[FFmpeg-user] converting to AAC audio duration changes

Francois Visagie francois.visagie at gmail.com
Tue Sep 17 08:44:40 CEST 2013

> -----Original Message-----
> From: ffmpeg-user-bounces at ffmpeg.org [mailto:ffmpeg-user-
> bounces at ffmpeg.org] On Behalf Of Jeanne Rich
> Sent: 17 September 2013 01:15
> To: FFmpeg user questions
> Subject: Re: [FFmpeg-user] converting to AAC audio duration changes
> ----- Original Message -----
> > Jeanne Rich <jrich <at> laika.com> writes:
> >
> > > Also can you take a look at the file that is used for the concat
> > > demux, and let me know if I'm doing something wrong there as well in
> > > specifying the duration.
> >
> > Sorry, I did not even know that the concat demuxer takes a duration
> > option...
> >
> Yes it has a duration directive according to the documentation.
> As for the conversion issue, I tried many things, including -async 1,
-copyts in
> the command line, and nothing seemed to do the trick.  I am not very up on
> the AAC encoder, so any suggestions at this point will help.  I will be
happy to
> come up with an example movie if need be.

Have you tried without the '-r 24' output option? From the documentation:

'-r[:stream_specifier] fps (input/output,per-stream)'

    Set frame rate (Hz value, fraction or abbreviation).

    As an input option, ignore any timestamps stored in the file and instead
generate timestamps assuming constant frame rate fps.

    As an output option, duplicate or drop input frames to achieve constant
output frame rate fps.

If you don't specify an output frame rate (and don't need to force constant
frame rate) ffmpeg usually defaults to the input frame rate quite sanely.

Unrelated to this, but what does the '-map_metadata' '-1:s' metadata mapping
achieve? According to the documentation file indices are zero-based, and I'd
be grateful if you wouldn't mind explaining what '-1' does.

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