Encoder Preliminary Signal Selection for Transform Coding
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Solution Overview
Problem
The existing coding method for combining CELP and transform coding techniques requires excessive workload due to the need to perform transform coding for all CELP suppressing coefficient candidates, leading to potential deterioration in encoding quality.
Innovation Solution
A coding apparatus and method that preliminary select a subset of suppressing coefficients based on input signal and residual spectrum analysis, reducing the number of transform coding processes and thereby minimizing workload while maintaining encoding quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If transform coding is performed for all CELP suppressing coefficient candidates, then encoding quality is improved, but workload at the coding apparatus increases excessively
Solution Approach 1:
The patent applies preliminary action by performing preliminary transform coding before the main transform coding process. This preliminary coding evaluates multiple CELP suppressing coefficient candidates and identifies promising candidates, so that the subsequent main coding process only needs to process a reduced subset of candidates, thereby reducing overall workload while maintaining encoding quality.
Solution Approach 2:
The patent segments the transform coding process into two distinct stages: preliminary transform coding and main transform coding. The preliminary stage processes all CELP suppressing coefficient candidates to identify promising ones, while the main stage processes only the selected subset. This segmentation divides the computationally intensive task into manageable phases, reducing the workload in the critical main coding path.
2Productivity
If the number of transform coding processes is reduced, then workload is decreased, but encoding quality may deteriorate
Solution Approach 1:
The preliminary transform coding acts as a filtering stage that evaluates all CELP suppressing coefficient candidates and selects only the most promising ones for main coding. This preliminary evaluation ensures that no potentially optimal coefficients are missed, while the reduction to a subset for main coding maintains encoding quality by focusing computational resources on the most relevant candidates.
Solution Approach 2:
The patent replaces the brute-force approach of processing all candidates in the main coding path with a two-stage system where preliminary coding identifies promising candidates. This substitution uses a simpler preliminary evaluation mechanism to filter candidates, allowing the complex main coding to operate on a reduced set, thereby reducing overall workload while preserving quality.
Data Source
AI summary
An encoder apparatus is provided that suppresses the quality degradation of encoding processes. An ultimate selection candidate limiting unit uses the spectrum of an input signal and a residual spectrum to designate a given number of pre-selected suppression factors to a CELP component suppressing unit, which uses the designated suppression factors to generate a suppressed spectrum. A CELP residual signal spectrum calculating unit, to which the suppressed spectrum is input, calculates a residual spectrum. A conversion encoding unit uses the residual spectrum to perform a second encoding process. A distortion evaluating unit determines one of the designated suppression factors by use of the spectrum of a second decoded signal generated by decoding a second code obtained by the second encoding process, and further by use of the suppressed spectrum and the spectrum of the input signal.