Adaptive Coding Method for PCM Compression
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Solution Overview
Problem
The prediction coding method's efficiency is low when the number of samples in a frame is small, leading to insufficient compression performance.
Innovation Solution
A coding method that selects between prediction coding and normalization coding based on which produces a smaller code amount, with the selection process involving comparison of code amounts from both methods and outputting the appropriate compression code along with a selection code.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If prediction coding method is used for small frame size, then linear prediction can be performed, but compression performance is insufficient
Solution Approach 1:
The patent dynamically switches between prediction coding and normalization coding based on frame characteristics. A selection determination unit evaluates each frame and chooses the most appropriate coding method, making the system adaptive rather than static. This resolves the contradiction by allowing the system to use prediction coding when appropriate while falling back to normalization coding when prediction efficiency is low.
Solution Approach 2:
The patent changes the coding parameter (coding method) based on frame conditions. When the frame size is small or prediction efficiency is low, the system switches from prediction coding to normalization coding. This parameter change allows the system to maintain good compression performance across different frame conditions without being constrained by the limitations of a single coding method.
2Device complexity
If only prediction coding method is used, then coding process is simple, but code amount is larger
Solution Approach 1:
The system dynamically selects between coding methods based on frame characteristics. The selection determination unit evaluates prediction efficiency and frame size, then chooses the method that produces smaller code amounts. This dynamic approach increases complexity slightly but significantly reduces the code amount by avoiding inefficient prediction coding in unsuitable conditions.
Solution Approach 2:
The patent implements both prediction coding and normalization coding paths, effectively creating a backup or alternative copy of the coding process. When prediction coding proves inefficient, the system can copy the frame data and apply normalization coding instead, ensuring smaller code amounts are achieved without losing the simplicity of the original prediction coding approach.
3Loss of time
If frame length is shortened to reduce delay, then transmission delay is reduced, but prediction efficiency decreases
Solution Approach 1:
The system dynamically adapts to different frame lengths by selecting the appropriate coding method. When frame length is shortened for reduced delay, the system detects the reduced prediction efficiency and dynamically switches to normalization coding, which does not rely on prediction and thus performs well with short frames. This resolves the contradiction between delay reduction and prediction efficiency.
Solution Approach 2:
The patent changes the coding parameter based on frame length. For short frames where prediction efficiency is inherently low, the system switches from prediction coding to normalization coding. This parameter change allows the system to maintain effective compression even when frame length is reduced for lower delay, without being constrained by the prediction efficiency limitation.
Data Source
AI summary
A lossless coding technique for near-logarithmic companded PCM that achieves high compression performance is provided. In coding, the coding method that produces the smaller code amount is selected between the prediction coding method, which performs linear prediction of samples in a frame and codes the amplitude of the prediction error, and the normalization coding method, which normalizes the amplitude of the samples in the frame and codes the normalized amplitude, and a selection code that indicates the selection result is output. The samples in the frame are coded according to the selected coding method to produce a compression code. In decoding, the compression code is decoded according to a decoding process corresponding to the coding method specified by the selection code.