Configurable QMF Filter Banks for Audio Codec Sample Rate Output

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Solution Overview

Problem

Current audio processing technologies face challenges in efficiently adapting output sampling rates of QMF-based audio codecs, particularly at low USAC bit rates, which are not compatible with low-cost hardware D/A converters and require additional computational resources for resampling.

Innovation Solution

The proposed solution involves a configurable audio signal processor with an analysis and synthesis filter bank system that allows for different configuration settings to achieve various sampling rates. This system includes a controller that adjusts the number of filter bank channels based on configuration settings, enabling the output signal to have a predetermined or adjusted sampling rate.

Engineering Contradictions & Design Principles

VSEngineering 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

Engineering Contradiction:

Improvesampling rate compatibilityVSAvoidresampling module complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges the resampling functionality with the existing QMF filter bank structure by adjusting the number of analysis and synthesis filter bank channels. Instead of adding separate resampling modules, the sampling rate adaptation is achieved by configuring the filter bank channel count, thereby reducing device complexity while maintaining sampling rate compatibility.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The QMF filter bank is designed to serve multiple functions: both audio signal processing and sampling rate adaptation. By making the number of analysis and synthesis filter bank channels configurable, the same filter bank structure can handle different sampling rates without requiring dedicated resampling hardware for each rate.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If additional resampling functional modules are used to adapt output sampling rate, then sampling rate compatibility is improved, but computational resources increase significantly

Engineering Contradiction:

Improvesampling rate compatibilityVSAvoidcomputational resources

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent combines resampling operations with the existing filter bank processing. The analysis filter bank decomposes the input signal into subbands, and the synthesis filter bank reconstructs the output signal, with the sampling rate adaptation achieved by adjusting channel counts rather than adding separate computational resampling stages.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The QMF filter bank structure is made self-sufficient for resampling by allowing its channel configuration to directly determine the output sampling rate. The filter bank performs both its traditional signal processing function and the resampling function simultaneously, eliminating the need for additional computational resources.

Inventive Principle:

Principle #25Self-service

3Device complexity

If the number of analysis and synthesis filter bank channels is adjusted to change sampling rate, then resampling complexity is reduced, but signal distortion may increase

Engineering Contradiction:

Improveresampling complexityVSAvoidsignal quality

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent changes the parameter of filter bank channel count to achieve sampling rate adaptation. By adjusting the number of analysis and synthesis filter bank channels, the output sampling rate is modified while maintaining signal quality through the inherent properties of the QMF filter bank design.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The filter bank channel configuration is made dynamic and configurable, allowing the system to adapt the number of channels based on the desired output sampling rate. This dynamic adjustment enables flexible sampling rate changes while maintaining optimal signal processing characteristics through proper filter bank design.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS20250046324A1Resampling output signals of QMF based audio codec

Publication Date: 2025.02.06 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

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.