Audio Signal Temporal Alignment for Coding Efficiency
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Solution Overview
Problem
In audio processing, the temporal offset between audio signals captured by multiple microphones leads to increased side channel energies, reducing coding efficiency due to misalignment and variations in shift estimates, especially in stereo encoding, causing sample repetition and artifact skipping.
Innovation Solution
A system that estimates and compensates for temporal shifts between audio signals from multiple microphones by determining a final shift value and using it to align the signals, thereby reducing side channel energies and improving coding efficiency through dynamic adjustment of coding modes based on shift values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stereo encoding is performed on audio signals from multiple microphones, then spatial audio quality is improved, but temporal offset between signals increases side channel energies reducing coding efficiency
Solution Approach 1:
The system performs preliminary temporal alignment by estimating the time offset between audio signals from multiple microphones before encoding. This preliminary action of aligning the signals in the time domain prevents excessive side channel energy from occurring during encoding, thereby maintaining coding efficiency while preserving spatial audio quality.
Solution Approach 2:
The system changes the temporal parameter of the audio signals by applying time shifts based on estimated offset values. This parameter change aligns the signals temporally, reducing the magnitude of side channel signals and improving coding efficiency without compromising the spatial characteristics needed for audio quality.
2Measurement precision
If frame-based shift estimation is used to handle temporal offsets, then alignment accuracy for specific frame types is improved, but variations in shift estimates cause sample repetition and artifact skipping
Solution Approach 1:
The system dynamically adjusts shift estimates across different frame types by smoothing transitions between voiced, unvoiced, and transition frames. This dynamic approach prevents abrupt changes in alignment that would cause sample repetition or artifact skipping, while maintaining accurate alignment where applicable.
Solution Approach 2:
The system applies smoothing or interpolation to shift estimates before encoding to cushion against variations that would cause artifacts. This preparatory measure ensures continuous and smooth signal alignment across frame boundaries, preventing sample repetition and artifact skipping.
3Productivity
If temporal alignment is applied to reduce side channel energies, then coding efficiency is improved, but complexity of determining shift values increases
Solution Approach 1:
The system segments the audio signal into different frame types (voiced, unvoiced, transition) and applies appropriate shift estimation methods to each segment. This segmentation allows the use of simpler estimation techniques for certain frame types while maintaining accuracy, reducing overall computational complexity.
Solution Approach 2:
The system applies partial alignment by focusing shift estimation on critical frame types or regions where temporal offset has the greatest impact on side channel energy. This selective approach reduces computational complexity compared to exhaustive alignment of all frames, while still achieving coding efficiency improvements.
Data Source
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AI summary
A device includes a processor and a transmitter. The processor is configured to determine a first mismatch value indicative of a first amount of a temporal mismatch between a first audio signal and a second audio signal. The processor is also configured to determine a second mismatch value indicative of a second amount of a temporal mismatch between the first audio signal and the second audio signal. The processor is further configured to determine an effective mismatch value based on the first mismatch value and the second mismatch value. The processor is also configured to generate at least one encoded signal having a bit allocation. The bit allocation is at least partially based on the effective mismatch value. The transmitter configured to transmit the at least one encoded signal to a second device.