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

John Kondis jkondis at yahoo.com
Fri May 6 01:39:18 UTC 2005


--- Cory Papenfuss <papenfuss at juneau.me.vt.edu> wrote:
>  	I'll bet that since mplayer is good enough to play
> with varying 
> PTS/DTS, it doesn't try to fix that.  I did mess
> with a few options like
> init_vpts, init_apts, vdelay, drop, tsaf,
> reorder.... nothing seemed to 
> help that issue.

I'm surprised at this.  Lots of tools that can "play"
an mpeg2 stream with errors OK, but can't transcode a
stream in a fault tolerant way.  Sad, if true.

BTW, I *do* use (digital) cable and I get these errors
all the time.  I get very unreliable service from my
cable provider (Hi, Comcast!), even though I've
complained to them a multitude of times.  (Peeve:
frequently the cable signal quality gets poor, and my
digital tuner won't reliably accept channel-change
signals from the RS-232 port because it's busy trying
to send info back to the cable company and can't
handle the bad upstream connection.  So, to fix this,
my channelchange script actually daemonizes and makes
up to 5 attempts at changing the channel - a value I
found could reliably change the channel in case the
signal quality gets poor.  It sends an extra
"back/exit" after each three digit channel number, so
that in case it missed a digit I don't go to channel
070 when I'm trying to go to 007.  This, in an effort
not to miss scheduled recordings just because those
fartknockers can't keep the signal level clean.  But I
digress...)

There *has* to be a way around this sync problem. 
Tell me this: does the mpeg2->mpeg4 transcoder in
mythtv fix the sync issues in the PVR-x50 generated
streams?  (My PVR 350 won't play mpeg4 very well since
it has to use the slow framebuffer.)  If so, couldn't
I then just transcode mpeg2->mpeg4->mpeg2 and end up
with a playable file, in the sense of playing on the
PVR-350's output as well as something still
convertible to DVD format that remains in sync?  How
would I go about doing that, in particular going
mpeg4->mpeg2?  I figure if I could get that done, then
I could easily script it to run as a user job, so that
by the time I intend to record something it will
likely be in a form that won't give my DVD player,
scripts, or me heartburn.

(FWIW I also tried lopping the file into a few pieces
using dd, but that was, err, unsuccessful. ;)

I promise if anyone can help point me towards a
solution, I'll post any successful results I get on
this list, as well as how I did it.  I might even buy
you a beer. ;)


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