[mythtvnz] Pixelation/Corrupt recordings

[Aaron Pelly]

Hi guys, I'm looking for some pointers to troubleshoot corrupt recordings.

At various times, with various degrees of intensity, my recordings are 
not happening cleanly. Sometimes it doesn't happen, sometimes it is mild 
enough to ignore, sometimes it makes a recording totally unwatchable. 
The messages below are the only thing I have managed to find in the logs 
(messages repeat during playback). The backend doesn't seem to complain 
during the recording, but that might be because I don't have the best 
logging options set.

Jul  7 10:08:56 crepitus mythfrontend.real: mythfrontend[25257]: E 
Decoder avformatdecoder.cpp:4709 (ProcessAudioPacket) AFD: Unknown audio 
decoding error
Jul  7 10:08:58 crepitus mythfrontend.real: mythfrontend[25257]: E 
Decoder videobuffers.cpp:283 (GetNextFreeFrame) GetNextFreeFrame() 
unable to lock frame 100 times. Discarding Frames.

Hardware:
- core2 duo ~3GHz
- 4G RAM
- many 7200rpm HDDs, but with only two configured as storage groups. 
drives are currently ntfs. This will change in the next few days.
- 2 HVR4000 tuners
- Cheapo Nvidia card, (gt9500?), doubt that's relevant.

I do have a motherboard with a core2 quad and 8G ram that I'll probably 
stick in the backend this week. Maybe I should just try that first?

I don't have a lot of (any?) clues showing up to help me track this 
annoyance down, but here is list, in no particular order, of a mixture 
of superstition, suspicion, notes, and anecdotes:

- mplayer can't play the recordings either
- it might be worse when there are multiple simultaneous recordings
- it comes and goes
- might be worse when the backend has low ram
- seems a bit better after rebooting the backend
- not sure if it affects dvbs or just dvbt
- i haven't done the math for required throughput for the HDDs or the 
PCI bus.

- I have seen this with gbpvr on the same hardware, using dvbs only and 
it seemed to be primarily caused by lack of ram. I doubt it's relevant, 
I only mention it for completeness.

Of course, this might be simply bad reception. I haven't seen any 
correlation with terrestrial weather. Have not looked at solar weather.

I feel lazy asking you guys for more help. I know I can solve this if I 
spend enough time googling, but I feel like so many things could be 
causing this. Some clues to narrow it down would be a bit of a treat really.

Thanks,
Aaron.