QMF Audio Codec Filter Banks for Low-Complexity Output Resampling
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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 proposed solution involves a configurable audio signal processor with analysis and synthesis filter banks that adjust the number of channels based on configuration settings, allowing for different sampling rates and reducing computational complexity by modifying the frequency domain representation, thereby eliminating the need for high-complexity resamplers.
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 patent combines the resampling functionality with the existing analysis and synthesis filter banks already present in the audio codec. By merging the resampling operation into the filter bank structure, the system achieves sampling rate adaptation without adding separate resampling modules, thus avoiding the associated computational overhead and complexity.
Solution Approach 2:
The analysis and synthesis filter banks are designed to serve multiple functions: both audio signal processing and sampling rate adaptation. By making the filter bank multi-functional, the system eliminates the need for dedicated resampling hardware, reducing overall device complexity while maintaining versatility in supporting different sampling rates.
2Manufacturing precision
If uncommon sampling rates are used to increase audio bandwidth and scalability, then audio quality is improved, but compatibility with low-cost hardware D/A converters is lost
Solution Approach 1:
The patent dynamically changes the sampling rate parameter based on the desired audio bandwidth and hardware capabilities. By adjusting the sampling rate as a configurable parameter rather than fixing it to uncommon values, the system maintains high audio bandwidth where needed while ensuring compatibility with standard hardware D/A converters in other scenarios.
Solution Approach 2:
The system employs dynamic sampling rate selection that adapts to different operating conditions and hardware capabilities. Rather than using fixed uncommon sampling rates, the sampling rate becomes a dynamic parameter that can be adjusted to match both audio quality requirements and hardware compatibility constraints.
3Productivity
If sampling rate is reduced at low bit rate operating points, then bit rate efficiency is improved, but audio bandwidth is limited to Nyquist frequency below human audible range
Solution Approach 1:
The patent addresses the bandwidth limitation by transforming the problem from the time domain to the frequency domain through the filter bank structure. This dimensional change allows for more flexible manipulation of spectral content, enabling the system to achieve extended audio bandwidth beyond the strict Nyquist limit of the reduced sampling rate by utilizing the filter bank's frequency domain processing capabilities.
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.