[mythtv-users] Help debugging XvMC freezes

[Scott D. Davilla]

>Scott D. Davilla wrote:
>>>>  It is likely a hardware driver issue.  Myth can't cause your machine
>>>>  to lock like that, only something at a very low level like a driver.
>>>>  I'd back down the nvidia version to something less recent and see if
>>>>  that helps (or even your previous version)
>>>
>>>  humm 7300LE, that's similar to the 7300 is in the AppleTV. I would
>>>  experience random freezes and green blocky video corruption using
>>>  XvMC until I under-clocked the gpu. See
>>>  http://code.google.com/p/atv-bootloader/wiki/UpdateNvidiaDriver for
>>>  details.
>
>Hmmm, interesting thought!  I tried underclocking it from 450 MHz to 400
>MHz, but got another freeze not too far in.  So I'm tending to think this is
>a nvidia driver issue.  (happy happy joy joy...   why did I buy this card
>again?)
>
>Actually, second thought...  did you underclock the GPU, or the memory?
>I've been focusing on the GPU, maybe I should underclock the graphics card's
>memory?
>
>I'll have to do some more playing around, see if I hit pay dirt with
>anything.
>

I went from 360Mhz on the GPU to 200MHz, and to compensate a little 
also when from 720MHz on VRAM to 800MHz. This drastic decrease in GPU 
clock did not effect XvMC very much. My testing show it was more 
sensitive to VRAM clock than GPU clock. At it is, this setting added 
5 percent or less to the CPU when doing XvMC decode of 1080i mpeg2. 
So in addition to solving the hang/video glitch I has quite happy 
that I still had the ponies to do 1080i mpeg2 decode.

make sure the under-clock was taken

nvidia-settings -q all

should show the new setting.

Driver version depends on which nvidia card you have, the AppleTVs 
7300 is a mobile chipset and mobile chipsets can only be under/over 
clocked using the 169.xx series and only by passing some module 
option, the atv-bootloader link has details on that.