CN101663896A - Method and apparatus for encoding video data, method and apparatus for decoding encoded video data and encoded video signal - Google Patents

Abstract

For two or more versions of a video with different spatial, temporal or SNR resolution, scalability can be achieved by generating a base layer (BL) and an enhancement layer (EL). When a version of a video is available that has higher color bit depth than can be displayed, a common solution is tone mapping. A more efficient compression method is proposed for the case where the two or more versionswith different color bit depth use different color encoding. The present invention is based on joint inter-layer prediction among the available color channels. Thus, color bit depth scalability can also be used where the two or more versions with different color bit depth use different color encoding. In this case the inter-layer prediction is a joint prediction based on all color components. Prediction may also include color space conversion and gamma correction.

Description

Method and device for encoding video data, method and device for decoding encoded video data and encoded video signal

technical field

The present invention relates to digital video coding. More specifically, the present invention relates to a method and a device for encoding video data, a method and a device for decoding encoded video data and a corresponding encoded video signal.

Background technique

In recent years, digital images/videos with a bit depth higher than 8 bits have become increasingly desirable in many application areas such as medical image processing, digital cinema workflows in production and post-production, and home theater related applications. State of the art image/video coding techniques are also advancing high bit depth coding. JVT standardized high bit-depth encoding with H.264 Fidelity Range Extensions (FRExt), which supports bit depths up to 14 bits and chroma sampling up to 4:4:4. On the other hand, moving picture JPEG2000 (Part 3) supports up to 32 bits per component.

Potentially, color bit depth scalability is very useful considering the fact that traditional 8-bit and high-bit digital imaging systems will co-exist in the market for a long time to come. There are several ways to handle the coexistence of 8-bit video and high-bit video. A first solution is to only give a high-bit encoded bitstream and enable the tone mapping method to give an 8-bit representation for a standard 8-bit display device. A second solution is to give a simulcast bitstream comprising an 8-bit encoded bitstream. Which bitstreams are chosen for decoding is a decoder preference. This means, for example, that a stronger decoder supporting the AVC High 10 profile can decode and output 10-bit video, while a conventional decoder can only output 8-bit video. Typically, the first solution is not compatible with H.264/AVC 8-bit decoders. The second solution is compatible with all current standards, but requires more overhead. However, a good compromise between bit reduction and backward standards compatibility can be a scalable solution. SVC (also known as the scalable extension of H.264/AVC) allows for support of bit depth scalability.

There hasn't been much research into methods for color bit depth scalability. Unlike spatial scalability, which can be achieved using spatial upsampling between different resolutions, it can be challenging to encode additional information from the reconstructed low-bit picture to the original high-bit picture, e.g., For 8-bit to 10-bit scalability, the additional information can also be up to 10 bits due to quantization errors introduced when encoding 8-bit pictures. Inter-layer bit-depth prediction is also not similar to FGS using bit-plane scanning in the transform domain.

Furthermore, different possibilities for color coding using different types of color spaces, chromaticity coordinates and gamma correction (eg RGB, YCrCb, HSV, XYZ) are known. Various conversion algorithms exist.

When a version of the video is available with a higher color bit depth than can be displayed, a general solution is tone mapping, where high dynamic range is reduced to a lower color bit depth, while maintaining contrast. When two or more video versions with different spatial, temporal or SNR resolutions are available, scalability can be achieved by creating a base layer (BL) and an enhancement layer (EL) to be combined with the BL.

However, an inherent problem with the tone mapping approach is that more data is transmitted than necessary. For situations where two or more versions with different color bit depths are encoded with different colors, more efficient compression methods are required.

Contents of the invention

The invention is based on the recognition of the fact that, generally in bit-depth scalable video coding, it is advantageous to perform joint inter-layer prediction between the available color channels. Thus, according to the invention, color bit depth scalability can also be used in cases where two or more versions with different color bit depths use different color encodings. In this case, the inter-layer prediction is based on the joint prediction of all color components. Prediction can also include color space conversion and gamma correction.

