Temporal Gain Adjustment for Band-Limited Audio Signal Quality
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Solution Overview
Problem
Existing speech coders face challenges in maintaining high voice quality at low bit rates, often introducing noise or distortion due to limited bit allocation, especially when encoding band-limited signals that lack high-band content.
Innovation Solution
The system adjusts temporal gain parameters based on high-band signal characteristics, limiting variability in gain shape parameters when the signal is band-limited, thereby reducing audible artifacts during encoding and decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If speech coding is performed at low bit rates to reduce data transmission, then data rate is reduced, but voice quality deteriorates due to noise and distortion
Solution Approach 1:
The patent changes the parameter of temporal gain adjustment by detecting high-band signal characteristics and selectively adjusting gain shape parameters. When the high-band signal floor exceeds a threshold, the system adjusts temporal gain parameters to prevent excessive gain variations, thereby maintaining voice quality at low bit rates without requiring increased data transmission
2Manufacturing precision
If temporal gain parameters are adjusted to improve voice quality, then voice quality is improved, but device complexity increases due to additional signal analysis and control logic
Solution Approach 1:
The patent performs preliminary detection of high-band signal characteristics before conducting speech coding. By calculating the high-band signal floor in advance and comparing it against a threshold, the system prepares the gain adjustment strategy beforehand, which simplifies the overall coding process by avoiding complex real-time adjustments during encoding
Solution Approach 2:
The system implements feedback by using the detected high-band signal characteristics to control the temporal gain adjustment process. The gain shape parameters are adjusted based on feedback from the high-band signal floor measurement, creating a closed-loop control mechanism that improves voice quality without requiring complex open-loop processing
3Device complexity
If standard speech coding models are used for band-limited signals, then coding simplicity is maintained, but audible artifacts increase due to mismatch with signal characteristics
Solution Approach 1:
The patent applies local quality by treating high-band and low-band signals differently based on their characteristics. When the high-band signal floor exceeds the threshold, the system selectively adjusts gain parameters for that specific band, rather than applying uniform processing to the entire signal. This localized approach reduces audible artifacts while maintaining overall coding simplicity
Data Source
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AI summary
The present disclosure provides techniques for adjusting a temporal gain parameter and for adjusting linear prediction coefficients. A value of the temporal gain parameter may be based on a comparison of a synthesized high-band portion of an audio signal to a high-band portion of the audio signal. If a signal characteristic of an upper frequency range of the high-band portion satisfies a first threshold, the temporal gain parameter may be adjusted. A linear prediction (LP) gain may be determined based on an LP gain operation that uses a first value for an LP order. The LP gain may be associated with an energy level of an LP synthesis filter. The LP order may be reduced if the LP gain satisfies a second threshold.