Jicheng An

Localized multiple adaptive interpolation filters with single-pass encoding

Adaptive interpolation filtering (AIF) algorithms have been proposed to enhance the hybrid video coding scheme recently. Although these algorithms can improve coding efficiency significantly, their encoders suffer huge increase in complexity in terms of latency and memory access due to its inherent multi-pass encoding procedure. In this paper, we present a novel single-pass solution for these algorithms, which allows optimal selection among different interpolation filters. In this solution, time-delayed interpolation filters are used to achieve single-pass encoding, and localized ratedistortion (RD) selection is used to compensate the possible coding loss from time-delayed filters. Experimental results show that the proposed method is efficient for All AIF techniques in current ITU-T/SG16 reference software. By using the proposed method, single-pass encoding with multiple AIF filters can be achieved while maintaining similar coding efficiency as multi-pass AIF.

Progressive motion vector resolution for HEVC

This paper proposes a progressive motion vector resolution (PMVR) method for High Efficiency Video Coding (HEVC). In the proposed scheme, high motion vector (MV) resolutions, e.g. 1/4 or 1/8 pixel resolution, are employed for MVs near to the motion vector predictor (MVP) and low MV resolutions are employed for MVs far from the MVP. The range of each MV resolution is indicated by a threshold parameter. And a new motion vector difference (MVD) derivation method is designed to encode MVD efficiently. Experimental results show that PMVR with 1/8 pixel motion search can achieve a BD-rate gain up to 16% with almost the same coding time with HM8.0, and for PMVR without 1/8 pixel motion search, up to 6.1% BD-rate gain can be achieved with 9% encoding time saving on average.

Symmetric intra block copy in video coding

In the screen content coding extension for HEVC, intra block copy (IBC) was adopted to explore the redundancy between reduplicated patterns, which often occurs in a picture with screen contents. Besides reduplication, symmetry is also often observed in screen-content and even in natural pictures. In this paper, symmetric intra block copy (SIBC) is therefore proposed to further improve IBC. By flipping the reference block of IBC horizontally or vertically, SIBC may provide better predictions than IBC for symmetric patterns. Experimental results show that SIBC can achieve 1.2% and 1.9% coding gains in all intra configurations on sequences in the category of YUV, text & graphics with motion, 1080p for lossy and lossless coding respectively.

A Single-Pass-Based Localized Adaptive Interpolation Filter for Video Coding

Recently, an efficient coding tool named adaptive interpolation filtering (AIF) has been proposed to hybrid video coding scheme. By introducing Wiener filter into the fractional-pixel interpolation procedure, AIF can reduce the inter-prediction error and improve coding efficiency significantly. However, the training-based Wiener filter mechanism brings AIF an inherent multi-pass encoding structure, which imposes big burdens on the encoder in terms of huge computational complexity and memory access. In this paper, we propose a single-pass-based localized adaptive interpolation filtering (SPL-AIF) algorithm for video coding, which can reduce the complexity of AIF dramatically without sacrifice of its outstanding coding performance. The proposed SPL-AIF algorithm is based on the observation that there is a high correlation among optimal interpolation filters of consecutive frames, and different regions in a frame often possess different statistical characteristics. Accordingly, the proposed algorithm can be designed including two major parts. First, a competitive filter set which includes the optimal interpolation filters of several previous frames as well as the fixed H.264/AVC interpolation filters is built up for the coding of the current frame. Then a rate-distortion optimization criterion is used to select the best one at macroblock (MB) level. In order to reduce overhead, a predictive coding method is used to compress the filter signaling flag for each MB. Experimental results show that, by using the proposed algorithm, the encoding complexity can be reduced significantly while the average coding gain in Bjöntegaard distortion bit-rate reduction can be improved about 1% compared with the multi-pass AIF. The proposed method has been adopted into the Video Coding Expert Group Key Technology Area software.

Segmental Prediction for Video Coding

The emerging standards for screen content coding (SCC) and 3D video coding known as High Efficiency Video Coding (HEVC)-SCC and 3D-HEVC, respectively, have been developed as extensions of HEVC. Compared with camera-captured video, screen content video and depth maps usually contain significantly fewer colors or sample intensities and much sharper edges in a frame. In this paper, a new coding method named segmental prediction is proposed to code screen content and depth maps more efficiently. First, samples in a prediction block are classified into several segments according to the sample intensities. Second, a particular predictor is calculated for each segment. Then an offset for a segment is derived at the encoder side and signaled to the decoder side. Finally, a single sample value is assigned to each segment in the reconstructed block. The experimental results show that the proposed approach can achieve a 2.2% average Bjontegaard Distortion-rate (BD-rate) saving under the HEVC-SCC common test conditions (CTCs) for sequences of the category YUV, text and graphics with motion, 1080p, with the all intra configuration. It can also achieve a 0.6% average BD-rate saving for synthesized views under the 3D-HEVC CTCs with the random access configuration.

Advanced motion information prediction and inheritance in 3D-HEVC

The 3D extension of High Efficiency Video Coding (3D-HEVC) is a new international video coding standard that has been developed by the Joint Collaborative Team on 3D Video Coding Extensions (JCT-3V). It aims at improving the coding efficiency of 3D and multi-view videos by introducing new coding tools to utilize the correlations between views and between texture and depth components. In this paper, we propose an inter-view motion prediction (inter-view merge candidate) and an inter-component motion prediction (texture merge candidate) to explore the inter-view and the inter-component redundancies. The proposed schemes were adopted in 3D-HEVC and the experimental results demonstrate that the proposed inter-view merge candidate and texture merge candidate achieve significant BD-rate reductions of 20% for dependent texture views and 9% for the synthesized texture views under the common test conditions used for 3D-HEVC standardization.