KR101291192B1 - Video encoding apparatus and method and video decoding apparatus and method - Google Patents

Abstract

Disclosed are a video encoding apparatus and method, and a video decoding apparatus and method. The apparatus for encoding an image may include obtaining a modified base quantization level using the extended quantization level obtained from the extended quantization coefficient, and generating a base layer bitstream including the modified base quantization level and the base quantization coefficient; Obtaining an extension index that compensates for the difference bit depth between the base bit depth and the extension bit depth from the extension quantization coefficient, and generating an extension layer bitstream including the extension index; And combining the base layer bitstream and the enhancement layer bitstream, and generating a scalable bitstream including an extension layer identifier.

Description

Image encoding apparatus and method and video decoding apparatus and method

1 is a view for explaining the concept of a video encoding apparatus and a video decoding apparatus according to the present invention;

2 is a diagram illustrating an example of a syntax of a scalable bitstream obtained from a video encoding apparatus according to the present invention;

3A to 3D are diagrams showing examples of information included in each base layer or extension layer shown in FIG. 2;

4 is a view showing an example of a start code as a section for loading an extended layer identifier in a video encoding apparatus according to the present invention;

5 is a block diagram showing a configuration of a first embodiment of a video encoding apparatus according to the present invention;

6 is a block diagram showing a configuration according to a first embodiment of an image decoding apparatus according to the present invention;

7 is a block diagram showing a configuration according to a second embodiment of a video encoding apparatus according to the present invention; and

8 is a block diagram showing a configuration of a second embodiment of an image decoding apparatus according to the present invention.

The present invention relates to an image encoding apparatus and method, and an image decoding apparatus and method, and more particularly, to an image encoding apparatus and method and an image decoding that can be decoded even if the bit depth or the bit depth and the image format are changed. An apparatus and method are provided.

In a typical video codec, for example, the bit depth of a basic encoder such as a VC-1 encoder is changed from a basic bit, i.e., 8 bits to an extended bit, for example 10 bits, or a video format of a basic encoder such as a VC-1 encoder. If we change from 4: 2: 0 to simply 4: 2: 2 or 4: 4: 4, the VC-1 decoder generates a bitstream generated from an enhanced encoder with extended bit depth or an improved encoder with changed video format. It is impossible to read and play it. In recent years, forward compatibility allows the VC-1 decoder and other advanced decoders to recover not only such fixed bit depths or fixed image formats, but also bitstreams encoded at various bit depths or various image formats. There is a great need to develop a video codec that is guaranteed.

That is, a new video codec that does not guarantee forward compatibility cannot support a terminal having only an existing basic video codec, and thus content reuse between terminals having different specifications is not possible. In addition, there is a disadvantage that it takes a long time before the new video codec takes place in the market because it has to overcome the already established video codec market.

The technical problem to be achieved by the present invention is to change the bit depth (depth) from the base bit to the extension bit, or change the bit depth from the base bit to the extension bit and change the first image format to the second or third image format The present invention provides an image encoding apparatus and method capable of encoding.

Another technical problem to be solved by the present invention is to change the bitstream or bit-depth obtained by encoding the basic bit and the first image format from the basic bit to the extended bit, or change the bit depth from the basic bit to the extended bit. The present invention provides an image decoding apparatus and method for decoding a scalable bitstream obtained by changing and encoding a first image format into a second or third image format.

In order to achieve the above technical problem, the image encoding apparatus according to the present invention obtains a modified basic quantization level using an extended quantization level, and generates a basic layer bitstream including the modified basic quantization level and the basic quantization coefficient. A hierarchical encoder; An extension for obtaining the extension quantization level from an extension quantization coefficient, an extension index for compensating the difference bit depth between the base bit depth and the extension bit depth, and generating an extension layer bitstream including the extension index A hierarchical encoder; And a bitstream combiner that combines the base layer bitstream and the enhancement layer bitstream and generates a scalable bitstream including an extension layer identifier.

In order to achieve the above technical problem, the image encoding method according to the present invention obtains a modified basic quantization level using an extended quantization level obtained from an extended quantization coefficient, and includes a base layer bit including the modified basic quantization level and the basic quantization coefficient. Generating a stream; Obtaining an extension index that compensates for the difference bit depth between the base bit depth and the extension bit depth from the extension quantization coefficient, and generating an extension layer bitstream including the extension index; And combining the base layer bitstream and the enhancement layer bitstream, and generating a scalable bitstream including an extension layer identifier.

In order to achieve the above technical problem, an image encoding apparatus according to the present invention obtains a modified basic quantization level using an extended quantization level, and includes a luminance block bitstream of a base layer including the modified basic quantization level and a basic quantization coefficient. A base layer encoding unit for generating a color difference block bitstream of the base layer from color difference data supporting the first image format; Obtaining the extended quantization level from the extended quantization coefficient, obtaining an extended index to compensate for the difference bit depth between the basic bit depth and the extended bit depth from the extended quantization coefficient, and a luminance block bitstream of the extended layer including the extended index; An extension layer encoding unit for generating a color difference block bitstream of an enhancement layer by using color difference data between the reconstructed color difference block of the second or third image format and the original color difference block of the second or third image format; And a bitstream combiner configured to combine the luminance block and the chrominance block bitstream of the base layer with the luminance block and the chrominance block bitstream of the enhancement layer, and generate a scalable bitstream including an extension layer identifier.

In order to achieve the above technical problem, the image encoding method according to the present invention obtains a modified basic quantization level by using an extended quantization level obtained from an extended quantization coefficient, and includes a base layer including the modified basic quantization level and the basic quantization coefficient. Generating a chrominance block bitstream of the base layer from the luminance block bitstream and the chrominance data supporting the first image format; Obtaining an extension index that compensates for the difference bit depth between the base bit depth and the extension bit depth from the extension quantization coefficient, and a luminance block bitstream of the extension layer including the extension index and a reconstructed color difference of a second or third image format Generating a chrominance block bitstream of the enhancement layer by using chrominance difference data between the block and the original chrominance block of the second or third image format; And combining the luminance block and the chrominance block bitstream of the base layer with the luminance block and the chrominance block bitstream of the enhancement layer, and generating a scalable bitstream including an extension layer identifier.

