All-zero blocks (AZB) denote blocks with all zero DCT coefficients after quantization. Early determination of AZB can
avoid unnecessary DCT/Q/IQ/IDCT computation. Existing techniques in the literature primarily address more efficient
thresholds for early determination of AZB. This paper deals with the selection of such thresholds based on low level
features including motion activity and texture information. This aspect is then utilized to avoid any: (1) unnecessary
quarter accuracy motion estimation, (2) unnecessary multiple reference frame motion estimation, and (3) unnecessary
DCT/Q/IQ/IDCT computation. The developed approach has been applied to two different format video sequences CIF
and QCIF. The results show that the computational complexity is significantly reduced while the video quality is
maintained at a tolerable loss level.
In the H.264/AVC video coding standard, the mode decision component involves a large amount of
computation. This paper presents a fast or computationally efficient mode prediction and selection
approach which has the following attributes: (a) both the spatial and temporal information are used to
achieve early termination using adaptive thresholds, (b) inclusion of a modulator capable of trading off
computational efficiency and accuracy, (c) a homogenous region detection procedure for 8×8 blocks based
on adaptive thresholds. The developed approach consists of three main steps: (1) mode prediction, (2) early
termination based on adaptive thresholds, and (3) refinement by checking all the modes. In addition, in
order to avoid sub-partitions into smaller block sizes for 8x8 blocks, texture information is utilized. It is
shown that the developed approach leads to a computationally efficient video coding implementation as
compared to the previous fast approaches. The results obtained on QCIF, CIF, and HD format video
sequences based on x264 are presented to demonstrate the computational efficiency of the developed
approach at the expense of acceptably low losses in video quality.
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