[mythtv-users] Glitches in firewire capture from DCT-6200

Steve Adeff adeffs at gmail.com
Sat Dec 17 18:28:53 EST 2005


On Saturday 17 December 2005 17:54, David Rudder wrote:
> According to Dan Dennedy (one of the linux1394 authors), data_rate is a
> code.  0 means 100Mbps.  1 means 200Mbps.  2 means 400Mbps.  If you have
> it set to 100Mbps in the Mythtv setup, Mythtv will cause this change.  I
> don't have the original email that has this info.  You can probably find
> it in the linux1394 mailing list archives.  You can try upping this
> value in Myth.  It might be worth a look at your disk speed, too.
>
> -Dave
>
> Alex Brekken wrote:
> > Steve, running the commands you and curtis specified:
> >
> > plugctl -n 2 opcr[0].channel=63
> > plugctl -n 2 opcr[0].bcast_connection=1
> >
> > greatly improves my firewire reliability.  However, I still find it
> > almost unusable due to some slowdown/stuttering in the image.  (I also
> > have a PVR-250 which works flawlessly)  I know it's not my network, so
> > I was very curious to try out the data_rate command you listed above,
> > thinking that it might fix this issue.  (plugctl -n 2
> > opcr[0].data_rate=3)
> >
> > Running this command and then plugreport shows that the data_rate
> > variable does get set to 3, (before it was zero), HOWEVER, as soon as
> > I begin to record a show or watch live TV, it immediately gets set
> > back to zero.  You mentioned that you run this through a cron job
> > every hour, although I'm finding that if I try to set the data_rate
> > back to 3 while something is recording, it immediately freezes and
> > stops recording.
> >
> > Any other tricks or ideas to somehow keep this setting  at 3?  (or
> > anything greater than zero)
> >
> > On 12/16/05, *David Rudder* < drig at noses.org <mailto:drig at noses.org>>
> > wrote:
> >
> >     Are you sure this isn't a drive-speed issue?  Check hdparm -v
> >     /dev/<device>.  Also, make sure you have at least a 7200 RPM drive.
> >     The dct-6200 will send out an mpeg stream.  I think MythTV just
> > copies it to disk.  So, there's very little CPU or memory involved.
> >
> >     You can try running test-mpeg2 (from the libiec61883 package).  It
> >     outputs the raw mpeg stream from the 6200.  If it gets the same
> >     corruption you see in myth, then you know it's not a myth issue.
> >     test-mpeg2 > file.mpg
> >     wait maybe 30 seconds, then hit ctrl-c.  mplayer file..mpg should
> >     display
> >     the file.
> >
> >     -Dave
> >
> >     Azmat wrote:
> >     >I've been using this script in a cron job for the last week, but I'm
> >     >still seeing glitching.  Its mostly occurring at the start of a show
> >     >and then clears up in the middle.  Is it possible that I might
> >
> >     need to
> >
> >     >use a faster processor or bump up my RAM?  Right now I'm running an
> >     >Athlon XP 2400+ with 1G of RAM.  Thanks in advance for the help.
> >     >
> >     >Azmat
> >     >
> >     >On 12/9/05, Steve Adeff <adeffs at gmail.com
> >
> >     <mailto:adeffs at gmail.com>> wrote:
> >     >>there was a thread a while back regarding this. You can search
> >
> >     on Gossamer for
> >
> >     >>more info. basically you want to run this bash script. It will
> >
> >     set the p2p or
> >
> >     >>broadcast connection to 1 depending on what your machine will
> >
> >     use. From what
> >
> >     >>I've found bcast is prefered when available, which is why it
> >
> >     comes second
> >
> >     >>(since its one or the other) p2p is sometimes only available and
> >
> >     when this is
> >
