and the like that reduce the time required for encoding a frame will be described.

  FIG. 1 is a configuration diagram showing a configuration of a content reproduction system S according to the present embodiment.

  As shown in FIG. 1, the content reproduction system S includes a transmission device 1 and a reproduction device 2. The transmission device 1 and the playback device 2 are connected by a network 3 so that they can communicate with each other.

  The content reproduction system S is a content reproduction system in which moving image content (hereinafter also simply referred to as content) held by the transmission device 1 is reproduced by one or more reproduction devices 2.

  The transmission device 1 is a transmission device that has content and transmits the content to the playback device 2 through the network 3. The transmission device 1 includes an encoding device 10 that compresses and encodes content (hereinafter also simply referred to as encoding). The encoding device 10 generates encoded data in which the amount of content data is reduced, and transmits the generated encoded data to the network 3.

  The playback device 2 is a playback device that receives content from the transmission device 1 via the network 3 and plays back the received content. The playback device 2 receives the encoded data generated by the encoding device 10 based on the moving image content held by the transmission device 1 through the network 3. The playback device 2 includes a decoding device 20 that decodes encoded data. The decoding device 20 restores the content by decoding the encoded data received from the network 3, and the playback device 2 plays back the restored content.

  The network 3 is a network that connects the transmission device 1 and the playback device 2 so that they can communicate with each other. Specifically, the network 3 is a wireless LAN (Local Area Network) conforming to the IEEE 802.11a, b, g, n standard or the like, or a wired LAN conforming to the IEEE 802.3 standard or the like.

  The content reproduction system S may include two or more reproduction devices 2. In that case, it is necessary that each of the two or more reproducing apparatuses 2 is connected to the network 3 and can receive the encoded data transmitted by the transmitting apparatus 1. When there are two or more playback devices 2, the transmission device 1 may perform unicast transmission to each of the two or more playback devices 2, or broadcast transmission so that the two or more playback devices 2 can receive. May be.

  FIG. 2 is a block diagram showing a hardware configuration of encoding apparatus 10 according to the present embodiment. Note that the decoding device 20 also has the same hardware configuration as the encoding device 10.

  As shown in FIG. 2, the encoding device 10 includes a CPU 11, a main memory 12, and a storage 13.

  The CPU 11 is a processor that executes a control program stored in the main memory 12 or the storage 13. The processing executed by the encoding device 10 can be realized by the CPU 11 executing a control program.

  The main memory 12 is a volatile storage area used as a work area used when the CPU 11 executes a control program.

  The storage 13 is a non-volatile storage device that stores data of frames constituting content. The storage 13 is, for example, an HDD (Hard Disk Drive), an SSD (Solid State Drive), or the like, and may be built in the encoding device 10 or a USB (Universal Serial Bus) standard. May be externally attached.

  Hereinafter, the encoding apparatus and decoding apparatus according to the present embodiment will be described in comparison with conventional encoding apparatuses and decoding apparatuses according to related art.

  FIG. 3 is a block diagram showing a configuration of encoding apparatus 10 according to the present embodiment.

  As illustrated in FIG. 3, the encoding device 10 includes a frame holding unit 100, an acquisition unit 101, a blocking filter 102, a conversion unit 103, a difference unit 104, a quantization unit 105, and an encoding unit 106. And an inverse quantization unit 107 and a reference holding unit 108.

  The frame holding unit 100 is a storage unit that holds data of frames constituting the content to be encoded. The frame holding unit 100 is realized by, for example, the main memory 12 or the like.

  The acquisition unit 101 is a processing unit that acquires an encoding target frame. The acquisition unit 101 acquires the frame to be encoded by reading out the encoding target frame from the frames included in the content stored in the frame holding unit 100. As the encoding target frame, for example, frames corresponding to current time information managed by the encoding device 10 among a plurality of frames constituting the content are sequentially assigned.

