glithy recordings with an ATi Theatre 550 card.

[banksie]

Okay got a screwy one here. Recently upgraded my processor/motherboard to a quad core machine and did a repair build plus reinstalled all the drivers.

Now when I make a recording with GBPVR I get small discontinuities in the stream, seemingly garbling a chunk of a frame. This is playing merry hell with GBPVR playback causing it to skip sections of the shows recorded semi-randomly.

Perversely LiveTV timeshifting mode works perfectly. So I am at something of a loss to explain this. I've included a debug log of the native recording service log to help. It seems to be the waking from standby to do just a recording sessions that suffer the worst - almost as though a processor sleep state is getting in the way or something.

Any thoughts or clues on how to diagnose this?

My one thought is that the ASUS P5K-V motherboard is currently running off two PATA drives linked in via the RAID chip. I am half wondering if this isn't causing the drive requests to be a little slower than normal and that getting a nice SATA drive or two will cure the problem...

[sub]

Nothing springs to mind, and unfortunately this is not the sort of thing that would show in the logs. Most likely some sort of motherboard DMA transfer or similar type of problem.

[prouton]

Have you ascertained that the recording is flawed, versus a problem at playback time? In other words, are the errors at exactly the same spot(s) every time you play the file?

Are you using Raid-1 or Raid-0? Raid-0 should be faster than a single drive. As for switching from PATA to SATA, I don't know that with current drives you would see a difference. The SATA specification allows for faster data transfer, but I don't believe 7200 rpm disks are capable of the theoretical transfer rate.

[banksie]

Have you ascertained that the recording is flawed, versus a problem at playback time? In other words, are the errors at exactly the same spot(s) every time you play the file?

Yes, it is definitely in the stream as it is repeatable at the same place everytime. I can also drop the files into media player classic and at the same spot I can see a garbled frame.

Are you using Raid-1 or Raid-0? Raid-0 should be faster than a single drive. As for switching from PATA to SATA, I don't know that with current drives you would see a difference. The SATA specification allows for faster data transfer, but I don't believe 7200 rpm disks are capable of the theoretical transfer rate.

The drives aren't in a RAID mode - they controller is operating in JBOD mode effectively behaving like an over glorified IDE controller and nothing else.

My sneaking suspicion is that it is an IRQ issue as the IDE controller is on a fairly heavily utilised IRQ. The reason I think SATA might sort it isn't because it has better transfer speeds but because it is off on an IRQ pretty much to itself. The RAID controller on this motherboard strikes me as being a bit of a last minute addition as it only does RAID with PATA drives internally or through an ESATA port out the back of the machine. So no internal SATA RAID at all. Weird eh?

Anyway I did some more tweaking and I think I *might* have stumbled on the solution - disabling write caching to the drives. I got a clean half hour recording last night after doing that but the acid test will be a cooking show my mother likes that seems to provoke this issue extremely well. I'll check it when I get home tonight from work and let people know if this does indeed cure it.

[banksie]

Yep, disabling write caching cures the issue nicely. Got a clean recording for a show which before was always glitchy.