Audio Waveform Timing Correction for MIDI Synchronization
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Solution Overview
Problem
Existing automatic performance systems using audio waveform data and MIDI data often experience timing deviations and sound quality deterioration when synchronizing tones, leading to an unnatural auditory impression, especially when time stretch control is applied to audio waveform data.
Innovation Solution
The system stores reference and correction position information with the audio waveform data to adjust the reproduction timing, evaluating deviations at reference timing points and correcting them at specific sync points where the amplitude is low or autocorrelation is high, preventing sound quality deterioration and ensuring synchronized reproduction with MIDI data at variable tempos.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If time stretch control is applied to audio waveform data to adjust reproduction tempo, then the performance tempo can be changed, but timing deviations accumulate and cause disharmony between MIDI and audio tones
Solution Approach 1:
The system continuously monitors the timing deviation between audio waveform reproduction and MIDI event reproduction, and dynamically adjusts the audio reproduction position based on this feedback. A deviation detection unit measures the timing difference, and a reproduction position adjustment unit corrects the audio playback position in real-time to maintain synchronization with MIDI events, preventing cumulative timing errors.
Solution Approach 2:
The patent replaces traditional mechanical time stretch control methods with a digital signal processing approach. Instead of physically stretching or compressing audio data, the system uses arithmetic operations on digital audio samples to achieve tempo adjustment while maintaining precise timing control through software-based synchronization mechanisms.
2Manufacturing precision
If audio waveform data is stretched or compressed on the time axis to match MIDI tempo, then tempo synchronization is achieved, but arithmetic errors cause slight timing deviations
Solution Approach 1:
The system implements continuous feedback monitoring of timing deviation between audio and MIDI reproduction. A deviation detection unit measures the actual timing difference, and this information feeds back to the reproduction position adjustment unit, which dynamically corrects the audio playback position to eliminate timing errors caused by arithmetic operations in time stretch control.
Solution Approach 2:
The system pre-calculates and stores optimal reproduction positions for audio waveform data at various time points during the time stretch process. By preparing correction data in advance based on the desired tempo and original audio timing, the system can apply precise corrections without introducing additional arithmetic errors during real-time playback.
3Reliability
If reproduction position of audio waveform data is corrected every predetermined period, then timing synchronization with MIDI data is improved, but sound quality deteriorates due to waveform discontinuity
Solution Approach 1:
The system pre-analyzes the audio waveform data to identify optimal correction positions where timing adjustment will have minimal impact on sound quality. By selecting correction points strategically in advance, the system can apply timing corrections while avoiding positions that would cause audible artifacts or waveform discontinuities.
Solution Approach 2:
The system applies different correction strategies at different positions within the audio waveform. Instead of uniform correction every predetermined period, the reproduction position adjustment unit selectively adjusts timing at specific locations based on the local characteristics of the waveform, minimizing disruption to the overall sound quality while achieving necessary synchronization.
Data Source
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Figure 3A~3B
AI summary
Waveform data are stored in advance together with reference position information indicative of reference positions, in the waveform data, corresponding to reference timing, such as beat timing, and correction position information indicative of correction positions in the waveform data that are different from the reference positions. With the passage of time, the reference timing is advanced, and the waveform data are reproduced. In response to arrival of the reference timing, a deviation between a current reproduction position of the currently reproduced waveform data and the reference position is evaluated. When the current reproduction position arrives at the correction position, the current reproduction position is corrected in accordance with the evaluated deviation. Namely, whereas measurement of the deviation, relative to the reference timing, of the currently reproduced wavefonn data is performed on the basis of the reference position, correction of the current reproduction position of the waveform data for compensating for the measured deviation is performed at the correction position.