[mythtv-users] mythbackend is fricking frying my cpu

[William Preston]

> I am running the latest cvs.
> My system:
> athlon 2100+ overclocked to 2.1ghz
> 512mb ddr ram
> geforce2mx
> asus a7v266 board
> wd 200gb 8mb cache drive
> hdparm -tT gives 270/51
> wintv 401 (i think - bought used) with btaudio working for digital and
> analog
> avertv stereo (btaudio only for analog which sucks)
> onboard cmedia sound
> soundblaster live (when i try to capture the line in is noisy as hell!)

So I have the same CPU, but running at stock speed.  I have the same
amount of ram, at 120Gig Seagate (2Meg), and the same capture card.  I'm
using my sound card to capture from line in--I don't think that would make
much of a difference, but perhaps sampling from btaudio (if that's what
you're doing) drags down the CPU?

I'm doing 720X480, quality 1->8, 4100 bitrate.  MP3 quality is at 9, which
does seem to reduce CPU utlization quite a bit.  Normally I sit at around
50-60% CPU utilization, but I enabled both the high quality codec options
the other day, and now sit at around 80-90% utlization (looks at LOT
better, though.)

Here's some stuff you might check out:

DMA for HDDs.  Run hdparm and see if you're clocking around 30-40MB/s.
Check that your CPU isn't totally maxxed out when that's going on...it
should spike, but not too badly.

Compile your kernel and MAKE SURE you have the right mainboard drivers
loaded into the kernel.  I don't know off the top of my head what chipset
that board uses.

Look in /proc/pci and see what your interrupts are like.  You should
probably make sure that your capture card and sound card(s) have their own
IRQ, and nothing else is sharing them.  Slots on your board WILL be
sharing IRQs, so find the ones that have a dedicated line and schtick
those two cards in those slots...I think all your other cards will share
IRQs without a problem, and are probably not that critical in the capture
process.

Set your disc staoring video to be ext3, and mount it with the flags
'noatime,data=ordered'.  The first doesn't update the atime record when
accessing each inode, the latter is the writeback mode for ext3 which
seems to be the fastest (for me).  The noatime option can sometimes really
help--especially when you're talking about liveTV keeping up.

That's all I can think of...I put 'athlon-xp' in the settings.pro file
when making myth, but I doubt that really has that much effect.


> Next problem:
> I get a very annoying poping sound whenever i change channels. Channel
> changing also takes at least 500ms.

That's a known problem with using btaudio as your audio capture.  You
might look into using one of your other cards, and definitely (if you're
not) using alsa.