Organisation internationale de normalisation

9.2CE6a Block based intra prediction

9.2.1.1.1.1.1.1.1JCTVC-D108 CE6 Subset A: Bidirectional intra prediction (JCTVC-C079) [Taichiro Shiodera, Akiyuki Tanizawa, Takeshi Chujoh, Tomoo Yamakage (Toshiba)]

This contribution presented the experimental results of Bidirectional Intra Prediction (BIP) for Core Experiment 6 (CE6) on intra prediction improvement. BIP was included in the CfP submission of JCTVC-A117 and was proposed in the contribution of JCTVC-C079 at the JCT-VC Guangzhou meeting.

In this document, experimental results in TMuC software version 0.9 under the common test conditions defined by CE6 were reported. For I slice only coding structure, the average BD BR gain was 2.0% on low complexity condition and 1.4% on high efficiency condition. Experimental results reportedly indicated that BIP can improve the coding efficiency for intra coding with minimum complexity increase.

BIP combines two unidirectional intra predictions results by a weighted sum according to the distance between the predicted pixel and the reference pixel(s) used for prediction. These unidirectional intra predictions are based on Unified Intra Prediction (UIP) integrated in current TMuC 0.9 software. The bidirectional modes are based on directions used in neighbored blocks and their counter-directions.

Encoding time 107/114% for HE/LC intra

Decoding time 106/110% for HE/LC intra

For 4x4 blocks, the gain by BIP + 17 UIP directions is reportedly higher than with 34 UIP directions (i.e. higher benefit of UIP modes)

9.2.1.1.1.1.1.1.2JCTVC-D066 CE6: Verification of Toshiba's contribution on BIP [Andrew Segall, Jie Zhao]

9.2.1.1.1.1.1.1.3JCTVC-D196 CE6: Cross verification of Toshiba bidirectional intra prediction [J. Lainema, K. Ugur (Nokia)]

9.2.1.1.1.1.1.1.4JCTVC-D350 CE6.a: Chroma intra prediction by reconstructed luma samples [J. Chen, V. Seregin, S. Lee, W.-J. Han (Samsung), J. Kim, B. Jeon (LG)]

This document reported results of the "Chroma intra prediction by reconstructed luma samples" method proposed in document JCTVC-C206 within the context of CE6. In the proposed method, chroma samples are predicted from luma samples of same block by linear model relationship (line equation with slope and intercept found by least-squares solution). Compared to the TMuC0.9, the average BD BR gain is 1.4%, 6.3% and 5.2% for intra configuration, the average BD BR gain is 0.7%, 5.8% and 3.7% for random access configuration, respectively for Y, Cb and Cr components. The encoding/decoding measurement and operation number analysis reportedly prove that complexity of proposed intra prediction method is similar and even smaller to the existing method in HEVC or AVC.

The least squares solution is computed at the decoder from the boundary samples of neighboring blocks (LM mode).

Two modes are suggested: "LM5" with 5 modes (horizontal/vertical/DC/LM/DM) and "LM3" (DC/LM/DM). LM3 is claimed to be less encoding time than anchor, decoding time not changed.

It was claimed that the gain would be higher for 4:2:2 or 4:4:4 YUV due to having a higher number of chroma samples.

One expert raises the issue that luma and chroma cannot be processed in parallel.

The perceptual quality was not tested.

The actual bit rate reduction is more in the range of the luma (may be around 2% for intra).

9.2.1.1.1.1.1.1.5JCTVC-D110 CE6 Subset A: Cross check report of Samsung's proposal (JCTVC-C206) from Toshiba [Akiyuki Tanizawa, Taichiro Shiodera (Toshiba)]

Confirms results for LM3

9.2.1.1.1.1.1.1.6JCTVC-D145 CE6: Cross-verification report for Samsung's proposal from Microsoft [J. Xu (Microsoft)] (missing prior, uploaded Tuesday 18th, before meeting)

Confirms results for LM5

9.2.1.1.1.1.1.1.7JCTVC-D398 CE6: Cross verification of Samsung chroma intra prediction [M. Coban]

9.2.1.1.1.1.1.1.8JCTVC-D026 CE6.a: Santa Clara University and Hisilicon Report on Block Based Intra Prediction [Guichun Li, Lingzhi Liu, Nam Ling, Jianhua Zheng, Philipp Zhang]

The Intra Plane Mode and Intra Bilinear Mode were implemented in Unified Intra Prediction (UIP) based on the TMuC version 0.9. Simulations were performed on different combinations of Intra Modes and the results were analyzed.

Multiple Predictor Sets (MPS) method was used for PUs with MaxMode == 36 (size of 8x8, 16x16, and 32x32). 36 intra predictors were grouped into 4 sets, with 9 in each. Each mode was represented by a Group number and Index number.

Bilinear mode was not used. MPS with plane mode reportedly gives a little gain (0.2% and 0.4% for HE and LC cases).

A slight increase in encoder run time (102%) was reported.

9.2.1.1.1.1.1.1.9JCTVC-D348 CE6.a: Cross-verification of intra prediction improvement from Santa Clara University and Hisilicon (JCTVC-D026) [J. Chen, J.-H. Min (Samsung)]