In order to achieve the above technical problem, an image decoding apparatus according to the present invention comprises: a bitstream analyzer for determining whether a received bitstream is a scalable bitstream; A basic decoding unit for performing decoding using the quantization level and the quantization coefficient included in the received bitstream when the received bitstream is not a scalable bitstream; And if the received bitstream is a scalable bitstream, the difference bit depth between the modified base quantization level and the base quantization coefficient included in the base layer bitstream, and the base bit depth and the extended bit depth included in the enhancement layer bitstream. And an expansion decoding unit that performs decoding using an expansion index that compensates for the loss.

According to an aspect of the present invention, there is provided a method of decoding an image, comprising: determining whether a received bitstream is a scalable bitstream; If the received bitstream is not a scalable bitstream, decoding using the quantization level and the quantization coefficient included in the received bitstream; And if the received bitstream is a scalable bitstream, the difference bit depth between the modified base quantization level and the base quantization coefficient included in the base layer bitstream, and the base bit depth and the extended bit depth included in the enhancement layer bitstream. Performing decoding using an expansion index that compensates for the error.

According to an aspect of the present invention, there is provided a video decoding apparatus including: a bitstream analyzer to determine whether a received bitstream includes an extended layer identifier; A basic decoding unit for decoding a luminance block and a chrominance block according to a first image format by using a quantization level and a quantization coefficient included in the received bitstream when the received bitstream does not include an extended layer identifier ; And when the received bitstream includes the enhancement layer identifier, a modified basic quantization level and a basic quantization coefficient included in the luminance block bitstream of the base layer, and a basic bit depth included in the luminance block bitstream of the enhancement layer. And decoding the luminance block using an extension index that compensates for the difference bit depth, and using chrominance data and chrominance difference data that support the first image format included in the chrominance block bitstream of the base layer. An extended decoding unit for decoding the color difference block.

According to an aspect of the present invention, there is provided a method of decoding an image, comprising: determining whether a received bitstream includes an extension layer identifier; If the received bitstream does not include an extended layer identifier, performing a decoding of a luminance block and a chrominance block according to a first image format by using a quantization level and a quantization coefficient included in the received bitstream; And when the received bitstream includes the enhancement layer identifier, a modified basic quantization level and a basic quantization coefficient included in the luminance block bitstream of the base layer, and a basic bit depth included in the luminance block bitstream of the enhancement layer. And decoding the luminance block using an extension index that compensates for the difference bit depth, and using chrominance data and chrominance difference data that support the first image format included in the chrominance block bitstream of the base layer. Performing decoding of the color difference block.

The video encoding method and the video decoding method may be embodied as a computer-readable recording medium that records a program for execution on a computer.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is for explaining the concept of a video encoding apparatus and a video decoding apparatus according to the present invention, the encoder part is a first encoder 113 to serve as a basic encoder and a second encoder 117 to serve as an improved encoder. For example, the decoder part serves as a basic decoder, and the second decoder corresponding to the second encoder 117 and the first decoder 153 corresponding to the first encoder 113 and the improved decoder. Take 157 as an example. In one embodiment, the first encoder 113 generates a bitstream according to the basic bit and the first image format, the second encoder 117 supports the basic bit and the extension bit, and scales according to the first image format Generates a flexible bitstream. In another embodiment, the first encoder 113 generates a bitstream according to the base bit and the first video format, the second encoder 117 supports the first and second video formats, and scales according to the base bit. Generates a flexible bitstream. In another embodiment, the first encoder 113 generates a bitstream according to the basic bit and the first image format, the second encoder 117 supports the basic bit and the extension bit, and the first and second images. A scalable bitstream supporting a format is generated, or a scalable bitstream supporting basic and extended bits and a first and third video formats are generated.

For convenience of explanation, the basic bit is 8 bits, the extension bit is 10 bits, the first video format is 4: 2: 0, the second video format is 4: 2: 2, and the third video format is 4: 4: 4. Let's take an example. Accordingly, as an example of the first encoder 113, a VC-1 encoder supporting 8 bit and 4: 2: 0 video format may be adopted.

Referring to FIG. 1, the bitstream 131 generated by the first encoder 113 may be decoded by the second decoder 157 as well as the first decoder 153. The scalable bitstream 137 generated by the second encoder 117 may be decoded by the second decoder 157, and the first decoder 153 may decode the enhancement layer bitstream included in the scalable bitstream. In the neglected state, decoding may be performed on the base layer bitstream. The second encoder 117 capable of providing such forward compatability corresponds to the video encoding apparatus of the present invention, and the second decoder 157 corresponds to the video decoding apparatus of the present invention.

2 shows an example of syntax of a scalable bitstream obtained from an image encoding apparatus according to the present invention, and includes a base layer bitstream and an extension layer bitstream.

Referring to FIG. 2, the scalable bitstream may include a base layer sequence level 211, an enhancement layer sequence level 213, a base layer GOP (Group Of Pictures) level 215, The enhancement layer GOP level 217, the enhancement layer picture level 219, the base layer picture level 221, the base layer picture data 223, and the enhancement layer picture data 225 are included. Here, although the enhancement layer picture level 219 is located in front of the base layer picture level 221, the enhancement layer picture level 219 may be located behind the base layer picture level 221.

Here, the sequence consists of at least one or more coded pictures or at least one or more GOPs. The GOP is composed of at least one coded picture, and an entry-point may be used for the VC-1 codec. Here, the first picture in each GOP may provide random access. On the other hand, the picture is decomposed into macroblocks, and when the image format is 4: 2: 0, each macroblock is composed of four luminance blocks and two color difference blocks.

