[mythtv-users] How to convert PCM audio track to AC3?

[Ian Trider]

On Mar 31, 2005 5:59 PM, William <wmunson at rochester.rr.com> wrote:
> I could use a little help with this one. I have searched but only got more
> confused so I will ask the experts.
> 
> I currently use avidemux2 to split my pvr-250 mpeg recordings into a raw
> video and an audio track that I think is raw pcm but it might be mp3. Its
> the default format created when doing a save audio. (The version of
> avidemux2 is an older one as the new version does not seem to work correctly
> anymore.) I then recombine them with mplex and burn the files to dvd. I
> would really like to convert the audio track to ac3 and then mplex that so
> its compatible with the player in the truck. Has anyone been able to do
> this? How do you do it?

Something that nobody has mentioned thus far in this thread is that it
is NOT mp3 OR PCM that the PVR-350 outputs -- in both PAL and NTSC
formats it puts out MPEG-1 Layer II audio.

Technically speaking, this is only DVD-compliant for PAL players,
however, I have yet to find an NTSC player that refuses it. PCM audio
is compliant in both systems, by the way.

Your post raises the question though; why are you even doing this? 
The output is already DVD-compliant if you record at 352, 704, or 720
x 480 (or 576 in PAL countries).  MythTV simply names the MPEG file
.nuv -- dvdauthor will take the file directly.

If you have tried authoring the file directory and have an (NTSC)
player that refuses the audio, congratulations, you've found the NTSC
player that I believed not to exist. ;)

Demuxing the audio and video is just asking for trouble -- PVR-350
audio and video streams aren't guaranteed perfect sync, but are kept
that way through PTS data, which is lost when you demux.

-- 
Ian Trider
iantri at gmail.com