US-20260129229-A1 - BIT-DEPTH SCALABILITY

Abstract

To increase efficiency of a bit-depth scalable data-stream an inter-layer prediction is obtained by mapping samples of the representation of the picture or video source data with a first picture sample bit-depth from a first dynamic range corresponding to the first picture sample bit-depth to a second dynamic range greater than the first dynamic range and corresponding to a second picture sample bit-depth being higher than the first picture sample bit-depth by use of one or more global mapping functions being constant within the picture or video source data or varying at a first granularity, and a local mapping function locally modifying the one or more global mapping functions and varying at a second granularity smaller than the first granularity, with forming the quality-scalable data-stream based on the local mapping function such that the local mapping function is derivable from the quality-scalable data-stream.

Inventors

• Thomas Wiegand
• Martin Winken

Assignees

• DOLBY VIDEO COMPRESSION, LLC

Dates

Publication Date

20260507

Application Date

20251022

Claims (1)

1. 1 . A method for decoding a data stream into which picture data of a picture of a video is encoded, the method comprising: entropy decoding a subset of the data stream to obtain residual data; combining a prediction signal and the residual data to form a lower quality reconstructed picture that contains sample values; extracting, from the data stream, a first syntax element and a second syntax element associated with a variable parameter and an offset parameter, wherein the variable parameter and the offset parameter define a local mapping function corresponding to a first block of the lower quality reconstructed picture, the first syntax element represents a fixed value associated with the variable parameter, and the second syntax element represents a difference value associated with the variable parameter; determining the variable parameter based on a combination of the fixed value and the difference value; and forming a higher quality reconstructed picture by applying a global mapping function to modify sample values of the lower quality reconstructed picture and applying the local mapping function using the variable parameter and the offset parameter to further modify a subset of sample values obtained after the application of the global mapping function, wherein the subset includes the first block in the lower quality reconstructed picture.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 18/344,329 filed Jun. 29, 2023, which is a continuation of U.S. application Ser. No. 17/208,805 filed Mar. 22, 2021, now U.S. Pat. No. 11,711,542, which is a continuation of U.S. application Ser. No. 16/434,286 filed Jun. 7, 2019, now U.S. Pat. No. 10,958,936, which is a continuation of U.S. application Ser. No. 14/626,946, filed Feb. 20, 2015, which is a continuation of U.S. application Ser. No. 12/937,759, filed Dec. 16, 2010, now U.S. Pat. No. 8,995,525, which is a 371 National Stage Entry of International Application No. PCT/EP2008/003047, filed Apr. 16, 2008. Each of the foregoing patents and patent applications is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION The present invention is concerned with picture and/or video coding, and in particular, quality-scalable coding enabling bit-depth scalability using quality-scalable data streams. The Joint Video Team (JVT) of the ISO/IEC Moving Pictures Experts Group (MPEG) and the ITU-T Video Coding Experts Group (VCEG) have recently finalized a scalable extension of the state-of-the-art video coding standard H.264/AVC called Scalable Video Coding (SVC). SVC supports temporal, spatial and SNR scalable coding of video sequences or any combination thereof. H.264/AVC as described in ITU-T Rec. & ISO/IEC 14496-10 AVC, “Advanced Video Coding for Generic Audiovisual Services,” version 3, 2005, specifies a hybrid video codec in which macroblock prediction signals are either generated in the temporal domain by motion-compensated prediction, or in the spatial domain by intra prediction, and both predictions are followed by residual coding. H.264/AVC coding without the scalability extension is referred to as single-layer H.264/AVC coding. Rate-distortion performance comparable to single-layer H.264/AVC means that the same visual reproduction quality is typically achieved at 10% bit-rate. Given the above, scalability is considered as a functionality for removal of parts of the bit-stream while achieving an R-D performance at any supported spatial, temporal or SNR resolution that is comparable to single-layer H.264/AVC coding at that particular resolution. The basic design of the scalable video coding (SVC) can be classified as a layered video codec. In each layer, the basic concepts of motion-compensated prediction and intra prediction are employed as in H.264/AVC. However, additional inter-layer prediction mechanisms have been integrated in order to exploit the redundancy between several spatial or SNR layers. SNR scalability is basically achieved by residual quantization, while for spatial scalability, a combination of motion-compensated prediction and oversampled pyramid decomposition is employed. The temporal scalability approach of H.264/AVC is maintained. In general, the coder structure depends on the scalability space that is necessitated by an application. For illustration, FIG. 8 shows a typical coder structure 900 with two spatial layers 902a, 902b. In each layer, an independent hierarchical motion-compensated prediction structure 904a,b with layer-specific motion parameters 906a, b is employed. The redundancy between consecutive layers 902a,b is exploited by inter-layer prediction concepts 908 that include prediction mechanisms for motion parameters 906a,b as well as texture data 910a,b. A base representation 912a,b of the input pictures 914a,b of each layer 902a,b is obtained by transform coding 916a,b similar to that of H.264/AVC, the corresponding NAL units (NAL-Network Abstraction Layer) contain motion information and texture data; the NAL units of the base representation of the lowest layer, i.e. 912a, are compatible with single-layer H.264/AVC. The resulting bit-streams output by the base layer coding 916a, b and the progressive SNR refinement texture coding 918a,b of the respective layers 902a,b, respectively, are multiplexed by a multiplexer 920 in order to result in the scalable bit-stream 922. This bit-stream 922 is scalable in time, space and SNR quality. Summarizing, in accordance with the above scalable ex-tension of the Video Coding Standard H.264/AVC, the temporal scalability is provided by using a hierarchical prediction structure. For this hierarchical prediction structure, the one of single-layer H.264/AVC standards may be used without any changes. For spatial and SNR scalability, additional tools have to be added to the single-layer H.264/MPEG4.AVC as described in the SVC extension of H.254/AVC. All three scalability types can be combined in order to generate a bit-stream that supports a large degree on combined scalability. Problems arise when a video source signal has a different dynamic range than necessitated by the decoder or player, respectively. In the above current SVC standard, the scalability tools are only specified for the case that both the base layer and enhancement layer represent a given video