Description of problem or question:
Can "Align A/V Start" option cause desync? Or are there are any other drawbacks of turning it on?
Can "Align A/V Start" option cause desync?
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- JohnAStebbins
- HandBrake Team
- Posts: 5723
- Joined: Sat Feb 09, 2008 7:21 pm
Re: Can "Align A/V Start" option cause desync?
In media files, it is possible for the first audio timestamp and the first video timestamp to be different, e.g. the audio starts at time X and the video starts at time Y. Align A/V start shortens or extends the duration of the first video frame to force X == Y. If the original difference in start times is significant, you may notice that the first video frame is momentarily "frozen", whereas with Align A/V sync disabled you would most likely see a black frame during that time.
The primary purpose of Align A/V sync was to work around bugs in some decoders that can't tolerate streams that don't start at exactly the same time.
The primary purpose of Align A/V sync was to work around bugs in some decoders that can't tolerate streams that don't start at exactly the same time.
Re: Can "Align A/V Start" option cause desync?
Is it possible even when I cut a clip from a middle of a longer movie? Both video and audio are well underway so start time should be irrelevant.
- JohnAStebbins
- HandBrake Team
- Posts: 5723
- Joined: Sat Feb 09, 2008 7:21 pm
Re: Can "Align A/V Start" option cause desync?
In this scenario is is almost guaranteed that the start times will not align. Audio frame and video frames have differing durations. So if you start an audio and video frame at the same time, they will not end at the same time.