3A to 3D show examples of information included in each base layer or extension layer shown in FIG. 2, and FIG. 3A is information included in the extension layer sequence level 213 and may be provided in the extension layer. Profile and level information 311 and bit depth information 313 that can be supported by the enhancement layer. Here, the image format information 315 may not be included in the enhancement layer sequence level 213 when it is possible to define the base layer sequence level 211. 3B is information included in the enhancement layer picture level 219 and includes an extended index (refined QP, hereinafter referred to as R) to indicate the remaining bit depth of the enhancement layer that cannot be represented in the base layer.

3C is information included in the base layer picture level 221 and includes a basic quantization coefficient of the first encoder 113. FIG. 3D is information included in the enhancement layer picture data region 225 and shows an encoded color difference image when the image formats of the first encoder 113 and the second encoder 117 are different. Although not shown, in the case of extending the bit depth according to the present invention, the extended quantization level is included in the base layer picture data region 223 instead of the basic quantization level, while the extended layer picture data region 225 includes the extended quantization level. This is not included.

FIG. 4 illustrates an area for loading information related to an extension layer, including an extension layer identifier, in a scalable bitstream obtained from an image encoding apparatus according to the present invention. When the first encoder 113 is a VC-1 encoder, in one embodiment, a start code of 4 bytes is used. In the case of the VC-1 encoder, the start code may be supported in an advanced profile or higher. On the other hand, the start code may be included in the first region in the header of each level.

A process of loading information related to an extension layer in a start code of VC-1 used as an embodiment will be described with reference to FIG. 4. In the start code, among reserved bitstream data unit (BDU) types defined in the suffix, reserved areas (451,452,453,454) reserved for future use are used to contain information related to the extension layer. Here, the BDU refers to a compressed data unit that can be parsed independently of other information in the same hierarchical level, and may be, for example, a sequence header, an entry point header, an encoded picture, or a slice. The remaining areas 411 to 421 other than the prohibited area 422 among the BDU types defined in the suffix of the start code are for containing information related to the base layer. Here, the start code is just an example, and other parts of the components of the bitstream may be used.

On the other hand, the enhancement layer includes a sequence level, a group of pictures (GOP) level, a frame level, a field level, and a slice level. The information of the extended layer may be included in any one of the second spare area 452 and the fourth spare area 454 in one embodiment. Specifically, the start code is included in the header for the sequence level of the extended layer in '0x09' in the second spare area 452 or '0x40' in the fourth spare area 454, and the second spare area 452 is included. The start code is included in the header for the GOP level of the extended layer in '0x08' or '0x3F' in the fourth spare area 454, and '0x07' or fourth spare area 454 in the second spare area 452. ), The start code is included in the header for the frame level of the extended layer in '0x3E', and the field level of the extended layer in '0x06' in the second spare area 452 or '0x3D' in the fourth spare area 454. The start code is included in the header for the start code, and the start code for the extended chrominance data is included in the header for the data of the extended layer in '0x06' in the second spare area 452 or '0x3C' in the fourth spare area 454. Included. This will be described in more detail as follows.

As information that can be included in the start code of the header for the extended layer sequence level defined at '0x09' in the second spare area 452, additional profile and level information that can be achieved by the extended layer in addition to the base layer. , And difference bit depth information. In detail, at the sequence level of the base layer, the profile is defined as 2 bits, '3' represents an advanced profile, and '0-2' represents a spare area. Level is defined as 3 bits, '000' is AP @ LO, '001' is AP @ L1, '010' is AP @ L2, '011' is AP @ L3, '100' is AP @ L4, ' 101-111 'represents a spare area. The bit depth information that may be achieved by the enhancement layer may be represented by a value of "N-8" (where N is the bit depth of the enhancement layer), and the bit depth information of the first encoder (113 in FIG. 1) corresponding to the base layer may be represented. Depending on the bit depth, a value other than 8 can be used. Meanwhile, the information on the extended layer may include changed video format information. The video format information may be represented by using a variable included in the sequence level of the base layer, for example, a 'COLORDIFF' variable in the case of the VC-1 encoder. The second preliminary region 452 may be included in '0x09'. That is, when the variable of the base layer is utilized, the extended layer does not need to transmit changed video format information. In the example of the 'COLORDIFF' variable, '1' is used to define the 4: 2: 0 video format, and '2' and '3' are designated as spare areas. And 4: 4: 4 video formats. Meanwhile, as information on the extended layer, an additional HRD (Hypothetical Reference Decoder) variable may be included. The HRD variable is a virtual video buffer variable that is referred to by the decoder for buffer operation.

The start code of the header for the extended layer GOP level defined at '0x08' in the second spare area 452 is designated as a spare area because it is unnecessary when the bit depth or the video format is not changed in GOP units. This is necessary when the video format is changed in units of GOP.

The start code for the picture level of the extended layer defined in '0x07' and '0x06' of the second preliminary region 452, that is, the frame level and the field level header, is generated according to progressive scan or interlaced scan. An extension index (R) for indicating the remaining bit depth of the extension layer that cannot be expressed in the base layer is included. In one embodiment, when the bit depth of the first encoder 113 is 8 bits, 'N-8' (where N defines the value of the extension index R for the second encoder 117). In this case, since the expansion index (R) is used for each picture unit, the expansion index (R) is included in the picture level. According to another embodiment, when the expansion index (R) is used for each slice unit, the expansion index (for macroblock units) is used. In the case of using R), it is included in the macroblock level, and in the block level when the expansion index R is used in units of blocks. In order to calculate an expansion index R for each slice, each macroblock, or each block, a process of calculating an expansion index R of a picture level described later may be applied.

