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FFMS / ffms2

An FFmpeg based source library and Avisynth/VapourSynth plugin for easy frame accurate access
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FFMS2 ignoring video delay #334

Closed CoffeeFlux closed 5 years ago

CoffeeFlux commented 5 years ago

This was reported as an issue in Aegisub.

Files with video delay do not appear to be properly delayed when loaded in ffms2. Here are two video files, one with delay and one without: http://0x0.st/sjNd.mkv http://0x0.st/sjNn.mkv

If you run program this on both files, the number of samples returned is identical, despite one of the two having delay: https://gist.github.com/CoffeeFlux/f52be108cb52cba607020a5b6e3741be

When actually played in mpv, the delay is present. This means that subtitles created in Aegisub will not line up with the video in playback. I think that when FFMS_DELAY_FIRST_VIDEO_TRACK is set, the audio should be shifted regardless of where the delay is set since it's relative, and that's not the current behavior.

CoffeeFlux commented 5 years ago

Is this considered intentional behavior and I need to adjust how I'm using ffms2? Is there willingness for a fix, but I'd need to implement it myself? I'm definitely willing to do that if it would actually get merged. I'd greatly appreciate some kind of response on this issue since it's causing problems in Aegisub in a very common real-world scenario.

dwbuiten commented 5 years ago

As discussed in the Aegisub IRC channel yesterday, this may be a a bug in Aegisub where it does not index video tracks when loading audio after FFMS_DoIndexing2 was added. Further testing is pending, as results are not clear yet.

CoffeeFlux commented 5 years ago

This is indeed a problem with not properly indexing the video tracks. Thanks again!