Macroblock Layer Rate Control Research Articles

Macroblock Layer Rate Control Based on Structural Similarity and Mean Absolute Difference for H.264

In the process of the H.264 video coding, special attention should be paid to the subjective quality of the image. This paper applies the structural similarity (SSIM) based subjective evaluation to the rate control in the H.264 coding and proposes to combine the SSIM and the mean absolute difference (MAD) to perform the macroblock layer bit allocation instead of the MAD. Experimental results show that the proposed method is correlating better with the human visual system and thus achieves better subjective image quality.

A Just Noticeable Distortion Based Rate Control Algorithm for Multiview Video Coding

To quantify human visual system characteristics to carry out rate controlling efficiently, this paper presents a new macroblock (MB) layer rate control algorithm for multi-view video coding (MVC) by improving quadratic rate-quantitative (R-Q) model based on the just noticeable distortion (JND) model. Firstly, the pixel-JND value of color image in multi-view video is stroked according to the related research in order to be used in the MB layer rate control. The proposed algorithm includes view layer, GOP layer, frame layer and MB layer, respectively. In the MB layer, the JND of the MB and mean absolute difference (MAD) in the quadratic R-Q model are firstly analyzed, the MAD is re-defined as perceptual MAD according to the JND with a pixel adjustment factor, and then QP of MB is computed through the re-defined quadratic R-Q model. Finally, a frequently-used image quality metric, peak signal-to-noise ratio (PSNR), is similarly re-defined as perceptual PSNR according to the JND. Experimental results show that the proposed algorithm can obtain higher image quality while precisely controls the bitrates. Moreover, the proposed algorithm not only can achieve better subjective quality, but also save the bitrates about 14.47% ~ 32.13%.

Effective macroblock layer rate control algorithm for H.264/AVC

Rate control plays a critical role in the video encoder. In this paper, an effective macroblock (MB) layer rate control algorithm is proposed for H.264/AVC to improve video quality and reduce the computational complexity. By thoroughly analyzing the temporal–spatial correlation and object direction, the mean absolute difference (MAD) value of current MB is a weighted combination of temporal MAD predicted by previous frame and spatial MAD predicted by current frame, and then four directional patterns are chosen adaptively for data point selection in quadratic rate-quantization (R-Q) model parameters estimation. Finally, a more accurate header bits prediction model is developed to improve the accuracy of allocated bits which can be used for quantization parameter (QP) calculation. Extensive experiment results show that compared with JVT-G012, the proposed algorithm achieves higher average peak signal to noise ratio (PSNR) up to 0.51 dB improvements and more accurate target bit rates.

A Context-Adaptive Prediction Scheme for Parameter Estimation in H.264/AVC Macroblock Layer Rate Control

In this paper, we present a novel context-adaptive model parameter prediction scheme for improving the estimation accuracy of the mean absolute difference (MAD) of texture and other model parameters in the linear rate quantization (R-Q) model-based H.264/AVC macroblock layer rate control for low bit rate real-time applications. The context-adaptive prediction scheme simultaneously exploits both spatial correlations and temporal correlations among the neighboring macroblocks within a so-called context of a macroblock. The location and shape of the context as well as the number of neighboring macroblocks in the context are adaptively computed according to local video signal characteristics using a Manhattan distance metric and an improved 2-D sliding window method. The proposed context-adaptive model parameter prediction scheme effectively suppresses the detrimental oscillations of estimated model parameters. Extensive experiments show that compared to the recent H.264/AVC reference software, macroblock layer rate control algorithm using our proposed context-adaptive prediction scheme significantly improves the MAD and model parameter prediction accuracy and bit achievement accuracy, and hence obtains much better rate distortion performance.

Efficient rate control scheme for low bit rate H.264/AVC video coding

This article presents an efficient rate control scheme for H.264/AVC video coding in low bit rate environment. In the proposed scheme, an improved rate-distortion (RD) model by both analytical and empirical approaches is developed. It involves an enhanced mean absolute difference estimating method and a more rate-robust distortion model. Based on this RD model, an efficient macroblock-layer rate control scheme for H.264/AVC video coding is proposed. Experimental results show that this model encodes video sequences with higher peak signal-to-noise ratio gains and generates bit stream closer to the target rate.

