Mono Audio Signal Synthesis via Parameter Domain Combination
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Solution Overview
Problem
Current audio coding systems require significant processing load to synthesize a mono audio signal from an encoded multichannel audio signal, especially when dealing with unbalanced multichannel inputs, leading to signal attenuation and reduced audio quality.
Innovation Solution
Combining parameter values of multiple channels in the parameter domain before decoding to synthesize a mono audio signal, using averaged or weighted gain factors and linear prediction coefficients, and selectively disregarding silent channel parameters to maintain spectral characteristics and signal level similar to the active channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate channel synthesis is performed for multichannel audio signals, then audio quality is maintained, but processing load increases significantly
Solution Approach 1:
The patent combines the synthesis operations for multiple channels into a single unified synthesis process. Instead of separately synthesizing each channel and then mixing them, the method synthesizes a single mono signal using combined parameter values from all channels, thereby reducing processing load while maintaining audio quality through proper parameter aggregation.
Solution Approach 2:
The synthesis filterbank is designed to handle both mono and multichannel inputs universally. By using a single synthesis filterbank that processes combined parameter values from multiple channels, the system achieves multi-functionality, eliminating the need for separate synthesis paths for each channel and reducing overall processing requirements.
2Productivity
If multichannel audio signals are downmixed to mono by simple averaging, then processing load is reduced, but signal attenuation occurs and audio quality deteriorates
Solution Approach 1:
The patent changes the parameters used in the synthesis process by aggregating parameter values (such as gain factors and linear prediction coefficients) from multiple channels before synthesis. This parameter transformation allows the system to maintain proper signal levels and spectral characteristics while using a single synthesis path, avoiding signal attenuation that occurs with simple averaging.
Solution Approach 2:
The method performs preliminary aggregation of parameter values from all channels before the actual synthesis process. By combining gain factors and linear prediction coefficients in advance, the system prepares consolidated parameters that preserve signal integrity and prevent attenuation during the subsequent single-channel synthesis operation.
3Device complexity
If parameter values from silent channels are included in synthesis, then processing is simplified, but spectral characteristics and signal level are compromised
Solution Approach 1:
The patent applies local quality by evaluating each channel's activity level and treating silent channels differently from active channels. The system identifies silent channels and excludes their parameter values from the synthesis process, while still maintaining the simplicity of a single synthesis path. This selective inclusion of parameters preserves spectral characteristics and signal level quality.
Data Source
AI summary
The invention relates to a method of synthesizing a mono audio signal 3 based on an available encoded multichannel audio signal 2. The encoded multichannel audio signal 2 is assumed to comprise at least for a part of an audio frequency band separate parameter values for each channel of the multichannel audio signal. In order to reduce the processing load in synthesizing the mono audio signal 2, it is proposed that the parameter values of the multiple channels are combined at least for a part of an audio frequency band in the parameter domain. The combined parameter values are then used for synthesizing the mono audio signal. The invention relates equally to a corresponding audio decoder, to a corresponding coding system and to a corresponding software program product.