[Discuss-gnuradio] Transmitting ATSC from computer to set-top box?

[dododge]

An ATSC capture card may soon be available for GNU/Linux
(www.pchdtv.com), so I'm starting to get ideas about building a
homebrew HD-PVR.

In my particular case I already have a display device in mind, but
it's a first-generation HDTV and has the limitation that it can only
sync to component 1080i. Other formats (480p, 720p, etc) have to be
converted to 1080i first.

The display can actually be tricked into taking 540p from a computer
if you get the hsync timing close enough to 1080i. Given a captured
MPEG transport stream, I assume(?) I could build a machine for xine to
do the playback and scan conversion.  I've never actually tried this
sort of playback, though, so I have no idea how well xine works in
terms of dropped frames, digital audio out, and so on; or what speed
CPU and video hardware would be needed.

But I've already got a set-top terrestrial DTV tuner (currently hooked
to a UHF antenna), and one of the few things this tuner does well is
decode and scale all SD and HD formats to a 1080i signal compatible
with my display.

So could GNU radio be used to repackage a captured MPEG transport
stream (using atsc_tx?), and transmit it to the set-top box over a few
feet of coax? Basically the same sort of thing a VCR does to transmit
to a TV on channel 3 or 4, but using ATSC and some fixed UHF channel
instead.  The computer would just capture and manage the transport
streams, rather than doing any real MPEG decoding or encoding of its
own.

Most everything I've seen about GNU Radio (and in particular using it
with ATSC) has to do with receive/capture rather than transmit. I've
read that doing the atsc_rx stuff in software isn't even close to
realtime at the moment. But how about the atsc_tx part?

Likewise the capture cards that are usually mentioned are in the
$1000+ range, but could transmit hardware for this specific purpose be
bought or cobbled together for significantly less?

Is this sort of arrangement even feasible or practical with current
computer hardware? I know almost nothing about radio and ATSC
processing, so if this idea isn't even worth pursuing I'm hoping
someone here can explain why not :-)

                                        -Dave Dodge/address@hidden