The start code for the header of the data of the extended layer defined in '0x05' of the second spare area 452 is unnecessary since it is unnecessary when the video format of the extended layer is not changed compared to the base layer. That is, when the video format of the base layer and the extension layer is the same as 4: 2: 0, data for four luminance blocks and two color difference blocks forming one macro block are transmitted in the base layer. On the other hand, if the video format of the base layer and the extended layer are different, for example, the video format of the base layer is 4: 2: 0 and the video format of the extension layer is 4: 2: 2, or the video format of the base layer is 4 : 2: 0 and the video format of the extended layer is 4: 4: 4. The video format allows the extended layer to support the changed video format while transmitting data for four luminance blocks and two chrominance blocks from the base layer. It transmits data for the difference color difference block corresponding to. On the other hand, since the data for the four luminance blocks are the same regardless of the image format, it is not necessary to transmit separate data in the extension layer.

On the other hand, the information related to the enhancement layer is not limited to the start code described in FIG. 4 and included in a reserved area reserved for future use at the sequence level, GOP level, picture level, macroblock level, and block level. Can be. In addition, in order to transmit the bitstream, the video bitstream may be used as a payload, and may include an extension layer identifier in various forms in various layers of a network protocol or a system layer for packaging the bitstream.

Next, a process of obtaining a scalable bitstream as the bit depth is expanded is as follows.

When the first encoder 113 is an 8-bit encoder and the second encoder 117 uses an N-bit encoder as an example, the start of the picture level of the enhancement layer bitstream included in the scalable bitstream obtained from the second encoder 117. The code is used to represent the rest of the bit depth that the first encoder 113 cannot express. For example, if the extended bit depth is N bits, and the extended quantization coefficient is QP _N , QP _N is obtained by using the basic quantization coefficient QP ₈ when the bit depth is 8 bits, and the extended index R. It may be represented as in Equation 1. Where the extended quantization coefficient QP _N Alternatively, the basic quantization coefficient QP ₈ is derived from 'PQINDEX' for the VC-1 encoder.

According to Equation 1, the expansion index R may be obtained by Equation 2 below.

에 해당한다. 여기서, 확장지수(R)의 범위는 실험적으로 혹은 통계적으로 상기 두가지 중 어느 한 가지로 정해지거나, 프레임 단위로 두가지 중 하나를 선택적으로 사용할 수 있다. 이 경우, 홀수번째 프레임인 경우에는 [-T, T-1]을, 짝수번째 프레임인 경우에는 [-T+1, T]가 사용되거나 그 역도 가능하다. 한편, QP_N 이 2^(N-8)의 배수인 경우에는 R은 0이다.Here, the expansion index (R) is in the range [-T, T-1] or [-T + 1, T], where T is

. Here, the range of the expansion index (R) may be experimentally or statistically determined by any one of the above two, or one of two may be selectively used in units of frames. In this case, [-T, T-1] is used for odd frames, and [-T + 1, T] is used for odd frames, or vice versa. Meanwhile, QP _N When this ^is a multiple of 2 ^(N-8) , R is 0.

이고, N이 10이고, 확장지수(R)의 범위가 [-T T-1]인 경우 각 확장 양자화계수 QP₁₀의 값에 따른 기본 양자화계수 QP₈의 값과 확장지수(R)의 값은 다음과 같다.At this time, the range of QP _N is

, N is 10, and the range of the extended index R is [-T T-1], the value of the basic quantization coefficient QP _{8 and} the value of the extended index R according to the value of each extended quantization coefficient QP ₁₀ is As follows.

According to the target extended quantization coefficient QP ₁₀ , the second encoder 117 divides the DCT coefficient by the extended quantization coefficient QP ₁₀ and quantizes the modified quantization level 'Level ₁₀ ' which can be derived from the extended quantization level 'Level ₁₀ '. The basic quantization level 'Level ₈ ' and the value of the basic quantization coefficient QP ₈ determined as described above are included in the picture level of the base layer among the scalable bitstreams and transmitted, and the value of the extension index R is the scalable bitstream. It is included in the picture level of the extended layer and transmitted. Here, the basic quantization level 'Level ₈ ' modified from the extended quantization level 'Level ₁₀ ' is obtained by the following process.

First, the extended quantization level 'Level _N ' may be expressed as in Equation 3 below.

Here, DCT _coeff represents a DCT coefficient.

On the other hand, the basic quantization level Level ₈ modified from Level _N can be obtained through the following equation (4).

Upon receiving such a scalable bitstream, the first decoder 153 reconstructs a DCT coefficient reconstructed using the modified basic quantization level 'Level ₈ ' and the basic quantization coefficient QP ₈ transmitted through the base layer, that is, Level ₈ X. Restoring the DCT coefficients through QP ₈ , the second decoder 157 performs the modified basic quantization level 'Level ₈ ' value transmitted through the base layer, the basic quantization coefficient QP ₈ , and the extended index transmitted through the extension layer ( Using R), the extended quantization level Level _N is obtained as shown in Equation 5 below.

과 같이 구할 수 있다.From the recovered extended quantization level Level _N , the DCT coefficients of the N-bit decoder are

Can be obtained as follows.

로 DCT 계수를 복원하고, 10 비트 디코더에서는 QP₈, Level₈, QP₁₀을 이용하여 Level₁₀을 구하고, 구해진 Level₁₀에 QP₁₀을 곱하여 DCT 계수를 복원한다.In other words, taking a 10-bit codec as an example, on the encoder side, the extended quantization level 'Level ₁₀ ' quantized to QP ₁₀ is transformed into a modified basic quantization level 'Level ₈ ', and the basic quantization level and the basic quantization coefficient modified by the base layer are Transmits an extension index (R) to the extension layer. On the other hand, on the decoder side, on the 8-bit decoder,

In a restore DCT coefficients, 10-bit decoder QP _8, Level _8, by using the QP ₁₀ to obtain a Level _10, the QP is multiplied by ₁₀ to ₁₀ Level obtained to recover the DCT coefficient.

