Up-sampling TV Audio Signals for Filter Response Accuracy
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Solution Overview
Problem
The BTSC system for television audio signal transmission introduces noise into the stereo and SAP channels due to the nature of FM modulation, and existing digital filters struggle to accurately match the ideal transfer functions defined in the BTSC standard, leading to degradation in audio performance.
Innovation Solution
The implementation of up-sampling digital audio signals to increase their sample rate, allowing for better matching of digital filter magnitude and phase responses to the ideal transfer functions, thereby improving audio performance and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If digital filters are used to process television audio signals according to BTSC standards, then the system complexity is reduced, but the accuracy of filter magnitude and phase responses deteriorates, leading to poor stereo separation and degraded audio parameters
Solution Approach 1:
The patent applies preliminary action by up-sampling the digital audio signal before filtering. By increasing the sample rate prior to digital filter processing, the system enables simpler filters to achieve better frequency response accuracy. The up-sampling operation inserts additional samples between original samples, allowing the subsequent digital filter to more accurately match the ideal transfer functions defined in BTSC standards, thereby improving stereo separation and audio parameters without increasing filter complexity.
2Adaptability or versatility
If FM modulation is used to transmit the Difference channel, then stereo audio transmission is enabled, but noise increases due to the nature of FM modulation
Solution Approach 1:
The patent applies parameter changes by modifying the sample rate parameter of the digital audio signal. By up-sampling to a higher sample rate before FM modulation, the system improves the effectiveness of digital filtering in reducing noise. The higher sample rate allows digital filters to more effectively attenuate high-frequency noise components introduced by FM modulation, while preserving the stereo transmission capability through proper filter design that matches ideal transfer functions.
Data Source
AI summary
A television audio signal encoder includes an up-sampler that inserts additional samples into a sum signal, a difference signal, and/or a secondary audio program signal to increase the sample rate of the corresponding signal or signals. The sum signal represents the sum of a left channel digital audio signal and a right channel digital audio signal and the difference signal represents the difference between the left and right audio signals.