On Wed, Jan 05, 2005 at 11:41:13PM -0800, Steven M. Schultz wrote:
> On Thu, 6 Jan 2005, Dave Dodge wrote:
[...]
> DV is not used for HD (and yes, the ADVC line is SD only).
I've seen several mentions of the term "HDV" (including at the Canopus site)
which appears to be some high-definition variant of DV. But it sounds like
it's still relatively new and expensive. Considering you have to agree
to a disclaimer just to download the form to apply for access to the
specification, details don't seem to be very free-flowing :-)
> so it's possible from my Powerbook to send the MPEG-TS files over
> the IEEE1394 bus to the ATSC receiver and that box will drive the TV.
I believe a friend has also done this with his Mitsubishi TV which
contains an integrated tuner and 1394 port.
> > - a video card with drivers supporting XvMC. Some NVIDIA cards do this
> > if you use NVIDIA's drivers. I don't know about ATI. If you want to
> > stay with open source drivers, then I don't know if there's any
> > solution; perhaps a _REALLY_REALLY_REALLY_ fast machine could do it.
>
> Even a ~2.8GHz IA32 system can't play back HD content reliably
> without XvMC. At least that's been my experience. A dual G5 can
> do a fairly good job of it though ;)
I've tried it on an Athlon XP2400+ _with_ XvMC and I wasn't completely
happy with the results, though it may have been fill rate issues in
the video card since it was a relatively low-end NVIDIA FX5200. This
was also about a year ago so the drivers and software may have improved.
> > - you need to select the proper PIDs, demux the stream, and so on,
> > to get the MPEG program that you want. With over-the-air ATSC
>
> If you're talking about demuxing, scaling, recoding HD content down
> to SD size you really need that FAST system :) And it won't be a
> real time process (not even close).
I was assuming the extraction of an SD program from the transport
stream.
Trying to demux and decompress HD, scale it, and then compress it into
DV I would expect to be infeasible on any normal home system. Even if
you use the video card to accelerate the MPEG and scaling stages, you
might still have issues getting the data back to the CPU fast enough to
do the remainder of the work. Perhaps newer machines and cards using
PCI Express will make this sort of thing practical.
> Very true. Some stations put up 4 or 5 ~4Mb/s SD programs. Others,
> such as the PBS (KCET) put 2 programs up - one ~14Mb/s HD and one 5Mb/s
> SD (the 2nd program is a digital version of their analog program).
The local PBS station has up to five programs going at once, with the
bandwidth allocation changing depending on the time of day.
> I'm thinking of getting the pchdtv card but after reading (on pchdtv's
> forums) about all the woes folks have had getting the drivers to work
> it sounds like a rough ride.
My only experience is with the original pchdtv 2000 card, which did
require at least being acquainted with kernel building and patching to
get it working. Once set up, it worked fine and was easily controlled
from the command line. I even managed to throw together a few quick
programs of my own, based on the example code, to do the exact
processing and tuning that I wanted. I don't know about the new 3000
card.
> I think one of the Eye500 units would be a lot simpler :-)
If it weren't for that "Mac only" aspect of it I'd probably consider
one in place of a pchdtv card, since it might move more of the
custom code into userspace instead of requiring a special driver in
the kernel. If the control protocol hasn't been intentionally
obfuscated someone might bother to reverse-engineer it eventually.
-Dave Dodge
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