QMF Audio Codec Output Resampling Through Adaptive Filter Bank Channels
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Solution Overview
Problem
Current audio processing technologies face challenges in efficiently handling different sampling rates, particularly at low bit rates, which require additional computational resources and are not compatible with low-cost hardware, limiting audio bandwidth and increasing complexity.
Innovation Solution
The implementation of a configurable audio signal processor with analysis and synthesis filter banks, along with a controller, allows for adjustable sampling rates by modifying the frequency domain representation, reducing the complexity of resampling and eliminating additional signal distortion through bandwidth changes in the frequency domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional resampling functional modules (interpolator, up sampler, down sampler) are used to adapt output sampling rate, then sampling rate compatibility is improved, but computational resources and device complexity increase significantly
Solution Approach 1:
The QMF filter bank is designed to perform both audio coding and resampling functions simultaneously. By configuring the analysis and synthesis filter banks with appropriate channel numbers, the system can adapt to different sampling rates without requiring separate dedicated resampling modules, thereby reducing overall device complexity while maintaining sampling rate compatibility
Solution Approach 2:
The invention changes the parameters of the QMF filter bank (specifically the number of analysis and synthesis filter bank channels) to achieve different resampling ratios. By adjusting these parameters according to the formula relationship between input and output sampling rates, the system can adapt to various sampling rates without adding complex resampling functionality
2Adaptability or versatility
If conventional resampling technology is used, then sampling rate adaptation is achieved, but signal distortion increases due to multiple processing stages
Solution Approach 1:
The invention merges the resampling operation with the QMF filter bank synthesis stage. Instead of performing resampling as a separate post-processing step, the synthesis filter bank directly generates the output signal at the desired sampling rate, eliminating intermediate processing stages that would otherwise introduce additional signal distortion
3Adaptability or versatility
If more different sample rates are supported, then audio processing versatility is improved, but the complexity of sample rate adaption increases
Solution Approach 1:
The system dynamically configures the number of analysis and synthesis filter bank channels based on the required sampling rate adaptation. The controller adjusts these parameters in real-time according to the relationship between input and output sampling rates, enabling flexible support for multiple sampling rates without requiring separate fixed configurations for each rate
Data Source
AI summary
An apparatus for processing an audio signal includes a configurable first audio signal processor for processing the audio signal in accordance with different configuration settings to obtain a processed audio signal, wherein the apparatus is adapted so that different configuration settings result in different sampling rates of the processed audio signal. The apparatus furthermore includes n analysis filter bank having a first number of analysis filter bank channels, a synthesis filter bank having a second number of synthesis filter bank channels, a second audio processor being adapted to receive and process an audio signal having a predetermined sampling rate, and a controller for controlling the first number of analysis filter bank channels or the second number of synthesis filter bank channels in accordance with a configuration setting.