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

Christian Ebert blacktrash at gmx.net
Sat Apr 15 11:21:13 EEST 2017


* Carl Eugen Hoyos on Saturday, April 15, 2017 at 00:44:43 +0200
> 2017-04-14 23:44 GMT+02:00 Mark Burton <mwjburton at gmail.com>:
>> I find it hard having to accept an encode will always play out of
>> sync on certain players.
> 
> Could you elaborate a little?
> So far, for every ticket, it either turned out that out-of-sync was
> not reproducible with MPlayer / vlc (and FFmpeg) or it was off-
> by-one-frame which I consider hard to reproduce...

In theory it is probably correct that it's the task of the
decoding application to make the aac priming work. In many real
world scenarios this does not happen.

I do a lot of segmenting, and can always reproduce it with the
hls muxer:

https://trac.ffmpeg.org/ticket/3859
I closed it because, as per last comment I finally resorted to
the workaround(?) mentioned here.
https://trac.ffmpeg.org/ticket/3859#comment:13
https://sourceforge.net/p/opencore-amr/mailman/message/32912437/

If you see a HLS playlist where the TARGETDURATION is higher than
the duration of any segments than the first you can bet it has
been created by ffmpeg.

And if you don't clip at the end, you can easily get invalid
audio-only segments as last segment, and end of video may not be
detected in the majority of real world scenarios, arguably when
you play HLS in a browser.

So, apart from introducing minimal async, it also has other
repercussions.

Why not a warning, ideally with a hint as to how to best deal
with the situation, similar to the one about pix_fmpt yuv420p:

Use -pix_fmt yuv420p for compatibility with outdated media players.

Maybe there is no correct solution, and the delay hint in the
verbose output was certainly helpful, at least in my case; it
also points to some awareness of a potential problem area. It
just took me a long time to find it.

-- 
  Was hei├čt hier Dogma, ich bin Underdogma!
[ What the hell do you mean dogma, I am underdogma. ]
free movies       --->>> https://blacktrash.org/underdogma
http://itunes.apple.com/podcast/underdogma-movies/id363423596


More information about the ffmpeg-user mailing list