[mythtv-users] CPU Performance required three dumb capture cards(WORKING!)

D Banerjee davatar at comcast.net
Sat Mar 27 17:16:28 EST 2004


It's 12 bits per pixel and 29.97fps, unless you have something exotic.. :)
If you had a VIA/MPX board that would explain the pci bandwidth issues.
It's more like 13MB/s per uncompressed stream.

> Don't forget to figure out your PCI bus budget.  The big advantage I
> found with the PVR cards is the relatively limited PCI bus bandwidth
> goes much farther.  You get a max of 133MB/sec.  I used to figure
> 640(hres) x 480(vres) x60(frames/sec) x3(bytes/pix) = 54MB/sec each;
> the PCI bus sees the raw format, plus the compressed stream.
> Now on top of that, you need to write those compressed streams to disk
> and read 1 stream from disk, plus the audio, plus a little more.
> Look at your lspci to see which devices are on what bus, maybe your
> HD won't count towards this.  But usually all PCI devices are on the
> same bus, unless you get an expensive MB.
> I found 2 cards plus a PVR was just over the max, and created
> lots of skips, sound drop outs, and other problems.
>
> I ended going 3 PVR cards and its been much better.
>
> Brian
>
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