[mythtv-users] CPU Performance required three dumb capture cards

James L. Paul james at mauibay.net
Fri Mar 26 18:56:17 EST 2004

Hash: SHA1

On Friday 26 March 2004 06:34, Adam Felson wrote:
> My multimedia computer's hardware is an asus a7v333, an athlon XP 2400,
> and 512MB DDR 3200 memory.
> When I had one video capture card (BT848), it ran like a champ able to
> do 640x480 mpeg4 encoding and tv output in real time with about 55% cpu
> load.
> With two cards (second is a bt878), it maxes out the CPU and can't keep
> up;  tv out will run with a 1/2 second pause every 4 seconds.

This makes sense. If software encoding one stream takes more than half the 
CPU, then you aren't going to be able to handle two simultaneously.

> Right now I've got it set to encode using rjpeg at 480x480 resolution.
> It is set to "transcode after recording" and the transcode profile is
> set to do mpeg4.  Is that how to set it up?  I have the
> default/tv/highq/lowq profiles set to do rjpeg and the transcode profile
> set to do mpeg4.  It seems to be mostly working although the system now
> crashes a lot -- it can only go about day between crashes.  Crashes are
> weird -- video stays up (audio will go in a loop), keyboard flashes and
> nothing ever gets written to a log file.
> This morning I tried to watch a previously recorded show while two
> channels were being recorded.  Mythtv couldn't keep up.

You obviously don't have enough CPU to handle it. You need to reduce to CPU 
load by reducing the number of simultaneous streams, or reducing your capture 
resolution, or using hardware encoders.

> Sheesh:  I want to network this thing and be able to capture two
> programs while watching a third.  It doesn't look like the fastest cpu
> that I can put on that motherboard (athlon xp3200,333mhz fsb) will be
> able to keep up.  My wife will kill me if I try to justify having two
> servers.

Software encoding of 3 streams at the same time takes a lot of CPU. That's why 
hardware encoder cards are so popular amongst this group. My Athlon 1.4GHz 
CPU is more than enough to handle 3 streams from my hardware encoder cards, 
but it can barely handle even one stream with software encoding. Don't try to 
justify another server, just justify new capture hardware. :)
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