  The blocking filter 102 is a processing unit that performs a blocking filter process on a block boundary that is a processing unit included in the encoding target frame acquired by the acquisition unit 101. The blocking filter process is a process to be performed before the conversion process in order to suppress discontinuity that may occur at a block boundary that is a processing unit of the conversion process (described later). The blocking filter 102 corresponds to a filter unit included in the encoding device 10.

  The conversion unit 103 is a processing unit that performs conversion processing for each block on the frame after the blocking filter 102 performs blocking filter processing. An example of the conversion process is a frequency conversion process. In the frequency conversion, a frame to be encoded is converted into a coefficient (frequency coefficient) in a case where the frame to be encoded is expressed as an addition of a plurality of base trigonometric functions. As the conversion process, an order conversion (for example, Hadamard conversion) process or the like may be employed.

  The difference unit 104 calculates the difference between the frame to be encoded (frequency coefficient) after the conversion unit 103 performs the conversion process and the reference frame held by the reference holding unit 108, thereby calculating the difference frame. Is a processing unit for generating The difference unit 104 reads the reference frame from the reference holding unit 108 before calculating the difference. The difference unit 104 calculates the difference when the encoding target frame is not a key frame, and does not calculate the difference when it is a key frame. Whether the encoding target frame is a key frame or not a key frame may be determined by the time when the difference unit 104 acquires the encoding target frame from the conversion unit 103, or for some control. The difference unit 104 may determine based on this. This control includes, for example, control by the control unit 111 in a modification described later.

  The timing at which the difference unit 104 reads the reference frame is after the timing at which the acquisition unit 101 reads the encoding target frame from the frame holding unit 100. This is because the processing of the blocking filter 102 and the conversion unit 103 is executed after the acquisition unit 101 reads out the encoding target frame from the frame holding unit 100, and then the difference unit 104 reads out the reference frame. In other words, it can be said that the blocking filter 102 and the conversion unit 103 function as a delay unit that delays the reading of the reference frame by the difference unit 104 with respect to the reading of the encoding target frame by the acquisition unit 101.

  The quantization unit 105 quantizes the encoding target frame after the conversion unit 103 performs the conversion process or the difference frame generated by the difference unit 104 (that is, converts the frame into a quantization coefficient). Part.

  The encoding unit 106 is a processing unit that generates encoded data by encoding the frame quantized by the quantization unit 105. The encoded data generated by the encoding unit 106 corresponds to content data transmitted by the encoding device 10.

  The inverse quantization unit 107 is a processing unit that inversely quantizes the frame after quantization by the quantization unit 105. The inverse quantization unit 107 performs inverse quantization when the frame after quantization by the quantization unit 105 is a key frame. The inverse quantization unit 107 stores the inversely quantized frame in the reference holding unit 108 as a reference frame.

  The reference holding unit 108 is a storage unit that holds the key frame after the inverse quantization unit 107 performs inverse quantization as a reference frame. The key frame held by the reference holding unit 108 is referred to by the difference unit 104 and used for the process of calculating the difference. The reference holding unit 108 is realized by the main memory 12, for example.

  Processing of the encoding device 10 configured as described above will be described.

  FIG. 4 is a flowchart showing processing of the encoding apparatus 10 according to the present embodiment.

  In step S <b> 101, the acquisition unit 101 acquires the encoding target frame by reading it from the frame holding unit 100.

  In step S <b> 102, the blocking filter 102 performs a blocking filter process on the block boundary in the encoding target frame acquired by the acquisition unit 101.

  In step S <b> 103, the conversion unit 103 performs conversion processing for each block on the frame after the blocking filter processing by the blocking filter 102.

  In step S104, the encoding apparatus 10 branches the process depending on whether the encoding target frame is a key frame. If the frame to be encoded is a key frame (Yes in step S104), the process proceeds to step S105. If not (No in step S104), the process proceeds to step S111.

  In step S105, the quantization unit 105 performs the quantization process on the encoding target frame after the conversion unit 103 performs the conversion process.

  In step S106, the inverse quantization unit 107 performs an inverse quantization process on the key frame quantized by the quantization unit 105.

