[mythtv-users] mplayer -dumpstream better than myth record
Ben
bluey at iguanaworks.net
Fri Sep 14 03:44:44 UTC 2007
On Thu, 2007-09-13 at 20:42 -0500, Kevin Kuphal wrote:
> 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?
Interesting idea about the IO. I doubt it though. Here's why: I am not
doing commflag on my records (or any other processing). NBC is fine at
broadcasts in 1920x1080i and ~100Mb/min. FOX, which gives me mild
problems, broadcasts 1280x720p and 110MB/min. The station that gives me
the most problems, is MNT, which broadcasts at 1920x1080i and ~95Mb/min.
So I'm not seeing a correlation with rmy ecording problems and how much
it saves to the disk. I temporarily moved the recordings directory to a
different hard drive from the database, but it made no difference. Any
more ideas?
Thanks,
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