Configurable QMF Filter Banks for Low-Complexity Audio Resampling
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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, especially in multimedia devices handling various audio sources.
Innovation Solution
The proposed solution involves a configurable audio signal processor with analysis and synthesis filter banks, controlled by a controller to adjust the number of channels and sampling rates, allowing for flexible sampling rate conversion by modifying the frequency domain representation, reducing the complexity of resampling and eliminating additional signal distortion.
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 device complexity and computational resources increase significantly
Solution Approach 1:
The patent merges the resampling functionality into the existing QMF filter bank structure by making the decimation factor M configurable. Instead of adding separate resampling modules, the same analysis and synthesis filter banks are used for both audio coding and sampling rate adaptation, eliminating the need for additional interpolators, up samplers, and down samplers.
Solution Approach 2:
The patent introduces dynamic configurability to the QMF filter bank by allowing the decimation factor M to be changed based on desired output sampling rates. This dynamic parameter adjustment enables the system to adapt to different sampling rate requirements without requiring multiple fixed-structure resampling modules for each possible sampling rate.
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 worsened
Solution Approach 1:
The patent changes the sampling rate parameter by adjusting the decimation factor M of the QMF filter bank. By selecting different integer values for M, the system can generate output sampling rates that are integer divisors of the input sampling rate, thereby achieving common sampling rates (such as 48 kHz, 44.1 kHz, 32 kHz) that are compatible with standard hardware D/A converters while maintaining the ability to achieve high audio bandwidth through the filter bank processing.
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 segments the audio spectrum into multiple frequency bands using the QMF filter bank structure. By dividing the spectrum into M subbands and selectively processing or transmitting these bands, the system can achieve efficient bit rate utilization while maintaining extended audio bandwidth through techniques like spectral band replication, where lower bands are used to synthesize higher frequency content that extends beyond the Nyquist frequency of the downsampled signal.
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.