[mythtv-users] High-Definition Playback performance data

[Jarod Wilson]

On Sunday 03 April 2005 21:48, Brad Templeton wrote:
> On Sun, Apr 03, 2005 at 08:51:50PM -0500, Pete wrote:
> > I'd like to know what I can do get that kind of performance. I've got an
> > Athlon XP 3000 (512 MB RAM) and an FX 5200 (AGP) running myth .17 and
> > FC3 (everything is from atrpms) where HD is close, but not quite. After
> > a lot of hacking to get the channels to work, it finally comes up, but
> > I'm getting lousy performance, with a lot of audio buffer underrun's
> > (using spdif through an on board nvidia audio chip) and video stutter's.
>
> We should try to build a list of all the things that can go wrong in
> making HD work smoothly.  There are many.

For reference, I'll try to answer all of those for my fully HD-functional 
Athlon XP 2600.

> They include:
>
>
>     a) Right drivers for card with your kernel

nvidia 7174 driver, GeForce 4 MX 8x AGP card.

>     b) Proper AGP bus speed and AGP interface driver in use

Running at 8x, works fine with both agpgart and nvagp.

>     c) Proper user of openGL sync for retrace

I'm using it.

>     d) Proper settings for deinterlace and, if used, xvmc

No XvMC, using kernel deint.

>     e) Proper sound settings and handling of 5.1 sound and multiple streams

Didn't do anything special here, this system isn't actually outputting 5.1, 
just using plain old OSS emulation through ALSA. My main HD box is passing 
raw AC3 and using ALSA devices though.

>     f) Real time scheduling of playback thread

I thought that was disabled in 0.17, due to stability issues, but I do have 
the checkbox for that enabled. I thought I had set the rtc max-user-freq to 
1024, but it appears I didn't, but that seems to help some folks. Add this 
to /etc/sysctl.conf on FC:

# Enable some RTC stuff for HDTV performance
dev.rtc.max-user-freq = 1024

(or just 'echo 1024 > /proc/sys/dev/rtc/max-user-freq')

>     g) Making sure disk or network speed is adequate

Remote frontend, all video being pulled over a 100Mbps switched network from 
ATA/100 disks.

>     h) Nothing else sucking up CPU on the machine

I have gone quite minimal on this box, turning off everything I possibly 
could, and switching the window manager to WindowMaker.

> And of course having the right cards and memory itself.

That too. And for reference, here's a database dump of the settings on this 
frontend, along with nvidia-settings and some brief notes:

http://wilsonet.com/mythtv/remotefe-settings.txt

-- 
Jarod Wilson
jarod at wilsonet.com

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