Audio Playback Speed Control Using Optimized Frame Overlap
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Solution Overview
Problem
Existing digital audio playback systems face challenges in efficiently controlling audio playback speed using techniques like SOLA and WSOLA due to the high computational requirements, making it difficult to apply these methods in devices with limited hardware resources.
Innovation Solution
An audio playback speed control method and apparatus that determines optimal frame lengths and overlapping regions based on audio sampling frequency and playback speed, allowing for efficient variation of playback speed with reduced calculation, using different overlapping and adding methods for speeding up or slowing down playback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If SOLA or WSOLA technique is used to control audio playback speed, then playback speed control is achieved, but calculation complexity increases significantly
Solution Approach 1:
The audio signal is divided into multiple frames, and each frame is processed independently through overlapping and adding operations. This segmentation allows the complex time-scale modification to be broken down into simpler, manageable frame-level operations, reducing overall calculation complexity while maintaining playback speed control functionality.
Solution Approach 2:
The patent changes the parameter of frame length to optimize the balance between playback speed control accuracy and calculation complexity. By carefully selecting frame lengths that are powers of 2, the system achieves efficient processing with reduced computational burden while maintaining effective playback speed variation.
2Productivity
If frame length is increased to improve processing efficiency, then calculation amount decreases, but pitch accuracy may deteriorate
Solution Approach 1:
The system dynamically adjusts frame length based on the desired playback speed. For faster playback speeds, shorter frame lengths are used to maintain pitch accuracy, while for slower playback speeds, longer frame lengths improve processing efficiency. This dynamic adaptation resolves the contradiction between efficiency and precision.
Solution Approach 2:
The patent systematically varies frame length parameters according to different playback speed requirements. By establishing a relationship between playback speed and optimal frame length, the system achieves both high processing efficiency and accurate pitch control across different playback conditions.
3Measurement precision
If cross-correlation calculation is performed to maximize frame synchronization, then playback speed control accuracy improves, but calculation time increases
Solution Approach 1:
The system performs preliminary frame alignment based on simple timing relationships before applying overlapping and adding operations. This preliminary action establishes a good initial synchronization that reduces the need for extensive cross-correlation calculations, thereby decreasing calculation time while maintaining sufficient synchronization accuracy.
Solution Approach 2:
Instead of performing complex cross-correlation calculations on every frame, the system uses copying of frame structures with predetermined offsets based on playback speed ratios. This approach achieves accurate frame synchronization with minimal calculation time by leveraging the regular structure of audio frames and the known relationship between playback speed and frame timing.
Data Source
AI summary
An audio playback speed control method and apparatus to control an audio playback speed using an optimal frame length with a small amount of calculation. The audio playback method includes extracting an audio sampling frequency and audio playback speed information from an audio signal which is reproduced, determining a length of an input frame, a length of an output frame, and a length of an overlapping region between frames, on a basis of the audio sampling frequency and the audio playback speed information and performing different overlapping and adding methods, according to the audio playback speeds, on a basis of the length of the input frame, the length of the output frame, and the length of the overlapping region between the frames.