Rate-distortion Optimization Technique Research Articles

Content-Based Distortion Control Scheme for High-Quality Wireless Multimedia Services

In recent years, the wireless mobile markets are witnessing an unprecedented growth. High-quality video service will be greatly needed as one of the hottest wireless multimedia services in the future generation wireless networks. In this paper, a novel content-based distortion control scheme is proposed to provide higher quality of the wireless video services. Our scheme adopts rate-distortion optimization techniques in state-of-the-art video coding standard H.264/AVC. In order to improve the subjective video quality in the process of encode, we create three visual distortion sensitivity models to minimize the perceptual distortion. We arrange more bits to visual distortion sensitive macroblocks during rate-distortion optimization process. The perceptual distortion in these regions is thus efficiently controlled with a relatively higher rate. Meanwhile, rate balance is achieved by allotting fewer bits to macroblocks that are perceptually less sensitive to distortion. Experiments results show that the subjective qualities of encoded video are improved without compromising PSNR.

An approach to selective intra coding and early inter skip prediction in H.264/AVC standard

This paper presents selective intra coding and early inter skip fast mode decision algorithm for H.264/AVC and compares performance of H.264/AVC with prior standards. Video coding standard H.264/AVC provides gains in compression efficiency of up to 50% over a wide range of bit rates and video resolutions compared to previous standards. In order to achieve this, a robust rate-distortion optimization (RDO) technique is employed to select best coding mode and reference frame for each macroblock. Also, the original and modification test models are compared for combined skip and intra prediction method in H.264/AVC encoder, when ? pictures are analyzed. Experimental results show that the coding time is reduced by 35-42% through early identification of macroblocks that are likely to be skipped during the coding process and through reducing the number of candidate modes. .

Fast Bit Rate Estimation for Mode Decision of H.264/AVC

To achieve the highest coding efficiency, H.264/AVC uses rate-distortion optimization technique. This means that the encoder has to code the video by exhaustively trying all the mode combinations including the different intra- and inter-prediction modes. Therefore, the complexity and computation load of video coding in H.264/AVC increase drastically compared to any previous standards. To reduce the complexity of rate-distortion cost computation, we propose a fast bit rate estimation technique to avoid the entropy coding method during intra- and inter-mode decision of H.264/AVC. The estimation method is based on the properties of context-based variable length coding (CAVLC). The proposed rate model predicts the rate of a 4 times 4 quantized residual block using five different tokens of CAVLC. Experimental results demonstrate that the proposed estimation method reduces about 47% of total encoding time on using intra-modes only and saves about 34% of total encoding time on using both inter- and intra-modes with ignorable degradation of coding performance when the fast motion search algorithm is used. When full search motion estimation algorithm is used, the proposed algorithm reduces about 17% of total encoding time.

Rate-Distortion Modeling for Efficient H.264/AVC Encoding

The rate-distortion (R-D) optimization technique plays an important role in optimizing video encoders. Modeling the rate and distortion functions accurately in acceptable complexity helps to make the optimization more practical. In this paper, we propose a bit-rate estimation function and a distortion measure by modeling the transform coefficients with spatial-domain variance. Furthermore, with quantization-based thresholding to determine the number, the absolute sum, and the squared sum of transform coefficients, the simplified transform-domain R-D measurement is introduced. The proposed algorithms can reduce the computation complexity for the R-D optimized mode-decision by using the new cost function evolving from the simplified transform-domain R-D model. Based on the proposed estimations, a rate-control scheme in the macroblock layer is also proposed to improve the coding efficiency

A Fast Intra Skip Detection Algorithm for H.264/AVC Video Encoding

A fast intra skip detection algorithm based on the rate-distortion (RD) cost for an inter frame (P-slices) is proposed for H.264/AVC video encoding. In the H.264/AVC coding standard, a robust rate-distortion optimization technique is used to select the best coding mode and reference frame for each macroblock (MB). There are three types of intra predictions according to profiles. These are 16×16 and 4×4 intra predictions for luminance and an 8×8 intra prediction for chroma. For the high profile, an 8×8 intra prediction has been added for luminance. The 4×4 prediction mode has 9 prediction directions with 4 directions for 16×16 and 8×8 luma, and 8×8 chrominance. In addition to the inter mode search procedure, an intra mode search causes a significant increase in the complexity and computational load for an inter frame. To reduce the computational load of the intra mode search at the inter frame, the RD costs of the neighborhood MBs for the current MB are used and we propose an adaptive thresholding scheme for the intra skip extraction. We verified the performance of the proposed scheme through comparative analysis of experimental results using joint model reference software. The overall encoding time was reduced up to 32% for the IPPP sequence type and 35% for the IBBPBBP sequence type.

