Audio Signal Decoding with Temporal Mismatch Compensation
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Solution Overview
Problem
In audio signal decoding, particularly in stereo or multi-channel configurations, the challenge lies in reducing the difference between output signals generated at a second device and the original audio signals received at a first device, especially under limited communication bandwidth, due to temporal shifts and phase mismatches between audio channels.
Innovation Solution
The solution involves an encoder that determines temporal mismatch values between audio signals from multiple microphones, adjusts the target audio signal to align with the reference signal, and generates encoded mid and side signals based on these alignments, optimizing bit allocation to minimize the difference between the original and synthesized audio signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If audio signals are transmitted with limited bandwidth, then communication efficiency is improved, but the difference between output signals and original audio signals increases
Solution Approach 1:
The audio signal is segmented into mid signal and side signal components, which are then independently encoded and transmitted. This segmentation allows for more efficient bandwidth utilization while maintaining signal fidelity, as the mid signal contains the core audio information and the side signal contains the differential information needed for reconstruction.
Solution Approach 2:
Temporal alignment is performed preliminarily at the encoder before encoding and transmission. The encoder determines temporal mismatch values and aligns the mid and side signals in advance, ensuring that when the signals are reconstructed at the decoder, minimal temporal distortion remains even under limited bandwidth conditions.
2Device complexity
If temporal alignment is performed without considering temporal shifts, then processing complexity is reduced, but phase mismatch between channels increases
Solution Approach 1:
The encoder performs preliminary temporal alignment by determining temporal mismatch values between the mid and side signals and applying appropriate shifts before encoding. This preliminary action ensures that phase coherence is maintained without requiring complex real-time processing at the decoder, thus balancing complexity and reliability.
Solution Approach 2:
The system uses feedback mechanisms where the encoder analyzes the temporal characteristics of the audio signals, determines mismatch values, and adjusts the alignment accordingly. This feedback loop ensures that phase coherence is actively maintained based on the actual signal characteristics rather than relying on fixed or assumed alignment parameters.
Data Source
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AI summary
A device includes a receiver and a decoder. The receiver is configured to receive bitstream parameters corresponding to at least an encoded mid signal. The decoder is configured to generate a synthesized mid signal based on the bitstream parameters. The decoder is also configured to generate one or more upmix parameters. An upmix parameter of the one or more upmix parameters having a first value or a second value based on determining whether the bitstream parameters correspond to an encoded side signal. The first value is based on a received downmix parameter. The second value is based at least in part on a default parameter value. The decoder is further configured to generate an output signal based on the synthesized mid signal and the one or more upmix parameters.