According to one aspect of the present invention, a method for encoding video data comprising base layer data and enhancement layer data, wherein the base layer and enhancement layer data comprises a plurality of color channels, e.g., Y, Cr, Cb or R, G, B, and the base layer and the enhancement layer data have different bit depths, the method includes the following steps: encoding the base layer data; respectively targeting the color channels, according to the base layer data to enhance the layer data predicting; and based on said predicted enhancement layer data, encoding the enhancement layer data separately for color channels, wherein, in at least one mode, jointly predicting each enhancement layer color channel from all available base layer color channels, said The method further comprises, for at least one enhancement layer color channel, the steps of: generating residual data which is the difference between the original enhancement layer color channel data and the predicted color channel data; encoding the original enhancement layer color channel data ; encoding residual data; selecting encoded raw enhancement layer color channel data, residual data, or encoded residual data for at least one enhancement layer color channel, wherein the selection is consistent with the selection of other enhancement layer color channels don't care; and providing the selected enhancement layer color channel data as enhancement layer output data and providing an indication of the selected encoding mode involving said enhancement layer color channel.

According to another aspect of the present invention, a method for decoding encoded video data having BL and EL data comprises the steps of: extracting BL data and EL data from encoded video data, wherein the BL data Both the and EL data include separate data for multiple color channels; at least for the first color channel of the enhancement layer, an indication of the encoding mode is extracted; base layer data for multiple color channels is decoded; base layer based on decoding predicting EL data, wherein, in at least one mode, jointly predicting each EL color channel from all available BL color channels; decoding EL data for multiple color channels, wherein a residual is obtained, and at least decoding for the first color channel according to the indicated encoding mode using the indication; and reconstructing EL data for a plurality of color channels based on the predicted EL data and the residual.

According to yet another aspect of the present invention, an apparatus for encoding video data comprising base layer data and enhancement layer data, wherein the base layer data and enhancement layer data comprise a plurality of color channels, and the base layer having a different bit depth from the enhancement layer, the apparatus comprising: means for encoding the base layer; means for predicting the enhancement layer from the base layer, for color channels respectively; enhancement layer, means for encoding the enhancement layer separately for color channels (e.g., R, G, B), wherein, in at least one mode, each enhancement layer color channel is jointly predicted from all available base layer color channels, so The apparatus further comprises, for at least one enhancement layer color channel: means for generating a residual, the residual being the difference between the original enhancement layer color channel image and the predicted color channel image; means for encoding an image; means for encoding a residual; means for selecting an encoded original enhancement layer color channel image, a residual, or an encoded residual for at least one enhancement layer color channel, wherein the said selection is independent of selection of other enhancement layer color channels; and means for providing selected enhancement layer color channel data as enhancement layer output data and providing an indication of a selected encoding mode involving said enhancement layer color channel.

According to another aspect of the present invention, an apparatus for decoding encoded video data having base layer data and enhancement layer data includes: for extracting base layer data and enhancement layer data from encoded video data The device, wherein, each of base layer data and enhancement layer data includes separation data of a plurality of color channels; means for extracting an indication indicating a coding mode at least for a first color channel of an enhancement layer; means for decoding base layer data of color channels; means for predicting enhancement layer data based on decoded base layer data, wherein, in at least one mode, for each enhancement layer according to all available base layer color channels joint prediction of color channels; means for decoding enhancement layer data of a plurality of color channels, and obtaining a residual, at least for said first color channel, according to the indicated coding mode, using said indication decoding; and means for reconstructing enhancement layer data for a plurality of color channels based on the predicted enhancement layer data and the residual.

According to another aspect, an encoded video signal includes base layer data and enhancement layer data, wherein the base layer data includes a plurality of color channels encoded in a first color and the enhancement layer data includes another color channel encoded in a second color. The plurality of color channels, the base layer data and the enhancement layer data have different color bit depths, and the signal further includes an indication of a coding mode indicating, for at least the first enhancement layer color channel, that it includes a coded residual The data is also coded macroblock data.

A particular advantage of the proposed encoding solution is that it complies with the H.264/AVC standard and is compatible with the kind of scalability supported in the H.264/AVC Scalable Extension (SVC).

At least one implementation proposes an H.264/AVC-compatible color bit-depth scalable coding solution, where low-bit (typically 8-bit) and high-bit (e.g., 10, 12 or 14-bit) sequences are separately coded as basic layers and enhancement layers. In one embodiment of the disclosed solution, inter-layer prediction between low-bit BL and high-bit EL is done at the macroblock (MB) level to exploit redundancy between low-bit and high-bit representations of the same video. Remain. Furthermore, the inter-layer color bit depth prediction for each color channel (eg, Y, Cb or Cr) is not independent. Instead, it is performed in a joint manner, whereby all (typically three) color channels of the reconstructed co-located base layer MB are used to determine the predicted version of each channel of the enhancement layer MB by joint inter-layer color bit depth prediction.

