Audio Channel Temporal Alignment via Predictive Interpolation
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Solution Overview
Problem
In wireless communication devices, audio signals from multiple microphones can be temporally misaligned due to differences in distance from the sound source, leading to increased differences between audio signals, which results in higher bit usage for encoding and audible artifacts like clicks during playback.
Innovation Solution
A method to adjust audio samples based on mismatch values between microphones, using interpolation techniques to smooth out discontinuities at frame boundaries, ensuring temporal alignment and reducing bit usage for encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If audio signals are temporally aligned by time-shifting frames, then the difference between audio signals is reduced and coding efficiency is improved, but discontinuities may be introduced at frame boundaries causing audible artifacts
Solution Approach 1:
The patent applies preliminary action by predicting future mismatch values before they occur. The encoder predicts a second mismatch value for a second frame based on the first mismatch value from the first frame, then adjusts the target channel samples in advance based on this prediction. This prevents discontinuities at frame boundaries by preparing the appropriate shift adjustment before the boundary is reached, thereby eliminating audible artifacts while maintaining temporal alignment precision.
2Reliability
If multiple audio channels are encoded separately, then channel independence is maintained, but coding efficiency is reduced and bit usage increases
Solution Approach 1:
The patent merges the encoding of multiple audio channels by encoding a reference channel and a target channel together to produce a single encoded output channel. The encoder combines the reference channel samples and adjusted target channel samples through addition, then applies quantization and encoding to the combined signal. This merging approach improves coding efficiency by exploiting the correlation between channels, reducing the total bit usage compared to encoding channels separately, while still maintaining the essential information from both independent channels.
3Measurement precision
If the shift value changes from frame to frame to adapt to distance variations, then temporal alignment accuracy is improved, but discontinuities are introduced at frame boundaries
Solution Approach 1:
The patent resolves the contradiction between temporal alignment accuracy and frame boundary continuity by performing preliminary action. The encoder predicts the second mismatch value before the second frame is processed, then uses this prediction to adjust the target channel samples in advance. This preliminary adjustment ensures that when the frame boundary is reached, the transition is smooth and continuous, preventing discontinuities while still allowing the shift value to adapt to distance variations between frames.
Solution Approach 2:
The patent applies dynamics by making the shift value adaptive rather than static. The mismatch value changes dynamically from frame to frame based on the varying distance between the sound source and microphones. The encoder determines a first mismatch value for the first frame, predicts a second mismatch value for the second frame, and adjusts the target channel accordingly. This dynamic adaptation maintains temporal alignment accuracy while the preliminary adjustment mechanism ensures continuity at frame boundaries.
Data Source
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AI summary
A method for multi-channel audio or speech signal processing includes receiving a reference channel and a target channel, determining a variation between a first mismatch value and a second mismatch value, and comparing the variation with a first threshold that may have a pre-determined value or may be adjusted based on a frame type or a smoothing factor. The method also includes adjusting a set of target samples of the target channel based on the variation and based on the comparison to generate an adjusted set of target samples. Adjusting the set of target samples includes selecting one among a first interpolation and a second interpolation based on the variation. The method further includes generating at least one encoded channel based on a set of reference samples and the adjusted set of target samples. The method also includes transmitting the at least one encoded channel to a second device.