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Video Compression
Published in Jerry D. Gibson, Mobile Communications Handbook, 2017
Do-Kyoung Kwon, Madhukar Budagavi, Vivienne Sze, Woo-Shik Kim
Two context-adaptive entropy coding methods are supported: context-adaptive variable length coding (CAVLC) and context-adaptive binary arithmetic coding (CABAC) [15]. CAVLC is applied only to the coding of transform coefficients while normal VLC is used for the coding of other syntax elements. CAVLC encodes transform coefficients using VLC tables that adapt based on the number of nonzero coefficients of neighboring blocks. CABAC is applied to the coding of all the MB-level syntax elements, including MB header and transform coefficients. CABAC is the combination of binary arithmetic coding technique with context modeling, which consists of three operations of binarization, context modeling, and binary arithmetic coding. A syntax element is first converted to binary symbols called bin string and each bin is arithmetic coded with an updated context model. The context modeling is the key to high coding efficiency of CABAC. Based on the statistics of previously coded syntax elements, the probability model of binary symbols is updated and used to encode them. CABAC improves coding efficiency by around 9–14% over CAVLC at the cost of increased complexity.
Video Compression and MPEG
Published in John Watkinson, The Art of Digital Video, 2013
Optionally, a further technique known as CABAC (context adaptive binary arithmetic coding) may be used in some profiles. This is a system that adjusts the coding dynamically according to the local statistics of the data instead of relying on statistics assumed at the design stage. It is more efficient and allows a coding gain of about 15% with more complexity. CAVLC performs the same function as RLC/VLC in MPEG-2 but it is more efficient. As in MPEG-2 it relies on the probability that coefficient values fall with increasing spatial frequency and that at the higher frequencies coefficients will be spaced apart by zero values.
Compression for Digital Cinema
Published in Charles S. Swartz, Understanding Digital Cinema, 2004
Modern compression systems use enhanced versions of VLC such as context-adaptive variable length coding (CAVLC) or more sophisticated entropy encoders such as arithmetic coding, and context adaptive binary arithmetic coding (CABAC). These technologies can adjust to varying statistics of the data and are a specialist subject in their own right.
A New Low Complexity Bit-truncation Based Motion Estimation and Its Efficient VLSI Architecture
Published in IETE Journal of Research, 2021
Sravan K. Vittapu, Souvik Kundu, Sumit K. Chatterjee
The main objective of video coding is to reduce the amount of data present in the video sequence without degrading its visual quality. From the time video encoding was developed, Motion Estimation (ME) techniques have been applied to reduce the temporal redundancies from the video sequences. Entropy coding techniques such as context-adaptive variable-length coding and context-adaptive binary arithmetic coding have been used to remove statistical redundancies. It should, however, be noted that the ME part is generally the most intricate as well as the most power consuming part of the video encoder [3]. To reduce the overall computational complexity of the video encoder, many ingenious ME methods have been suggested in the literature. However, hardware implementations of these ME methods are few and far between.