Pitch-Invariant Audio Resampling for Media Synchronization
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Solution Overview
Problem
Existing media synchronization methods fail to effectively adjust audio streams to match video streams, leading to inconsistent viewer experiences due to audio-video desynchronization, often resulting in noticeable artifacts or distortion.
Innovation Solution
Perform dynamic audio resampling during transcoding, using time-stretching filters to adjust audio frame sizes without modifying pitch, ensuring synchronization with video by applying heuristics to determine appropriate resampling techniques for individual frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If container metadata (STTS atom) is used to force audio track duration to match video track duration, then audio-video synchronization is improved, but audio quality deteriorates due to hard compensation artifacts or distortion
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting audio frame duration parameters through resampling. Instead of forcing fixed duration matching via metadata, the system modifies the actual audio stream parameters (frame duration, sample rate) to achieve synchronization. This allows flexible adjustment of audio timing parameters to match video duration while maintaining audio quality through soft compensation techniques.
Solution Approach 2:
The system implements dynamics by making audio frame duration adjustable rather than fixed. Through dynamic resampling, the audio frames can be stretched or compressed to match the video track duration. This dynamic adjustment allows the audio stream to adapt to different timing requirements without relying on rigid metadata forcing, thereby avoiding hard compensation artifacts.
2Reliability
If hard compensation is applied by dropping audio frames or inserting silent frames, then audio-video synchronization is maintained, but audio quality deteriorates due to audible artifacts
Solution Approach 1:
Instead of dropping frames or inserting silence, the system changes the temporal parameters of existing audio frames through resampling. The audio frames are stretched or compressed to match the required duration, which maintains synchronization without creating audible artifacts. This parameter transformation approach preserves audio continuity while achieving synchronization.
Solution Approach 2:
The system creates a resampled copy of the audio stream with adjusted frame durations. Rather than modifying the original audio by dropping or inserting frames, the system generates a new audio stream that replicates the original content but with corrected timing parameters. This copying approach maintains audio integrity while achieving synchronization.
3Reliability
If audio resampling is performed to adjust audio frame sizes, then audio-video synchronization is improved, but processing complexity increases
Solution Approach 1:
The patent applies segmentation by processing audio frames individually rather than treating the entire audio stream as a whole. Each audio frame is resampled independently to adjust its duration, which simplifies the overall processing complexity. This segmented approach allows the system to handle synchronization issues locally in each frame without requiring complex global resampling algorithms.
Solution Approach 2:
The system performs preliminary analysis of the audio and video streams to identify synchronization issues before resampling. By detecting timing discrepancies in advance, the system can plan and execute resampling operations more efficiently. This preliminary action reduces the complexity of the main resampling process by providing guidance on which frames need adjustment and by what amount.
Data Source
AI summary
Approaches provided herein can provide for adjustments to audio data. In particular, an audio resampling process can be performed wherein the correct audio frame size is determined. A “target” audio stream duration, as may be indicated by a time-to-sample atom (STTS) atom, can be used to apply one or more pitch-invariant, time-stretching audio filters to the audio data as that data is decoded during a media transcode process. A resulting output media metadata can specify accurate, constant audio frame durations, and the audio stream duration can match the corresponding video stream duration in a media file.