[FFmpeg-user] Audio advanced when encoding from ProRes to H.264

Michael Connolly michael at emptysea.com
Tue Aug 19 19:37:53 CEST 2014

> * Michael Connolly on Monday, August 18, 2014 at 00:40:53 -0700
>> I'm new-ish to encoding with FFMPEG and am hoping you guys can
>> assist on a confusing issue.
>> I'm transcoding from ProRes with PCM audio to H.264 with AAC
>> audio.  After transcoding, my audio track is advanced (appears
>> earlier in the file) by about 1.5 frames.  This doesn't occur
>> if I trancode from H.264 to H.264 at a different bitrate.  In
>> that case the audio is preserved.    I did try converting from
>> XDCAM -> h.264 as well and encountered the same issue -- the
>> audio is advanced.
> I _always_ experience a video delay of about half a frame with
> x264, even when encoding x264 -> x264:
> https://trac.ffmpeg.org/ticket

A little more info:  My sync problem persists in the following cases:

ffmpeg using internal AAC library
ffmpeg using FDK-AAC library

It does not exist in HandBrake-CLI, which does a perfect job of lining up the streams.

Interestingly, Adobe Media Encoder advances the audio stream by the same amount of "partial" frame, but not the whole frame delta.  That is, if the audio is advanced by about 1.3 frames total, Adobe Media Encoder advances it by exactly 0.3 frames instead.  This is very odd to me.  

More information about the ffmpeg-user mailing list