Yimin Zhou

New rate-distortion modeling and efficient rate control for H.264/AVC video coding

Rate control (RC) is crucial in controlling compression bit rates and qualities for networked video applications. In this paper, we propose a new rate-distortion (R-D) model and an efficient rate control scheme for H.264/AVC video coding, which elegantly resolve the inter-dependency problem between rate-distortion optimization and rate control by eliminating the need of coding complexity prediction for an inter-frame. The objective is to achieve accurate bit rate, obtain optimal video quality while reducing quality variations and simultaneously handling buffer fullness effectively. The proposed algorithm encapsulates a number of new features, including a coding complexity measure for intra-frames, a rate-distortion model, an accurate quantization parameter (QP) estimation for intra-frames, an incremental quantization parameter calculation method for inter-frames, a proportional+integral+derivative (PID) buffer controller, and an intelligent bit-allocation-balancing technique. Our experimental results demonstrate that the proposed scheme outperforms the JVT-G012 solution by providing accurate rate regulation, effectively reducing frame skipping, and finally improving coding quality by up to 1.80dB.

PID-Based Bit Allocation Strategy for H.264/AVC Rate Control

To achieve the best visual quality under the minimum bit rate and the limited buffer size, the rate control allocates appropriate and smooth bits to each frame. This brief proposes an effective bit-allocation strategy for the H.264/Advanced Video Coding rate control. Based on the different characteristics of intraframes and interframes, we introduce the different bit-allocation approaches for them, respectively. A proportional-integer-derivative controller is adopted to minimize the deviation between the target buffer level and the current buffer fullness. To avoid buffer overflow or underflow, a novel setting method for the bit-allocation boundary is presented. Experimental results demonstrate that the proposed bit allocation strategy achieves smooth target bits while better buffer control and visual quality are derived.

New rate-complexity-quantization modeling and efficient rate control for H.264/AVC

In this paper, we propose a novel rate control scheme for H.264/AVC standard, including a new coding complexity measure for intra-frames, a new rate-complexity-quantization (R-C-Q) model, an accurate quantization parameter (QP) estimation for intra-frames, an incremental-control-based QP calculation for inter-frames, and a bit-allocation-balancing technique. Our experimental results demonstrate that, the proposed scheme outperforms the JVT-G012 solution by providing more accurate QP prediction, reducing frame skipping, depressing quality fluctuations, and finally, improving coding quality.

Analysis of quadratic R-D model in H.264/AVC video coding

Due to the high performance in the rate control of MPEG-4, the quadratic Rate-Distortion model has been widely proved. The rate control module in the reference software of H.264/AVC directly inherits the quadratic model. However, the introduction of Rate Distortion Optimization (RDO) in H.264/AVC makes rate control more complex than previous standards. Based on theoretical derivation and extensive experiments, this paper analyzes the model error of the quadratic model and the prediction error of MAD in H.264/AVC. Simulation results demonstrate that our proposed linear MAD model achieves higher prediction accuracy than the quadratic mode does.

Incremental rate control for H.264 AVC scalable extension

The emerging H.264 Scalable Video Coding (H.264/SVC) requires the rate control algorithm to regulate the output bit rate of all the coarse-grain-scalability, temporal, spatial and combined enhancement layers. In order to address this topic, in this research, we propose an incremental rate control algorithm for H.264/SVC to control each layer’s encoding rate close to the target bit rate. The proposed algorithm introduces a number of efficient methods. First, based on our previous work on H.264/AVC rate control, a Rate-Complexity-Quantization (R-C-Q) model is extended in scalable video coding. Second, a complexity measure for Intra-frames based on their gradient and histogram information is used to precisely determine Quantization Parameters (QPs) for Intra-frames using the R-C-Q model. Third, we adopt an incremental approach to compute QPs of inter-frames. Fourth, a Proportional + Integral + Derivative (PID) buffer controller is presented to provide robust buffer control for each layer of H.264/SVC bitstream. Finally the QPs for hierarchical B-frames are adaptively decided by their neighbor inter-frames. Our extensive simulation results demonstrate that, our algorithm outperforms JVT-W043 rate control algorithm, adopted in the H.264/SVC reference software, by providing more accurate output bit rate for each layer, maintaining stable buffer fullness, reducing frame skipping finally, improving the overall coding quality.

