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

Mark Burton mwjburton at gmail.com
Tue May 16 20:18:20 EEST 2017

On 9 May 2017, 15:42 +0100, Mark Burton <mwjburton 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
> 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.

Carl is there a chance you’ve had time to further review this with the sample file provided?

I know there are literally thousands of areas of focus you must have to be looking into, but I really wouldn’t keep banging on this door if I didn’t genuinely feel this was a worthwhile cause. I’m aware also that the list COD asks us not to assume our issue is the most important, so I say that with the greatest respect.

I honestly don’t think it would be a stretch to say that, at preset, the ffmpeg MOV muxer appears to be incompatible with regards to way it handles aac priming with the Quicktime format. If there is anything else I can provide or test, please do ask, I’ll do whatever I can to help nail this down.

Thank you and regards,

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