> >     >>the case its fine. data_rate doesn't need to be 3, but it
> >
> >     increases speed if
> >
> >     >>your using firewire for capture and not just channel changing. I
> >
> >     have it run
> >
> >     >>before mythbackend starts when I run it via init.d and I've
> >
> >     found it resets
> >
> >     >>sometimes so I run it hourly as a cron job.
> >     >>
> >     >>oh, and the -n # is which node it is. In case you have more than
> >
> >     one firewire
> >
> >     >>connection have it run for each connection as well.
> >     >>
> >     >>#!/bin/bash
> >     >>plugctl -n 2 opcr[0].channel=63
> >     >>plugctl -n 2 opcr[0].n_p2p_connections=1
> >     >>plugctl -n 2 opcr[0].bcast_connection=1
> >     >>plugctl -n 2 opcr[0].data_rate=3
> >     >>
> >     >>--
> >     >>Steve
> >     >>
> >     >>On Friday 09 December 2005 14:52, Azmat wrote:
> >     >>>Here's my plugreport output:
> >     >>>Host Adapter 0
> >     >>>==============
> >     >>>
> >     >>>Node 0 GUID 0x0000d10080357942
> >     >>>------------------------------
> >     >>>libiec61883 error: error reading oMPR
> >     >>>libiec61883 error: error reading iMPR
> >     >>>
> >     >>>Node 1 GUID 0x4279358080357942
> >     >>>------------------------------
> >     >>>libiec61883 error: error reading oMPR
> >     >>>libiec61883 error: error reading iMPR
> >     >>>
> >     >>>Node 2 GUID 0x000f9ffffe103008
> >     >>>------------------------------
> >     >>>oMPR n_plugs=1, data_rate=2, bcast_channel=63
> >     >>>oPCR[0] online=1, bcast_connection=0, n_p2p_connections=0
> >     >>>        channel=63, data_rate=0, overhead_id=0, payload=376
> >     >>>iMPR n_plugs=0, data_rate=2
> >     >>>
> >     >>>On 12/9/05, Steve Adeff <adeffs at gmail.com
> >
> >     <mailto:adeffs at gmail.com>> wrote:
> >     >>>>On Friday 09 December 2005 12:44, Azmat wrote:
> >     >>>>>Hi,
> >     >>>>>
> >     >>>>>My mythtv system is running on an AMD Athlon XP 2400+ (2 GHz)
> >
> >     with 1G
> >
> >     >>>>>RAM, a PVR-350 and firewire capture from my Motorola DCT-6200
> >
> >     cable
> >
> >     >>>>>box.  Whenever I do firewire capture from the box through
> >
> >     Myth, the
> >
> >     >>>>>recording exhibits a audio/video glitching.  The picture will
> >     >>>>>momentarily become pixelated and there will be a brief
> >
> >     skip.  I can
> >
> >     >>>>>tell the glitch is in the recording because when I rewind and
> >
> >     playback
> >
> >     >>>>>it is reproducible.  There is no pattern or regularity to the
> >     >>>>>glitching.  Sometimes it will be at the start of the show and
> >
> >     will
> >
> >     >>>>>disappear in the middle, only to reappear later.  It doesn't
> >
> >     prevent
> >
> >     >>>>>me from recording shows, but is just become a huge annoyance
> >
> >     that I'd
> >
> >     >>>>>like to take care of.  Does anyone have any idea what might
> >
> >     be wrong?
> >
> >     >>>>>Do you think a faster processor would help?
> >     >>>>>
> >     >>>>>Thanks in advance,
> >     >>>>>
> >     >>>>>Azmat
> >     >>>>
> >     >>>>run plugreport and paste the output.
> >     >>>>
> >     >>>>--
> >     >>>>Steve
> >     >>>
> >     >>>--
> >     >>>
> >     >>>
> >     >>>Azmat
> >     >
> >     >--
> >     >
> >     >
> >     >Azmat

Right, Myth changes the settings when you have it set to capture over 
firewire, so change the value there. Though for most things 100Mbps should be 
fast enough.

describe the slowdown/stuttering. Do you see any signs of the mpeg breaking up 
(from lost data) or is it more like slow-mo/pausing?

Steve


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