Audio Encoder Mode Switching With Artificial Overlap
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Solution Overview
Problem
The AMR-WB+ codec experiences audible artifacts when switching from a standard AMR-WB mode to an extension mode due to the lack of an artificial overlap signal, which is not generated in the standard mode, leading to invalid overlapping signals during coding.
Innovation Solution
The solution involves ensuring that after a switch from the first coder mode to the second coder mode, the first coding model is used for the first section of the audio signal, and an artificial overlap signal is generated based on the first section's information if the second coding model is selected for subsequent sections, preventing the use of invalid overlapping signals and ensuring smooth switching between modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second coding model (requiring overlap signal) is used immediately after switching from the first coder mode, then coding flexibility and audio quality are improved, but invalid overlapping signals cause audible artifacts
Solution Approach 1:
The patent applies preliminary action by forcing the use of the first coding model for the first section after mode switching, ensuring that a valid overlap signal is generated before the second coding model can be applied. This preliminary step prevents the harmful effect of invalid overlap signals that would otherwise cause audible artifacts.
Solution Approach 2:
The patent uses beforehand cushioning by generating a valid overlap signal through the first coding model before transitioning to the second coding model. This cushioning measure ensures that when the second coding model is applied, the required overlap signal is already available and valid, preventing audible artifacts.
2Reliability
If the first coding model is always used after mode switching, then audio quality is maintained, but coding flexibility and adaptation to signal properties are reduced
Solution Approach 1:
The patent applies preliminary action by using the first coding model for only the first section after mode switching to establish valid overlap signals, then allowing the second coding model to be used for subsequent sections. This enables coding flexibility and adaptation to signal properties while maintaining audio quality through the preliminary initialization step.
3Productivity
If quantization tools are not initialized properly during mode switching, then encoding speed is maintained, but audio quality degrades due to improper quantization
Solution Approach 1:
The patent applies preliminary action by forcing the use of the first coding model for the first section after mode switching. This ensures that quantization tools are properly initialized with valid data before the more complex second coding model is applied, maintaining both encoding efficiency and audio quality.
Data Source
AI summary
The invention relates to a method for supporting an encoding of an audio signal, wherein a first coder mode and a second coder mode are available for encoding a respective section of an audio signal. The second coder mode enables a coding of a respective section based on a first coding model, which requires for an encoding of a respective section only information from the section itself, and based on a second coding model, which requires for an encoding of a respective section in addition an overlap signal with information from a preceding section. After a switch from the first coder mode to the second coder mode, always the first coding model is used for encoding a first section of the audio signal. This section can then be employed to generate an artificial overlap signal for a subsequent section, which is possibly to be encoded with the second coding model.