Advantageous embodiments of the invention are disclosed in the appended claims, the following description and the drawings.

Description of drawings

Example embodiments of the invention are described with reference to the accompanying drawings, in which

Figure 1 is a framework for color bit depth scalable coding;

Figure 2 is the joint inter-layer prediction in intra-frame coding;

Fig. 3 is joint inter-layer prediction in inter coding; and

Figure 4 is an adaptive inter-layer color bit depth prediction in inter-frame coding.

Detailed ways

Without loss of generality, assume that there are two layers of color bit depth scalability: one layer is an 8-bit video sequence, and the other layer is a 10-bit video sequence. For at least one implementation, the proposed framework for color bit-depth scalable coding is shown in FIG. 1 .

The scalable encoder Enc generates a bit-depth scalable bit-stream SBS in which BL and EL coded pictures are multiplexed. The scalable decoder Dec can generate 8-bit video by decoding only the BL bitstream, or 10-bit video by decoding the entire scalable bitstream SBS. Providing multiple versions of the same visual content with different bit depths to different clients enables device adaptation through the proposed color bit depth scalable encoding.

It should be emphasized that the two input sequences, 8-bit and 10-bit video sequences, may differ not only in bit depth. Thus, inter-layer predictions can include, for example:

1) Adjustments for different gamma corrections and different chromaticity coordinates, for example, conversion from RGB color space (Rec.BT.601) to RGB color space (Rec.BT.709), RGB color space (Rec.BT.601 ) to device-specified RGB color space conversion.

2) Color space conversion (including adjustments for different gamma corrections), for example, conversion from XYZ color space to sRGB color space, conversion from YCbCr color space (Rec.BT.709) to RGB color space (Rec.BT.709) Conversion, conversion from YCbCr color space (Rec.BT.601) to YCbCr color space (Rec.BT.709).

3) Hue format conversion, for example, YCbCr 4:2:0 to YCbCr 4:2:2, YCbCr 4:2:0 to YCbCr 4:4:4,

4) color correction, and

5) A combination of the above items.

Cases 1), 2) and 3) may involve nonlinear transformations, while in case 4), the relationship between the two considered sequences is as complex as a look-up table (LUT). Furthermore, case 2) can also involve processing across different color channels. For example, the conversion from YCbCr color space (Rec.BT.709) to RGB color space (Rec.BT.709) is mathematically modeled as a matrix operation such that for each pixel, a linear combination of the values of Y, Cb, and Cr to calculate the value of R (G or B). At least one implementation proposes joint inter-layer prediction involving processing across different color channels, which can be done at picture level or MB level.

In the following, an encoding/decoding method for realizing joint inter-layer color bit depth prediction is given. In this section, details of various implementations are provided. Such implementations may also be discussed in other sections. At least one implementation provides a technical solution for AVC compatible joint inter-layer prediction for color bit depth scalability. The corresponding diagrams of a color bit depth scalable encoder in intra and inter coding with MB-level inter-layer color bit depth prediction are shown in FIGS. 2 and 3 . Without loss of generality, it is assumed that inter-layer color bit depth prediction involves conversion from YCbCr color space (Rec.BT.709) to RGB color space (Rec.BT.709). The decoding process is the inverse of the encoding process in intra and inter encoding.

With regard to Figures 2 and 3, it should be noted that the three rate-distortion optimized blocks (RDOs) RDOr, RDOg, RDOb are independent of each other. That is, for each color channel, it can be decided separately whether to directly intra/inter code the enhancement layer without prediction, or to perform prediction in some other way, produce a residual, and directly intra / Inter coding, or transform (T), quantization (Q) and entropy coding before the rate-distortion optimization decision. During RDO, the best trade-off between data rate and distortion is determined and the corresponding signal is selected. In case of inter prediction, as shown in Fig. 3, motion vectors 305r, 305g, 305b from the base layer MB may be used in the enhancement layer.

An indication of the selected encoding type may be included in the syntax (eg, in the MB type field).

