how-to block ads
|
dru
join:2000-09-14
Corona, CA
| reply to Jerm
Re: This is what ADSL was designed for!
Well, HDTV, IMHO, is still "over the rainbow" and even though it is starting to appear, I think that any DSL or broadband delivery system will be lucky to push VHS-quality signals to customers, such as the typical video-on-demand systems in hotel rooms.
I know I am glossing over and over-simplifying details, but here's what I understand about video. As an example and reference, Digital satellite system (DISH and DirecTV) use variable data rates of around 4mbits to produce full 30fps pictures using MPEG2 with stereo. The pictures are far from HDTV and artifacts are visible, but quality is respectable. I have also seen full-motion video using MPEG1 compression with data rates of 1.4mbits and if you're not too picky (VHS running 6 hour mode looks OK to you) it's watchable. Most digital cable systems also use compression to squeeze more channels within the spectrum available.
Standard North American TV (Analog NTSC video) requires 6mhz per channel, roughly analogous to 6mbits. However, when you sample and quantize an analog video signal into digital, it can take (depending on original signal quality) 50 to 80mbits of bandwidth to record or transmit an UN-compressed signal.
Definitely, there are ADSL products that, provided they are working and provisioned properly, would support decent-quality compressed video signals suitable for watching movies.
While "this is what ADSL was meant for" we seem to always have to go through the crawl phase before we walk phase.
My questions and concerns would be:
1. What bandwidth/data rate are they running? Are the pictures sent "real time" or are they buffering to hard disk/memory? (by giving a stream at least a few minutes of buffered "head start" more quality could be obtained by averaging out the scenes, which vary in data needed after compression)
2. I am sure their first DSL "Partners" are those who can provision 4-8mb ADSL and have local video servers rather than relying on internet bandwidth, but do they have their own facilities? For example, the typical central office DSLAM setup may not have enough back-end bandwidth to support hundreds of broadband video streams over ATM, at least not the current implementations.
3. How do they deal with data rates and distance limits? Or do these systems generally only work with multi-tenant/multi-dwelling situations (big apartment complexes)?
It occurs to me that people in the "test markets" have never heard of the mentioned ISP "partners" because they are "in-house" MDU vendors or ones with developer contracts to offer exclusive services in specific housing tracts.
[text was edited by author 2000-12-21 01:22:30] | |
lml2000
Whazzup
join:2000-08-17
Los Angeles, CA
 ·RoadRunner Cable
| Good critical post, dru. A couple comments.
HDTV
I would not even begin to address HDTV over DSL at this point. Most likely it will never happen. Even the MSOs are loathe to deliver HD over their pipes. Presently, HD is going to be limited to satellite and over-the-air transmission. Until this market more fully develops, I don't expect the MSOs to budge an inch. The economics of HD make it economical for bandwidth constrained MSOs to push HD. DSL is no different, and arguably, even more constrained. Also note that HD over DBS is already available. DirecTV offers 2 channels, one HBO, the other pay-per-view, each broadcasted from a different satellite, so one needs an elliptical dish equipped with special LNB as well as a special digital receiver that is designed to decode the HD signals into analog for viewing. But all this does not preclude the eventual migration to pure or "standard" digital TV.
VOD over DSL
It is indisputable that the video content will be delivered in compressed format. Uncompressed format is just not going to happen, and is just not economical. Content will be delivered, most likely from remote video servers deployed deep in the loop as far as what I would term "premium" content is concerned. I just don't think the studios are going to offer their most valuable IP into the home where it can be stored onto a hard drive and subject to copyright infringement by very motivated hackers. Imagine the monetary damages to the studio and the artists if just one recent studio release is downloaded onto a TiVo, hacked onto a hard drive, then duplicated and distributed over the Internet. I just think the risks today are too great. In light of this I foresee remote video servers offering bit streams that are buffered onsite.
As I disclosed elsewhere on DSLReports, my loop is not being outfitted with an OC-12 from which 2 OC-3s will feed into the several neighborhood gateways along the loop. The question is where along this ring would a video server likely be installed and capable of meeting the downstream demand of all subs along the loop? As you note, VOD from the gateway to the subscriber's premises will be delivered over a DSL connection that should accommodate 3-4 Mbps of bandwidth. If your familiar with SBC's Pronto project, you will not that though basis DSL service up to 1.5 Mbps, the architecture can provide up to 6 Mbps, if the customer wants to pay a premium for a continuous connection. But, because of the use of SVCs, the customer will also be able to "fatten" his pipe on a temporary switched basis to accommodate a VOD bit stream. With "up to 6 Mbps," VOD requiring 3-4 Mbps will offer a good quality feed.
With respect to MDUs, you present an interesting issue. Possibly, for large MDUs we might even see a video server onsite but locked in a secure room away from the sub where the content is at least "physically" secure.
--
Regards,
lml | |
|
