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The rate allocation tradeoff between motion vectors and transform coefficients has a major importance when it comes to efficient video compression. This paper introduces a new coding mode for an H.264/AVC-like video coder, which improves the management of this resource allocation. The proposed technique can be used within any hybrid video encoder allowing a different coding mode for any macroblock. The key tool of the new mode is the lossy coding of motion vectors, obtained via quantization: while the transformed motion-compensated residual is computed with a high-precision motion vector, the motion vector itself is quantized before being sent to the decoder, in a rate/distortion optimized way. Several problems have to be faced with in order to get an efficient implementation of the coding mode, especially the coding and prediction of the quantized motion vectors, and the selection and encoding of the quantization steps. This new coding mode improves the performance of the hybrid video encoder over several sequences at different resolutions. [ABSTRACT FROM AUTHOR]

Quality criteria for image coding are often based on mean square error. However, this is not always a relevant measure of visual quality at low bit rates. Here, we investigate the properties of a distortion measure based on the conditional differential entropy of the input signal given its quantized value. The proposed measure appears to be a correct representation of the amount of information lost by quantization. An adaptive bit allocation algorithm is proposed in order to take advantage of this criterion. Experimental results illustrate the behavior of the proposed distortion measure and exhibit interesting visual properties for low bit-rate subband image coding. [ABSTRACT FROM AUTHOR]

Wavelet-based coding is emerging as a promising framework for efficient and scalable compression of video. Nevertheless, a number of basic tools currently employed in this field have been conceived for hybrid block-based transform coding. This is the case of motion estimation, which generally aims to minimize the energy or the absolute sum of prediction error. However, as wavelet video coders do not employ predictive coding, this is no longer an optimal approach. In this paper we study the problem of the theoretical optimal criterion for wavelet-based video coders, using coding gain as merit figure. A simple solution has been found for a peculiar but useful class of temporal filters. Experiments confirm that the optimally estimated vectors increase the coding gain as well as the performance of a complete video coder, but at the cost of an augmented complexity. [ABSTRACT FROM AUTHOR]

We present a simple yet efficient scalable scheme for wavelet-based video coders, able to provide on-demand spatial, temporal, and SNR scalability, and fully compatible with the still-image coding standard JPEG2000. Whereas hybrid video coders must undergo significant changes in order to support scalability, our coder only requires a specific wavelet filter for temporal analysis, as well as an adapted bit allocation procedure based on models of rate-distortion curves. Our study shows that scalably encoded sequences have the same or almost the same quality than nonscalably encoded ones, without a significant increase in complexity. A full compatibility with Motion JPEG2000, which tends to be a serious candidate for the compression of high-definition video sequences, is ensured. [ABSTRACT FROM AUTHOR]

The objective of this paper is to propose an efficient model-based bit allocation process optimizing the performances of a wavelet coder for semiregular meshes. More precisely, this process should compute the best quantizers for the wavelet coefficient subbands that minimize the reconstructed mean square error for one specific target bitrate. In order to design a fast and low complex allocation process, we propose an approximation of the reconstructed mean square error relative to the coding of semiregular mesh geometry. This error is expressed directly from the quantization errors of each coefficient subband. For that purpose, we have to take into account the influence of the wavelet filters on the quantized coefficients. Furthermore, we propose a specific approximation for wavelet transforms based on lifting schemes. Experimentally, we show that, in comparison with a "naïve" approximation (depending on the subband levels), using the proposed approximation as distortion criterion during the model-based allocation process improves the performances of a wavelet-based coder for any model, any bitrate, and any lifting scheme. [ABSTRACT FROM AUTHOR]

Wavelet coding has been shown to achieve better compression than DCT coding and moreover allows scalability. 2D DWT can be easily extended to 3D and thus applied to video coding. However, 3D subband coding of video suffers from two drawbacks. The first is the amount of memory required for coding large 3D blocks; the second is the lack of temporal quality due to the sequence temporal splitting. In fact, 3D block-based video coders produce jerks. They appear at blocks temporal borders during video playback. In this paper, we propose a new temporal scan-based wavelet transform method for video coding combining the advantages of wavelet coding (performance, scalability) with acceptable reduced memory requirements, no additional CPU complexity, and avoiding jerks.We also propose an efficient quality allocation procedure to ensure a constant quality over time. [ABSTRACT FROM AUTHOR]