  In step S107, the inverse quantization unit 107 stores the frame subjected to the inverse quantization in step S106 in the reference holding unit 108.

  In step S111, the difference unit 104 generates, as a difference frame, a difference between the encoding target frame after the conversion unit 103 performs the conversion process and the reference frame read from the reference holding unit 108.

  In step S112, the quantization unit 105 quantizes the difference frame after the difference unit 104 performs the conversion process.

  In step S108, the encoding unit 106 encodes the key frame quantized by the quantization unit 105 to generate encoded data. The generated encoded data is transmitted to the reproduction device 2 by the transmission device 1.

  FIG. 5 is a block diagram showing a configuration of decoding apparatus 20 according to the present embodiment.

  As illustrated in FIG. 5, the decoding device 20 includes a decoding unit 201, an addition unit 202, an inverse quantization unit 203, a reference holding unit 204, an inverse transformation unit 205, a deblocking filter 206, and a generation Unit 207.

  The decoding unit 201 is a processing unit that receives and decodes encoded data that is content data transmitted by the encoding device 10 as a decoding target frame. A frame generated by decoding by the decoding unit 201 is a frame to be encoded (quantization coefficient) that is original data that has been encoded by the encoding unit 106.

  The addition unit 202 is a processing unit that generates an addition frame (quantization coefficient) by adding the decoding target frame decoded by the decoding unit 201 and the reference frame held by the reference holding unit 204. . The addition unit 202 reads the reference frame from the reference holding unit 204 before performing the above addition process.

  The inverse quantization unit 203 is a processing unit that calculates a decoding target frame (frequency coefficient) by inversely quantizing the addition frame generated by the addition unit 202 through the addition process. The processing of the inverse quantization unit 203 is the same as that of the inverse quantization unit 107 of the encoding device 10.

  The reference holding unit 204 is a storage unit that holds a key frame of the decoding target frames generated by the inverse quantization unit 203 as a reference frame. The key frame held by the reference holding unit 204 is referred to by the adding unit 202 and used for the addition process. The reference holding unit 204 is realized by the main memory 12 or the like, for example.

  The inverse transform unit 205 is a processing unit that performs an inverse transform process on a decoding target frame (frequency coefficient) generated by the inverse quantization unit 203 through inverse quantization. In the inverse conversion process, conversion opposite to the conversion by the conversion unit 103 of the encoding device 10 is performed. Specifically, the inverse conversion process is an inverse frequency conversion process when the conversion unit 103 performs frequency conversion, and an inverse order conversion process when the conversion unit 103 performs order conversion.

  The deblocking filter 206 is a processing unit that performs a deblocking filter process on the block boundary in the decoding target frame after the inverse conversion unit 205 performs the inverse conversion process. The deblocking filter 206 corresponds to a filter unit included in the decoding device 20.

  The generation unit 207 is a processing unit that acquires an addition frame that has been subjected to deblocking filter processing by the deblocking filter 206, generates a frame by adding attribute information or the like to the acquired addition frame, and passes the frame to subsequent processing. is there.

  Processing of the decoding device 20 configured as described above will be described.

  FIG. 6 is a flowchart showing processing of the decoding device 20 according to the present embodiment.

  In step S201, the decoding unit 201 receives and decodes encoded data to obtain a decoding target frame.

  In step S202, the decryption apparatus 20 branches the process depending on whether or not the decryption target frame is a key frame. If the frame to be decrypted is a key frame (Yes in step S202), the process proceeds to step S203. If not (No in step S202), the process proceeds to step S211.

  In step S203, the inverse quantization unit 203 inversely quantizes the key frame that is the decoding target frame.

  In step S204, the inverse quantization unit 203 stores the key frame inversely quantized in step S203 in the reference holding unit 204.

  In step S <b> 205, the inverse transform unit 205 performs an inverse transform process on the addition frame that is inversely quantized by the inverse quantization unit 203.

  In step S206, the deblocking filter 206 performs a deblocking filter process on the block boundary in the addition frame after the inverse transform unit 205 performs the inverse transform process.

