[opendtv] Re: 625 video quality is good enough....

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 19 Oct 2004 12:31:48 -0400

Craig Birkmaier wrote:

> MPEG-2 TS is widely used and has the flexibility to
> evolve since it is just a packet data format with
> headers and descriptors. The only real question is
> whether it is the most efficient transport available?

Compared with what? It's certainly more flexible than,
say, Ethernet. I don't see this as a major issue.

> It would be a worthwhile endeavor to revisit this
> issue to see what the optimum packet size(s) should
> be for various channels with different BERs.

Yes, but MPEG-2 TS does not limit you to just one
size. In fact, ATSC and DVB-T use different size
packets for program streams.

In any event, for synchronous streams, you don't want
large frames. For data, MPEG-2 TS as used in A/90 goes
way up to something like 4500 or 10,000 bytes,
depending on profile used. Which is right up there
with the best of the link layer techniques.

> There may be some validity in moving to something
> like TCP/IP, if for no other reason than to
> minimize packet repacking for transmission.

You're confusing the link layer (e.g. MPEG-2 TS or
Ethernet) with the transport layer (e.g. IP).

IP packets are carried inside MPEG-2 TS frames, just
like IP packets are carried inside Ethernet frames
in wired LANs, or inside 802.11 frames in WLANs.

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