Audio Signal Synthesizer With Selective Patching for Spectral Band Replication
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Solution Overview
Problem
The existing MPEG-4 Audio standard lacks flexibility in adapting patching algorithms for different audio signals and coding schemes, leading to inefficient high-frequency signal generation in spectral band replication, which results in perceptual degradation and limited bit rate reduction.
Innovation Solution
An audio signal synthesizer that employs a patch generator capable of selecting between multiple patching algorithms based on control information, allowing for independent operation of patching and further processing in different domains, enabling flexible application of patching algorithms and improved spectral band replication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single patching algorithm is used for all audio signals in the MPEG-4 standard, then the implementation is simple and resource-efficient, but the system lacks flexibility to adapt to different audio signals and coding schemes
Solution Approach 1:
The patent implements dynamic selection of patching algorithms based on signal characteristics. The system switches between different patching algorithms (e.g., spectral copying, spectral transformation) depending on whether the input signal is speech, music, or mixed content, allowing optimal performance for each signal type while maintaining a unified implementation framework.
Solution Approach 2:
The system changes parameters such as the patching algorithm type, transformation function selection, and spectral band allocation based on signal analysis results. By adjusting these parameters dynamically, the system adapts to different audio content without requiring completely separate processing paths for each signal type.
2Manufacturing precision
If spectral band replication is used to generate high frequency signals, then bandwidth extension and audio quality are improved, but the processing complexity and resource requirements increase
Solution Approach 1:
The patent divides the frequency spectrum into multiple bands and applies different processing strategies to each band. By segmenting the spectral replication process into distinct frequency regions, the system can apply computationally efficient methods to certain bands while using more complex methods only where necessary, reducing overall processing complexity.
Solution Approach 2:
The system uses spectral copying methods where high-frequency spectral components are generated by copying and transforming low-frequency components. This copying approach is computationally more efficient than generating high-frequency content from scratch, while still achieving perceptually acceptable audio quality through subsequent envelope adjustment and noise floor processing.
3Productivity
If the patching operation is combined with further processing in the same filterbank domain, then implementation is efficient, but flexibility to implement different patching algorithms is reduced
Solution Approach 1:
The patent introduces an intermediary spectral domain representation layer between the patching operation and further processing. Different patching algorithms operate on this intermediate spectral representation, which is then converted back to the time domain or filterbank domain for subsequent processing. This intermediary layer decouples the patching algorithm selection from the processing pipeline, enabling flexibility without sacrificing efficiency.
Data Source
AI summary
An audio signal synthesizer generates a synthesis audio signal having a first frequency band and a second synthesized frequency band derived from the first frequency band and comprises a patch generator, a spectral converter, a raw signal processor and a combiner. The patch generator performs at least two different patching algorithms, each patching algorithm generating a raw signal. The patch generator is adapted to select one of the at least two different patching algorithms in response to a control information. The spectral converter converts the raw signal into a raw signal spectral representation. The raw signal processor processes the raw signal spectral representation in response to spectral domain spectral band replication parameters to obtain an adjusted raw signal spectral representation.