Speech Signal Encoding With Adaptive LTP for Lower Bit Consumption
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Solution Overview
Problem
In speech coding, the Long-Term Prediction (LTP) processing consumes too many bits when the speech signal is less periodic, leading to reduced compression performance due to unnecessary pitch gain quantization.
Innovation Solution
A method that adaptively determines a long-term flag to decide whether to consider LTP processing results, disabling LTP processing when the flag is set to a second flag, thus avoiding unnecessary bit consumption and improving compression performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LTP processing is always performed for speech signals, then the tone structure of voiced speech is preserved, but the bit consumption increases significantly when the speech signal is less periodic
Solution Approach 1:
The patent applies dynamics by making the LTP processing adaptive rather than static. The long-term flag is dynamically set based on the periodicity of the speech signal, allowing the system to switch between LTP processing and non-LTP processing modes. This resolves the contradiction by preserving tone structure only when necessary (periodic signals) while avoiding unnecessary bit consumption for aperiodic signals.
Solution Approach 2:
The patent changes the parameter of LTP processing activation based on speech signal characteristics. By introducing the long-term flag that can take different values (indicating whether LTP should be applied), the system adapts the processing parameter to match the speech signal's periodicity, thus resolving the contradiction between maintaining tone structure and reducing bit consumption.
2Measurement precision
If pitch gain quantization is performed for all speech signals, then the encoding accuracy is maintained, but the compression performance deteriorates for less periodic signals
Solution Approach 1:
The patent makes pitch gain quantization dynamic by conditionally applying it only when the long-term flag indicates periodic speech signals. This adaptive approach maintains encoding accuracy for voiced sounds while improving compression performance for aperiodic signals by skipping unnecessary quantization steps.
Solution Approach 2:
The patent changes the quantization parameter based on the long-term flag state. When the flag indicates aperiodic signals, the pitch gain quantization parameter is effectively disabled or reduced, thus maintaining accuracy for periodic signals while improving overall compression performance across different signal types.
3Reliability
If LTP processing is applied to all speech frames, then the fine structure of spectrum is preserved, but the encoding complexity increases unnecessarily
Solution Approach 1:
The patent applies dynamics by making LTP processing conditional rather than unconditional. The long-term flag dynamically controls whether LTP processing is applied to each speech frame based on its periodicity characteristics, thus preserving spectrum fine structure only when needed while reducing encoding complexity for aperiodic frames.
Solution Approach 2:
The patent changes the processing parameter (LTP application) based on speech frame characteristics indicated by the long-term flag. This allows the system to maintain spectrum fine structure for periodic signals while avoiding unnecessary processing complexity for aperiodic signals.
Data Source
AI summary
Method, apparatus, and system for encoding and decoding signals are disclosed. The encoding method includes: converting a first-domain signal into a second-domain signal; performing Linear Prediction (LP) processing and Long-Term Prediction (LTP) processing for the second-domain signal; obtaining a long-term flag according to a decision criterion; obtaining a second-domain predictive signal according to the LP processing result and the LTP processing result when the long-term flag is a first flag; or obtaining a second-domain predictive signal according to the LP processing result when the long-term flag is a second flag; converting the second-domain predictive signal into a first-domain predictive signal, calculating a first-domain predictive residual signal; and outputting a bit stream that includes the first-domain predictive residual signal. Subsequent encoding or decoding process is performed adaptively according to the long-term flag; and it is not always necessary to consider the LTP processing result, thus improving the compression performance of codec.