Synthesis Filter Status Synchronization for Speech Encoding Rate Switching
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Solution Overview
Problem
The synchronization between the reconstructed signals of CELP encoder and decoder terminals is affected when switching between different encoding rates in the G.729.1 speech encoding/decoding standard, leading to inconsistencies and degraded quality of the reconstructed signal.
Innovation Solution
A method and device for updating the statuses of synthesis filters, where an independent synthesis filter is used for each encoding rate, and after each frame is encoded, the status of the synthesis filter corresponding to the current rate is updated, along with the statuses of other rates, ensuring synchronization between the synthesis filters at the encoding terminal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the CELP encoder switches between different encoding rates (8kb/s and 12kb/s), then the adaptability to different channel conditions is improved, but the synchronization between the reconstructed signals of the encoding and decoding terminals deteriorates
Solution Approach 1:
The patent applies preliminary action by updating the status of synthesis filters for other encoding rates in advance before actually switching to those rates. Specifically, when encoding at 8kb/s, the synthesis filter status for 12kb/s is updated using the current reconstructed signal, and vice versa. This ensures that when a rate switch occurs, both encoder and decoder are already synchronized to the same filter status, preventing synchronization errors while maintaining adaptability to different channel conditions
2Manufacturing precision
If independent synthesis filters are used for each encoding rate, then the quality of synthesized speech is improved, but the complexity of the encoding device increases
Solution Approach 1:
The patent merges the functionality of multiple independent synthesis filters by having them share a common status update mechanism. Instead of maintaining completely separate filter instances, the synthesis filters for different encoding rates (8kb/s and 12kb/s) share the same filter structure and coefficients, with their statuses being updated in a coordinated manner. This reduces device complexity while still allowing high-quality synthesis at each rate through the use of rate-specific excitation signals
3Productivity
If the status of synthesis filters is updated only for the current encoding rate, then the processing speed is improved, but the synchronization between encoder and decoder deteriorates when switching rates
Solution Approach 1:
The patent applies preliminary action by performing status updates for future encoding rates in advance. When currently encoding at one rate, the system proactively updates the synthesis filter status for the alternative rate using the current reconstructed signal. This preliminary update ensures that when a rate switch occurs, the decoder already has the correct synchronized status, maintaining reliability without requiring complex real-time synchronization protocols that would slow processing
Data Source
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AI summary
A method and device for updating statuses of synthesis filters are provided. The method includes: exciting a synthesis filter corresponding to a first encoding rate by using an excitation signal of the first encoding rate, outputting reconstructed signal information, and updating status information of the synthesis filter and a synthesis filter corresponding to a second encoding rate. The device includes a plurality of synthesis filters, and a status updating module adapted to synchronously update status information of the synthesis filters. In the present invention, it is allowed to use an independent synthesis filter at each encoding rate during the encoding process; and after each frame is encoded, not only the status of the synthesis filter corresponding to the current rate is updated, but also the statuses of the synthesis filters at other rates is updated. Thus, the synchronization between the statuses of the synthesis filters corresponding to different rates at the encoding terminal is realized, thereby ensuring the consistency of the reconstructed signals of the encoding and decoding terminals when the encoding rate is switched, and improving the quality of the reconstructed signal of the decoding terminal.