Joint Collaborative Team on Video Coding (jct-vc) Contribution

5.20Non-normative: Encoder optimization, decoder speed improvement, post filtering, loss concealment [not done yet]

JCTVC-I0142 Multiplication free interpolation filter implementation [B. Li, H. Li (USTC), H. Yang (Huawei)]

(Reviewed in Track A.)

This contribution proposes multiplication free interpolation filter implementation. It is only an optimization at code level without any RD performance difference. With this multiplication free implementation, about 10% encoding time saving and 8% decoding time saving was obtained.

This would be non-normative implementation optimization (no text change). It was suggested to communicate with the SW coordinator whether this is desirable. Comment by one expert: It may sometimes be better if the reference software is not deviating too much from the text description.

The software coordinator thought it would be cleaner to not have this in the codebase.

JCTVC-I0055 Picture quality evaluation of non-local means post filtering by SSIM [M. Matsumura, S. Takamura, A. Shimizu (NTT)]

This contribution reports the picture quality evaluation of non-local means post filtering by SSIM. Especially, SSIM improves up to 0.0043 in the condition of low-rate (QP: 37). Average BD-rate improvements of 1.1% calculated by SSIM instead of PSNR were obtained and the improvement of subjective quality in various regions was confirmed. SSIM-based RDO might be useful for improving the subjective quality. The maximum reportedly gain was 5.1% for the sequence "SlideEditing".

For information. The filter strength is selected by the encoder, and a post filter hint would be necessary as an SEI message.

JCTVC-I0094 Improvement of the rate control based on pixel-based URQ model for HEVC [H. Choi, J. Nam, J. Yoo, D. Sim (KWU), I. V. Bajić (SFU)]

This contribution presents a refinement of a rate control algorithm based on the proposed rate control in JCTVC-H0213. This document includes two additional conditions on the previous rate control implementation. One is initial QP setting for beginning of a sequence, the other is boundary for target bits in the frame level rate control. The initial QP is automatically calculated based on bit per pixel (bpp) with target bitrate. Therefore, the QP value in the configuration file is ignored. The boundary for target bits of a frame is used to conform with the hypothetical reference decoder (HRD) requirement, so the target bits are clipped by lower and upper bounds. In addition, the rate control in JCTVC-H0213 is modified according to experts' comments in the preceding meeting in San Jose, especially using quantization step (Q-Step) in rate-quantization model (RQ model) instead of directly using QP value. The refinement of the rate control is implemented on HM6.1 and evaluated on diverse conditions.

Compared to the current RC algorithm in HM, the BD rate loss is reduced from 0.83% to 0.74%. It is not clear whether this reduces encoder run time.

No action.

JCTVC-I0426 QP determination by lambda value [B. Li, D. Zhang, H. Li (USTC), J. Xu (Microsoft)]

This contribution presents the QP determination algorithm in HEVC. Usually, to improve the coding efficiency multiple-QP optimization (including slice level, LCU level, and sub-LCU level) can be applied in HEVC. In the multiple-QP optimization, lambda value is fixed and the QP value, which provides the smallest RD cost, is selected as the best QP. But this multiple-QP optimization increases the encoding complexity significantly. If 3 QPs are used in the RDO process, roughly 300% encoding time is required. In the document, QP is determined by the lambda value, according to the pre-trained QP-lambda relationship. When applying the proposed method to HM-6.0, about 1.8%, 1.7%, 1.4%, and 1.4% luma bits saving is obtained for RA-Main, RA-HE10, LD-Main, and LD-HE10 respectively. The bits saving on U and V are reported somewhat larger than that on Y. The method in this contribution only includes non-normative modifications.

Training was done for classes C and D, but gain also applies to the other classes.

The change of QP over the different levels is more aggressive – QP+2 or QP+3 instead of QP+1. This may be one of the main reasons for the BD rate saving, as the PSNR fluctuations become larger and due to the computation of mean frame PSNRs larger fluctuation gives better mean values. Visual quality?

Keeping same QP and training the lambda would be more desirable, but that would be difficult for the current HM. In fact, it is said that currently loss was observed for intra coding in this case.

Visual quality?

Requires better understanding – further study

Proponent will provide software in an update of the contribution.

JCTVC-I0573 Cross-check of QP Determination by Lambda Value (JCTVC-I0426) [Y. Chiu, W. Zhang (Intel)] [late]
JCTVC-I0433 Adaptive Rate Control for HEVC [J. Si, S. Ma, W. Gao (Peking Univ.), M. Yang (Huawei)]

This contribution provides a frame level rate control scheme for HEVC, which originates from ABR (Adaptive Bitrate) used in the popular x264 codec with fine tuning for HEVC. The proposed rate control scheme is designed deliberately for Low delay and Random Access coding respectively and implemented into HM6.1. Compared with the original rate control scheme proposed by JCTVC-H0213, the average BD-RATE computed using piece-wise cubic interpolation can be up to -23.7% for RA-main (for LP-main: -18.3%; LB-main: -19.1%).

Larger rate fluctuations than with current HM rate control scheme?

BD rate is not a valuable measure in this case, makes most sense in case of constant QP

CPB occupancy variation in comparison to current algorithm

Visual quality is more important to judge rate control algorithms

Further study.

5.21To be allocated

JCTVC-I0020 WG 11 National Body Comments on ISO/IEC CD 23008-2 Ballot [SC 29 Secretariat]

TBA

JCTVC-I0607 On allocation of NAL unit types [Y.-K. Wang (Qualcomm)]

This was requested information (see notes in section on I0011), providing an overview and suggesting using a different grouping. It was provided and reviewed on the final day of the meeting (7 May).

A "sub-AU-level SEI" NUT was suggested. This was not supported.

Decision: The rest of the suggested rearrangement was agreed.