Entropy Decoder Mode Switching for Complexity-Efficiency 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 appropriate entropy decoding/encoding schemes based on probability estimates and control parameters, allowing for adaptive processing of media data streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If arithmetic coding schemes are used, 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 requirements and data stream conditions. The decoder can adaptively select the appropriate entropy decoding scheme, allowing high efficiency when needed while reducing complexity for baseline profile compatibility, thus resolving the contradiction between coding efficiency and device complexity
Solution Approach 2:
The patent changes the parameter of entropy decoding scheme selection based on profile parameters and data stream analysis. By dynamically adjusting which decoding scheme is active (CABAC vs CAVLC), the system optimizes the balance between coding efficiency and computational complexity according to specific application requirements
2Productivity
If main profile conform decoders are made to support arithmetic coding, then coding efficiency is improved, but energy consumption increases
Solution Approach 1:
The patent enables dynamic activation of arithmetic decoding (CABAC) only when required by the profile or data stream conditions, rather than permanently enabling it. This allows handheld devices to consume less energy by using simpler CAVLC decoding when possible, while still supporting high-efficiency CABAC decoding when needed, thus resolving the energy consumption contradiction
3Device complexity
If baseline profile decoders are used, then device complexity is reduced, but coding efficiency decreases
Solution Approach 1:
The patent designs a universal decoder architecture that can operate in multiple modes (both CAVLC and CABAC). This allows a single decoder to serve both baseline profile applications (using simple CAVLC for low complexity) and main profile applications (using efficient CABAC for high efficiency), thus resolving the contradiction between complexity reduction and efficiency maintenance
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.