Specifically, in the second encoder 117, when the DCT coefficient is '482' and the extended quantization coefficient QP ₁₀ is '13', the base layer has a modified default quantization level "Level ₈ " and '40' and a basic quantization coefficient. A scalable bitstream including '3', which is QP ₈ and '1', which is an extended index (R) value, is formed and transmitted to the extension layer.

Meanwhile, the first decoder 153 receiving the scalable bitstream obtains '120' (= 40 X 3) as the reconstructed DCT coefficients, and the second decoder 157 restores the extended quantization level Level ₁₀ to '37. And the restored DCT coefficient is '481' (= 37 X 13).

Meanwhile, a process of obtaining a scalable bitstream by changing an image format will be described below.

When the image formats of the first encoder 113 and the second encoder 117 are different from each other, a scalable bitstream is formed by applying a concept of spatial scalability. For example, when the video format of the first encoder 113 is 4: 2: 0 and the video format of the second encoder 117 is 4: 2: 2, the color difference before input to the first encoder 113 is shown. The down-sampling of the block in the vertical direction is performed 1/2 times to reconstruct the 4: 2: 0 image format. The reconstructed 4: 2: 0 image is encoded by the first encoder 113 and forms a base layer bitstream. On the other hand, before being input to the second encoder 117, up-double sampling is performed in the vertical direction with respect to the reconstructed image of the 4: 2: 0 image transmitted to the base layer, and the up-sampling result is obtained. Obtain the color difference image between 4: 2: 2 reconstructed image and 4: 2: 2 original image. The obtained color difference image is encoded together with the coded block pattern (CBP) in the second encoder 117 to form an extended layer bitstream.

On the other hand, in another example, when the video format of the first encoder 113 is 4: 2: 0 and the video format of the second encoder 117 is 4: 4: 4, it is input to the first encoder 113. Prior to this, 1/2 times down sampling is performed on the color difference block in the horizontal and vertical directions to reconstruct the 4: 2: 0 image format. The reconstructed 4: 2: 0 image is encoded by the first encoder 113 and forms a base layer bitstream. On the other hand, before input to the second encoder 117, to perform the up-sampling (up sampling) twice in the horizontal and vertical direction for the reconstructed image of the 4: 2: 0 image transmitted to the base layer, The resulting color difference image between 4: 4: 4 reconstructed image and 4: 4: 4 original image is obtained. The obtained color difference image is encoded together with the coded block pattern (CBP) in the second encoder 117 to form an extended layer bitstream.

Here, the CBP used in the base layer encoder (510 of FIG. 5) of the first encoder 113 or the second encoder 117 is 6 bits in the 4: 2: 0 video format, and the 4: 2: 2 video format. In the case of 8 bits, the 4: 4: 4 video format has 12 bits. On the other hand, the CBP used in the enhancement layer encoder (530 of FIG. 5) of the second encoder 117 is performed only for the chrominance block, so that the 4: 2: 2 image format is 2 bits, which is 4: 4: 4. In case of video format, it consists of 4 bits.

FIG. 5 is a block diagram illustrating a configuration of a video encoding apparatus according to a first embodiment of the present invention, including a base layer encoder 510, an enhancement layer encoder 530, and a bitstream combiner 550. Is done. The first embodiment of the image encoding apparatus may be applied when the encoder and the decoder have different bit depths.

Referring to FIG. 5, the base layer encoder 510 encodes image data to generate a base layer bitstream supporting a bit depth corresponding to a base bit, and the base layer bitstream includes a modified base quantization level and a basic quantization. Coefficients are included. Here, the modified basic quantization level is derived from the extended quantization level generated during quantization during the encoding process of the enhancement layer encoder 530.

The enhancement layer encoder 530 encodes the image data to generate an enhancement layer bitstream supporting bit depths corresponding to the extension bits, and the extension layer bitstream includes only the extension index R as shown in FIG. 3B. The quantization level is not included.

The bitstream combiner 550 combines the base layer bitstream and the enhancement layer bitstream independently of each other to generate a scalable bitstream having the syntax illustrated in FIG. 2.

6 is a block diagram showing a configuration according to a first embodiment of an image decoding apparatus according to the present invention, which includes a bitstream analyzer 610, a basic decoding unit 620, and an expansion decoding unit 680. The extended decoding unit 680 includes a base layer decoder 630, an extended layer decoder 650, and a bit depth recovery unit 670.

Referring to FIG. 6, the bitstream analyzer 610 analyzes the received bitstream to determine whether the received bitstream is a scalable bitstream according to whether an extension layer identifier exists.

If the received bitstream is not the scalable bitstream, the basic decoding unit 620 performs decoding using the quantization level and the quantization coefficient included in the received bitstream.

When the received bitstream is a scalable bitstream having an extended bit depth, the extended decoding unit 680 includes a modified basic quantization level and a basic quantization coefficient included in the base layer bitstream among the scalable bitstreams, and an extension layer bit. Decoding is performed using an extension index that compensates for the difference bit depth between the base bit depth and the extension bit depth included in the stream. This will be described in more detail as follows.

In the extended decoding unit 680, the base layer decoder 630 decodes the base layer bitstream separated from the scalable bitstream to obtain a modified base quantization level and a base quantization coefficient, thereby obtaining a bit depth recovery unit 670. To provide.

The enhancement layer decoding unit 650 decodes the enhancement layer bitstream separated from the scalable bitstream, and provides the bit depth reconstruction unit 670 with an extension index R obtained from the header of the picture level of the enhancement layer.

The bit depth reconstruction unit 670 uses the modified base quantization level and the basic quantization coefficient provided from the base layer decoding unit 630 and the extension index R provided from the enhancement layer decoding unit 650 to store the extended bits. Restoring the corresponding bit depth, restoring the DCT coefficients using the extended quantization level and the extended quantization coefficient corresponding to the restored bit depth, and performing a subsequent decoding process such as inverse transform to generate an extended reconstructed image.

