[FFmpeg-user] Audio/Video Synchronization Issue

[Ben Murphy]

I tried to transcode a video and the audio and video went out of sync. I tried to use the async option but this did not improve the video. In fact the video produced was exactly the same. I think the issue might have something to do with a warning message ffmpeg throws up when it tries to read the file:

Seems stream 1 codec frame rate differs from container frame rate: 5994.00 (5994/1) -> 29.97 (2997/100)

If I read the metadata of the original file I get:

<MovieHeaderBox CreationTime="3387511922" ModificationTime="3387511923" TimeScale="2997" Duration="123900" NextTrackID="3">
<TrackHeaderBox CreationTime="3387511889" ModificationTime="3387511923" TrackID="1" Duration="123900" Volume="1.00">
<EditListEntry Duration="123900" MediaTime="0" MediaRate="1"/>
<MediaHeaderBox CreationTime="3387511922" ModificationTime="3387511922" TimeScale="44100" Duration="1823744" LanguageCode="eng">
<TrackHeaderBox CreationTime="3387511889" ModificationTime="3387511923" TrackID="2" Duration="123900" Width="640.00" Height="480.00">
<EditListEntry Duration="123900" MediaTime="0" MediaRate="1"/>
<MediaHeaderBox CreationTime="3387511922" ModificationTime="3387511923" TimeScale="2997" Duration="123900" LanguageCode="eng">

According to the TrackHeaderBoxes the two tracks have the same duration but according to the mediaheaderbox/movieheaderbox the durations are slightly different.

In the transcoded file the TrackHeaderBoxes of the two tracks have different durations:

<MovieHeaderBox CreationTime="2082844800" ModificationTime="2082844800" TimeScale="1000" Duration="41360" NextTrackID="3">
<TrackHeaderBox CreationTime="2082844800" ModificationTime="2082844800" TrackID="1" Duration="41360" Width="320.00" Height="240.00">
<MediaHeaderBox CreationTime="2082844800" ModificationTime="2082844800" TimeScale="25" Duration="1034" LanguageCode="eng">
<TrackHeaderBox CreationTime="2082844800" ModificationTime="2082844800" TrackID="2" Duration="41152" Volume="1.00">
<MediaHeaderBox CreationTime="2082844800" ModificationTime="2082844800" TimeScale="16000" Duration="658432" LanguageCode="eng">

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Ben Murphy | Developer | Mobile Interactive Group

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