[mythtv-users] How to locate the correct audio track when transcoding?

David Watkins watkinshome at gmail.com
Mon Dec 11 21:46:42 UTC 2006

On 11/12/06, Neil Milne <neil.milne at gmail.com> wrote:
> On 11/12/06, Robin Neatherway <robthebob at gmail.com> wrote:
> > On 12/11/06, David Watkins <watkinshome at gmail.com> wrote:
> > > Bearing in mind that mythtv always selects the right audio track when
> > > playing back the original recording, how do I extract this information
> > > and supply it to the transcoding process so that I get just the audio
> > > track that I need into the transcoded file?
> >
> > In my experience, it is always the lower of the two PIDs associated
> > with the two audio tracks. The following perl subroutine is what I use
> > in an encoding script to get the PIDs of the video, audio and subtitle
> > tracks:
> >
> I don't believe it's always the lower PID - it seems to switch around
> a bit, although I might be mistaken.

No I think you're right.  That would explain why sometimes I get the
right track and sometimes I don't.  I assume mencoder picks the first
audio track unless it's told otherwise?

>You can run ffmpeg -i on the mpg file and the audio track you want to pick is
> the stereo high bitrate one, not the mono lower bitrate one.

Thanks Neil, that was the bit of information I was looking for.  I'm
doing a few transcodes now, so I'll see if I can improve my rate of


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