HDTV and Computers

Archived from groups: alt.video.digital-tv (More info?)

"Ron" <rgraham1@maine.rr.com> wrote in message
news:1a366fd4.0405300400.6c93079b@posting.google.com...
> I've been interested in viewing HDTV directly from a set-top cable-box
> on a computer screen for some time and I seem to get a variety of
> different statements of facts about whether this is possible? I
> wonder if someone could set us all straight on the important aspects
> of this issue?
>
> I've read that it is not possible for video input cards to receive
> HDTV composite input from a cable box because the bandwidth
> requirements are too high for the video card. Is this true or are the
> reasons more technical, legal, or political?
>
> Can someone clearly and concisely state the reasons why ATI and/or
> other video card manufacturers have not offered a video input card for
> sale that will receive high resolution HDTV from an HD cable box?

These guys can help if you have a Mac http://www.aja.com/products.html

I know there is at least one box that sits (electrically) between the CPU
and the monitor and switches the monitor between the CPU and its own
internal TV tuner. My nephew has one, which I think he got at Office
Depot, where he works. Now if that li'l baby did HD ... you'd be there.

Archived from groups: alt.video.digital-tv (More info?)

Ron wrote:
> I've been interested in viewing HDTV directly from a set-top cable-box
> on a computer screen for some time and I seem to get a variety of
> different statements of facts about whether this is possible? I
> wonder if someone could set us all straight on the important aspects
> of this issue?
>
> I've read that it is not possible for video input cards to receive
> HDTV composite input from a cable box because the bandwidth
> requirements are too high for the video card. Is this true or are the
> reasons more technical, legal, or political?

There isn't really an HDTV composite signal... There is an HDTV component
signal - which is an analogue component signal but with a much higher
bandwith than a conventional 480/60i component signal (and there aren't many
video capture cards that offer component at 480i - most are composite or
S-video - though there are a few exceptions)

The A/D sampling and high bandwith required to capture HDTV analogue
component signals as delivered by a set-top box make these kind of cards
still quite high-end and expensive... For a domestic installation you would
probably want to recompress to MPEG2 or similar to record to a hard-drive if
you were capturing analogue HD component - as 1920x1080x30 is a lot of
samples per second (even if you run at subsampled chroma) This
recompression would not improve quality - so you would be paying for a
high-end solution but not getting the best quality.

More common are cards that will accept an aerial input (or antenna to you
guys in the US) and receive the digital TV over the air transmissions - HDTV
and/or SDTV. (DVB-T in Europe, ATSC in the US - not sure if there is a
cable equivalent available in the US, though I believe a few cable cos are
distributing ATSC?) This allows the PC to record the HD or SD broadcast
cleanly, without having to decompress it from MPEG2 to analogue component,
and then grab the analogue version. It also means the recording on the PC
is a direct copy of the broadcast so is cleaner - it is also a lot cheaper
as there is no esoteric A/D hardware, just a tuner and digital front-end
from an HDTV receiver on the PC card.

A third alternative is that some US STBs (ATSC and Digital cable) have (or
can be modified?) to deliver HD MPEG2 over Firewire - either to feed a PC or
a D-VHS VCR? This again is a lossless recording replay system - whereas a
component analogue capture system would required decompression, and probably
recompression.

> Can someone clearly and concisely state the reasons why ATI and/or
> other video card manufacturers have not offered a video input card for
> sale that will receive high resolution HDTV from an HD cable box?

Expensive electronics required for component HDTV capture - and there isn't
a large market for it. Broadcasters don't use component analogue for signal
routing (they use HDSDI or similar) in the main, and domestic systems are
likely to go down the digital reception route, as it is higher quality, and
subsidised by the set-top box and HD TV manufacturers by economies of scale?


Just my view - from the UK. We don't have HD - but we do have loads of SDTV
digital capture cards, which allow reception and recording of the direct
broadcast signal (from satellite or over-the-air aerial/antenna), which in
turn allows loss-less burning to DVD. All SD (though 16:9 and component/RGB
quality - not composite or S-video) - but still better than VHS, S-VHS, or
even a domestic DVD+/-RW recorder fed RGB from a digital
satellite/terrestrial set-top box.

Steve