  In step S207, the generation unit 207 generates a frame and passes it to a subsequent process.

  In step S211, the addition unit 202 adds the frame generated by the decoding unit 201 by decoding and the reference frame read from the reference holding unit 607 to generate an addition frame.

  In step S212, the inverse quantization unit 203 is a processing unit that performs inverse quantization on the addition frame generated by the addition unit 202 through the addition process.

  Next, an encoding device and a decoding device according to related technology will be described. The related art is an example of a conventional encoding device and decoding device that require a relatively long time for encoding a frame.

  FIG. 7 is a block diagram illustrating a configuration of the encoding device 50 according to the related art. The encoding device 50 is an example of an encoding device conventionally used as the encoding device 10 in FIG.

  As illustrated in FIG. 7, the encoding device 50 includes a frame holding unit 500, an acquisition unit 501, a difference unit 502, a blocking filter 503, a conversion unit 504, a quantization unit 505, and an encoding unit 506. , An inverse quantization unit 507, an inverse transform unit 508, a deblocking filter 509, and a reference holding unit 510.

  Here, the difference between the encoding device 50 and the encoding device 10 is that the difference unit 502 is arranged at the subsequent stage of the acquisition unit 501 and the inverse conversion unit 508 and the deblocking filter at the subsequent stage of the inverse quantization unit 507. 509.

  The difference unit 502 is a processing unit that generates a difference frame by calculating a difference between the encoding target frame acquired by the acquisition unit 501 and the reference frame held by the reference holding unit 510. The difference unit 502 calculates the difference when the encoding target frame is not a key frame, and does not calculate the difference when it is a key frame.

  The inverse transform unit 508 is a processing unit that performs an inverse transform process on the key frame that is inversely quantized by the inverse quantization unit 507. The inverse transform unit 508 performs the same processing as the inverse transform unit 205.

  The deblocking filter 509 is a processing unit that performs the deblocking filter process on the block boundary in the key frame after the inverse conversion unit 508 performs the inverse conversion process.

  The reference holding unit 510 holds a copy of the difference frame generated by the deblocking filter 509.

  Note that the frame holding unit 500, the acquisition unit 501, the blocking filter 503, the transform unit 504, the quantization unit 505, the encoding unit 506, and the inverse quantization unit 507 have the same names in the encoding device 10. Since it is the same as a component, description is abbreviate | omitted.

  FIG. 8 is a block diagram showing a configuration of a decoding device 60 according to the related art.

  As illustrated in FIG. 8, the decoding device 60 includes a decoding unit 601, an inverse quantization unit 602, an inverse transformation unit 603, a deblocking filter 604, an addition unit 605, a generation unit 606, and a reference hold. Unit 607.

  Here, the decoding device 60 is different from the decoding device 20 in that an adding unit 605 is provided in the subsequent stage of the deblocking filter 604.

  The adding unit 605 is a processing unit that generates an added frame by adding the frame after the deblocking filter 604 performs the deblocking filter process and the reference frame held by the reference holding unit 607. is there.

  The reference holding unit 607 holds a copy of the frame generated by the generation unit 606.

  Note that the decoding unit 601, the inverse quantization unit 602, the inverse transform unit 603, the deblocking filter 604, and the generation unit 606 are the same as the components of the same name in the decoding device 20, and thus description thereof is omitted.

  There are the following two factors that increase the time required for the encoding process by the encoding apparatus 50 according to the related art.

(1) Points with a relatively large number of processing blocks Each processing performed by the processing blocks shown in FIG. 7 is realized by calculation processing. For this reason, if the number of processing blocks is relatively large, a relatively large amount of calculation processing is required, and as a result, encoding processing takes time.

(2) Points in which the memory access time difference is relatively small As shown in FIG. 7, the difference unit 502, before performing the process of calculating the difference, the encoding target frame that is the two frames that are the target of the process, The reference frame is acquired from the main memory 12. At this time, two memory accesses for reading a frame occur substantially simultaneously, and a predetermined time may be required for these memory accesses. In order to perform the two memory accesses without requiring the predetermined time, there may be a countermeasure for increasing the buffer size for memory access. However, using this countermeasure is not desirable because it may affect other functional blocks.

