[mythtv-users] Tuner Card w/ Svideo Inputs & PCI Sound Transfer

[Kyle Rose]

"Ian Neubert" <ian at ianneubert.com> writes:

> Thanks for the clarification Kyle. I will be using 5 MPEG/ATSC cards, so
> they won't use framegrabber, ie much less bandwidth on the PCI bus than 5
> analog tuners, where analog means that they spew out analog video data to
> the PCI bus.

Even though it's clear you understand, one still can never be too
precise with the terminology. :) I have one analog tuner (PVR-350) and
intend to get another (PVR-250), plus a digital tuner (pcHDTV).  All
output in digital mode, though, because PCI wouldn't do too well with
analog signals running across it. :) ("This doesn't look like a clock
edge... more like a clock slope.")

Better to say what format the output takes: this is why I distinguish
between encoders and frame grabbers, because that's where the real
difference appears (and also because it points out the desirability of
an MPEG encoder even to those of us with very powerful main
processors).  I.e., just for NTSC 480i:

  MPEG: 500 Mbytes/sec

  Frame grabbing: 60 half-frames/sec => 30 frames/sec
        720x480x32bit = 1.32 Mbytes/frame
                      = 39.5 Mbytes/sec

Just three of those and your PCI bus is toast; never mind the hard
drives or HDTV! :)

Cheers,
Kyle