[mythtv-users] Stuttering/corruption on program change in LiveTV

[shiftybugger at gmail.com]

Hi all,

I have a problem on my Mytbuntu 9.10 (MythTV .22) setup such that on every  
program change (usually, but not always, at the top or bottom of the hour)  
whilst watching Live TV, the picture will freeze and artifact for a second  
before continuing, losing the second in between.

Link to logs at bottom

Hardware:
BE: Nvidia 9300 board, 4gb ram, E8400, HDDs out the wazoo (O/S is Samsung  
750gb SATA, Myth drive is a WD 320gb SATA), Asus U3100 usb tuners x3
FE1: Zotac ION board, 2gb ram, Fujitsu 120gb hdd SATA
FE2: Asrock ION, 2gb, WD 160gb hdd SATA

I cannot remember it doing this before upgrading to Myth .22 and Ubuntu  
9.10 and swapping out my old IDE drive. I can't see how that can be true  
though, given my results below. I'll list my theories and what I have done  
to try to confirm or dismiss them. Feel free to poke holes in my logic!

Theory: Something HDD related
- Replaced HDD
- changed and tuned various filesystems (ext3/4, xfs)
- dedicated drive for recordings
- copied image to old IDE drive and various sata drives
- tried setting to IDE mode, SATA mode, AHCI
- tried switching HDDs to different ports etc.
- iostat, iotop etc confirm that under my current setup IO is not stressed  
at all.

Theory: It is something to do with having seperate FE/BE, or network issues.
- installed Mythbuntu 9.10 as combined FE/BE on seperate disk running on my  
current BE hardware
- installed Mythbuntu 9.10 as combined FE/BE on seperate disk running on my  
current FE hardware

Theory: I noticed that there is now a proprietry driver listed for DVB  
tuner under Mythbuntu 9.10. Maybe this or some other driver issue, or some  
other Myth 0.22 or Ubuntu 9.10 issue, or 64bit vs 32bit
- installed Mythbuntu 9.10 64 bit as combined FE/BE on my current FE  
hardware
- installed Mythbuntu 9.04 64 bit as combined FE/BE on my current FE  
hardware
- installed Mythbuntu 8.10 32 bit as combined FE/BE on my current FE  
hardware
- tried various Nvidia graphics drivers (185, 180, 177, 173)

Theory: My TV signal isn't good enough
- bought a signal strength meter and rejigged my cables/splitters etc such  
that my tuners get close to the full output from my antenna.

Theory: My settings for FE or BE are wrong
- went through both and set them all to the same as when I had my working  
setup. Went back and tried various combos of options.
- removed separate storage group for LiveTV

Theory: something to do with VDPAU
- used Slim and CPU-- profiles whilst using the FE hardware builds.
- Yet to try switching back to CPU++ on the backend's currently unused FE,  
just thought of that.

After all of this, the problem still persists. It can't see it being  
software or I'd have hit on a working combination by now. It can't be  
hardware because I've tried completely different sets (although both are  
Nvidia chipsets). Only things that I can think of (and please add to this  
list if you can) is:

-Tuners. I'm using ASUS U3100s  
(http://www.mythtv.org/wiki/Asus_My_Cinema_U3100_mini). However I was using  
those before when it all worked fine.
-something HDD related that I haven't thought about... for some reason I  
have it in my head that the problem has something to do with the backend  
ceasing to write to one file, opening a new file, and starting to write to  
that, and somewhere in the middle taking enough time for the frontend to  
notice.
-some configuration setting that is too obscure for me to find...
- related to Ticket #7435  
(http://www.gossamer-threads.com/lists/mythtv/commits/404325)
- something to do with line 218: "AFD Error: Unknown audio decoding error"  
causing audio to skip, then forcing Myth to wrap the video to the audio.

Verbose playback Logs: http://pastebin.com/6gGa6QCs

Any help appreciated!
Thanks,
Kris
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