Region-of-interest based rate control for low-bit-rate video conferencing

We present a region of interest (ROI) based rate control for H.263 compatible video conferencing. A face detection and tracking scheme with very low complexity is proposed for segmentation. By analyzing quadratic rate models in frame layer, video object plane (VOP) layer, and macroblock (MB) layer extracted from the test data, a quadratic rate model at the MB layer with a modified physical meaning is proposed to improve the model accuracy. The basic idea is to use a group of uncoded MBs in the current VOP instead of individual MBs to update model parameters. A joint VOP layer and MB layer rate control algorithm is proposed. The VOP layer rate control assigns target bit rate for each VOP based on the coding complexity and visual importance, and determines an average quantization parameter (QP) for each VOP. Some new features of MB layer rate control are designed to utilize both average statistics of a VOP and individual statistics of MB together. The performance is compared with conventional TMN8 and object-based VM8 rate control, better peak SNR (PSNR) for ROI, and more accurate rate control can be achieved for various video sequences. The proposed rate control algorithm can be extended for H.264 ROI-based scalable video coding.

A Region-Based H.263+ Codec and Its Rate Control for Low VBR Video

This paper presents a region-based video codec, which is compatible with the H.263+ standard, and its associated rate control algorithm for low variable-bit-rate (VBR) video. The proposed region-based coding scheme is a hybrid method that incorporates traditional block DCT coding as well as object-based coding. To achieve this, we adopt H.263+ as the platform, and develop a fast macroblock-based segmentation method to implement the new region-based codec. The associated rate control solution includes rate control in three levels: encoding frame selection, frame-layer rate control and macroblock-layer rate control. The goal is to improve human visual perceptual quality at low bit rates. The efficiency of the proposed rate control algorithm applied to the region-based H.263+ codec is demonstrated via several typical test sequences.

Modified TMN8 Rate Control for Low-Delay Video Communications

The existing macroblock-layer rate control schemes in the literature calculate quantization parameters of all macroblocks (MBs) in a frame in a raster scan order, and then encode the MBs in the same order. Actually, the quantization distortion is heavily dependent upon the coding order of MBs. This work investigates the relationship between quantization distortion and the coding order. Then we present a scheme where we modify the encoding order of MBs in TMN8 to favor the more complex MBs. We implement TMN8 and the modified version in H.263 video codec. The experimental results indicate that our scheme achieves average PSNR gain of 1.05 dB over TMN8. In addition, it performs better in buffer overflow and underflow, and the average bit rate achieved is closer to the target channel rate. The new rate control scheme is fully compliant to H.263 coding standard.

Classification-based macroblock layer rate control for low delay transmission of H.263 video

Puri and Aravind's method of macroblock bit count estimation for video rate control is based on the classification of the macroblock data into discrete classes and assigning a unique nonlinear estimate for each class and quantization parameter pair. This method stands apart from other methods in the literature, since the model of the bit count versus the quantization parameter relation, parameterized by macroblock variance, is a discrete model generated solely from measurements. We extend their technique for low-delay video rate control (tight buffer regulation) in two ways. We propose a strategy of near-uniform quantization parameter assignments to the macroblocks of a frame that can come close to maximizing an objective spatial quality function, such as PSNR, over the entire frame. We also adaptively update the quantization parameter assignments for the yet to be coded macroblocks, after the encoding of each macroblock, to compensate for any errors in the bit count estimation of the encoded macroblock. Our experiments demonstrate that the proposed rate control method can more accurately control the number of bits expended for a frame, as well as yield a higher objective spatial quality than the method adopted by TMN8.

Real-time encoding frame rate control for H.263+ video over the Internet

Most existing H.263+ rate control algorithms, e.g. the one adopted in the test model of the near-term (TMN8), focus on the macroblock layer rate control and low latency under the assumptions of a constant frame rate and through a constant bit rate (CBR) channel. These algorithms do not accommodate the transmission bandwidth fluctuation efficiently, and the resulting video quality can be degraded. In this work, we propose a new H.263+ rate control scheme which supports the variable bit rate (VBR) channel through the adjustment of the encoding frame rate and quantization parameter. A fast algorithm for the encoding frame rate control based on the inherent motion information within a sliding window in the underlying video is developed to efficiently pursue a good tradeoff between spatial and temporal quality. The proposed rate control algorithm also takes the time-varying bandwidth characteristic of the Internet into account and is able to accommodate the change accordingly. Experimental results are provided to demonstrate the superior performance of the proposed scheme.

A New Bit Rate Control of MPEG with Predictive and AdaptivePerceptual Quantization

Bit rate control has been proved to be an important technique used to transmit the variable rate bit stream over a fixed rate channel in MPEG coding. In this paper, a hybrid algorithm is proposed to achieve the rate control and obtain a good picture quality. In the picture layer, the algorithm estimates numbers of bits required for different type of frames. In the macroblock layer, it utilizes the predictive and adaptive perceptual techniques in the regulation of the quantization scale to allocate the target bits. In the upper and left boundary of the picture, the macroblocks are quantized with the perceptual basis to adjust the quantization scale and in the other part of the picture a predictive method is used to update the quantization scale. By using the proposed scheme, the distortion of coding is uniformly distributed in the picture layer as well as in the macroblock layer and better bit rate control is achieved.