[FFmpeg-user] JPG->jpg ; MOV->mp4 ; jpgs and mp4s to 1024x576 ; concat => audio sync probs

Nicolas George george at nsup.org
Thu Jun 6 17:31:54 EEST 2019

Philip Rhoades (12019-06-06):
> 2. Use ImageMagick to convert the JPGs to 1024x576 jpgs.
> 3. Use ffmpeg to convert the MOVs to 1024x576 mp4s.

Since you are transcoding everything anyway, better do everything at
once with ffmpeg and the concat filter.

But anyway, let us try to find the cause of your problem.

> 5. Since concatenating these created mp4s with the mp4s from the MOVs caused
> audio sync problems, I had to also add an audio track to the jpg-mp4s with
> something like this:
> ffmpeg -ar 44100 -acodec pcm_s16le -f s16le -ac 2 -i /dev/zero \
>   -i output${i}.mp4 \
>   -vcodec copy \
>   -acodec aac \
>   -shortest output${i}_silent.mp4

Can you check the exact duration of the audio stream?

Anyway, using a lossy codec for intermediate storage is a recipe for bad
results. Use simple PCM.


  Nicolas George
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