[mythtv-users] DVD recording sync issues with PVR 350

John Kondis jkondis at yahoo.com
Wed May 4 21:02:43 UTC 2005


I've spent a *lot* of time on this problem and can't
seem to find a solution.  I really hope someone can
help me with this.

I am writing some of my MythTV recordings to DVD and I
get a-v sync drifts during the DVD recording, up to a
second or two near the end of a two-hour recording
(playing within myth is fine, though).  I've noticed
that many people have this problem, but all the
solutions I've tried that people suggested haven't
worked for me.  For reference, I'm using a PVR-350,
Myth 0.18, ivtv-0.2.0-rc3e, on a headless system
running on a Celeron 566 with SuSE Linux 9.2.

To burn to DVD, I have a script crafted after the
mythtv docs ala the blurb at the end of
http://mythtv.org/docs/mythtv-HOWTO-22.html.  This
involves splitting the audio and video streams with
mpeg2desc, remultiplexing them with mplex, creating a
dvd file structure with dvdauthor, and writing an iso
file system directly to DVD with growisofs.

Basically, I've tried:

1) Changing the encoded stream type to "DVD Special 2"
in Myth.  Still have the sync issue.
2) Trying to re-encode using mencoder like the
following: 

> mencoder <nuv file> -of mpeg -oac copy -ovc copy -o
<new nuv file>

mencoder seems to do just fine, but when I do this,
mpeg2desc or mplex complain that they don't understand
the file format.
3) Trying to re-encode using ffmpeg, setting the
output format to mpeg2video, making sure that audio
bitrate is the same (384kpbs), and preserving the
stream mappings.  The command looks something like

> ffmpeg -i <nuv file> -f mpegts -vcodec mpegvideo -ab
384 -b 4500 -maxrate 6000 -bufsize 200 <new nuv file>

Again, does just fine, but mpeg2desc or mplex complain
that they don't like the resulting file format.

...and a few other things, including using mpgtx to
cut the file into segments or nuvexport (I get myriad
complaints about formats or obscure errors). 
Regarding the file format complaints, I've looked for
settings to try that won't make mplex or mpeg2desc
barf, but I can't find any.  The errors look like
this:

   INFO: [mplex] mplex version 1.6.2 (2.2.3 $Date:
2004/01/13 20:45:26 $)
**ERROR: [mplex] File  unrecogniseable!
**ERROR: [mplex] File  unrecogniseable!
**ERROR: [mplex] Unrecogniseable file(s)... exiting.

In any case, it seems the initial problem comes from
errors that are generated by the PVR350's encoder. 
So, it seems the right approach would be some tool
that can re-encode the streams while preserving the
stream format (and the sync!) and cleaning up the
stream errors generated by the PVR.  Keeping it
playable on the PVR-350's output would be ideal, then
I can try some user job in myth to do this to all the
recordings automatically.  (In fact, maybe take a
couple Mbps out of the file in the process.)

Is there a simple, idiot-proof way to do this?  Since
I'm running my myth system headless, something easily
scriptable, and non-GUI is what I'm after.  I really
hope somebody who has solved this problem can show me
the way.

Thanks!


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