Figure 4 shows the use of additional skip modes in each EL branch such that the RDO has 4 inputs: A new mode (so-called skip mode) is introduced to skip the EL residual signal. If skip mode is selected via RDO, the EL does not contain the bits of the current MB. At the decoder, only the BL MB is decoded, and the inter-layer color bit depth prediction is performed to obtain the reconstructed ELMB. Intra-layer prediction works in principle in the same way.

The following list provides an abbreviated listing of the various implementations. This list is not exhaustive, but only provides a brief description of a small number of the many possible implementations.

2 and 3, a method for encoding video data including base layer data and enhancement layer data, wherein the base layer and enhancement layer data includes multiple color channels (e.g., Y, Cr, Cb or R, G, B), and, base layer and enhancement layer data have different bit depths, the method comprises the following steps:

encoding base layer data 201y, 201cr, 201cb; predicting enhancement layer data from the base layer data for color channels respectively; and based on said predicted enhancement layer data, respectively for color channels (e.g. R, G, B) encode the enhancement layer data,

Wherein, in at least one mode, each enhancement layer color channel is jointly predicted 200 according to all available base layer color channels, and the method further comprises the following steps for at least one (or some or all) enhancement layer color channels :

generating residual data R _res , B _res , G _res , said residual data being the difference between the original enhancement layer color channel data R _EL , G _EL , B _EL and the predicted color channel data;

Encoding 202r, 202g, 202b raw enhancement layer color channel data;

Encoding residual data 203r, 203g, 203b, 204r, 204g, 204b;

Selection of RDO _r , RDO _g , RDO _b encoded raw enhancement layer color channel data, residual data, or encoded residual data for at least one enhancement layer color channel, wherein said selection is consistent with selection of other enhancement layer color channels irrelevant; and

Selected enhancement layer color channel data is provided as enhancement layer output data and an indication of a selected encoding mode involving said enhancement layer color channel is provided.

In one embodiment, the base layer and enhancement layer use different color coding (e.g., Y, CR, CB and R, G, B), and the inter-layer prediction 200 also includes color space conversion for intra and inter coding .

In one embodiment, the color space conversion includes conversion from YCbCr color space (Rec. BT.709) to RGB color space (Rec. BT.709).

In one embodiment, encoding the residual comprises entropy encoding 204r, 204g, 204b.

In one embodiment, additional coding modes for enhancement layer color channel data include a skip mode 405 at the macroblock level; in skip mode, the enhancement layer data does not contain bits of the corresponding macroblock.

In one embodiment, in the step of selecting RDO _r , RDO _g , RDO _b , said selection is based on data rate and distortion minimization.

In one embodiment, prediction 200 across different color channels is performed at the picture level.

In one embodiment, prediction across different color channels is performed at the macroblock level.

In one embodiment, the method further includes: performing entropy encoding EC _Y,BL , EC _Cb,BL , EC _Cr,BL , EC _Y,EL , EC _Cb,EL for each base layer and enhancement layer color channel respectively , EC _{Cr, EL} .

According to another aspect of the invention, a method for decoding encoded video data having BL data and EL data comprises the steps of:

Base layer data and enhancement layer data are extracted from encoded video data, wherein the base layer data and enhancement layer data each comprise separate data for a plurality of color channels; at least for a first color channel of the enhancement layer, an encoding mode is indicated extracting an indication of; decoding base layer data for a plurality of color channels; predicting enhancement layer data based on the decoded base layer data, wherein, in at least one mode, for each enhancement layer according to all available base layer color channels jointly predicting color channels; decoding enhancement layer data for a plurality of color channels, wherein a residual is obtained and decoding is performed using said indication, at least for said first color channel, according to an indicated coding mode; and based on The predicted enhancement layer data and the residual are used to reconstruct the enhancement layer data of a plurality of color channels.

The following embodiments relate to methods for decoding. In one embodiment, the base layer and the enhancement layer use different color coding (eg, Y, CR, CB or R, G, B), and the prediction step further includes: color space conversion for intra and inter coding.

In one embodiment, the color space conversion includes YCbCr color space to RGB color space conversion.

In one embodiment, decoding the residual comprises entropy decoding.

In one embodiment, additional decoding modes for enhancement layer color channels are employed, including a skip mode at the macroblock level, wherein in skip mode the enhancement layer data does not contain bits of the corresponding macroblock.

In one embodiment, prediction across different color channels is performed at picture level.

In one embodiment, prediction across different color channels is performed at the macroblock level.

