[mythtv-users] mplayer -dumpstream better than myth record

Kevin Kuphal kuphal at dls.net
Fri Sep 14 01:42:40 UTC 2007

On 9/13/07, Ben <bluey at iguanaworks.net> wrote:
> I have two channels that I can record perfectly with mplayer but not
> with mythtv. Using the command
> mplayer dvb://CHANNEL -dumpstream
> I can then play the file back with mplayer (or whatever) and it is
> great. If instead, I have mythtv record the program, then when I play it
> back it is missing a lot of frames and jumps around and sometimes cuts
> on entirely. This happens if I play it back in mythtv-frontend or with
> mplayer.
> Since I'm doing the playback with the same program (mplayer) clearly,
> the dump of the tv signal is different when recorded from mythtv than
> mplayer. Why? And this is only true on some channels... for example, FOX
> has this problem, but ABC and NBC do not. These are HDTV signals over
> the air.
> I have an air2pc card with 2.6.22 kernel (debian sid) and myth-0.20.2.
> All the channels receive >80% signal using dtvsignal.  My first thought
> was that mplayer was using a different frequency than mythtv was for the
> channels. Looking at the mysql database, I see under
> mythconverg/dtv_multiplex/frequency that for the channel in question I'm
> using the frequency 503000000 and mplayer (in .mplayer/channels.conf) is
> using 503028615. So I changed the line in the sql database and restarted
> mythtv, but that didn't make a difference. I undid that change and added
> 28615 to the mythconverg/channels/finetune but that too had no effect.
> I'm stumped as to why saving the stream is different. Any ideas? Both
> mplayer and myth are running as unprivileged users without suid or
> anything.
> It goes without saying, but live TV of these channels with mythtv also
> doesn't work well, but "mplayer dvb://CHANNEL" is fine. And finally, is
> there a way to have mythtv-backend use mplayer to save recording and
> just circumvent whatever problem this is?
> Do you commflag your recordings?  If so, there is basically double the
disk I/O happening.  Also, there is more going on when myth is recording (DB
writes, etc) which also increase the I/O over what mplayer is doing with
dumpstream.  Does your database share the same disk as your recordings?

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