Region-adaptive probability model selection for the arithmetic coding of video texture

In video coding systems using adaptive arithmetic coding to compress texture information, the employed symbol probability models need to be retrained every time the coding process moves into an area with different texture. To avoid this inefficiency, we propose to replace the probability models used in the original coder with multiple switchable sets of probability models. We determine the model set to use in each spatial region in an optimal manner, taking into account the additional signaling overhead. Experimental results show that this approach, when applied to H. 264/AVC's context-based adaptive binary arithmetic coder (CABAC), yields significant bit-rate savings, which are comparable to or higher than those obtained using alternative improvements to CABAC previously proposed in the literature

Transcoding of H.264/AVC to SVC with motion data refinement

In this paper, we present motion-refined transcoding of H.264/AVC streams to SVC in the transform domain. By accurately taking into account both rate and distortion in the different layers on the one hand, and the SVC inter-layer motion prediction mechanisms on the other hand, the proposed transcoding architecture is able to improve rate-distortion performance over existing approaches. We propose a multilayer control mechanism that trades off performance between the different layers, resulting in 0.5 dB gains in the output SVC base layer

Dyadic spatial resolution reduction transcoding for H.264/AVC

In this paper, we examine spatial resolution downscaling transcoding for H.264/AVC video coding. A number of advanced coding tools limit the applicability of techniques, which were developed for previous video coding standards. We present a spatial resolution reduction transcoding architecture for H.264/AVC, which extends open-loop transcoding with a low-complexity compensation technique in the reduced-resolution domain. The proposed architecture tackles the problems in H.264/AVC and avoids visual artifacts in the transcoded sequence, while keeping complexity significantly lower than more traditional cascaded decoder-encoder architectures. The refinement step of the proposed architecture can be used to further improve rate-distortion performance, at the cost of additional complexity. In this way, a dynamic-complexity transcoder is rendered possible. We present a thorough investigation of the problems related to motion and residual data mapping, leading to a transcoding solution resulting in fully compliant reduced-size H.264/AVC bitstreams

Design method for a fast switching color filter based on ECB cells.

A

Constrained inter prediction: Removing dependencies between different data partitions

With the growing demand for low delay video streaming in errorprone environments, error resilience tools, such as the data partitioning tool in the H.264/AVC specification, are becoming more and more important. In this paper, the introduction of constrained inter prediction into the H.264/AVC specification is proposed. Constrained inter prediction can help the data partitioning tool by removing the dependencies between partitions B and C, thereby making it possible to process partition C if partition B is lost. From the experimental results it is observed that the cost for introducing this technique can be neglected. Furthermore, when constrained inter prediction is used in combination with constrained intra prediction, resulting bitstreams have an increased peak signal-to-noise ratio of up to 1.8 dB in error-prone environments compared to when only constrained intra prediction is used

Complexity and quality assessment of MPEG-2 to H.264/AVC intra transcoding architectures

Transcoding is used in order to enable elegant adaptation of video sequences without fully decoding and recoding. For efficiency reasons, special attention is paid to transform-domain adaptation of video sequences, hereby avoiding the cost of forward and inverse DCT or, in the case of H.264/AVC, integer transforms. In this paper we compare different architectures for MPEG-2 to H.264/AVC intra transcoding, both in pixel and transform domain. We provide a complexity and quality discussion of both architectures, and propose an alternative architecture which results in improved quality over the transform-domain approach at reduced computational complexity. We show that the complexity can be even further reduced by using a combination of different techniques. This results in the fastest transcoding architecture for all intra prediction modes while approaching the visual quality of the optimal rate-distortion curve

Evaluation of transform performance when using shape-adaptive partitioning in video coding

When combining non-rectangular (shape-adaptive) partitioning of inter pictures with a rectangular block transform, some of the transforms will be applied to a residual signal which originates from two different predictions. This is a condition that is never encountered in any of the existing video coding standards, and the impact of this on the performance of the transforrn coder has not been investigated. In this paper we investigate the effect of these mixed-signal blocks on the coding gain for various transforms, and we compare these against the optimal KLT gain. We find that, despite the transformed residual block being composed of two parts that were predicted from different areas of the reference picture, correlation within mixed blocks is very similar to that of normal blocks. The DCT is only marginally suboptimal w.r.t. KLT. KLT has practical issues that will reduce its coding gain or increase the signaling overhead: transform bases need to be quantized and transmitted, or a number of fixed bases needs to be chosen offline. Therefore we recommend DCT be used for all types of blocks

Leveraging the quantization offset for improved requantization transcoding of H.264/AVC video

Requantization transcoding is a method for reducing the bit rate of compressed video bitstreams. Most research on re-quantization is concerned with the architectural design, the selection of a suitable quantizer, or the reduction of requantization errors. In this paper, we propose to incorporate a new dimension in requantization transcoding: the quantization offset. We compare two requantization methods: increasing the quantization step size and decreasing the quantization offset. Furthermore, we propose a novel heuristic for requantization transcoding based on a theoretical rate-distortion analysis. The experimental results for H.264/AVC video show that requantization is improved in rate-distortion sense with gains up to 1 dB for open-loop requantization of B pictures compared to requantization with fixed quantization offset