Incremental Rate Control for H.264 Scalable Video Coding

The emerging H.264 Scalable Video Coding (H.264/SVC) requires the rate control algorithm to regulate the output bit rate of all the coarse-grain-scalability, temporal, spatial and combined enhancement layers. In this research, we propose an incremental rate control algorithm for H.264/SVC. First, a Rate-Complexity-Quantization (R-C-Q) model is extended in scalable video coding based on our previous work on H.264/AVC. Second, a complexity measure for Intra-frames is used to precisely determine QPs (Quantization Parameters) for Intra-frames. Finally, we adopt an incremental approach to compute QPs of inter-frames and a Proportional + Integral + Derivative (PID) buffer controller to provide robust buffer control for each layer. Our simulation results demonstrate that, our algorithm outperforms JVT-W043 rate control algorithm by providing more accurate output bit rate for each layer, maintaining stable buffer fullness, reducing frame skipping and quality fluctuation, finally, improving the overall coding quality.

An incremental basic unit level QP determination algorithm for H.264/AVC rate control

In this paper, we propose an incremental-based basic unit (BU) level quantization parameter (QP) determination algorithm for H.264/AVC rate control. Unlike traditional BU level QP computation in existing rate control schemes, the proposed algorithm does not perform target bit allocation and predict coding complexities. Instead, it exploits bit increment to directly determine QP for a BU, aiming at reducing the variations of encoding bits used among BUs within a frame and improve subjective visual quality. To better handle buffer fullness and reduce buffer overflow/ underflow, we explore an enhanced Proportional-Integral-Derivative buffer controller. In addition, the algorithm can also effectively intra-code all frames in a video sequence and has low computational complexity making it suitable for real-time applications. Our experimental results demonstrate that, the proposed algorithm outperforms the rate control algorithm JVT-W042, adopted in the recent H.264/AVC reference model JM13.2, by achieving accurate rate regulation, reducing frame skipping, decreasing quality fluctuation, and improving coding quality up to 1 dB.

Novel rate control scheme for intra frame video coding with exponential rate-distortion model on H.264/AVC

Rate control regulates the output bit rate of a video encoder in order to obtain optimum visual quality within the available network bandwidth and to maintain buffer fullness within a specified tolerance range. Due to the benefits of intra-only encoding, such as less computational cost and less latency, it has been more and more widely used. In this paper, we propose an accurate intra-only rate control scheme for H.264/AVC, which includes a novel complexity measurement and a new rate-distortion (R-D) model. We also propose a linear rate-complexity model which takes the intercept into consideration to reduce the estimation error. The proposed R-D model is integrated by the linear rate-complexity model and an exponential rate-quantization model. Based on theoretical analysis and experimental validation, the proposed scheme has high bits prediction precision, and it can also accurately handle buffer fullness. Compared with JVT-W042, our algorithm achieves higher average PSNR and improves the coding quality up to 0.35dB.

Joint Rate-Distortion model for H.264/AVC rate control

This paper presents a novel rate control algorithm for H.264/AVC video coding. Pertinent to the algorithm, the paper introduces a joint R-D model, a coding bit estimation approach, a picture complexity measurement, and a model update method. Specifically, the proposed picture complexity measurement employs a Harmonic Mean based approach to predict the coding complexity of a frame. These techniques collectively enhance the overall rate control performance. Experimental results demonstrate that the proposed algorithm outperforms JVT-W042 in providing robust buffer control, reducing frame skipping, and improving coding quality.

Effective Frame Level Rate Control for H.264/AVC Video Coding

In this paper, we present a robost frame level rate control algorithm for H.264/AVC compression standard. Particularly, we propose a simple yet effective approach to deal with B frames, including a PSNR-QP model and an adaptive QP computation method for B frames. The objective is to reduce PSNR variations among frames and improve subjective visual quality. To better handle buffer fullness and reduce buffer overflow/underflow, we develop an enhanced proportional- integral-derivative (PID) buffer controller. Our experimental results demonstrate that the proposed algorithm outperforms the JVT-W042 solution by achieving accurate rate regulation, reducing frame skipping, depressing quality fluctuations, and finally, improving coding quality up to 1.43 dB.