7 is a block diagram illustrating a configuration of a video encoding apparatus according to a second embodiment of the present invention, wherein a first base layer encoder 710, a first enhancement layer encoder 715, and a bit depth converter 720 are shown. ), A down sampling unit 725, a second base layer encoder 730, a base layer decoder 735, an upsampling unit 740, a bit depth recovery unit 745, a subtraction unit 750, a second The enhancement layer encoder 755 and the bitstream combiner 760 are included. The second embodiment of the video encoding apparatus may be applied when the encoder and the decoder have different bit depths and video formats. Here, the first base layer encoder 710, the bit depth converter 720, the down sampling unit 725, and the second base layer encoder 730 form the base layer encoding unit 765. Meanwhile, the first enhancement layer encoder 715, the color difference image generator 770, and the second enhancement layer encoder 755 form an enhancement layer encoding unit. Meanwhile, the color difference image generating unit 770 includes a bit depth converter 720, a down sampling unit 725, a second base layer encoder 730, a base layer decoder 735, and an upsampling unit 940. , A bit depth recovery unit 745, and a subtraction unit 750.

Referring to FIG. 7, the first base layer encoder 710 encodes a luminance block of image data to generate a luminance block bitstream of a base layer supporting a bit depth corresponding to a base bit, and a luminance block of the base layer. The bitstream includes the modified base quantization level and the base quantization coefficient. Here, the modified basic quantization level is derived from the extended quantization level generated during quantization during the encoding process of the enhancement layer encoder 530.

The first enhancement layer encoder 715 encodes the luminance block of the image data to generate a luminance block bitstream of the enhancement layer that supports the bit depth corresponding to the extension bit, and the luminance block bitstream of the enhancement layer is shown in FIG. The expansion index (R) is included.

The bit depth converter 720 divides the color difference block of the image data into 2 ^{n2 - n1} to convert the bit depth. Here, n2 represents an extended bit and n1 represents a basic bit.

The down sampling unit 725 performs down sampling on the color difference block in which the bit depth is converted by the bit depth converter 720. At this time, downsampling is performed only in the vertical direction or downsampling is performed in the horizontal and vertical directions according to the video format to be supported. For example, when the image format of the input image data is 4: 2: 2, the down sampling unit 725 performs 1/22 down sampling in the vertical direction with respect to the color difference block to perform 4: 2 down sampling. : 0 Reconstruct the video format. In addition, when the image format of the input image data is 4: 4: 4, the down sampling unit 725 performs 1/2 times down sampling on the color difference block in the horizontal and vertical directions to perform 4: 2 down sampling. : 0 Reconstruct the video format.

The second base layer encoder 730 encodes the color difference block provided from the down sampling unit 725 to generate a color difference block bitstream of the base layer that supports the first image format.

The base layer decoder 735 decodes the color difference block of the encoded first image format. The up sampling unit 740 performs up sampling on the color difference block of the decoded first image format. At this time, upsampling is performed in response to the down sampling unit 725. That is, upsampling is performed only in the vertical direction or upsampling is performed in the horizontal and vertical directions according to the video format to be supported.

The bit depth reconstruction unit 745 uses the extension index R obtained by the first enhancement layer encoder 715 to determine the bit depth of the color difference block of the decoded first image format provided from the upsampling unit 745. Restore Like the luminance block, the bit depths may be restored by applying the above Equations 3 to 5.

The subtractor 750 may extract a color difference image between the reconstructed color difference block of the second or third image format provided from the bit depth reconstruction unit 740 and the color difference block of the original image of the input second or third image format. Obtain The second enhancement layer encoder 755 encodes the color difference image to generate a color difference block bitstream of the enhancement layer.

The bitstream combiner 760 generates a base layer bitstream by combining the luminance block bitstream of the base layer and the color difference block bitstream of the base layer, and generates the luminance block bitstream of the enhancement layer and the color difference block bitstream of the enhancement layer. By combining to generate an enhancement layer bitstream, and combining the base layer bitstream and the enhancement layer bitstream independently of each other to generate a scalable bitstream as an example in FIG.

8 is a block diagram showing a configuration according to a second embodiment of an image decoding apparatus according to the present invention, which is comprised of a bitstream analyzer 810, a basic decoding unit 815, and an expansion decoding unit 895. The decoding unit 895 includes a first base layer decoder 820, a first enhancement layer decoder 830, a first bit depth recovery unit 840, a second base layer decoder 850, and a second extension layer. The decoder 860 includes an upsampling unit 870, a second bit depth reconstructor 880, and an adder 890. Here, the second base layer decoder 850, the upsampling unit 870, and the second bit depth reconstructor 880 constitute a basic color difference reconstructed image generator 895.

Referring to FIG. 8, the bitstream analyzer 810 analyzes the received bitstream to determine whether the received bitstream is a scalable bitstream according to whether an extension layer identifier exists.

If the received bitstream is not a scalable bitstream, that is, the basic decoding unit 815 has a basic bit depth and a first image format, the basic decoding unit 815 uses the quantization level and the quantization coefficient included in the received bitstream. Decrypt the block and the chrominance block.

The extended decoding unit 895 is a modified basic quantization included in the base layer bitstream of the scalable bitstream when the received bitstream is a scalable bitstream having an extended bit depth and a second video format or a third video format. Decoding the luminance block using the level, the basic quantization coefficient, and an expansion index that compensates for the difference bit depth between the basic bit depth and the extended bit depth included in the enhancement layer bitstream, and performs decoding of the second or third image format. Decode the chrominance block. This will be described in more detail as follows.