Inter-View Direct Mode for Multiview Video Coding

Global disparity between views is usually caused by the displacement between cameras, which can be accurately represented by a global geometric transformation. In this paper, we first propose an inter-view motion model in terms of the global geometric transformation to represent the motion correlation between two adjacent views. Specifically, the motion vector of a pixel in one view may be directly derived from that in another view according to the inter-view motion model. Further, we propose an inter-view direct mode to signal the decoder that the motion of a macroblock (MB) can be achieved from the coded view without any coding bits. The proposed inter-view direct mode is further incorporated in the existing multiview video coding (MVC) schemes (i.e., AVC-based MVC and 4-D wavelet-based MVC), working together with the other classical coding modes. The mode selection at each MB is accomplished with the rate-distortion optimization technique. The proposed inter-view direct mode can significantly reduce bits to code motion vectors especially at low bit rates, thus improving the coding efficiency

Fast Coding Mode Selection With Rate-Distortion Optimization for MPEG-4 Part-10 AVC/H.264

The MPEG-4 Part-10 AVC/H.264 standard employs several powerful coding methods to obtain high compression efficiency. To reduce the temporal and spatial redundancy more effectively, motion compensation uses variable block sizes, and directional intra prediction investigates all available coding modes to decide the best one. When the rate-distortion (R-D) optimization technique is used, an encoder finds the coding mode having minimum R-D cost. Due to the large number of combinations of coding modes, the decision process requires extremely high computation. To reduce the complexity, we propose two methods: early SKIP mode decision and selective intra mode decision. In the simulation results, the proposed methods are verified to significantly reduce the entire encoding time by about 60% with only negligible coding loss

Improved fast intra prediction algorithm of H.264/AVC

With advanced prediction modes of intra prediction, intra coding of H.264/AVC offers significant coding gains compared with previous video coding standards. It uses an important tool called Lagrangian rate-distortion optimization (RDO) technique to decide the best coding mode for a block, but the computational burden is extremely high. In this paper, we proposed an improved fast intra prediction algorithm including block type selection and mode decision algorithm based on analysis of edge feature of a block. Our algorithm filters out unlikely block type and candidate modes to reduce the RDO calculations. Experimental results showed that the proposed algorithm can reduce the computation complexity of intra prediction from 52.90% to 56.31%, with 0.04 dB PSNR degradation and 2% increase of bit rate.

Fast mode decision algorithm for intraprediction in H.264/AVC video coding

The H.264/AVC video coding standard aims to enable significantly improved compression performance compared to all existing video coding standards. In order to achieve this, a robust rate-distortion optimization (RDO) technique is employed to select the best coding mode and reference frame for each macroblock. As a result, the complexity and computation load increase drastically. This paper presents a fast mode decision algorithm for H.264/AVC intraprediction based on local edge information. Prior to intraprediction, an edge map is created and a local edge direction histogram is then established for each subblock. Based on the distribution of the edge direction histogram, only a small part of intraprediction modes are chosen for RDO calculation. Experimental results show that the fast intraprediction mode decision scheme increases the speed of intracoding significantly with negligible loss of peak signal-to-noise ratio.

Compression of 3-D triangle mesh sequences based on vertex-wise motion vector prediction

We propose an efficient geometry compression algorithm for three-dimensional (3-D) mesh sequences based on the two-stage vertex-wise motion vector (MV) prediction. In general, the MV of a vertex is highly correlated to those of the adjacent vertices. To exploit this high correlation, we define the neighborhood of a vertex, and predict the MV of the vertex from those of the neighborhood. The error vectors are related to the local shape changes of 3-D objects, and still have redundancy. To remove the redundancy, the error vectors are also predicted, at the second stage, spatially or temporally by using a rate-distortion optimization technique. It is shown that the proposed algorithm has simpler structure than the existing segment-based algorithm, and yields better compression performance.

Matching-pursuit video coding .II. Operational models for rate and distortion

For pt. I see ibid., vol.12 , no.1, (2000).We introduce two models for predicting the rate and distortion of the matching-pursuit video codec. The first model is based on a pre-coding analysis pass using the full matching-pursuit dictionary. The second model is based on a reduced-complexity analysis pass. We evaluate these models for use within existing rate-distortion optimization techniques. Our prediction results suggest that the models have sufficient accuracy to be useful in this context, and that significant complexity reductions could be achieved compared to exact rate-distortion computation.