USAC Codec Configurable Upsampling for Temporal Resolution
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Solution Overview
Problem
The Unified Speech and Audio Codec (USAC) has a limited temporal resolution due to its fixed frame size, which restricts the performance of audio processing tools like ACELP, SBR, and MPEG Surround, especially at mid-bitrate ranges, where the current sampling rate is too low for optimal operation.
Innovation Solution
A new operating mode is introduced that allows configurable upsampling and downsampling of audio signals, enabling higher sampling rates for SBR and MPEG Surround while maintaining a lower sampling rate for ACELP, thereby increasing temporal granularity without altering the frame size for core-coders, and modifying resampling ratios to optimize tool performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sampling rate is increased to improve temporal resolution, then the temporal granularity is improved, but the ACELP tool performance deteriorates significantly at higher sampling rates
Solution Approach 1:
The audio signal processing is segmented into two distinct sampling rate domains: a lower sampling rate (e.g., 17075 Hz) for the ACELP tool and a higher sampling rate (e.g., 44100 Hz) for the transform coder, SBR, and MPEG Surround tools. This segmentation allows each tool to operate at its optimal sampling rate independently, resolving the contradiction between temporal resolution and ACELP performance.
Solution Approach 2:
An intermediary upsampling mechanism is introduced that converts the lower sampling rate signal to a higher sampling rate signal using a configurable upsampling factor. This intermediary process enables the higher sampling rate tools to receive properly resampled input without directly affecting the ACELP tool's operating conditions, thus mediating between the conflicting requirements.
2Measurement precision
If the frame size is reduced to increase temporal granularity, then the temporal resolution is improved, but the system complexity increases due to multiple sampling rate configurations
Solution Approach 1:
The system introduces dynamic configurability through a configurator that adapts the upsampling factor based on the ratio between the second configurable number of samples and the first configurable number of samples. This dynamic adjustment mechanism allows the system to optimize temporal granularity while managing complexity through automated configuration rather than fixed rigid structures.
Solution Approach 2:
The invention changes the sampling rate parameter from a fixed value to a configurable parameter with multiple possible values. By allowing the sampling rate to be adjusted according to specific application requirements and by introducing a configurator to manage these parameter changes, the system achieves improved temporal granularity while controlling complexity through systematic parameter management.
3Productivity
If different sampling rates are used for different tools, then tool performance is optimized, but the device complexity increases due to multiple processing paths
Solution Approach 1:
The upsampling mechanism serves multiple functions: it resamples the signal for higher sampling rate tools, maintains compatibility with the fixed frame size structure, and provides a unified interface between different sampling rate domains. This multi-functionality reduces the need for separate dedicated processing paths for each tool, thereby optimizing performance while controlling complexity.
Data Source
AI summary
An apparatus for processing an audio signal is provided. The apparatus has a signal processor and a configurator. The configurator is adapted to configure the signal processor based on configuration information such that a configurable upsampling factor is equal to a first upsampling value when a first ratio of the second configurable number of samples to a first configurable number of samples has a first ratio value. Moreover, the configurator is adapted to configure the signal processor such that the configurable upsampling factor is equal to a different second upsampling value, when a different second ratio of the second configurable number of samples to the first configurable number of samples has a different second ratio value. The first or the second ratio value is not an integer value.