In one embodiment, the method further comprises: entropy decoding for each base layer and enhancement layer color channel separately.

According to another aspect, an apparatus for encoding video data comprising base layer data and enhancement layer data, wherein the base layer data and enhancement layer data comprise a plurality of color channels (e.g., Y, CR, CB or R, G, B), and the base layer and the enhancement layer have different bit depths, the device comprising:

means 201y, 201cr, 201cb for encoding the base layer;

means 200 for predicting the enhancement layer from the base layer for the color channels respectively; and

Means for encoding enhancement layers for color channels R, G, B, respectively, based on said predicted enhancement layers, wherein, in at least one mode, jointly predicting 200 each enhancement layer from all available base layer color channels color channels R, G, B, and the device further comprises, for at least one enhancement layer color channel:

means for generating residuals R _res , B _res , G _res , said residuals being the difference between the original enhancement layer color channels R _EL , G _EL , B _EL and the predicted color channel image; means for encoding layer color channel images 202r, 202g, 202b; means for encoding residuals 203r, 203g, 203b, 204r, 204g, 204b; for selecting an encoded original enhancement for at least one enhancement layer color channel means RDO _r , RDO _g , RDO _b of layer color channel images, residuals or coded residuals, wherein said selection is independent of the selection of other enhancement layer color channels; and for providing selected enhancement layer color channel data means for outputting data as an enhancement layer and providing an indication of a selected encoding mode involving color channels of said enhancement layer.

The following embodiments relate to devices for encoding video data.

In one embodiment, the base layer and the enhancement layer use different color codes Y, CR, CB, R, G, B, and the apparatus 200 for performing inter-frame prediction further includes: for intra-frame and inter-frame coding A device that performs color space conversion.

In one embodiment, the color space conversion includes YCbCr color space (Rec. BT.709) to RGB color space (Rec. BT.709) conversion.

In one embodiment, the means for encoding the residual comprises: means for performing entropy encoding 204r, 204g, 204b.

In one embodiment, the apparatus further comprises: means 405 for performing a skip mode as an additional coding mode at the macroblock level for enhancement layer color channels, wherein in skip mode the enhancement layer does not contain the corresponding bits of the macroblock.

According to another aspect of the present invention, an apparatus for decoding encoded video data having base layer data and enhancement layer data includes:

means for extracting base layer data and enhancement layer data from encoded video data, wherein the base layer data and enhancement layer data comprise separate data for a plurality of color channels; for at least a first color channel of the enhancement layer, means for extracting an indication indicating a coding mode; means for decoding base layer data for a plurality of color channels; means for predicting enhancement layer data based on the decoded base layer data, wherein at least one mode, jointly predicting each enhancement layer color channel from all available base layer color channels; means for decoding enhancement layer data of a plurality of color channels, wherein a residual is obtained, and at least for said first a color channel, according to the indicated encoding mode, decoded using said indication; and means for reconstructing enhancement layer data for a plurality of color channels based on predicted enhancement layer data and said residual.

The following embodiments relate to apparatus for decoding encoded video data.

In one embodiment, the base layer and the enhancement layer use different color coding means for Y, CR, CB color spaces or R, G, B color spaces respectively, and the means for predicting further includes: for intra-frame and Means for performing color space conversion in case of inter coding.

In one embodiment, the means for performing color space conversion comprises: means for performing YCbCr color space to RGB color space conversion.

In one embodiment, means for decoding a residual comprises: means for entropy decoding.

In one embodiment, the apparatus further comprises means for performing skip mode decoding at macroblock level as an additional decoding mode for at least one enhancement layer color channel, wherein in skip mode the enhancement Layer data does not contain bits of the corresponding macroblock.

In one embodiment, the means for performing prediction across different color channels operates on a picture level.

In one embodiment, the means for performing prediction across different color channels operates on a macroblock level.

In one embodiment, the apparatus further comprises means for entropy decoding each base layer and enhancement layer color channel respectively.

According to yet another aspect, an encoded video signal comprising base layer data and enhancement layer data, wherein the base layer data comprises a plurality of color channels encoded in a first color, such as Y, Cr, Cb, and the enhancement layer The data includes a plurality of color channels R, G, B encoded in another second color, wherein the base layer data and the enhancement layer data have different color bit depths, and the signal further includes an indication of a coding mode, the coding mode Indicates, at least for the first enhancement layer color channel, whether it comprises encoded residual data or encoded macroblock data.

