[mythtv-users] bttv0: skipped frame. no signal? high irq latency?

[Joe Votour]

I don't receive the same error message that you do,
but I do lose a lot of frames, and get the
"rebuffering" messages that you do.

The idea here is that your bttv card is for one reason
or another, dropping frames (well, duh!).  The reason
for it, could be due to many factors:
1. You don't have an adequate CPU to handle the load.
2. There could be an issue with IRQ sharing on your
motherboard.  That's what the message seems to
indicate.
3. You, like me, could be having a problem with the
signal you're feeding your bttv card.

In my case, I have an Athlon XP 2400+, VIA KT400
chipset, 512MB of PC2700 RAM and UDMA100 working on my
Western Digital hard drive.  I also tried running Myth
on my desktop machine, which is a Pentium 4 2.4GHz
(533MHz FSB), 512MB of PC3200 RAM and an i875P
chipset, and had the same problems.  I also had
problems even when I tried a PVR-250 card.

For the most part, I can watch "live TV" at any
resolution, but I do run into stuttering a fair
amount.   Typically what happens for me is I can go
minutes (sometimes even 10 minutes) without any
stuttering, and then I'll get a lot of stuttering,
then it will be fine again. It varies from channel to
channel, and show to show.  The cable tech found that
my line has a lot of ingress in it, and needs to be
replaced.  My cable modem works, but I get a lot of
corrupted packets according to it's counters.

So, I would try these things:
1. Do a cat /proc/interrupt, see what devices are
assigned to each interrupt.  Try to get as few devices
per interrupt as possible.  Mine reads:
           CPU0
  0:    3702509          XT-PIC  timer
  1:         37          XT-PIC  keyboard
  2:          0          XT-PIC  cascade
  5:     307806          XT-PIC  usb-uhci, bttv
  8:          1          XT-PIC  rtc
 10:    3209131          XT-PIC  usb-uhci, EMU10K1
 11:       5112          XT-PIC  usb-uhci, eth0
 12:         19          XT-PIC  PS/2 Mouse
 14:     270612          XT-PIC  ide0
NMI:          0
ERR:          0

Short of disabling USB completely, I can't get rid of
usb-uhci on any of the interrupts (and I use an ATI
Remote Wonder right now).

Secondly, try hooking something else up to your cable
input (like a VCR or DVD player), and try using Myth
with that.  If it's a problem in your cable signal,
then you shouldn't have any problems dropping frames
with this test.

Finally, try getting a PVR-250 and see if that helps. 
However, if your system is already fragile with
interrupts, the card might actually make things worse
(I was getting segfaults in MythTV with it, whereas my
bttv card works fine, but I'm not completely sure what
caused it).

-- Joe

--- Reza Naima <reza at reza.net> wrote:
> 
> I've been getting a lot of these : 
> 
> Sep  7 03:48:33 pvr kernel: bttv0: skipped frame. no
> signal? high irq latency?
> 
> I was wondering if anyone else has been getting
> them, and if so, if you
> have any information on what might be causing them,
> and what might be
> done to help fix them.
> 
> I'm also suffering from rebuffering issues -- anyone
> know what could
> cause them?  Just running out of recorded video to
> play?  If it's not
> the harddrive, what else could be causing it?
> 
> thanks,
> reza
> 
> 
> > _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
>
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> 


__________________________________
Do you Yahoo!?
Yahoo! SiteBuilder - Free, easy-to-use web site design software
http://sitebuilder.yahoo.com