Audio Encoder Temporal Alignment for Stereo Coding Efficiency
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Solution Overview
Problem
In audio signal encoding, the temporal mismatch between multiple microphones leads to increased redundancy and bit usage, reducing coding efficiency in stereo-encoding techniques like Mid-Side (MS) and Parametric Stereo (PS), especially when sound sources are closer to one microphone than the other, causing delays and misalignment of audio signals.
Innovation Solution
An encoder determines the temporal shift between audio signals from multiple microphones, adjusts the target channel to align with the reference channel, and generates encoded signals using a signal-adaptive flexible stereo coder that transforms signals into the frequency domain to estimate stereo cues and reduce bit usage by minimizing the difference between aligned signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If audio signals from multiple microphones are encoded using traditional stereo-encoding techniques, then the encoding process is simple, but temporal mismatch between signals increases bit usage and reduces coding efficiency
Solution Approach 1:
The patent applies preliminary action by performing temporal alignment of audio signals from multiple microphones before encoding. The system determines time shifts between signals and adjusts them to align properly, ensuring that the encoding process works with synchronized signals. This preliminary alignment prevents temporal mismatch from increasing bit usage and maintains coding efficiency throughout the encoding process.
2Productivity
If audio signals are aligned to reduce temporal mismatch, then bit usage decreases and coding efficiency improves, but the processing complexity increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting temporal parameters (time shifts) of audio signals based on measured mismatch values. The system calculates the degree of misalignment between signals from different microphones and applies corrective time shifts to align them. This parameter adjustment approach efficiently reduces bit usage while maintaining manageable processing complexity through mathematical operations on signal timing parameters.
3Speed
If traditional stereo-encoding is used without temporal alignment, then the encoding process is faster, but more bits are required to encode the side channel signal
Solution Approach 1:
The patent applies preliminary action by performing temporal alignment of audio signals from multiple microphones before encoding. The system determines time shifts between signals and adjusts them to align properly, ensuring that the encoding process works with synchronized signals. This preliminary alignment prevents temporal mismatch from increasing bit usage and maintains coding efficiency throughout the encoding process.
Data Source
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AI summary
A device includes an encoder and a transmitter. The encoder is configured to determine a mismatch value indicative of an amount of temporal mismatch between a reference channel and a target channel. The encoder is also configured to determine whether to perform a first temporal-shift operation on the target channel at least based on the mismatch value and a coding mode to generate an adjusted target channel. The encoder is further configured to perform a first transform operation on the reference channel to generate a frequency-domain reference channel and perform a second transform operation on the adjusted target channel to generate a frequency-domain adjusted target channel. The encoder is also configured to estimate one or more stereo cues based on the frequency-domain reference channel and the frequency-domain adjusted target channel. The transmitter is configured to transmit the one or more stereo cues to a receiver.