  Therefore, in the encoding apparatus 10 according to the present embodiment, the above factors are eliminated as follows.

(1) Number of processing blocks As shown in FIG. 7, the reference frame held by the reference holding unit 510 of the encoding device 50 is inversely quantized with respect to the difference frame quantized by the quantization unit 505. Processing by the unit 507, the inverse transform unit 508, and the deblocking filter 509 is performed.

  On the other hand, as shown in FIG. 3, the reference frame held by the reference holding unit 108 of the encoding device 10 is processed by the inverse quantization unit 107 on the difference frame quantized by the quantization unit 105. It was made. That is, the time required until the reference frame is generated is reduced in the encoding device 10 by the time required for processing by the inverse transform unit 508 and the deblocking filter 509 in the encoding device 50.

  In this way, the encoding device 10 has a reduced number of processing blocks for processing required for encoding as compared to the encoding device 50, and the time required for encoding processing is reduced.

(2) Regarding Memory Access Time Difference As shown in FIG. 7, the difference unit 502 included in the encoding device 50 encodes two frames that are targets of difference processing when performing a process of calculating a difference. The target frame and the reference frame are acquired from the main memory 12. At this time, two memory accesses for reading a frame occur substantially simultaneously, and a predetermined time may be required for these memory accesses.

  On the other hand, as shown in FIG. 3, in the encoding device 10, the blocking filter 102 and the conversion unit 103 include the timing at which the acquisition unit 101 reads the encoding target frame and the timing at which the difference unit 104 reads the reference frame. A time difference corresponding to the processing time is generated. Therefore, it is possible to avoid two memory accesses to the main memory 12 substantially simultaneously.

  As described above, the encoding apparatus 10 avoids a situation in which memory access for referring to two frames is performed substantially simultaneously. At this time, it is not necessary to take measures such as increasing the buffer size for memory access.

  Note that the number of processing blocks provided in the encoding device 10 according to the present embodiment is small because the number of logical blocks is reduced when the encoding device 10 is realized by a field-programmable gate array (FPGA) or the like. Connected. This point is also an advantage of the encoding apparatus 10 according to the present embodiment.

  As described above, the encoding apparatus according to the present embodiment can reduce the time required for encoding a frame.

(Modification of the embodiment)
In this modification, for an encoding device and a decoding device that reduce the time required to encode a frame, a new frame is intra-coded according to the result of the encoding process, or between frames A technique for appropriately determining which frame to encode, in other words, which frame to use as a key frame will be described.

  FIG. 9 is a block diagram showing a configuration of coding apparatus 10A according to a modification of the present embodiment.

  As illustrated in FIG. 9, the encoding device 10A includes a frame holding unit 100, an acquisition unit 101, a blocking filter 102, a conversion unit 103, a difference unit 104A, a quantization unit 105, and an encoding unit 106. An inverse quantization unit 107, a reference holding unit 108, a control unit 111, and a switching unit 112.

  Here, the frame holding unit 100, the acquiring unit 101, the blocking filter 102, the transforming unit 103, the quantizing unit 105, the encoding unit 106, the inverse quantization unit 107, and the reference holding unit 108 are described. Has the same function as the component of the same name in the above embodiment, and detailed description thereof is omitted.

  Similar to the difference unit 104 in the above embodiment, the difference unit 104A calculates the difference between the encoding target frame after the conversion unit 103 performs the conversion process and the reference frame held by the reference holding unit 108. , A processing unit that generates a difference frame. At the time when the difference unit 104A acquires a frame from the conversion unit 103, it is not determined whether this frame is a key frame or a difference frame, and the state of the switching unit 112 is controlled by the control unit 111 in the subsequent stage. Thus, it is determined whether this frame becomes a key frame or a difference frame. When the frame input to the difference unit 104A is inter-frame encoded (becomes a difference frame), the frame is provided to the quantization unit 105 through the subsequent switching unit 112. On the other hand, when the frame input to the difference unit 104A is intra-frame encoded (becomes a key frame), the frame input to the difference unit 104A is provided to the quantization unit 105, and the difference unit 104A generates The difference frame is not used for subsequent processing.

