Window Function Audio Sample Rate Mismatch Compensation
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Solution Overview
Problem
In telecommunications systems, differences in clock frequencies between network access devices lead to data rate mismatches, causing artifacts such as clicks and pops in audio signals when reconstructed from digital samples, with existing methods like adding or removing zero samples introducing discontinuity or being computationally expensive.
Innovation Solution
The method involves using window functions to adjust frames of audio samples, either by removing or adding samples, to match different sample rates, thereby compensating for data rate mismatches without introducing audible artifacts, using a combination of gradually increasing and decreasing window functions to recreate the original frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If zero samples or repeat samples are added or removed from a digital signal, then data rate mismatch is compensated, but discontinuity is introduced and audible artifacts (clicks or pops) are generated
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing window function values that gradually increase from 0 to 1 across the frame duration. These pre-computed window values are then applied to smoothly transition between samples when adding or removing samples to compensate for data rate mismatches, preventing the introduction of discontinuities and audible artifacts.
Solution Approach 2:
The patent employs periodic action by applying window functions in a periodic manner across each frame of audio samples. The window function values are applied cyclically to frames as they are processed, with each frame receiving the same periodic windowing treatment to maintain smooth transitions and eliminate artifacts while compensating for data rate differences.
2Object-generated harmful factors
If average samples of surrounding samples are introduced, then some artifact reduction is achieved, but audible artifacts are not completely resolved
Solution Approach 1:
The patent applies parameter changes by systematically varying the window function values across the frame duration, transitioning from 0 to 1 in gradual increments. This parameter variation allows for precise control over the interpolation process, enabling exact sample rate matching while completely eliminating audible artifacts through mathematically smooth transitions between samples.
3Object-generated harmful factors
If prediction based on historical data is used, then sample rate mismatch compensation is achieved, but computational expense becomes too high for embedded applications
Solution Approach 1:
The patent applies this principle by using simple, pre-computed window function values that can be disposed of after a single use in each frame processing. Rather than performing complex predictive calculations on historical data, the system uses inexpensive, pre-calculated window values that require minimal computational resources, making the solution suitable for embedded applications with limited processing power and energy constraints.
Data Source
AI summary
Differing first and second audio signal sample rates from first and second audio signals are matched to each other. If signal sample rates are different, a frame of samples of the first audio signal is duplicated. The duplicate copies are multiplied by a window function and its inverse to produce “windowed frames” first and last samples of which can be deleted or added to increase or decrease a frame rate.