Predictive Coherence Coding for Stereo Comfort Noise Sync
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Solution Overview
Problem
Conventional methods for generating comfort noise in stereo DTX systems fail to adapt to changes in the stereo image of the background noise and lack synchronization between channels, leading to audible artifacts and an inconsistent stereo image.
Innovation Solution
A method is introduced to encode a channel coherence parameter using a predictive scheme with adaptive inter-frame prediction and variable bit rate entropy coding, where coherence vectors are encoded and decoded to maintain synchronization and adapt to changes in the stereo image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional comfort noise generation methods are used in stereo DTX systems, then the implementation is simple, but the stereo image consistency deteriorates and audible artifacts increase
Solution Approach 1:
The patent applies preliminary action by encoding the coherence parameter before the comfort noise generation process. The coherence parameter, which describes the stereo image characteristics, is encoded and transmitted in advance so that the decoder can use it to generate consistent stereo comfort noise. This preliminary encoding ensures that the stereo image consistency is maintained without complicating the actual noise generation process.
Solution Approach 2:
The patent implements feedback by using the decoded coherence parameter to adjust and control the comfort noise generation process. The coherence parameter provides feedback information about the stereo image characteristics, allowing the system to adapt the comfort noise generation to maintain stereo consistency. This feedback mechanism ensures reliability without requiring complex implementation.
2Device complexity
If conventional comfort noise generation methods are used in stereo DTX systems, then the system complexity is low, but synchronization between channels deteriorates
Solution Approach 1:
The patent introduces an intermediary element - the coherence parameter - that mediates between the two channels. This parameter captures the stereo image information and serves as a common reference for both channels during comfort noise generation. By using this intermediary, the system achieves channel synchronization without increasing overall system complexity, as the coherence parameter is encoded once and used by both channels.
3Adaptability or versatility
If adaptive inter-frame prediction is used for coherence parameter encoding, then the stereo image adaptability is improved, but the encoding complexity increases
Solution Approach 1:
The patent applies dynamics by implementing adaptive inter-frame prediction for the coherence parameter encoding. The prediction process dynamically adjusts based on previous frame information, allowing the system to adapt to changes in stereo image characteristics. This dynamic approach improves stereo image adaptability while keeping encoding complexity manageable through efficient prediction algorithms that leverage temporal correlations.
Solution Approach 2:
The patent utilizes parameter changes by modifying the coherence parameter encoding based on inter-frame predictions. The encoding process adapts by changing the representation of the coherence parameter according to predictions from previous frames, reducing the amount of information that needs to be transmitted. This parameter adaptation improves stereo image versatility without proportionally increasing encoding complexity.
Data Source
AI summary
A method, system, and computer program to encode and decode a channel coherence parameter applied on a frequency band basis, where the coherence parameters of each frequency band form a coherence vector. The coherence vector is encoded and decoded using a predictive scheme followed by a variable bit rate entropy coding.