Multi-Channel Audio Encoding With Down-Mix Level Compensation
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Solution Overview
Problem
Existing methods for encoding and decoding multi-channel audio signals often result in signal level attenuation during down-mixing, leading to signal distortion and quality deterioration due to the offset of channel levels, which cannot be fully addressed by varying the energy level in a predetermined frequency domain.
Innovation Solution
The method involves calculating a compensation parameter based on the multi-channel audio signal and down-mix signal to generate additional information that compensates for the attenuation, allowing for effective encoding and decoding of multi-channel audio signals by combining spatial information and the compensation parameter into a bitstream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a multi-channel audio signal is down-mixed into a mono or stereo signal for encoding, then the encoding complexity is reduced and bitrate is lowered, but signal level attenuation occurs causing distortion and quality deterioration
Solution Approach 1:
The patent calculates compensation parameters in advance during the encoding process, storing them alongside spatial information. These pre-calculated parameters compensate for the level attenuation that will occur during down-mixing, allowing the decoder to restore accurate signal levels without adding complexity to the decoding operation.
Solution Approach 2:
The patent introduces compensation parameters as an intermediary element between the down-mixed signal and the original multi-channel signal. These parameters act as a mediator that carries information about the level attenuation, enabling the decoder to accurately reconstruct the original signal levels by applying the compensation during the up-mixing process.
2Productivity
If channel signals are added up during down-mixing, then the down-mix signal is generated efficiently, but level attenuation occurs because channels offset each other rather than overlapping
Solution Approach 1:
The patent implements a feedback mechanism where the encoder calculates compensation parameters based on the actual level attenuation observed during down-mixing. These parameters are fed back into the bitstream and used by the decoder to correct the level inaccuracies, creating a closed-loop system that maintains level accuracy despite the efficient down-mixing process.
Solution Approach 2:
The patent changes the parameter representation by introducing compensation parameters that explicitly encode the level attenuation characteristics. Instead of trying to preserve exact levels through complex down-mixing algorithms, the system allows level parameters to be adjusted and corrected using the compensation data stored in the bitstream.
3Manufacturing precision
If spatial information is used to restore the original multi-channel audio signal, then the multi-channel quality is improved, but the relationship between channel levels becomes inaccurate due to prior attenuation
Solution Approach 1:
The compensation parameters are calculated and stored in advance during encoding, preserving the level relationship information before it is lost during down-mixing. This preliminary action ensures that when the decoder restores the multi-channel signal using spatial information, the original level relationships are accurately recovered through application of these pre-stored compensation values.
Data Source
AI summary
Methods and apparatuses for encoding and decoding a multi-channel audio signal are provided. In the encoding method, spatial information is calculated based on a multi-channel audio signal and a down-mix signal, and a compensation parameter that compensates for the down-mix signal is calculated based on the multi-channel audio signal and the down-mix signal. Thereafter, a bitstream is generated by encoding the spatial information, the compensation parameter, and the down-mix signal and combining the results of the encoding. Therefore, it is possible to prevent deterioration of the quality of sound regarding a multi-channel audio signal by compensating for the multi-channel audio signal using a compensation parameter that compensates for a down-mix signal.