Why didn't you... ;)

Hi Nathan ---

I've passed your question on to Vic ... He'll get back to you soon.

jlm@ZV

Nathan,

First of all, sorry for the delayed reply. As you might have guessed, these were points of great debate. Regarding ATSC vs. QAM, we felt that:

- The source for other channels on the in-home cable could either be Cable, Satellite, or Over the Air. Of those, the majority of customers subscribe to cable, which implies that the other channels on their coax are QAM. With our channel also being QAM, they don't need to change modes to see one or the other. Many TVs make switching between those modes very difficult - usually a deep menu setting

- It's very difficult to fit an ATSC channel into a QAM channel plan. The frequencies don't line up, which makes finding a hole harder.

- We were worried about HDTVs not having QAM tuners. Most do not show having it on their specs. We learned that most of the sets sold in the past few years do, even if they don't claim it. That was reinforced by the roughly 30 models that we have here. We did find that sets manufactured just when they changed from HD Ready to HD compatible may not have had QAM, but that only lasted for a short time. Standalone tuners like the Samsung that they sell at Best Buy support QAM. Those findings made us much more comfortable with QAM.

- ATSC requires you to license the technology from the patent holders. We're happy to do so, but there are hundreds of patents spread over many holders. We simply haven't undertaken the effort (yet). There is an organization (MPEG-LA) that licenses ATSC, but that's only for receivers. There is no such blanket license for a transmitter. The legal investigations that we did showed that QAM did not require licensing. (We do license MPEG).

Regarding the Component input - you're very correct - we can do that fairly easily. Our initial product was simplified as much as possible to attack the much larger opportunity for bringing PC content to the HDTV (online video sites have millions of active users, many of which would love to see the content in the living room). That said, we do recognize the opportunity to work with the custom installer market. We'll be at CEDIA in a few weeks, and would enjoy talking about the feature set that the 'right' product would have. Stop by if you'll be there!

Vic

Just in case this is a better place to post my question, here goes.

What is the data output rate employed by the ZvBox? A QAM256 CATV channel generally operates at 38.8 Mb/s and can contain a multiplexed pair of HD channels, each running at 19.4 Mb/s (which is the ATSC data rate for a local broadcast station)?

It would be much more useful to input Y, Pb,Pr and output either a 19.4 Mb/s QAM64 signal, or better yet, a 19.4 Mb/s 8VSB signal. The licensing requirement for using 8VSB is not nearly as complicated as that for a broadcast "transmitter" since you are delivering a signal only within a closed system. In fact, the ATSC contemplated that cable systems would use 16VSB for cable distribution although QAM256 was adopted.

Is it possible to limit the output data rate of the ZvBox to stay below 19.4 Mb/s so that more devices can pass or record its data transport stream?

Günter Marksteiner
Chief Engineer, WHDT

I found this on Amazon:

Brian says:
OK guys. This is Brian from ZeeVee. This is what my engineers tell me about bit rate:

We use as much bandwidth as we need. If you generate a lot of motion, our data transmit rate can go as high as 25 or 28 Mb/s. Keep in mind that we are actually transmitting 38 Mb/s, but a lot of it is just filler (stuffing). QAM does not allow you to just stop sending.

The bit rate ZvBox uses is similar to that used by typical cable providers as well as over the air broadcasters. An RF channel is 6MegaHertz wide in the RF spectrum. The coding technique - for us and the cable companies - is QAM256. This allows for theoretical maximum of 38Mbps of data to be carried on the RF channel. Your cable company will typically carry two high definition programs, each coded to a data rate of 19Mbps, in one of those 6MHz wide RF channels. As a point of reference, the maximum data rate for over-the-air broadcasts is also 19Mbps. ZvBox is designed to fit into that rough guideline of 19Mbps. The quality of motion is as much a function of the coding techniques and computing horsepower applied as the Mbps available in the channel.

I like using my Xbox 360 as a media extender but I'd like to be able to send it to multiple displays. It would also be neat to be able to capture hi-def gaming with a QAM capture card, but I guess you'd need 2 PC's for that.

If I wanted to put an Xbox 360 through this via its VGA output would it be possible to "trick" the ZeeVee box by removing the VGA from the computer and connecting the Xbox with the exact same resolution and refresh rate? I'd then connect the audio to the line in on the computer so hopefully that would get passed on the coax too.

If you guys can actually do a standalone vga/component to qam product with halfway decent quality with a similar price-point you'll be undercutting some very expensive gear out there. Every videophile in the world will want one. It seems like it shouldn't be too hard to add a firewire video out port either since the heavy lifting with the mpeg-2 encoding is already handled.