Venki Iyer wrote: > but I read this as a non-tech (well, OK, non-IP, non-XML, > non-RSS, take your pick) editor/writer trying to describe > what can and is being done with RSS (which uses XML) and > IP-based protocols (like BT, for example). Except that the part "and IP-based protocols" is exactly what we are trying to identify. To say "IP-based protocols" is *not* to say that mentioning IP is enough. IP is a routing protocol, layer 3, described in RFC 791. It doesn't begin to specify what an IPTV (or any other DTV) needs to interoperate with client hosts. Kon may be correct that all IPTV schemes use XML for layers 5-7, I have no way of knowing. I've never seen a comprehensive survey of IPTV systems deployed so far. (But I would be amazed if they were interoperable.) The same applies to ATSC and DVB-T. It's hardly enough to limit the definition to MPEG-2 TS. For exactly the same reasons. How does the client interpret the bit stream? Even the new media darling, Bit Torrent, doesn't get away with any of this. BT is essentially a layer 5 scheme, session layer. It works on top of TCP, and it orchestrates a choreography of TCP downloads from a number of different servers. The question remains, after the download is reconsituted into the appropriate file, what have you downloaded and how is it read? Is it a big MS Word file? Is it Acrobat? Is with WM10? Heck, is it ATSC over MPEG-2 TS (why not?). You need this info for clients to decode the stream they're receiving. And you are also making assumptions of how powerful the client hardware is, whether it's cabable of coping with this bit stream. > Maybe this makes Kon's point, that IBM and Harris are not > exactly the shining examples of the leading edge here, Kon focused on XML as the choice. I don't think that was the thrust of Loring Wirbel's column. As I indicated, he was saying that only Harris and Microsoft seemed to grasp that merely specifying "IP" is simply not enough. And I tried to make the point more clearly by tying this back to the discussion of what it takes to define a DTT system. The concepts are the same, whether it's IP or other digital protocol at layers 2 and 3. The ATSC and the DVB have devised a very efficient way to fully define DTT streams. Furthermore, with A/90 and the DVB equivalent (whatever that is), they have opened the doors to almost limitless options for upgrading the standard, subject only to the one-way broadcast environment DTT operates in. In principle, even XML and some one-way version of Bit Torrent could be transmitted over ATSC and DVB-T. (Imagine for example a tuner being told to tune simultaneously to x different stations, download the separate streams, store in a PVR, reconstitute the original file, then interpret the file.) So, my objections continue to be (1) that a vague mention of "IP" is not enough to describe a TV systems that works, (2) that the same applies to MPEG-2 TS for a TV system, and (3) the claim that ATSC is "not extensible" is way off the mark. Bert ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.