I think I've figured out the reason why chroma-key OSD helps:
It f*&ks up the horizontal scaling so that the picture is
streatched horizontally so that only about 70% of it is
on-screen (it's the left-hand 70%). Throwing away 30% of the
pixels apparenlty makes things work a lot more smoothly.

It looks like the only way I can get the video scaled correctly
is to disable chroma-key OSD by enabling XvmcUsesTextures.

Methinks it's time to try some older NVidia drivers.

_________________
Grant

It's not the actual chroma-key OSD that helps with stuttering
an OSD-related problems, it's disabling XvmcUsesTextures. With
that disabled, the horizontal video scaling is screwed up and
about 20% of the picture is off-screen (to the right).
Apparently, throwing away 20% of the picture helps. With
XvmcUsesTextures disabled, I get the same results whether
chroma-key OSD is enabled or not.

With XvmcUsesTextures enabled, the video scaling is correct,
but anytime the OSD is on (even if it's completely static), CPU
usage goes to 100%, video playback drops to about 2 frames per
second, and audio drops out completely. There seems to be
something very broken about the OSD implementation. After the
OSD goes away, video playback resumes and the audio will come
back after some period of time ranging from a few seconds to a
few minutes.

It doesn't really look like it would help. As-is, only 34K of
swap is used and almost 300MB of RAM is being used as
disk-block cache. That means only 200MB of RAM is being used
for resident program pages.

_________________
Grant

I've tried nvidia driver versions 9361 and 7185 with identical
results. If I enable XvmcUsesTextures, I get good HD playback
with rather high CPU usage of 60-70% and no "prebuffering"
messages nor any video or audio artifacts.

However, as soon as the OSD display _anything_, playback falls
down hard: video drops to a couple frames per second and audio
stops after a burst of NVP: prebuffering messages. When the OSD
goes away, smooth video playback resumes immediately but audio
is broken. Sometimes the audio comes back in a few seconds but
continues to spew prebuffering messages. Sometimes it takes
several minutes for the audio to come back on.

Can anybody point me to documenation on what the "NVP:
prebuffering pause" message actually _means_? That question
has come up several times in the mythtv mailing list, but it
never seems to get answered. Gotta love those cryptic log
messages...

_________________
Grant

Just FYI I turned on UseChromaKeyOSD and set XvmcUsesTextures to false and it didn't change my horizontal scaling at all. My OSD is now in color with Xvmc.

When you disabled UseChromaKeyOSD, how did you unpoke this line from the SQL database?

This should do it.

Note that I've left off the hostname so it does all of them. To be more fine grained:

You could also do a delete, but turning it off should do the trick and it's convenient to keep it around.

Thanks tjc! I always like to be able to undo what I've done, just in case...

I tried building the latest nvidia driver, but xvmc doesn't
work at all with that because it's incompatible with the xvmc
library in /usr/lib.

None of the instructions I found on building the latest driver
for Knoppmyth mentioned updating the xvmc drivers, and the
nvidia installer log didn't show anything relelvent either.

It looks like I'm screwed.

_________________
Grant

So as not to hijack this thread I've posted a script to do this over here: http://mysettopbox.tv/phpBB2/viewtopic.php?p=100401#100401

gante,

Have you had any luck with this issue? I've got the same thing happening with my system. HD works considerably better when not using XvMC, even though the CPU is at 92% (compared to 43% with XvMC). I also have loads of the NVP: Prebuffering pause messages.

Nope. No matter what driver version I try or what settings I
use, playback collapses when the OSD comes up (unless I disable
XvmcUsesTextures, in which case I only see the left-hand 70% of
the picture). If you're patient enough and don't mind having
no audio for a few minutes after the OSD goes away playback
will eventually resume normally and the NVP: prebuffering
messages will stop.

And I've still got absolutely no clue what that message means
or what one should do about it. Without XVMC, I get 100% CPU
usage and stuttering video/audio, so that's not really an
option.

I don't think I have much choice other than admit defeat and
build a new box. Probably an Asus M2NPV-VM and low-power AMD
X2 3800+ CPU. People report good results with that board.

But, I don't know whether to try to build a nice little FE box
and leave my current box as a BE, or build a FE/BE box that
completely replaces my current box. And I can't find a case I
really like. Life is tough. So it goes. Poo-tee-wheet.

_________________
Grant

Am having the same problem, also have FX5200, have tried lots of different things and although sometimes it plays for several minutes, I still get those NVP: prebuffering pause errors and shuttering every 5-10 minutes or so.

Yea, I've come to the conclusion that the oft-seen advice that
any old FX5200 or FX6200 board should work is bogus. Some
boards work in some configurations with some motherboards.

You pays your money and you takes your chances.

_________________
Grant

It worked fine with previous version of myth (the same exact video card/motherboard/memory (1gb)/processor (3.0) , but when I upgraded myth it now has those annoying pauses, seems to have nothing to do with OSD as it does it during normal playback

grante,

please try 100.14.19

I tried that tonight and although it wasn't perfect, I did notice less shuttering(pausing)

http://www.nvidia.com/object/unix.html

I used:
# install-nvidia-debian.sh 100.14.19 -force

I want to know if the prebuffering pausing is better for you also, or if its just in my head.

I did. I wasn't able to get xvmc to work at all with 100.14.19,
but I'll try again.



That's what I tried, and it didn't actually install anything,
though it did download the installer. Only three of the five
"install-nvidia-debian.sh" commands shown in the wiki actually
installed a working driver for me:

http://www.knoppmythwiki.org/index.php? ... iversR5F27

To get 100.14.19 installed, I had to download the installer
from nvidia and run it by hand after replacing one of the .h
files in the kernel headers:


That got me a mostly-working 100.14.19 driver, but I never
could get xvmc to work at all with that version.

_________________
Grant