Shanshe Wang

Rate-GOP Based Rate Control for High Efficiency Video Coding

In this paper, a Rate-GOP based frame level rate control scheme is proposed for High Efficiency Video Coding (HEVC). The proposed scheme is developed with the consideration of the new coding tools adopted into HEVC, including the quad-tree coding structure and the new reference frame selection mechanism, called reference picture set (RPS). The contributions of this paper mainly include the following three aspects. Firstly, a RPS based hierarchical rate control structure is designed to maintain the high video quality of the key frames. Secondly, the inter-frame dependency based distortion model and bit rate model are proposed, considering the dependency between a coding frame and its reference frame. Thus the distortion and bit rate of the coding frame can be represented by the distortion and bit rate of its reference frame. Accordingly, the Rate-GOP based distortion model and rate model can be achieved via the inter-frame dependency based distortion model and bit rate model. Thirdly, based on these models and a mixed Laplacian distribution of residual information, a new ρ-domain Rate-GOP based rate control is proposed. Experimental results demonstrate the proposed Rate-GOP based rate control has much better R-D performance. Compared with the two state-of-the-art rate control schemes for HEVC, the coding gain with BD-PSNR can be up to 0.87 dB and 0.13 dB on average respectively for all testing configurations. Especially for random access low complexity testing configuration, the BD-PSNR gain can be up to 1.30 dB and 0.23 dB respectively.

Low Complexity Rate Distortion Optimization for HEVC

The emerging High Efficiency Video Coding (HEVC) standard has improved the coding efficiency drastically, and can provide equivalent subjective quality with more than 50% bit rate reduction compared to its predecessor H.264/AVC. As expected, the improvement on coding efficiency is obtained at the expense of more intensive computation complexity. In this paper, based on an overall analysis of computation complexity in HEVC encoder, a low complexity rate distortion optimization (RDO) coding scheme is proposed by reducing the number of available candidates for evaluation in terms of the intra prediction mode decision, reference frame selection and CU splitting. With the proposed scheme, the RDO technique of HEVC can be implemented in a low-complexity way for complexity-constrained encoders. Experimental results demonstrate that, compared with the original HEVC reference encoder implementation, the proposed algorithms can achieve about 30% reduced encoding time on average with ignorable coding performance degradation (0.8%).

A study on the rate distortion modeling for High Efficiency Video Coding

This paper gives a study on the rate distortion modeling for High Efficiency Video Coding (HEVC) and new rate distortion models are proposed by considering the coding framework change of HEVC. Although HEVC is also characterized by the traditional prediction/transform hybrid coding framework with more improved coding tools, e.g. large size coding unit (CU), prediction unit (PU) and transform unit (TU), two new coding modules are added as sample adaptive offset(SAO) and adaptive loop filter(ALF). SAO and ALF are added after the motion compensation reconstruction, which would reduce the distortion of the reconstructed image. With considerations on these changes, new rate distortion models are proposed. For rate modeling, this paper proposes a separate model for header bits and coefficient bits respectively. For distortion modeling, the quantization distortion and the distortion reduction induced by SAO/ALF are modeled jointly. The experimental results show that the coding rate and distortion can be estimated by the proposed model accurately. These models can be used for rate distortion cost estimation for mode decision or rate control in the future.

Fast multi reference frame motion estimation for high efficiency video coding

In this paper, a fast multi reference frame motion estimation algorithm is proposed to reduce the computational complexity for high efficiency video coding (HEVC). Firstly, according to the reference frame distribution, we define the motion complexity for a frame. Based on the motion complexity, an initial reference frame set (RFS) is constructed to reduce the number of the reference frame for motion estimation. Then for each prediction unit (PU), the average distortion per pixel together with the motion vector difference (MVD) in the first reference frame is employed to shrink the RFS in order to early terminate the motion estimation process. In addition, to enhance the robustness of the proposed scheme, an expansion method for RFS is proposed to guarantee the video quality. Experimental results demonstrate that the proposed scheme can significantly save the encoding time. For Low Delay testing configuration, over 30% of time saving can be achieved on average with ignorable performance loss.

Quadratic ρ-domain based rate control algorithm for HEVC

In this paper, a novel quadratic ρ-domain frame layer rate control algorithm is proposed for Low Delay (LD) configuration in High Efficiency Video Coding (HEVC). Firstly, we propose a quadratic ρ-domain rate quantization (R-Q) model to establish the relationship between bit rate and quantization parameter. Subsequently, inspired by the specialized QP determination and reference picture set (RPS) mechanism, we design a RPS based hierarchical partition structure for rate control. Based on the hierarchical partition, an efficient hierarchical bit allocation scheme is provided. Finally, the quantization parameter (QP) is calculated via the proposed R-Q model after the bit allocation to meet the target bits. Experimental results demonstrate the proposed algorithm can significantly improve the R-D performance compared to the state-of-the-art rate control scheme for HEVC. Moreover, our proposed algorithm also provides smaller mismatch between the target bit rate and the actual bit rate.

