Audio Signal Processing Apparatus Phase Synchronization
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Solution Overview
Problem
Conventional vocoder methods for audio waveform processing result in significant phase changes during time stretching and pitch shifting, leading to auditory discomfort due to phase lag or lead, especially in stereo audio, making it difficult to achieve high-quality time stretching and pitch shifting.
Innovation Solution
An audio signal processing apparatus and method that divides the input audio signal into frequency bands, performs time stretching and pitch shifting on each band, and applies phase synchronization processing at regular intervals to reduce phase changes by cross-fading between bands, ensuring the final output waveform maintains the original phase relationship.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional vocoder method is used for time stretching and pitch shifting, then time axis expansion/compression and frequency scaling are achieved, but significant phase changes occur causing auditory discomfort
Solution Approach 1:
The audio signal is divided into multiple frequency bands using a frequency band dividing unit. Each band is processed independently by separate time stretch/pitch shift processing units, allowing phase control to be applied band-by-band rather than to the entire spectrum at once. This segmentation enables finer control over phase changes in different frequency regions.
Solution Approach 2:
Phase synchronization processing dynamically adjusts the phase parameter of each frequency band based on the original phase relationship. By changing the phase parameter adaptively while maintaining the temporal structure, the system preserves the original phase relationships between frequency components, eliminating auditory discomfort caused by phase distortion.
2Object-affected harmful factors
If phase synchronization processing is applied to each frequency band, then phase changes are reduced and sound quality improves, but device complexity increases
Solution Approach 1:
The phase synchronization processing unit performs multiple functions: it analyzes the original phase relationship, calculates phase correction amounts for each frequency band, and applies the corrections. This multi-functional approach consolidates what would otherwise require separate dedicated units for each function, reducing overall system complexity while achieving phase change reduction.
Solution Approach 2:
The phase synchronization processing unit acts as an intermediary between the frequency band dividing unit and the time stretch/pitch shift processing units. It receives band-divided signals, calculates appropriate phase corrections, and feeds these corrections back to the processing units, coordinating their operation without requiring direct complex interactions between all components.
3Measurement precision
If frequency band division is performed, then phase control precision improves, but processing time and computational load increase
Solution Approach 1:
The system applies phase synchronization processing selectively to each frequency band rather than uniformly across the entire audio signal. By focusing computational resources on partial processing of individual bands where phase control is most critical, the system achieves high precision phase control without the excessive computational load of processing the entire spectrum at maximum detail.
Data Source
AI summary
An audio waveform processing not imparting any feeling of strangeness and high in definition, in which time stretch and pitch shift are performed by a vocoder method, and the variation of phase over the whole waveform caused by the vocoder method at all times is reduced. An audio input waveform is handled as one band as it is or subjected to frequency band division into bands. While performing time stretch and pitch shift of each band waveform like conventional vocoder methods, the waveforms are combined. The combined waveform of the band is phase-synchronized at regular intervals to reduce the variation of phase. The phase-synchronized waveforms of the band are added, thus obtaining the final output waveform.