[mythtv-users] frontend CPU utilization after change from sw to hwencoding

Joseph A. Caputo jcaputo1 at comcast.net
Mon Aug 25 13:17:05 EDT 2003


> -----Original Message-----
> From: mythtv-users-bounces at mythtv.org
> [mailto:mythtv-users-bounces at mythtv.org]On Behalf Of macksold
> Sent: Sunday, August 24, 2003 12:19 PM
> To: Discussion about mythtv
> Subject: [mythtv-users] frontend CPU utilization after change from sw to
> hwencoding
>
>
> I wonder if somebody might take a stab at helping me understand the CPU
> utilization I am experiencing now that I have changed my setup.  I have
> gone from software encoding to hardware, while I was at it I switched
> machines from 1.2GHz Athlon to a PIII 600MHz, since HW encoding would
> use less CPU.
>
> Here are the before and after setup, both have frontend and backend
> running and watching live tv.
>
> Before:
> AMD Athlon 1.2GHz 512MB RAM
> GeForce 4
> Hauppauge WinTVPCI
> MPEG-4 Live TV profile
> backend uses 75% or so CPU
> frontend uses around %5
>
> After:
> Pentium III 600MHz 384MB RAM
> GeForce 4 (same as before)
> Hauppauge PVR-250
> Hardware MPEG2 Live TV profile
> backend uses 5%
> frontend uses 75%
>
> I am surprised at the frontend cpu utilization on the PIII setup, an
> ideas?

Well, even though you're encoding in hardware, you're still DE-coding in
software.  Naturally a 600MHz machine will have to work harder than a 1.2GHz
machine to decode full-screen video at 30fps.  Also, you've switched from
MPEG-4 to MPEG-2.  I don't know which one is easier to decode, but I do know
that MPEG-2 will require the decoder to process anywhere from 2-4 times more
data (as in bits/second), because the MPEG-2 files are 2-4 times as large as
the MPEG-4 files (depending on your capture settings, of course).  Since
what you're capturing now is probably close to DVD-resolution (in terms of
picture size, not necessarily quality; MPEG-2 is DVD compression, though you
might not be capturing the full 720x480 or whatever), and a 500MHz machine
is about the bare minimum required for full-screen software DVD playback,
you can see why a 600MHz machine might carry a relatively heavy load to do
LiveTV.  All that being said, is 75% reasonable?  I don't know; maybe
someone with a similar system can comment.  Also, see what CPU utilization
you get playing a DVD with mplayer or xine for comparison.

-JAC



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