Audio Sampling Rate Selection for Constrained Playback Hardware
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Solution Overview
Problem
Constrained devices such as mobile phones and personal data assistants often struggle to play digital audio due to limited processing capabilities, lack of audio hardware support, or unsupported sampling rates, leading to noise introduction and reduced maximum frequency reconstruction during sampling rate conversion.
Innovation Solution
A method is implemented to identify the source sampling rate and select the most appropriate playback sampling rate from supported groups, favoring down-sampling over up-sampling to minimize noise and ensure optimal frequency reconstruction, using predefined groups like 5.5 kHz, 11 kHz, 22 kHz, and 44 kHz, or 8 kHz, 16 kHz, and 32 kHz, to determine the playback rate based on the device's capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If server-side conversion of digital audio is used to support constrained devices, then playback compatibility is improved, but processing time and resource consumption increase
Solution Approach 1:
The patent pre-calculates and stores mapping relationships between source sampling rates and supported playback sampling rates during system initialization or device manufacturing. This preliminary action eliminates the need for real-time conversion decisions, allowing the playback device to quickly select appropriate sampling rates from pre-determined mappings, thus resolving the contradiction between playback compatibility and processing time.
2Adaptability or versatility
If digital audio is re-sampled to unsupported sampling rates, then playback compatibility is improved, but noise is introduced and frequency reconstruction is reduced
Solution Approach 1:
The patent changes the approach from direct re-sampling to selective playback rate selection. Instead of converting the audio signal to a different sampling rate, the system identifies the source sampling rate, determines the device's supported playback sampling rates, and selects the most appropriate rate from pre-defined groups (e.g., 5.5 kHz, 11 kHz, 22 kHz, 44 kHz or 8 kHz, 16 kHz, 32 kHz). This parameter selection approach avoids the noise introduction and frequency reconstruction loss inherent in traditional re-sampling methods.
3Adaptability or versatility
If uncompressed digital audio is re-sampled at the device, then playback compatibility is improved, but processing capability demands increase
Solution Approach 1:
The patent extracts the sampling rate selection logic from the complex re-sampling process. Instead of performing full uncompressed re-sampling operations on constrained devices, the system extracts only the essential function of selecting the appropriate playback sampling rate from supported groups. This extraction significantly reduces processing capability demands while maintaining playback compatibility, as the device only needs to select from pre-defined rates rather than perform computationally intensive conversion operations.
Data Source
AI summary
A source sampling rate is associated with first or second groups of sampling rates. A playback rate is determined by: (a) selecting the source sampling rate if the source sampling rate is supported by a playback environment; (b) otherwise if there is a highest first rate from the first or second groups of playback sampling rates which is supported by the playback environment and is lower than the source sampling rate, selecting the first rate; (c) otherwise if there is a slowest second rate from the group that the source sampling rate is associated with that is supported by the playback environment and is higher than the source sampling rate, selecting the second rate; (d) otherwise selecting the slowest sampling rate supported by the playback environment from the group that the source sampling rate is not associated with as the playback rate.