  The control unit 111 is a processing unit that performs determination based on the encoded data generated by the encoding unit 106 by encoding, and controls encoding of a new encoding target frame according to the determination result.

  The control unit 111 acquires encoded data (or a copy of the encoded data) generated by the encoding unit 106 by encoding, and indicates whether or not the frame included in the encoded data is a key frame. Information and the data size of the encoded data are obtained. Then, a determination is made based on the information and the data size, and whether a new encoding target frame to be encoded next by the encoding apparatus 10A is intra-frame encoded or inter-frame encoded (in other words, For example, which frame is the key frame and which frame is the difference frame). Then, the control unit 111 controls the state of the switching unit 112 according to the determination result. A method of determination by the control unit 111 will be described in detail later.

  Whether the switching unit 112 sets the frame provided to the quantization unit 105 in the subsequent stage as a frame after the conversion unit 103 performs the conversion process or the difference frame generated by the difference unit 104A through the difference process. It is the switching part which switches. A state in which the switching unit 112 provides the frame after the conversion unit 103 performs the conversion process to the quantization unit 105, that is, a state in which the terminal a and the terminal c in FIG. A state in which the switching unit 112 provides the difference frame generated by the difference processing by the difference unit 104A to the quantization unit 105, that is, a state in which the terminal b and the terminal c are connected in the drawing is referred to as a state B. Whether the switching unit 112 takes the state A or the state B is controlled by the control unit 111.

  Note that the operations of the difference unit 104A and the switching unit 112 calculate the difference when the encoding target frame is not a key frame by the difference unit 104 of the above embodiment, and the difference when the frame is a key frame. This is the same as the operation of not calculating. That is, the difference unit 104A and the switching unit 112 are more specifically described by dividing the difference unit 104 of the above-described embodiment into two components.

  The processing of the encoding apparatus 10A configured as described above will be described using a flowchart.

  FIG. 10 is a flowchart showing the processing of the encoding device 10A according to this modification.

  The processing in steps S101 to S112 in FIG. 10 is substantially the same as the step with the same name shown in FIG. Here, step S104A is a more specific content of the process of step S104.

  In step S <b> 104 </ b> A, the control unit 111 switches whether the encoding target frame is intra-frame encoded or inter-frame encoded according to the state of the switching unit 112. That is, when the switching unit 112 is in the state A (“intraframe encoding” in step S104A), a series of processes (steps S105 to S107) for intraframe encoding of the encoding target frame is performed. On the other hand, when the switching unit 112 is in the state B (“interframe encoding” in step S104A), a series of processes (steps S111 to S112) for interframe encoding of the encoding target frame is performed.

  The processing after step S108 will be described below.

  In step S122, the control unit 111 acquires a copy of the frame encoded by the encoding unit 106, and determines whether or not this frame is a key frame. If it is a key frame, the process proceeds to step S123; otherwise, the process proceeds to step S131.

  In step S123, the control unit 111 performs control so that the next encoding target frame is inter-frame encoded (set to a difference frame). Specifically, the control unit 111 changes the switching unit 112 to the state B (when the state B is already in the state B, the state B is maintained).

  In step S131, the control unit 111 determines whether the data size of the encoded data is greater than or equal to a threshold value. If the data size of the encoded data is greater than or equal to the threshold (Yes in step S131), the process proceeds to step S131. If not (No in step S131), the process proceeds to step S132. Note that the threshold value may be a predetermined fixed value, or may be a fluctuation value calculated by multiplying the data size of the immediately preceding key frame by a predetermined value. The predetermined value is, for example, a value not less than 0 and not more than 1, and more specifically can be ½ times or 2/3 times.

