[FFmpeg-user] Create an AAC stream matching the Core Media Audio packet format / priming etc?

Mark Burton mwjburton at gmail.com
Tue May 9 17:42:22 EEST 2017

On 9 May 2017, at 15:21, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>> Do you not see the same behaviour?
> No, unfortunately not.

Can I ask - are you playing back your encoded file on macOS in either Quicktime Player 7.x or Quicktime Player 10.x?
I don’t believe you will see this unless you are using a Quicktime based decoder.

> If you say audio is off by one frame, I am not the right person
> to talk to because I have no idea how to reproduce.

Sorry if this is not correct way to share a file, I’ll remove and re-share if asked of course:
https://www.dropbox.com/s/qz5c64rk6l8415o/SyncTest24p.mov?dl=0 <https://www.dropbox.com/s/qz5c64rk6l8415o/SyncTest24p.mov?dl=0>

This is a simple 2 second sync test Quicktime file (DNx115, 24fps with PCM audio) with a sync pop on the head and tail frame.

If you have time, please could you try to encode this as follows and playback in a Quicktime based player.

ffmpeg -i SyncTest24p.mov -c:v libx264 -pix_fmt yuv420p -movflags faststart -c:a aac -b:a 128k ffmpeg.mov

- Do you hear a sync pop on the first frame of the encode when played back in Quicktime based player?
- Does the tail sync pop sound on frame :23 or frame :22?

> If the effect can be multiplied by encoding several times with
> FFmpeg, things would of course be different: Is that the case?

No, it does not get any worse by encoding it many times in a row.

Many thanks for your continued help, its hugely appreciated.

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