New HDTV Capture / Output Card

[Jerry Jones]

Interesting:
http://www.etown.com/news/article.jhtml?articleID=3677

[A_BIT]

The DTV-200, on the other hand, records full-quality HDTV programs to the computer's hard disc. It actually passes the full MPEG bitstream to the drive. According to Newstead, an hour's worth of 1080i HDTV occupies 7.7 Gigabytes of space, or about 2.2 Megabytes per second.

What is the compression method used here. It doesn't seem possible that MPEG2 at this resolution can be compressed to such a degree.

[jeff b]

The 2.2 megabytes/second does seem a bit tight, doesn't it? But apparently, that's about what they're sending out over the air. As I understand it, the bitstream for one 1080i program on air is roughly 19 megaBITS per second, which translates out to roughly the same 2.2 megabytes per second. Uncompressed, the full 1080i bitstream is up around 1.2 to 1.5 gigaBITS per second, or around 150 to 180 megabytes per second. When I see numbers like that, I can only wonder how they're compressing 80:1 with MPEG-2 and getting anything that could look so absolutely incredible on the receiving end. If you've seen any 1080i broadcasts on a nice large screen HDTV system, you'll understand what I'm saying here.

As far as this DTV-200 card is concerned, though, it really doesn't seem clear what you'd get on your computer monitor, other than some kind of scaled down and cropped picture on live viewing of over the air signals. But, at least, they do seem sure that they've got a product there, and that it will at least get the digital signal off an antenna and into the computer (at last!).

I had been eagerly awaiting the release of the Pinnacle HDTV card, which was announced on their website many months ago. Now that they've apparently scrapped the whole project, it makes me wonder about the where their design engineers came from. This DTV-200 seems like it might be a compromise solution to problems that I can only guess at, but it looks like they've at least got EE's on their staff that have been around long enough to have a little working knowledge of how to design things.

I've seen this kind of thing creep into the picture before, where designers are at odds with two paradigms. On the one hand, you've got the older analog paradigm, and on the other you've got the newer digital paradigm of electronic design. Where some (younger) designers think that analog ideas aren't worth knowing, they completely miss the boat and constrict themselves with a strictly digital viewpoint. Products designed with that limited view tend to have odd jitter problems in the digital realm of video and audio, for instance. They don't think they have to pay attention to their power supply design, for example, and they miss the boat on design possibilities that could afford more robust performance. The current crop of low priced DVD players demonstrate high rates of dropout due to the poor transient and line noise filtering in the power supplies.

Another area where these paradigms come into play is SDI products for video and audio. Some designers have incredibly clever schemes that not only utilize various DAC's and ADC's in ways they were never intended to be used, but also have some fairly old technology in there alongside everything else that makes the products inexpensive and yet robust. Meanwhile, the new crop of digital EE's slave away through long drawn out design abortions that ultimately make their products so expensive that it turns out to be unviable (eh Pinnacle?).

At any rate, I'll get off my soapbox now, and look forward to the release of the DTV-200, and users' feedback. I really REALLY want to have an inexpensive HDTV receiver in my computer, and it's been frustrating to not see any manufacturers tap this potential market for HDTV and finally put something on the table. After all, Hi-Def really OUGHT to look pretty darn GOOD on a computer monitor, when you think about it...

Jeff B