QMF Audio Codec Filter Banks for Low-Complexity Sample Rate Conversion
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Solution Overview
Problem
Current audio processing technologies face challenges in efficiently adapting to different sampling rates, particularly at low bit rates, which limits compatibility with low-cost hardware and increases computational resources due to the need for additional resampling steps and high complexity in resampling processes.
Innovation Solution
The proposed solution involves a configurable audio signal processor with analysis and synthesis filter banks that can adjust the number of channels based on configuration settings, allowing for different sampling rates by modifying the frequency domain representation and reducing the complexity of filter banks through transform length adjustments, thereby eliminating the need for high-complexity resamplers and reducing computational resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional resampling functional modules are used to adapt the output sampling rate, then sampling rate compatibility is improved, but computational resources and device complexity increase significantly
Solution Approach 1:
The patent merges the resampling functionality with the existing analysis and synthesis filter banks by adjusting their channel numbers. Instead of adding separate resampling modules, the filter banks are configured to directly produce output at the desired sampling rate by changing the number of analysis and synthesis channels, thereby reducing device complexity while maintaining sampling rate adaptability.
Solution Approach 2:
The analysis and synthesis filter banks are designed to serve multiple functions: both audio processing and sampling rate adaptation. By making the number of channels configurable, the same filter bank structure can adapt to different sampling rates without requiring dedicated resampling hardware, thus reducing overall system complexity.
2Adaptability or versatility
If the number of analysis and synthesis filter bank channels is increased to support multiple sampling rates, then sampling rate flexibility is improved, but computational resources increase
Solution Approach 1:
The patent implements dynamic configuration of the filter bank channel numbers based on the desired sampling rate. Rather than maintaining a fixed large number of channels for all possible sampling rates, the system dynamically adjusts the channel count to match the specific sampling rate requirement, optimizing computational resource usage while maintaining flexibility.
Solution Approach 2:
The system changes the operational parameters (number of channels) of the filter banks to adapt to different sampling rates. By modifying the channel configuration parameter rather than adding physical hardware, the system achieves sampling rate flexibility with minimal increase in computational resources.
3Adaptability or versatility
If conventional resampling techniques are used, then sampling rate adaptation is achieved, but signal distortion increases
Solution Approach 1:
The patent uses the filter bank transformation as an intermediary process for sampling rate adaptation. Instead of directly resampling which causes distortion, the signal is transformed through the filter bank domain where sampling rate changes are achieved by channel number adjustment, preserving signal accuracy while enabling adaptation.
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.