[mythtv] change in cablebox behavior / firewire lockup

Martin Purschke mlp00 at optonline.net
Sat Sep 5 22:14:14 UTC 2009

I could need some advice to overcome an annoying problem that cropped up

Cablevision on Long Island switched a number of channels to
"switched-video", meaning that the (SA4250HD) cablebox talks to some
upstream server to request that particular video stream, rather than
just picking from streams that arrive all the time. That results in a
long channel change delay, 10-15s or so. The backend process gets a lock
on the firewire early on from the channel that the box had been tuned to
before and starts recording, but then loses the lock after the channel
change actually takes effect. The end result is a recording of a few
seconds, a few hundred KB; the recording stops after that.

What's worse, the backend process seems to lock up when that happens.
While it's still there, I have to kill and restart it.

My current workaround is that I preset the box to the next-requested
channel, but that obviously works only when I'm around to do that.

I have been looking for a way to delay the onset of the actual
recording, that is, issue the change-channel command, then wait an
adjustable delay until all is settled. Or, probably better, have the
recording start on time but issue the channel change command some 10-15s
before that.

Maybe someone knows how to accomplish that, or has any other suggestion,
else I'm ready to chip in some coding work (I was thinking one could add
a field with that per-channel delay to the channels table in the DB to
tune that. That could also be used to cut out the typical few seconds of
previous-channel footage at the start of a recording even in the absence
of an actual problem). I'm a programmer in my professional life but
would probably need some time to get up to speed with the procedures to
submit patches etc.

Here's the version info -

> MythTV Version   : 19961
> MythTV Branch    : branches/release-0-21-fixes
> Library API      : 0.21.20080304-1
> Network Protocol : 40
> Options compiled in:
>  linux profile using_oss using_alsa using_backend using_dbox2 using_dvb using_firewire using_frontend using_hdhomerun using_iptv using_ivtv using_joystick_menu using_lirc using_opengl_vsync using_v4l using_x11 using_xrandr using_xv using_glx_proc_addr_arb using_bindings_perl using_bindings_python using_opengl using_ffmpeg_threads using_libavc_5_3 using_live

and below is a piece of the log when the recording failed.

Thanks for any advice/hints/suggestions.


> 2009-09-05 16:45:06.543 FireDev(001CEA9098680000): Requesting STB Power State
> 2009-09-05 16:45:06.551 FireDev(001CEA9098680000): STB Power State: On
> 2009-09-05 16:45:06.554 SM(001cea9098680000)::AddFlags: Seen(STB,) Match(STB,) Wait()
> 2009-09-05 16:45:06.555 FireChan(001cea9098680000): Retune()
> 2009-09-05 16:45:06.558 FireDev(001CEA9098680000): Requesting STB Power State
> 2009-09-05 16:45:06.566 FireDev(001CEA9098680000): STB Power State: On
> 2009-09-05 16:45:06.568 SetChannelByNumber(833)
> 2009-09-05 16:45:06.572 FireDev(001CEA9098680000): Requesting STB Power State
> 2009-09-05 16:45:06.579 FireDev(001CEA9098680000): STB Power State: On
> 2009-09-05 16:45:06.580 SetChannel(model SA4200HD, alt 0, chan 833)
> 2009-09-05 16:45:06.584 SetChannel() -- locked
> 2009-09-05 16:45:06.602 SetLastChannel(833): cleared: no
> 2009-09-05 16:45:06.653 FireSM(001cea9098680000): UpdateValues() -- Waiting for table monitor to start
> 2009-09-05 16:45:06.653 FireSM(001cea9098680000): RunTableMonitor(): -- begin
> 2009-09-05 16:45:06.654 FireSM(001cea9098680000): UpdateValues() -- Table monitor started
> 2009-09-05 16:45:06.661 LFireDev(001CEA9098680000): Starting Port Handler Thread
> 2009-09-05 16:45:06.677 LFireDev(001CEA9098680000): Starting Port Handler Thread -- locked
> 2009-09-05 16:45:06.687 LFireDev(001CEA9098680000): OpenPort()
> 2009-09-05 16:45:06.693 LFireDev(001CEA9098680000): OpenPort() -- got lock
> 2009-09-05 16:45:06.701 FireDev(001CEA9098680000): AddListener() 1
> 2009-09-05 16:45:06.716 LFireDev(001CEA9098680000): Opening P2P connection
> libiec61883 warning: Established connection on channel 0.
> You may need to manually set the channel on the receiving node.
> 2009-09-05 16:45:06.889 LFireDev(001CEA9098680000): OpenAVStream
> 2009-09-05 16:45:06.890 LFireDev(001CEA9098680000): Opening A/V stream object
> 2009-09-05 16:45:06.900 LFireDev(001CEA9098680000): Buffered packets 2000 (8000 KB)
> 2009-09-05 16:45:06.905 LFireDev(001CEA9098680000): Starting A/V streaming -- really
> 2009-09-05 16:45:06.925 LFireDev(001CEA9098680000): Starting A/V streaming -- done
> 2009-09-05 16:45:06.926 LFireDev(001CEA9098680000), Warning: No Input in 50 msec...
> 2009-09-05 16:45:06.984 LFireDev(001CEA9098680000), Warning: No Input in 100 msec...
..and so on

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