Low complexity encoder optimization for HEVC

Considering the content characteristic of different PU, an optimization scheme is proposed.Based on the R-D cost distribution, an early termination scheme of coding unit (CU) splitting is proposed.Based on the reference frame distribution, an adaptive reference frame selection scheme is proposed. High Efficiency Video Coding (HEVC) improved the coding efficiency significantly. Compared to its predecessor H.264/AVC, it can provide equivalent subjective quality with more than 57% bit rate reduction. However, the improvement on coding efficiency is obtained at the expense of much more intensive computation complexity. In this paper, based on an overall analysis of computation complexity at the HEVC encoder, a low complexity encoder optimization scheme is proposed by reducing the number of available candidates for evaluation in terms of the intra prediction mode decision, early termination of coding unit (CU) splitting and adaptive reference frame selection. With the proposed scheme, the rate distortion optimization (RDO) technique of HEVC can be implemented in a low-complexity way for complexity-constrained encoders. Experimental results demonstrate that, compared with the original HEVC reference encoder implementation, the proposed optimization scheme can achieve more than 40% complexity reduction on average with coding performance degradation as only 0.43% which can be ignorable.

Adaptive frame level rate control in 3D-HEVC

In this paper, we propose a new frame level rate control algorithm for the high efficiency video coding (HEVC) based 3D video (3DV) compression standard. In the proposed scheme, a new initial quantization parameter (QP) decision scheme is provided, and the bit allocation for each view is investigated to smooth the bitrate fluctuation and reach accurate rate control. Meanwhile, a simplified complexity estimation method for the extended view is introduced to reduce the computational complexity while improves the coding performance. The experimental results on 3DV test sequences demonstrate that the proposed algorithm can achieve better R-D performance and more accurate rate control compared to the benchmark algorithms in HTM10.0. The maximum performance improvement can be up to 12.4% and the average BD-rate gain for each view is 5.2%, 6.5% and 6.6% respectively.

A fast intra optimization algorithm for HEVC

High Efficiency Video Coding (HEVC) has drastically improved the coding efficiency, and can provide more than 23% bit rate reduction compared to its predecessor H264/AVC for all intra (AI) configuration. However, the improvement on coding efficiency is obtained at the expense of much more intensive computation complexity. In this paper, a fast intra optimization scheme is proposed. Firstly, a shrinkage scheme for the number of mode prediction is proposed based on gradient variance. Then a novel estimation model for rate distortion cost is provided based on Hadamard transform and quantization to better determine the mode prediction for RQT. Experimental results demonstrate that, compared with the original HEVC reference encoder implementation in AI configuration, the proposed algorithms can achieve more than 26% coding complexity reduction on average with ignorable coding performance degradation.

Lagrange multiplier based perceptual optimization for high efficiency video coding

In this paper, a Lagrange multiplier based perceptual optimization scheme is proposed for high efficiency video coding (HEVC). Firstly, we propose a non-linear adjustment scheme for the Lagrange multiplier based on the specialized coding structure of HEVC and human visual system (HVS) characteristic. Then the Lagrange multiplier is incorporated into the rate distortion optimization for mode decision. Experimental results demonstrate the proposed scheme can significantly improve the subjective video quality. Compared to the HM anchor, the maximum subjective quality improvement can be up to 30% and the average subjective performance improvement is over 7%, 11% and 10% for random access, low delay P and low delay B testing configurations respectively.

Multi layer based rate control algorithm for HEVC

The specialized QP determination and reference picture set (RPS) mechanism in High Efficiency Video Coding (HEVC) significantly improves the coding efficiency. In this paper, we propose a frame layer rate control algorithm for HEVC based on this specialized mechanism. Firstly, we design a RPS based hierarchical partition structure. Then an efficient hierarchical bit allocation scheme is proposed. Moreover, a novel header bits ratio prediction method is also provided to further improve the accuracy of bit allocation. Finally, an improved mean of absolute difference (MAD) prediction scheme is provided for quadratic R-Q model to calculate an accurate quantization parameter. Experimental results demonstrate the proposed algorithm has much better R-D performance. Compared with the state-of-the-art rate control scheme for HEVC, the BD-Rate gain can be up to 30% and BD-PSNR gain can be 0.6dB on average in Low_Delay configuration. Moreover, our proposed algorithm also provides smaller mismatch between the target bit rate and the actual bit rate.