Bit Allocation Based on Motion Vector Analysis for H.264/AVC

Mohammed, H.; Färber, N.; Thoma, Herbert

doi:10.1109/dcc.2007.17

Cited by 3 publications

(2 citation statements)

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“…As a proof of concept we proposed a simple modulation scheme for the QP at the macroblock level, which assigns higher quality to those macroblocks which have a higher descendance. Our results are coherent with those by Mohammed et al, 13 and show potentially high gains for "talking-head" sequences with little motion and static background, while the improvement for more complex sequences is in fact negligible.…”

Section: Introductionsupporting

confidence: 95%

“…smaller coded units such as macroblocks are not considered. Mohammed et al 13 modulate the quantization parameter (QP) at the macroblock level in H.264/AVC video, giving higher priority to those macroblocks that contain pixels used later as predictors, using a two-pass procedure. In our previous work, 14 we model temporal dependencies induced by MCP at the pixel granularity, as trees rooted in the first Intra-predicted frame of a group of pictures (GOP), where each predicted pixel is a node in the tree.…”

Section: Introductionmentioning

confidence: 99%

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Dependent video coding using a tree representation of pixel dependencies

et al. 2011

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Motion-compensated prediction induces a chain of coding dependencies between pixels in video. In principle, an optimal selection of encoding parameters (motion vectors, quantization parameters, coding modes) should take into account the whole temporal horizon of a GOP. However, in practical coding schemes, these choices are made on a frame-by-frame basis, thus with a possible loss of performance. In this paper we describe a tree-based model for pixelwise coding dependencies: each pixel in a frame is the child of a pixel in a previous reference frame. We show that some tree structures are more favorable than others from a rate-distortion perspective, e.g., because they entail a large descendance of pixels which are well predicted from a common ancestor. In those cases, a higher quality has to be assigned to pixels at the top of such trees. We promote the creation of these structures by adding a special discount term to the conventional Lagrangian cost adopted at the encoder. The proposed model can be implemented through a double-pass encoding procedure. Specifically, we devise heuristic cost functions to drive the selection of quantization parameters and of motion vectors, which can be readily implemented into a state-of-the-art H.264/AVC encoder. Our experiments demonstrate that coding efficiency is improved for video sequences with low motion, while there are no apparent gains for more complex motion. We argue that this is due to both the presence of complex encoder features not captured by the model, and to the complexity of the source to be encoded.

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Section: Introductionsupporting

confidence: 95%

Section: Introductionmentioning

confidence: 99%