The first base layer decoder 820 decodes the luminance block bitstream of the base layer separated from the scalable bitstream and provides the modified base quantization level and the basic quantization coefficient to the first bit depth reconstruction unit 840.

The first enhancement layer decoder 830 decodes the luminance block bitstream of the enhancement layer among the scalable bitstreams, and provides an extension index R obtained as a result of the decoding to the first bit depth reconstruction unit 840.

The first bit depth reconstructor 840 includes a modified base quantization level and a basic quantization coefficient provided from the first base layer decoder 820, and an extension index R provided from the first enhancement layer decoder 830. Restores the bit depth corresponding to the extended bit, restores the DCT coefficients using the extended quantization level and the extended quantization coefficient corresponding to the restored bit depth, and performs a subsequent decoding process such as inverse transform to obtain the extended reconstructed image. To produce.

The second base layer decoder 850 generates color difference data of the base layer by decoding the color difference block bitstream of the base layer among the scalable bitstreams.

The second enhancement layer decoder 860 decodes the color difference image of the enhancement layer in the scalable bitstream and provides the decoded color difference image to the adder 890.

The upsampling unit 870 performs upsampling on the color difference data of the base layer provided from the second base layer decoder 850 and provides it to the second bit depth reconstruction unit 880. At this time, upsampling is performed only in the vertical direction or upsampling is performed in the horizontal and vertical directions according to the image format used in the enhancement layer during encoding. That is, when the image format of the input image data is 4: 2: 2, the upsampling unit 870 performs twice the upsampling in the vertical direction with respect to the color difference block of the decoded 4: 2: 0 image format. Do this. In addition, when the image format of the input image data is 4: 4: 4, the upsampling unit 870 doubles up-sampling in the horizontal and vertical directions with respect to the color difference block of the decoded 4: 2: 0 image format. sampling).

The second bit depth reconstructor 880 uses the extended index R obtained by the first enhancement layer encoder 830 to determine the color difference of the decoded second or third image format provided from the upsampling unit 870. Restore the bit depth of the block. Like the luminance block, the bit depths may be restored by applying the above Equations 3 to 5.

The adder 890 adds the color difference data of the base layer in which the bit depth and image format are matched by the second bit depth reconstructor 880 and the color difference image decoded by the second enhancement layer decoder 860 to expand the extended layer. Create a color difference reconstructed image of.

A final extension reconstruction image is generated by using the luminance reconstruction image of the extension layer generated by the first extension layer decoder 830 and the color difference reconstruction image of the extension layer generated by the adder 890.

In the above-described embodiment, at least one of a bit depth or an image format supports two codecs different from each other based on an embodiment in which a scalable bitstream has one basic bitstream and one extended bitstream. However, it is also possible to support more than one codec by having multiple extension bitstreams. In addition, in the present embodiment, although the value of the basic bit is larger than the extension bit in the bit depth as an example, various design changes are possible even when the direction of changing the bit depth, that is, the basic bit is smaller than the extension bit. In addition, various design changes are possible according to the shape of the first to third image formats. In addition, in the present exemplary embodiment, the expansion index R is allocated for each picture level. However, the expansion index R may be allocated for each slice level, for each macroblock level, or for each block level.

The present invention can also be embodied as computer-readable codes on a computer-readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like. On the other hand, another example of the recording medium may be a buffer for temporarily storing the bitstream at the rear of the image encoding apparatus or a buffer for temporarily storing the bitstream at the front of the image decoding apparatus. The computer readable recording medium may also be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner. And functional programs, codes, and code segments for implementing the present invention can be easily inferred by programmers skilled in the art to which the present invention pertains.

In the drawings and specification, there have been disclosed preferred embodiments. Although specific terms have been employed herein, they are used for purposes of illustration only and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

According to the present invention as described above, in order to provide a new video codec with guaranteed forward compatibility, the scalable video encoder generates a scalable bitstream consisting of a base layer bitstream and an extension layer bitstream, and a scalable bitstream The existing base decoder that receives Rx performs decoding using the base layer bitstream obtained from the scalable bitstream, and the improved decoder uses both the base layer bitstream and the enhancement layer bitstream included in the scalable bitstream. By performing the decoding, there is an advantage that the improved video codec and the existing video codec are compatible with each other and coexist. Accordingly, in particular, there is an advantage that the existing window media video (WMV) codec or the VC-1 codec and a video codec supporting a new bit depth and a new video format can be used together.

As described above, the video codec according to the present invention provides forward compatibility, so that the video codec of the present invention can be used not only in an improved video codec installed in a wired or wireless electronic device such as a mobile phone, a DVD player, a portable music player, or a car stereo, but also in an existing basic video codec. It can be applied to various video codecs regardless of the bit depth or image format supported.

Claims (21)

