[mythtv-users] Audio sync problems with exported Myth recordings - not with manual recordings

Scott Alfter mythtv at salfter.dyndns.org
Mon Dec 13 22:40:31 UTC 2004

On Mon, Dec 13, 2004 at 03:22:19PM -0600, Lane Schwartz wrote:
> I've hit a big snag - when I export the recordings and cut the
> commercials with nuvexport (MPEG2->MPEG2), the audio on the exported
> recording is way out of sync. Note that when I play the original files
> in Myth or mplayer, the audio sync is just fine.
> I tried opening the recording with avidemux, cutting the commercials,
> exporting raw audio and video, then manually remuxing them with mplex
> (as per instructions in section 21.19 of Mythtv.org docs). I still get
> a final mpg with out-of-sync audio.

Since the files play back properly, that would rule out MythTV and ivtv as
the source of the problem.  nuvexport appears to not work at all for me...it
grinds away for several minutes but ends up producing nothing.

I have copied several MPEG-2 program streams over to a Windows box and
edited them with a combination of DVD2AVI, Avisynth, LAME, BeSweet, and
TMPGEnc.  The DVDs that I've made from shows processed this way have all
worked flawlessly, with no sync problems.  That would also rule out MythTV
and ivtv as the source of your problem; it sounds more like an issue with
nuvexport and/or the apps nuvexport calls on to do its work.

(What those issues would be, though, I don't know.  I haven't had much time
to play with nuvexport yet, and I suspect that if I want to put Enterprise
on DVD at 4400 kbps video, I'd probably get better quality by recording at a
higher (6000-8000 kbps) rate, editing, and reencoding with TMPGEnc at 4400
kbps VBR than by recording at 4400 kbps (the PVRx50's encoder is CBR,
right?) and dumping that to DVD.  I've not tried a comparison of the two,
but my gut instinct is that at a given target bitrate, a non-real-time
software encoder can produce better results than a real-time hardware

 / v \ Scott Alfter
(IIGS( http://alfter.us/            Top-posting!
 \_^_/ rm -rf /bin/laden            >What's the most annoying thing on Usenet?

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