Entropy Coding Mode Switching for Decoder 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 resources, where simpler codecs are needed for lower complexity but at the cost of reduced efficiency, and more complex codecs provide better efficiency but with increased complexity and backward compatibility requirements.
Innovation Solution
A decoder and encoder system that switches between low-complexity and high-efficiency modes by selecting appropriate entropy decoding/encoding schemes based on probability estimates, allowing for arithmetic decoding/encoding with varying control parameters to adapt to different 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 (arithmetic coding) and CAVLC (variable length coding) based on profile identification. The decoder dynamically selects the appropriate entropy decoding scheme by checking profile identifiers in the bitstream, allowing arithmetic coding to be used only when needed for high efficiency profiles while maintaining simple implementation for baseline profiles.
Solution Approach 2:
The patent changes the operational parameters of the entropy decoding engine by switching between different coding modes (CABAC vs CAVLC) based on the identified profile. This parameter change allows the system to adapt its complexity level to match the required coding efficiency, using arithmetic coding only when the high efficiency profile is detected.
2Productivity
If high efficiency mode is activated to improve coding efficiency, then coding efficiency is improved, but energy consumption increases
Solution Approach 1:
The patent dynamically adjusts the decoding complexity and corresponding energy consumption by switching between CABAC and CAVLC modes based on profile identification. Handheld devices can identify the profile and activate the appropriate mode, ensuring that high efficiency (and thus higher energy consumption) is only used when necessary, while low power mode is used for baseline profiles.
3Device complexity
If low complexity mode is used to reduce device complexity, then device complexity is reduced, but coding efficiency deteriorates
Solution Approach 1:
The patent creates a universal decoder that can handle both baseline and high efficiency profiles by implementing both CAVLC and CABAC entropy decoding capabilities. The decoder identifies the profile type and activates the appropriate decoding scheme, making a single decoder universally compatible with different complexity requirements while maintaining optimal efficiency for each profile type.
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.