Entropy Decoding Mode Switching for Codec Complexity Tradeoffs
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Solution Overview
Problem
Current media codecs face challenges in achieving a balance between coding complexity and efficiency, particularly in handheld devices with limited energy, where simpler codecs are needed for lower complexity but more complex codecs offer better efficiency and backwards compatibility.
Innovation Solution
A decoder and encoder system that switches between low-complexity and high-efficiency modes by selecting from multiple entropy decoding/encoding schemes, using arithmetic decoding/encoding with varying probability estimates and control parameters based on data stream conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If arithmetic coding schemes are used to improve coding efficiency, then coding efficiency is improved, but device complexity increases
Solution Approach 1:
The patent implements dynamic mode switching between CABAC (high efficiency) and CAVLC (low complexity) entropy decoding schemes based on profile/level parameters in the bitstream. The decoder adapts its complexity level dynamically by selecting the appropriate decoding mode, allowing it to optimize between coding efficiency and device complexity requirements for different H.264 profiles and applications.
2Productivity
If high-efficiency coding modes are implemented to improve compression, then coding efficiency is improved, but energy consumption increases
Solution Approach 1:
The patent changes operational parameters by selecting different entropy decoding schemes (CABAC vs CAVLC) based on profile/level indicators in the bitstream. This parameter change allows the decoder to adjust its computational workload and energy consumption to match the available resources in handheld devices, thereby reducing energy usage while maintaining acceptable compression efficiency.
3Device complexity
If simple coding schemes are used to reduce complexity, then device complexity is reduced, but coding efficiency deteriorates
Solution Approach 1:
The patent creates a universal decoder that can perform both CABAC and CAVLC entropy decoding functions within a single implementation. By incorporating both decoding schemes and using profile/level parameters to select the appropriate mode, the decoder achieves multi-functionality that serves both low-complexity and high-efficiency requirements across different H.264 profiles and application scenarios.
Data Source
AI summary
A decoder for decoding a data stream into which media data is coded has a mode switch configured to activate a low-complexity mode or a high-efficiency mode depending on the data stream, an entropy decoding engine configured to retrieve each symbol of a sequence of symbols by entropy decoding using a selected one of a plurality of entropy decoding schemes, a desymbolizer configured to desymbolize the sequence of symbols to obtain a sequence of syntax elements, a reconstructor configured to reconstruct the media data based on the sequence of syntax elements, selection depending on the activated low-complexity mode or the high-efficiency mode. In another aspect, a desymbolizer is configured to perform desymbolization such that the control parameter varies in accordance with the data stream at a first rate in case of the high-efficiency mode being activated and the control parameter is constant irrespective of the data stream or changes depending on the data stream, but at a second lower rate in case of the low-complexity mode being activated.