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

[Michael T. Dean]

John Kondis wrote:

>  --- 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.

Cory's theory makes sense, though.  If MPlayer can handle MPEG with 
varying sync, why re-write it to constant sync during a transcode?

>  BTW, I *do* use (digital) cable and I get these errors all the time.
>  ...

Me too.  Satellite here and a friend has cable.  I have a few errors in 
my recordings and have had a really hard time trying to get some of his 
recordings to DVD.

>  There *has* to be a way around this sync problem.
>  ...

I just tried demuxing a couple of particularly nasty 2-hour recordings 
(recorded from the cable connection) with Project X ( 
http://www.lucike.info/page_projectx.htm ) and it seems to have cleaned 
up the streams very well.

Before Project X, I tried opening directly with Avidemux2 and had a 5s 
A/V offset at the end of the recording.  After using remux to "average" 
the sync ;), I was still off by 3s at the end of the recording.  I also 
tried using mencoder to copy the MPEG Elementary Streams into an AVI 
container, then open the AVI in Avidemux2 (and let it rebuild frames), 
but was still off by a couple of seconds at the end.  Tried using 
tcextract and transcode and didn't have any luck with any of them.  In 
all cases the offset varied throughout the video.

So, as suggested by Nick in this thread, I tried Project X.  I just 
opened the video and demux'ed with default settings.  It threw away a 
ton of broken video (11.278 seconds total!  Started at 2:05:55.422 and 
ended at 2:05:44.144).  Afterwards, I could open the video in Avidemux2, 
specify an external MPEG audio stream, and the recording was in sync.

Since I needed to cut commercials (and wanted to cut both audio and 
video from the commercials :), I remux'ed the streams with:

mplex -f 3 -b 300 -V -r 9600 ${FILE}.mpa ${FILE}.m2v -o ${FILE}.mpg

The multiplexed stream opened without problems in Avidemux2 and sync is 
dead on throughout the video.  Now to cut, save, and burn...

Unfortunately, Project X is slow.  It took 2hr 20min to demux each 2hr 
5min video.  Well, it's still better than re-encoding...  And it would 
be nice if it were command-line capable.  At least I can specify a whole 
slew of recordings in a collection and demux them all at once (limited 
only be available drive space).

Also interesting is the fact that Avidemux2 plays the cleaned up streams 
nicely (normally, all my recordings stutter and play back slower than 
real time in Avidemux2, but play fine in xine and MPlayer).  It seem 
that the errors in the stream cause Avidemux2 a lot of difficulty.

>  (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. ;)

HTH.

Mike