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To: MikeM54321 who wrote (7412)	6/26/2000 8:45:00 AM
From: Peter Ecclesine	Respond to of 12823

Hi Mike, There are several HDTV forms, and I think MPEG2 takes ~20Mbps to represent 780i. MPEG2 digital TV bursts up to 8Mbps for panning camera, and DVD burst to 11 Mbps. MPEG2 is a Variable Bit Rate coding. petere

To: MikeM54321 who wrote (7412)	6/26/2000 9:15:00 AM
From: Frank A. Coluccio	Read Replies (2) \| Respond to of 12823

Hi Mike, Yes, 50 Mb/s is a nice round number that I think will be very convenient for those whose line rates hit the ceiling at 51.x Mb/s. What am I missing here? ... How is the VDSL pipe ever going to scale up to 200 channels like it's competitors offer today? Does the telco's VDSL TV model require VOD? ie, one channel at a time that is unique to the customer. The VDSL Switched Digital Video mode is not broadcast and select like analog broadcast signals. In VDSL, only a single (or up to some limited number of simultaneous) sessions are permitted to take place at any point in time. This is one of the points I was making upstream concerning the limitations of VDSLs capabilities to carry on HDTV and other sessions, in addition to being able to simultaneously carry high speed Internet access. Or another way to look at it(again from just what I read), 1 HDTV channel is like 5 digital TV(DTV) channels. And 1 analog channel equates to 4 or 5 DTV channels. Kind of interesting rules of thumb. But again, I have no idea if they're accurate. I'm just quoting something I read somewhere and doing my best to remember the rules of thumb. It seems that the actual transmission system (cable, wireless, whatever) throughput rates necessary to support HDTV depend on multiple factors, not the least of which is the phase of translation and encoding you are at during the life cycle of an HDTV signal when you send it. It starts out in life as a 1.5 Gb/s, which, one may argue is its uncompressed mode (but I would argue against purely on semantic grounds), and then gets cut down <!!> to 270Mb/s. From there it can be further compressed to speeds which are more amenable to lower bit-rate systems. As a result of my previous 1.5 Gb/s statement, Dave Horne and I have been having a sidebar discussion in PM with the preponderance of good information coming from Dave on this topic. I see that it's now time to reproduce that dialog on the public boards, which is something I had intended, earlier, to do on FCTF, and may still do, if I have the time later on. I'll let you know when I get around to threading it. But the main gist of the PMs is captured in this post by Dave, which I reproduce here with his permission, providing the foundation for more discussion: -----begin Dave H on HDTV: Ah, yes, that's perfect. Now I understand what they mean. The 1.5Gbps is the raw serial feed which replaces the 270Mbps feed within the studio, for the 1080-I mode of HDTV. Since 1080I is the "greatest common factor" all the timing for the other modes can be generated from this. So by shipping this mode around the studio they have full flexibility of which mode they choose to broadcast, whereas if they were to ship any other mode around the studio, they are essentially locked in to broadcasting that "lesser" mode, after compression. This (original master) signal is stored locally on a disk array such as: digitalvideo.de So for HDTV applications this 1.5 Gbps serialized 10-bit 4:2:2 component video signal is the in-studio replacement for the 270Mbps serialized 10-bit 4:2:2 component video used today. According to "Issues in Advanced Television technology" by S M Weiss,the absolute upper bound for broadcast bitrate of the compressed signal in this mode is 100Mbps, so the 120Mbps I've seen in some of the product links I just browsed thru must include some headroom to do multilayer broadcasts. ---------End Dave H on HDTV I'll transcribe the entire discussion at a later time on the FCTF. FAC