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

John Goerzen jgoerzen at complete.org
Fri Jun 3 20:48:58 UTC 2005


On Fri, Jun 03, 2005 at 03:01:23PM -0400, Michael T. Dean wrote:
> John Goerzen wrote:
> 
> >I am trying to find a way to squeeze down a 5.5MB PVR-350 recording so
> >it fits on a single DVD.
> >
> Wow.  I've been fitting 5 hours of TV (with commercials cut) on a single 
> DVD--with as much as 10MB to spare--I couldn't have set my recording 
> parameters better if I had tried.

It was a 2-hour program that I recorded on my high-quality setting for
some reason.  Sigh.

> >Originally, I used replex to demux it, then ran tcrequant on the result.
> >It made it smaller, but I had serious sync issues.
> >
> Yep.  Happens on all the recordings I've seen from the local cable 
> company--up to 5 seconds off at the end of a 1 hour recording.  Some 
> (fortunate) people only see it with recordings off a VCR.  My DISH 

Interestingly, most of my stuff is recorded off DISH too, and I have a
high-quality SVideo cable from the DISH receiver to my PVR-250.  I have
no idea why I have problems but others don't.

Anyway, when I don't use tcrequant, and just replex (without ever
splitting it out into separate files), things work fine with *most* DVD
players.  mplayer works fine, ogle doesn't, my hardware player works
fine.  Those that don't, don't see skipping, but rather exhibit other
strange behavior -- not reading the disk at all, timestamps getting off,
skipping audio, etc.  I suspect it is all a symptom of the original
problem, but since it works on at least one player on my computer and my
hardware DVD player, I'm happy enough.

[snip]

> process...  In other words, without seeing the whole process--step by 
> step and command by command (and explicit version numbers of each 
> command)--there are way to many variables to guess what's causing the 
> problem.

OK, here's what I tried... these are verbatim commands except for a
couple of filenames; I took notes as I went:

java -jar ~/programs/projectx/ProjectX.jar -c ~/programs/projectx/X.ini \
  -o output_dir input.nuv
cat output_dir/file.m2v | buffer -s 50k -m30m | tcrequant -f 1.33 | \
   buffer -m10m > vid &
mplex -f 8 -V -o dvdmpeg1 output_dir/file.mpa vid &
dvdauthor -o DVD dvdmpeg1
dvdauthor -T -o DVD

Of these, vid and dvdmpeg1 are FIFOs.

The buffer command comes from earlier (pre-ProjectX) experiences, which
showed deadlocks when I used a bunch of FIFOs... I can probably
eliminate it here.  It's just something that basically acts like cat,
but will store data in memory as it sends it.  So in this case, it will
store up to 30MB in RAM if cat yields data faster than tcrequant, but it
sends the exact same data across as cat does.  No changes.

When I don't have to reduce the size of my recordings, this is my usual
process:

replex -i PS -v 0xe0 -a 0xc0 -k -t DVD -o dvdmpeg1 n.nuv &
dvdauthor -o DVD dvdmpeg1
dvdauthor -T -o DVD

This results in DVDs playable as I mentioned above.  In this example,
dvdmpeg1 is a FIFO.

Versions:

ProjectX 0.82.1.02
replex 0.1.3
dvdauthor 0.6.11
transcode 0.6.14 (provides the tcrequant binary)
mjpegtools 1.6.2 (provides the mplex binary)

> However, if you get the process working, I highly recommend you watch 
> the DVD recording before deleting the original--especially if the 

Thank you for the tip.  I do tend to spot-check the result, especially
near the end, and appreciate this suggestion.

> Everything I've seen about Project X says it does demux well, but 
> everything else (including re-encoding) not so well--i.e. Project X only 

Thanks for that valuable bit of experience as well.

-- John


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