[mythtv-users] How to minimize CPU usage

[Jerry Rubinow]

On 1/30/06, Dan Seddon <dan.seddon at framestore-cfc.com> wrote:
> Hi Jerry
>
> Video comes to about 30 Mbytes per second  - which would be about 240
> Mbits per second, as you're almost a multiple of 3 bigger I'm guessing
> you assumed 24bits per colour channel? Where it is actually 8bits per
> colour channel (PAL is 3*720*576*25 bytes). This ought to be well inside
> the speed of PCI - if you think about it, uncompressed PVRs have existed
> for some years now and the harddrives on these use the PCI bus. So, it's
> unlikely you've exceeded the bandwidth. 60 frame/sec is interlaced NTSC
> (720p is progressive) - I wouldn't think this would increase the
> bandwidth unless you were doing something like bob deinterlace on your
> CPU (I'm guessing here), as each frame should have half the number of
> lines. I don't know about XvMC - I don't know how compressed the data is
> by the time it gets to the card - you'd hope it was a little compressed
> though!
>
> Ta
>
> Dan

Hi Dan,

PVRs have existed for a while, but not HD-resolution PVRs - they're
pretty recent.  If X is in a 24-bit depth mode, then I don't see where
my numbers are off - 24 (bit depth) * 1280 * 720 (screen res) * 30
(fps) = 630+ Mbits/sec.  XvMC is a mystery to me - compressed data
must be sent to the card for decompression, but I don't know how big
that factor is, or whether it has to travel back to the CPU again
before being sent for display.  Anyway, thanks for your comments.

-Jerry