[mythtv] 6200 & Firewire weird degradation of video over time

Rich richietommy at yahoo.com
Wed Jun 29 04:02:36 UTC 2005

So after a lot of struggling to get mythTV to work in
ubuntu on my new box with firewire/6200 support (the
only way was to follow the ubuntu guide start to end,
compile libiec61883 and libraw1394 from source, and
compile mythTV 0.18.1 from source into a .deb package
and install it), I have a strange problem.  The system
is as follows - Athlon 64 3200, DFI lanparty (NForce4
ultra chipset, VIA firewire controller on board),
GeForce 6600GT video, plenty of storage/ram/other
stuff.  The machine is its own backend.

What happens is when I first boot the machine, I can
watch video over firewire perfectly (looks really nice
in hi-def), then after about 10-20 minutes (seems to
happen faster if I am recording a show, and it doesn't
matter if I am tuned to analog, digital, or hi-def
cable on the 6200), it starts glitching and choking
once a second or so for a couple of frames.  It gets
worse with funky mpeg green noise and all that over
time.  After a couple of hours, it gives up.

Restarting the computer will always fix it - for 10-20
minutes.  Killing the backend daemon and running both
the backend and frontend from separate terminals (so I
can see the verbose/output) reveals some interesting

This is what plugreport tells me:

Node 2 GUID 0x000ce5fffe4365b3
oMPR n_plugs=1, data_rate=2, bcast_channel=63
oPCR[0] online=1, bcast_connection=0,
        channel=0, data_rate=2, overhead_id=0,
iMPR n_plugs=0, data_rate=2

.  I have it set up in MythTV as a firewire input
device, DCT-6200, Point to Point, Port 0, Node 2,
100Mbps, MPEG2TS.

First, the backend will start out normally:

2005-06-28 22:00:08.756 Firewire: Initializing Port:
0, Node: 2, Speed: 100Mbps
2005-06-28 22:00:08.756 Firewire: Creating P2P
Connection with Node: 2
libiec61883 warning: Overlayed connection on channel
You may need to manually set the channel on the
receiving node.
2005-06-28 22:00:08.760 Firewire: Created Channel: 0,
Bandwidth Allocation: 0
2005-06-28 22:00:08.760 Firewire: Changing Speed
200Mbps -> 100Mbps

Then when the frontend is fired up for live TV or
recording, the terminal output for the backend goes to

2005-06-28 22:02:25.676 Firewire: 1 packet(s) dropped.
2005-06-28 22:02:25.676 Firewire: 1 packet(s) dropped.

and viewing the terminal over the video, the packet
dropping seems to go with the momentary freezes.  When
the video signal gets worse, it will increase to
several packets will be dropped at once.  When it gets
really bad (unrecognizable video), the backend starts
spitting out stuff like this:

[mpeg2video @ 0xb7805010]00 motion_type at 17 22
[mpeg2video @ 0xb7805010]invalid cbp at 5 23
[mpeg2video @ 0xb7805010]invalid mb type in P Frame at
1 24
[mpeg2video @ 0xb7805010]00 motion_type at 7 25

The whole while the front end spits out stuff like
this at the terminal: 

2005-06-28 23:49:21.450 prebuffering pause
2005-06-28 23:49:27.775 prebuffering pause

and every once in a while this:

2005-06-28 23:49:36.649 Audio buffer overflow, audio
data lost!
2005-06-28 23:50:43.081 RemoteFile::Read() failed in


Everything else on the computer works well.  The cable
box used to capture and display perfectly under
windowsXP on another machine using VLC and DVHS
drivers.  I want to load this other machine up with
mythTV and linux, but I am hesitant if I can't get it
working on my slightly newer and better machine first.

If anyone as ideas on this, I would love to hear them.
 I'm not that great with linux and I am kind of at my
wit's end with this.  I am thinking that either the
VIA IEEE1394 chip on my DFI motherboard is trash, the
linux firewire modules have a glitch, or it is
something I will never figure out.  I do have a
SB-Audigy with firewire to play with as well as some 5
port firewire card that was free after a rebate (NEC
chip maybe?), though that 5 port card caused similar
glitching in windows on another machine that I haven't
mentioned yet.  The integrated firewire on my shuttle
athlon XP box (VIA 333 something-rather chipset)
always worked flawlessly with this cable box under
windows.  TIA,


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