Audio Encoding Threshold Adjustment for Transform Coefficient Extraction
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Solution Overview
Problem
Existing methods for extracting transform coefficients in extension bands require significant calculation, especially when the number of coefficients is small, leading to inefficiencies in determining the correct threshold for accurate correlation calculation, which affects the quality and accuracy of sound encoding.
Innovation Solution
A coding apparatus that calculates an initial high threshold to extract a limited number of large-amplitude transform coefficients, then iteratively lowers the threshold to achieve the desired number of coefficients, reducing the number of loops and calculation required for extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all transform coefficients in the extension-band subband are used to calculate the value of correlation, then the accuracy of correlation calculation is improved, but the amount of calculation increases significantly
Solution Approach 1:
The patent extracts only the necessary subset of transform coefficients (those with large amplitudes) from the extension-band subband for correlation calculation, rather than using all coefficients. This extraction is performed by comparing coefficient amplitudes and selecting those that exceed a certain threshold or rank, thereby reducing the calculation load while preserving the accuracy needed for identifying the subband with the largest correlation value.
Solution Approach 2:
The patent applies different processing to different parts of the transform coefficients based on their local characteristics (amplitude values). Coefficients with large amplitudes are selected for correlation calculation, while those with small amplitudes are discarded. This local quality approach ensures that only the most significant coefficients contribute to the correlation calculation, optimizing both accuracy and computational efficiency.
2Reliability
If the number of transform coefficients to be extracted is increased to improve accuracy, then the reliability of correlation calculation is improved, but the amount of calculation increases
Solution Approach 1:
The patent performs partial action by extracting only the necessary number of transform coefficients with the largest amplitudes, rather than processing all coefficients. By extracting a limited number of top-ranked coefficients (e.g., the top 10% or a fixed small number), the patent achieves sufficient reliability for correlation calculation while keeping the computational burden manageable. This partial action is sufficient because the most significant coefficients dominate the correlation result.
3Productivity
If transform coefficients are extracted by setting a threshold based on statistical parameters, then the amount of calculation is reduced, but it becomes difficult to obtain a reliable threshold when the number of coefficients is small
Solution Approach 1:
The patent performs preliminary sorting or ranking of transform coefficients by amplitude before the correlation calculation stage. By pre-organizing the coefficients in descending order of amplitude, the system can easily select the top N coefficients without needing to compute statistical parameters like mean and standard deviation. This preliminary action ensures reliable coefficient selection while minimizing calculation, especially important when the total number of coefficients is small and statistical estimation would be unreliable.
Data Source
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AI summary
Provided is an encoding apparatus. A threshold value calculating unit (32) calculates a threshold value from a statistical amount of conversion factors of an extended band. A representative conversion factor extracting unit (33) uses the calculated threshold value to extract conversion factors having large amplitudes. If the number of extracted conversion factors does not reach a specified number, the threshold value calculating unit (32) determines, in accordance with a lacking number of conversion factors, an amount by which the threshold value should be lowered, and modifies the threshold value accordingly. The representative conversion factor extracting unit (33) uses the threshold value, which has been modified, to extract conversion factors. Such threshold value modification by the threshold value difference calculating unit (32) and such conversion factor extraction by the representative conversion factor extracting unit (33) are repeated until the number of extracted conversion factors reaches the specified number.