According to one aspect, joint inter-layer prediction is performed by predicting each color channel of an enhancement layer MB from all (typically three) reconstructed color channels of a co-located base layer MB.

This disclosure describes various implementations. However, features and aspects of the described implementations are also applicable to other implementations. For example, signaling may be implemented using a variety of different techniques including, but not limited to, SPS syntax, other high-level syntax, non-high-level syntax, out-of-band information, and implicit signaling. Additionally, various encoding techniques can be used. Accordingly, although implementations described herein may be described in a specific context, such description should not be viewed as limiting on the features and concepts of such implementation or context.

Implementations described herein may be implemented, for example, as a method or process, an apparatus, or a software program. Even if only discussed in the context of a single form of implementation (eg, discussed only as a method), a discussed implementation or feature may also be implemented in other forms (eg, an apparatus or program). For example, a device can be implemented in suitable hardware, software, and firmware. For example, methods may be implemented in a device such as a computer or other processing device. Furthermore, methods may also be implemented by instructions executed by a processing device or other device, and such instructions may be stored on a computer-readable medium, eg, a CD or other computer-readable storage device, or an integrated circuit.

Implementations may also generate signals formatted to carry information that may, for example, be stored or transmitted, as will be apparent to those skilled in the art. This information may include, for example, instructions for performing a method, or data produced by one of the described implementations. For example, a signal may be formatted to carry as data the value of a particular syntax (or even the syntax instruction itself if syntax is being transmitted). Furthermore, various implementations may be implemented in an encoder or a decoder or both.

Furthermore, other implementations are contemplated by this disclosure. For example, additional implementations can be created by combining, deleting, modifying or supplementing various features of the disclosed implementations.

It will be understood that the present invention has been described by way of example only and modifications of detail may be made without departing from the scope of the invention.

Each feature disclosed in the description and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination. These features may (where appropriate) be implemented in hardware, software, or a combination of both. Where applicable, the connection may be implemented as a wireless connection or a wired connection, and not necessarily a direct or dedicated connection. Reference signs appearing in the claims are by way of illustration only and shall have no limiting effect on the scope of the claims.

Claims (15)

