Multimedia Time-Stretching Audio Pitch Control
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Solution Overview
Problem
Existing digital video playback technologies cannot adjust the speed of multimedia presentations without affecting the pitch of the audio, leading to undesirable changes such as 'chipmunking' or audible artifacts when speeding up or slowing down videos.
Innovation Solution
Implementing a time-stretching process that alters the number of audio samples while maintaining the same sampling rate, allowing for synchronized speed adjustment of both video and audio without changing the pitch, and providing techniques for controlled pitch modification during playback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the playback rate of audio is increased to speed up video playback, then the video playback speed is improved, but the audio pitch changes (chipmunking effect)
Solution Approach 1:
The audio signal is divided into individual samples, and the system selectively deletes or duplicates specific samples to achieve time stretching without uniformly scaling the entire signal. This granular approach allows speed adjustment while preserving pitch characteristics.
Solution Approach 2:
The system changes the temporal parameter of audio samples (number of samples, sampling intervals) independently from the frequency parameter (pitch). By modifying only the time domain characteristics while maintaining frequency domain properties, the system achieves speed control without pitch distortion.
2Speed
If audio samples are deleted or duplicated to change playback rate, then the video playback speed is improved, but audible artifacts (clicks, pops) are generated
Solution Approach 1:
The system carefully controls the temporal parameters of audio samples during deletion or duplication operations. By maintaining appropriate sampling rates and transition smoothness, the system achieves speed adjustment while avoiding the generation of clicks and pops.
3Speed
If the frame rate is changed to adjust video speed, then the video playback speed is improved, but audio-video synchronization is lost
Solution Approach 1:
The time stretching technique serves multiple functions simultaneously: it adjusts video playback speed, maintains audio pitch, prevents audible artifacts, and preserves audio-video synchronization. This multi-functional approach resolves the contradiction by making the speed adjustment mechanism universally applicable to both audio and video components.
Data Source
AI summary
The invention is related to methods and apparatus that can advantageously alter a playback rate of a multimedia presentation, such as a video clip. One embodiment of the invention permits a multimedia presentation to be sped up or slowed down with a controlled change in pitch of the sped up or slowed down audio. In one embodiment, this controlled change in the pitch permits the sped up or slowed down audio to retain a same sounding pitch as at normal playback speeds. In one embodiment, a duration is specified and playback of the video clip is advantageously sped to complete playback within the specified duration. In another embodiment, a finish by a time is specified, and the playback of the video clip is advantageously sped to complete playback by the specified time.