I've been getting nasty tearing/flashing effects on PVR-250 playback. The effect is, every minute or so a frame appears that is offset by a random amount. (What do I search for on Google? "Offsetting"?)

I have a Shuttle SS40G system, PVR-250, and a Bt878 K-World card. Two HD's using DMA on two IDE controllers. I'm using KnoppMyth R4 with latest apt-get upgrade.

Any ideas? Any idea at least on what this effect is called, so I can Google it?

Thanks
Steve

Oh! I forgot to mention that the flashing occurs repeatedly.. that is, it is probably due to the recording process and not playback. (I guess?)

I would look in your /var/log/messages and /var/log/mythtv/mythbackend.log files for any clues like not enough free buffer lines or anything out of the ordinary, the .qt lines are normal.

Hmm, I didn't see anything in mythtv's log. But I found these in /var/log/messages:

Feb 26 23:13:11 pvr kernel: blk: queue c0331e54, I/O limit 4095Mb (mask 0xffffffff)
Feb 26 23:13:11 pvr kernel: blk: queue c03319e0, I/O limit 4095Mb (mask 0xffffffff)

Another interesting thing about this bug -- I can freeze-frame a corrupt frame, and I see that it lost sync somewhere in the middle of a frame, offsetting the remainder horizontally by several pixels. Some frames have only one field offset like this.

My /proc/interrupts looks like this:

CPU0
0: 219726 XT-PIC timer
1: 198 XT-PIC keyboard
2: 0 XT-PIC cascade
8: 4 XT-PIC rtc
10: 95251 XT-PIC ivtv: iTVC15/16 mpg2 encoder chip
11: 5720 XT-PIC bttv, eth0
12: 36450 XT-PIC CMI8738-MC6
14: 19485 XT-PIC ide0
15: 16021 XT-PIC ide1
NMI: 0
LOC: 219696
ERR: 52
MIS: 0

what size are the hard drives and how are they setup in the bios? are they setup for LBA?

The 8GB drive is, the 200 GB is not -- I thought the kernel took care of figuring that stuff out anyway. The problem happens during Live TV (on the 8 GB) or recording (on the 200 GB).

Well the problem you're having seems to be an issue with ide and autodetection of that kind of stuff. some places said if you set it wrong in the bios it causes the problem, but they said to have it on, and the 8Gb is the only drive that would be old enough not to autonegotiate with the kernel. why did you want to use the 8Gb drive anyways?

I really don't know what to tell you other than search google for I/O limit 4095Mb (mask 0xffffffff) that's how I found the articles I was looking at.

I had something similar happen on my pvr-250. Not sure if its the same as yours but shutting down the machine and powering off, then restarting fixed the problem. It suddenly started this one day where recordings would have blocks missing, garbled frames and then the out of sequence frames you describe. I also checked that the card was still seated correctly while the machine was off (this could have also done it). The recordings where actually corrupt and I had to delete them all. The trick of changing inputs to reset the pvr's firmware didn't work in this case (fixes the blue/green verticle stripes problem).