1. A method for encoding video data comprising base layer (BL) data and enhancement layer (EL) data, wherein the base layer and enhancement layer data comprise a plurality of color channels (Y, Cr, Cb , R, G, B), and the base layer and enhancement layer data have different bit depths, the method includes the following steps: - Encoding of base layer data (201y, 201cr, 201cb); - predicting (200) enhancement layer data from base layer data, respectively for said color channels; and - encoding enhancement layer data for said color channels (R, G, B) respectively based on said predicted enhancement layer data; Wherein, in at least one mode, each enhancement layer color channel is jointly predicted (200) according to all available base layer color channels, and the method further includes the following additional steps for at least one enhancement layer color channel: - generating residual data (R _res , B _res , G _res ) which is the difference between the original enhancement layer color channel (R _EL , G _EL , B _EL ) and the predicted color channel data; - encoding (202r, 202g, 202b) of raw enhancement layer color channel data; - encoding the residual data (203r, 203g, 203b, 204r, 204g, 204b); - selection (RDO _r , RDO _g , RDO _b ) of encoded raw enhancement layer color channel data, residual data or encoded residual data for at least one enhancement layer color channel, wherein the selection is related to other enhancement layer color channels The choice of channel is irrelevant; and - providing selected enhancement layer color channel data as enhancement layer output data and providing an indication of a selected encoding mode involving said enhancement layer color channel. 2. The method according to claim 1, wherein the base layer and the enhancement layer use different color coding (Y, CR, CB, R, G, B), and the inter-layer prediction (200) also includes Color space conversion for inter-coding. 3. The method according to claim 2, wherein the color space conversion comprises: conversion from YCbCr color space (Rec. BT.709) to RGB color space (Rec. BT.709). 4. The method of one of the preceding claims, wherein encoding the residual comprises entropy encoding (204r, 204g, 204b). 5. The method according to one of the preceding claims, wherein additional coding modes for enhancement layer color channel data include a skip mode (405) on macroblock level; in skip mode, enhancement layer data does not contain code for bits of the corresponding macroblock. 6. Method according to one of the preceding claims, wherein in said selecting ( _RDOr , _RDOg , _RDOb ) step said selection is based on data rate and distortion minimization. 7. The method according to one of the preceding claims, wherein the prediction (200) across different color channels is performed at picture level. 8. The method according to one of the preceding claims, wherein prediction across different color channels is performed at macroblock level. 9. The method according to one of the preceding claims, further comprising entropy coding (EC _{Y, BL} , EC _{Cb, BL} , EC _{Cr, BL} , EC _{Y, EL} , EC _{Cb, EL} , EC _{Cr, EL} ). 10. A method for decoding encoded video data having BL data and EL data comprising the steps of: - extracting base layer data and enhancement layer data from the encoded video data, wherein both the base layer data and the enhancement layer data comprise separate data for a plurality of color channels; - extracting, at least for the first color channel of the enhancement layer, an indication indicating a coding mode; - Decode base layer data for multiple color channels; - prediction of enhancement layer data based on decoded base layer data, wherein, in at least one mode, each enhancement layer color channel is jointly predicted from all available base layer color channels; - decoding enhancement layer data for a plurality of color channels, wherein a residual is obtained and decoded using said indication, at least for said first color channel, according to the indicated coding mode; and - Reconstructing enhancement layer data for a plurality of color channels based on predicted enhancement layer data and said residual. 11. An apparatus for encoding video data comprising a base layer (BL) and an enhancement layer (EL), wherein the base layer and enhancement layer data comprise a plurality of color channels (Y, Cr, Cb, R , G, B), and the base layer and the enhancement layer have different bit depths, the device includes: - means (201y, 201cr, 201cb) for encoding the base layer; - means (200) for predicting the enhancement layer from the base layer, respectively for the color channels; and - means for encoding the enhancement layer for each color channel (R, G, B) based on said predicted enhancement layer; Wherein, in at least one mode, each enhancement layer color channel (R, G, B) is jointly predicted (200) according to all available base layer color channels, and the device further includes for at least one enhancement layer color channel: - means for generating residuals (R _res , B _res , G _res ) that are the difference between the original enhancement layer color channels (R _EL , G _EL , B _EL ) and the predicted color channel images; - means (202r, 202g, 202b) for encoding raw enhancement layer color channel images; - means for encoding residuals (203r, 203g, 203b, 204r, 204g, 204b); - means (RDO _r , RDO _g , RDO _b ) for selecting a coded original enhancement layer color channel image, a residual or a coded residual for at least one enhancement layer color channel, wherein said selection is related to other enhancement The selection of the layer color channel is irrelevant; and - Means for providing selected enhancement layer color channel data as enhancement layer output data and providing an indication of a selected encoding mode relating to said enhancement layer color channel. 12. The device according to the preceding claim, wherein the base layer and the enhancement layer use different color coding (Y, CR, CB, R, G, B), the means (200) for performing inter-layer prediction further comprising : means for performing color space conversion for intra and inter coding. 13. An apparatus for decoding encoded video data having base layer and enhancement layer data, comprising: - means for extracting base layer data and enhancement layer data from encoded video data, Wherein, both the base layer data and the enhancement layer data include separation data of multiple color channels; - means for extracting, at least for a first color channel of an enhancement layer, an indication indicating a coding mode; - means for decoding base layer data of a plurality of color channels; - means for predicting enhancement layer data based on decoded base layer data, wherein, in at least one mode, each enhancement layer color channel is jointly predicted from all available base layer color channels; - means for decoding enhancement layer data of a plurality of color channels, wherein a residual is obtained and, at least for said first color channel, is decoded using said indication according to the indicated coding mode; and - Means for reconstructing enhancement layer data for a plurality of color channels based on predicted enhancement layer data and said residual. 14. The device according to the preceding claim, wherein the base layer and the enhancement layer use different color coding (Y, CR, CB, R, G, B), the means for predicting further comprises: for intra and inter-coding means to perform color space conversion. 15. An encoded video signal comprising base layer (BL) and enhancement layer (EL) data, wherein the base layer data comprises a plurality of color channels (Y, Cr, Cb) encoded in a first color, and the enhancement layer data comprises a plurality of color channels (R, G, B) encoded in different second colors, wherein the base layer data and the enhancement layer data have different color bit depths, and the signal further comprises an encoding mode indication, The encoding mode indicates, at least for the first enhancement layer color channel, whether it comprises encoded residual data or encoded macroblock data.

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