Speech Decoder Pitch Lag Adjustment for Continuous Frame Errors
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Solution Overview
Problem
Existing speech decoding technologies face issues with excessive periodicity and reduced decoding accuracy due to continuous frame errors, particularly in ACELP-based systems, where pitch lag parameters are not effectively managed, leading to sharp noise and quality deterioration.
Innovation Solution
A method and apparatus that calculate and determine the pitch lag parameter of erroneous frames by adjusting it based on the number of continuous erroneous frames, ensuring the value fluctuates within a set range, thereby reducing accumulated errors and avoiding excessive periodicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the pitch lag parameter of the previous frame is used repeatedly for continuous erroneous frames, then the decoding process is simple, but excessive periodicity occurs and decoding accuracy deteriorates
Solution Approach 1:
The pitch lag parameter for erroneous frames is made dynamic by introducing a fluctuation mechanism. Instead of using a fixed previous frame value, the patent applies a dynamic adjustment formula that adds a random fluctuation component to the pitch lag parameter, allowing it to vary within a reasonable range while maintaining continuity. This resolves the contradiction by preventing excessive periodicity without significantly increasing decoding complexity.
Solution Approach 2:
The patent changes the pitch lag parameter by introducing a fluctuation term that varies the parameter value for consecutive erroneous frames. The formula T0(n) = T0(n-1) + fluctuation creates parameter variation that prevents excessive periodicity while keeping the adjustment simple and computationally efficient, thus maintaining low decoding complexity while improving accuracy.
2Measurement precision
If the pitch lag parameter is adjusted to avoid excessive periodicity, then decoding accuracy improves, but accumulated errors increase continuously
Solution Approach 1:
The patent implements a periodic reset mechanism where the pitch lag parameter fluctuation is bounded and periodically anchored to the received value when frame errors stop occurring. This periodic action prevents accumulated errors from growing indefinitely while maintaining the benefits of fluctuation during error periods, thus resolving the contradiction between avoiding excessive periodicity and preventing accumulated errors.
Solution Approach 2:
The patent uses feedback by monitoring the continuity of frame errors and adjusting the pitch lag parameter accordingly. When frame errors occur, the fluctuation mechanism is activated; when errors stop, the parameter is reset to the received value. This feedback-based control prevents accumulated errors while maintaining decoding accuracy during error conditions.
3Measurement precision
If signal classification is performed to determine pitch lag parameters, then decoding accuracy improves, but calculation complexity increases
Solution Approach 1:
The patent extracts and removes the complex signal classification step from the pitch lag determination process. Instead of classifying signals to determine pitch lag parameters, the patent directly applies a simplified fluctuation-based adjustment to the pitch lag parameter, eliminating the need for complex classification calculations while maintaining improved decoding accuracy.
Data Source
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AI summary
The present invention relates to a decoding method and apparatus. The method includes: receiving data frames from the coder; if any erroneous frame appears, calculating and determining a pitch lag parameter of the erroneous frame; decoding the data frames according to the determined pitch lag parameter of the erroneous frame, and obtaining decoded data. The process of determining the pitch lag parameter of the erroneous frame includes: first, determining the number of continuous erroneous frames and the pitch lag parameter of the previous frame; secondly, adjusting the pitch lag parameter of the previous frame according to the number of the continuous erroneous frames and a preset adjustment policy, and calculating and determining the pitch lag parameter of a current erroneous frame, where the preset adjustment policy is: with change of the number of the continuous erroneous frames, the determined pitch lag parameter of the current erroneous frame fluctuates within a set value range. Therefore, excessive periodicity in the decoding process is overcome, and the decoding accuracy is ensured.