  In step S132, the control unit 111 performs control so that the next encoding target frame is intra-frame encoded (set as a key frame). Specifically, the control unit 111 changes the switching unit 112 to the state A (if the state is already in the state A, the state A is maintained).

  In this way, the encoding device 10A encodes the encoding target frame to be encoded next as a key frame based on the data size of the encoded data actually generated by the encoding device 10A. Whether to perform (intraframe encoding) or to encode as a difference frame (interframe encoding) is appropriately determined.

  Specifically, if the data size of the encoded data generated by inter-frame encoding as the difference frame is equal to or larger than the threshold value, intra-frame encoding is performed using the next encoding target frame as a key frame (in step S131). Yes, S132). This situation indicates that the difference in data size between the encoding target frame and the immediately preceding key frame is relatively large, so that the advantage of differential encoding cannot be exhibited, and a new key frame is inserted. This is because a reduction in the data size of the encoded data is expected.

  If the data size of the encoded data generated by inter-frame encoding as the difference frame is less than the threshold, the next encoding target frame is inter-frame encoded as the difference frame (No in step S131, S123). ). This situation indicates that the difference in data size between the encoding target frame and the immediately preceding key frame is relatively small, so that the advantage of differential encoding can be exhibited, and this situation is continued. This is because it is desirable.

  If encoded data is generated as a key frame by intra-frame encoding, inter-frame encoding is performed using the next encoding target frame as a difference frame (step S123). As a result, it is possible to avoid an increase in the amount of data due to subsequent intra-frame encoding of the encoding target frame.

  As described above, the encoding apparatus according to the present embodiment performs memory access at two points when the acquisition unit acquires the encoding target frame and when the difference unit acquires the reference frame. Considering the order of processing by the encoding device, after the memory access by the acquisition unit, the processing by the filter unit and the conversion unit is performed, and then the memory access by the difference unit is performed. Therefore, the timing at which the two memory accesses are performed is not simultaneous (or substantially simultaneous). For this reason, if two memory accesses are performed substantially simultaneously, a waiting time that may occur can be avoided. As described above, the encoding apparatus can reduce the time required for encoding a frame.

  In addition, the difference unit is used for a process of calculating a difference using a frame obtained by dequantizing the quantized frame as a reference frame. Therefore, it is possible to generate the reference frame in a shorter time than when the reference frame is generated by performing a larger number of processes than the above. Therefore, the encoding device can reduce the time required for encoding the frame.

  Further, the control unit controls whether the next frame is intra-frame encoded or inter-frame encoded based on the data size of the encoded data generated by the actual encoding. Therefore, the encoding device can more appropriately control the encoding of the next frame based on the actual encoding result, and avoid an increase in processing time that occurs if the encoding is performed again. it can.

  In addition, the control unit determines whether or not the effect of differential encoding (interframe encoding) according to the size of the data size is properly exhibited, and if it is not properly demonstrated, a new encoding is performed. By performing intra-frame encoding of the target frame, control can be performed so as to exert the effect of differential encoding.

  Further, the control unit can perform control so as to exert the effect of differential encoding by performing inter-frame encoding after intra-frame encoding.

  The encoding device and decoding device of the present invention have been described above based on the embodiment, but the present invention is not limited to this embodiment. Unless it deviates from the meaning of this invention, the form which carried out the various deformation | transformation which those skilled in the art can think to this embodiment, and the structure constructed | assembled combining the component in different embodiment is also contained in the scope of the present invention. .

  The present invention can be used for an encoding apparatus and a decoding apparatus that reduce the time required for encoding a frame. Specifically, it is installed in a public space or a commercial facility, and can be used for a playback device that plays back images and the like, a transmission device that provides content to the playback device, and the like.

