International organisation for standardisation organisation internationale de normalisation

SCE1 primary contributions (2)

14.1.97.1.1.1.1.1.119JCTVC-P0128 SCE1: Results on Core Experiment on Colour Gamut and Bit-Depth Scalability, tests 1A & 1B [P. Bordes, P. Andrivon, E. Francois (Technicolor)]

This contribution reports a performance analysis of SCE1 on Colour Gamut and Bit-Depth Scalability, based on the use of 3D colour Look-Up Tables (CLUT) to perform inter-layer prediction. Results of tests 1.A and 1.B for use cases 1 and 2, described in SCE1 description (JCTVC-O1101) are provided.

Considering use case 1 (one single SPS, PPS inserted at the sequence start), it is reported that compared with the SCE1 anchor (SHM4.0 with Weighted-Prediction (WP) enabled on inter-layer prediction), the CLUT method achieves an average BD rate gain of {−2.2%, −5.1%, −4.1%} for Y, U, V in AI, and {−3.3%, −4.6%, −5.8%} for Y, U, V in RA using 8-bit base layer and 10-bit enhancement layer, and an average BD rate gain of {−0.9%, −4.1%, −3.3%} for Y, U, V in AI, and {−2.6%, −4.2%, −5.8%} for Y, U, V in RA using 10-bit base layer and 10-bit enhancement layer.

Considering use case 2 (one SPS, PPS inserted at RAP periodicity of one second), it is reported that compared with the SCE1 anchor (SHM4.0 with Weighted-Prediction (WP) enabled on inter-layer prediction), the CLUT method achieves an average BD rate gain of {−5.9%, −8.0%, −10.0%} for Y, U, V in AI, and {−5.1%, −6.1%, −9.3%} for Y, U, V in RA using 8-bit base layer and 10-bit enhancement layer, and an average BD rate gain of {−5.6%, −7.8%, −9.9%} for Y, U, V in AI, and {−5.1%, −6.1%, −9.7%} for Y, U, V in RA using 10-bit base layer and 10-bit enhancement layer.

It was reported the complexity of the proposed method, compared to the anchors, is slightly lower.

Complexity analysis is presented, assuming that LUT and upsampling are applied on the fly such that no additional memory is required. It is also reported that the number of multiplications and additions is reduced compared to WP anchors. However, some doubt is raised that more systematic analysis would be required, in particular considering the irregularity of LUT operations. Furthermore, due to the need to access all three colour components, it is likely more complex in terms of memory access than WP.

Further, the assessment that worst case complexity is equivalent to WP is not fully correct, as WP could be used in the enhancement layer anyway (unless explicitly disabled in a scalable profile), and the LUT operations are additionally necessary in the inter-layer processing stage.

14.1.97.1.1.1.1.1.120JCTVC-P0186 SCE1: Combined bit-depth and colour gamut conversion with 3D LUT for SHVC colour gamut scalability [Y. He, Y. Ye, J. Dong (InterDigital)]

This proposal tested the combined bit-depth and colour gamut conversion method with online 3D LUT derivation for SHVC colour gamut scalability (CGS) proposed in JCTVC-O0161 with SCE1 test conditions. Two usecases with two tests are considered. For usecase 1 test, compared to SCE1 anchors, the proposed scheme reportedly achieves average {Y, U, V} BD rate gain of {−3.1%, −5.6%, −5.0%} and {−3.9%, −5.1%, −7.1%} for AI and RA-2x, respectively. For usecase 2 test, the proposed scheme reportedly achieves average {Y, U, V} BD rate gain of {−7.8%, −8.9%, −11.5%}, and {−6.2%, −6.5%, −10.8%} for AI and RA-2x, respectively.

Differences between P0128 and P0186 (P0186 performs better in both use cases):

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  Main reason for performance difference is the parameter estimation, which is more complex in P0186.
  

Two normative differences:

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  P0186 does 8-to-10 bit conversion before upsampling
  
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  P0186 uses additional filtering for alignment of luma with chroma samples
  

P0186 achieves better performance by higher complexity (both encoder and decoder)

3.