Obtaining a modified base quantization level using the extended quantization level obtained from the extended quantization coefficient, and generating a base layer bitstream including the modified base quantization level and the base quantization coefficient; Obtaining an extension index that compensates for the difference bit depth between the base bit depth and the extension bit depth from the extension quantization coefficient, and generating an extension layer bitstream including the extension index; And And combining the base layer bitstream and the enhancement layer bitstream, and generating a scalable bitstream including an extension layer identifier. The image encoding method of claim 1, wherein the enhancement layer identifier is included in at least one of a sequence level, a GOP level, a picture level, a macroblock level, and a block level. The video encoding method of claim 1, wherein the enhancement layer identifier is included in a spare area of the base layer bitstream. The image encoding method of claim 1, wherein the enhancement layer identifier is at least one of an additional profile and a level, and the difference bit depth. The method of claim 1, wherein the expansion index is [-T, T-1] or [-T + 1, T], where T is 2 ^(EB) / 2, B is a basic bit depth, and E is an extended bit depth. Video encoding method). The method of claim 1, wherein the expansion index is [-T, T-1] and [-T + 1, T], where T is 2 ^(EB) / 2, B is a basic bit depth, and E is an extended bit depth. And a different range on a frame-by-frame basis. The method of claim 1, wherein the modified basic quantization level is Level _MB = Level _E + Round (RX Level _E / (QP _B X 2 ^(EB) ) or Level _MB = Round ((QP _E X Level _E ) / (QP _B X 2 ^(EB) ) (Here, Level _MB Is the modified basic quantization level, Level _E is the extended quantization level, R is the extended index, Level _E is the extended quantization level, QP _B is the basic quantization coefficient, QP _E is the extended quantization coefficient, B is the basic bit depth, and E is the extended bit. Each shows depth) Video encoding method, characterized in that Determining whether the received bitstream is a scalable bitstream; If the received bitstream is not a scalable bitstream, decoding using the quantization level and the quantization coefficient included in the received bitstream; And If the received bitstream is a scalable bitstream, the difference bit depth between the modified base quantization level and the base quantization coefficient included in the base layer bitstream, and the base bit depth and the extended bit depth included in the enhancement layer bitstream is determined. And performing decoding using a compensating expansion index. 10. The method of claim 8, wherein the extended layer identifier determines whether the received bitstream is a scalable bitstream. The method of claim 9, wherein the enhancement layer identifier is included in at least one of a sequence level, a GOP level, a picture level, a macroblock level, and a block level. 10. The method of claim 9, wherein the enhancement layer identifier is included in a spare area of the base layer bitstream. 10. The method of claim 9, wherein the enhancement layer identifier is at least one of an additional profile and a level and the difference bit depth. A modified base quantization level is obtained using the extended quantization level obtained from the extended quantization coefficient, and a luminance block bitstream of the base layer including the modified base quantization level and the base quantization coefficient and color difference data supporting the first image format. Generating a color difference block bitstream of a base layer; Obtaining an extension index that compensates for the difference bit depth between the base bit depth and the extension bit depth from the extension quantization coefficient, and a luminance block bitstream of the extension layer including the extension index and a reconstructed color difference of a second or third image format Generating a chrominance block bitstream of the enhancement layer by using chrominance difference data between the block and the original chrominance block of the second or third image format; And And combining the luminance block and the chrominance block bitstream of the base layer with the luminance block and the chrominance block bitstream of the enhancement layer, and generating a scalable bitstream including an extension layer identifier. Way. The method of claim 13, wherein the enhancement layer identifier is an image format and at least one of an additional profile and a level and the difference bit depth. Determining whether the received bitstream includes an enhancement layer identifier; If the received bitstream does not include an extended layer identifier, performing a decoding of a luminance block and a chrominance block according to a first image format by using a quantization level and a quantization coefficient included in the received bitstream; And When the received bitstream includes the enhancement layer identifier, the modified basic quantization level and basic quantization coefficient included in the luminance block bitstream of the base layer, and the basic bit depth included in the luminance block bitstream of the enhancement layer Difference between Extended Bit Depth A luminance block is decoded using an extended index that compensates for a bit depth, and a color difference is obtained by using color difference data and color difference data that support a first image format included in a color difference block bitstream of a base layer. And decoding the block. A base layer encoder for obtaining a modified base quantization level using an extended quantization level and generating a base layer bitstream including the modified base quantization level and the base quantization coefficient; An extended layer for obtaining the extended quantization level from the extended quantization coefficient, an extended index for compensating the difference bit depth between the basic bit depth and the extended bit depth, from the extended quantization coefficient, and generating an extended layer bitstream including the extended index An encoder; And And a bitstream combiner which combines the base layer bitstream and the enhancement layer bitstream and generates a scalable bitstream including an extension layer identifier. A modified base quantization level is obtained by using an extended quantization level, and a luminance block bitstream of a base layer including the modified base quantization level and a base quantization coefficient and color difference data of the base layer using color difference data supporting a first image format. A base layer coding unit for generating a block bitstream; Obtaining the extension quantization level from the extended quantization coefficient, obtaining an extension index that compensates the difference bit depth between the base bit depth and the extension bit depth from the extension quantization coefficient, and obtaining a luminance block bitstream of the extension layer including the extension index; An extension layer encoding unit for generating a color difference block bitstream of an enhancement layer by using color difference difference data between the restored color difference block of the second or third image format and the original color difference block of the second or third image format; And And a bitstream combiner for combining the luminance block and the chrominance block bitstream of the base layer with the luminance block and the chrominance block bitstream of the enhancement layer, and generating a scalable bitstream including an extension layer identifier. Video encoding device. A bitstream analyzer to determine whether the received bitstream is a scalable bitstream; A basic decoding unit for performing decoding using the quantization level and the quantization coefficient included in the received bitstream when the received bitstream is not a scalable bitstream; And If the received bitstream is a scalable bitstream, the difference bit depth between the modified base quantization level and the base quantization coefficient included in the base layer bitstream, and the base bit depth and the extended bit depth included in the enhancement layer bitstream is determined. And an extended decoding unit for performing decoding by using an extended index for compensating. A bitstream analyzer to determine whether the received bitstream includes an enhancement layer identifier; A basic decoding unit for decoding a luminance block and a chrominance block according to a first image format by using a quantization level and a quantization coefficient included in the received bitstream when the received bitstream does not include an extended layer identifier ; And When the received bitstream includes the enhancement layer identifier, the modified basic quantization level and basic quantization coefficient included in the luminance block bitstream of the base layer, and the basic bit depth included in the luminance block bitstream of the enhancement layer Difference between Extended Bit Depth A luminance block is decoded using an extended index that compensates for a bit depth, and a color difference is obtained by using color difference data and color difference data that support a first image format included in a color difference block bitstream of a base layer. And an extended decoding unit for decoding a block. A computer-readable recording medium describing a program capable of executing the video encoding method according to claim 1. A computer-readable recording medium describing a program capable of executing the video decoding method according to claim 8 or 15.

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