DESCRIPTION OF SYMBOLS 1 Transmission apparatus 2 Playback apparatus 3 Network 10, 10A, 50 Encoding apparatus 11 CPU
12 Main memory 13 Storage 20, 60 Decoding device 100, 500 Frame holding unit 101, 501 Acquisition unit 102, 503 Blocking filter 103, 504 Conversion unit 104, 104A, 502 Difference unit 105, 505 Quantization unit 106, 506 Encoding unit 107, 203, 507, 602 Inverse quantization unit 108, 204, 510, 607 Reference holding unit 111 Control unit 112 Switching unit 201, 601 Decoding unit 202, 605 Addition unit 205, 508, 603 Inverse conversion unit 206, 509, 604 Deblocking filter 207, 606 Generation unit S Content playback system

Claims (8)

An acquisition unit for acquiring a frame to be encoded from a memory;
A filter unit that performs a filtering process on a block boundary that is a processing unit included in the encoding target frame acquired by the acquisition unit;
A conversion unit that performs a conversion process including a frequency conversion or an order conversion for each block on the encoding target frame after the filtering process;
A difference unit that obtains a reference frame from the memory, and calculates a difference between the obtained reference frame and the encoding target frame after the conversion process as a difference frame;
A quantization unit that quantizes the difference frame calculated by the difference unit;
An encoding device comprising: an encoding unit that encodes the difference frame quantized by the quantization unit to generate encoded data. When the encoding target frame is a key frame, the quantization unit quantizes the encoding target frame after the conversion processing by the conversion unit,
The encoding device further includes:
When the difference frame is a key frame, comprising: an inverse quantization unit that inversely quantizes the difference frame after quantization by the quantization unit and stores the difference frame in a memory;
The difference unit is
The encoding device according to claim 1, wherein the difference is calculated using the key frame stored in the memory by the inverse quantization unit as the reference frame. The encoding device further includes:
A control unit that controls whether a new encoding target frame is intra-frame encoded or inter-frame encoded based on a data size of encoded data generated by the encoding unit. Or the encoding apparatus of 2. The controller is
Determining whether or not the data size of the encoded data generated by the inter-frame encoding by the encoding unit is greater than or equal to a threshold;
(A) When the data size is equal to or larger than the threshold, control is performed so that a new encoding target frame is intra-frame encoded,
The encoding apparatus according to claim 3, wherein (b) when the data size is less than the threshold, control is performed so that a new encoding target frame is inter-frame encoded. The controller is
The encoding apparatus according to claim 3 or 4, wherein when the encoding unit generates the encoded data by performing intra-frame encoding, a new encoding target frame is controlled to be inter-frame encoded. An adder that obtains a reference frame from a memory and adds the obtained reference frame and the encoded data to generate an addition frame;
An inverse quantization unit that performs inverse quantization on the addition frame generated by the addition unit;
An inverse transform unit that performs an inverse transform process including an inverse frequency transform or an inverse order transform for each block that is a processing unit included in the addition frame inversely quantized by the inverse quantizer;
A filter unit that performs a filtering process on a boundary of the block in the addition frame after the inverse transform process;
And a generation unit configured to generate a frame based on the added frame after the filtering process. An acquisition step of acquiring an encoding target frame from a memory;
A filter step of performing a filtering process on a block boundary which is a processing unit included in the encoding target frame acquired in the acquisition step;
A conversion step for performing a conversion process including frequency conversion or order conversion for each block on the encoding target frame after the filter process;
A difference step of acquiring a reference frame from the memory, and calculating a difference between the acquired reference frame and the encoding target frame after the conversion process as a difference frame;
A quantization step for quantizing the difference frame calculated in the difference step;
A coding step including coding the difference frame quantized in the quantization step to generate coded data. An adding step of acquiring a reference frame from a memory, and adding the acquired reference frame and the encoded data to generate an added frame;
An inverse quantization step of performing inverse quantization on the addition frame generated in the addition step;
An inverse transform step of performing an inverse transform process including an inverse frequency transform or an inverse order transform for each block that is a processing unit included in the addition frame inversely quantized in the inverse quantization step;
A filter step of performing a filter process on a boundary of the block in the addition frame after the inverse transform process;
And a generation step of generating a frame based on the added frame after the filtering process.

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