Subject: Forward from Art Alison: WGLC ULE

From: Gorry Fairhurst <[email-masked]>
Date: Mon, 31 Jan 2005 17:20:26 +0000

WG please read and respond to this message.

The following message was received on January 22nd before WGLC, but was 
dropped because the email source address was not verified by the list server.

The exact text of the message follows.

best wishes,

Gorry
(ipdvb WG Chair)

-----

Thanks for considering my previous input...
I note that the new draft has an editorial oversight in that it contains two
definitions of PSI. I suggest the second should be deleted.

I previously made a comment about the ancillary requirements when adding a
TS logical channel to a TS multiplex and asserted there appeared to be under
specification. Perhaps it was viewed as out of scope, or perhaps I simply
don't recognize the change that resulted.  I can not find what stream_type
is required to be used for the ULE stream when a "TS Logical Channel" is
added to a multiplex.

I suggest at least an informative note be added in Section 6 (after the
third line which says: "These are transmitted using a single TS Logical
Channel over a TS Multiplex.") The note should say "PSI entries to be
consistent with [ISO-MPEG] when constructing a conformant TS Multiplex and
means for Receivers to locate each such TS Logical Channel are outside the
scope of this recommendation."

Reason:
Just inserting a "TS Logical Channel" without including a
TS_Program_map_section that lists the PID and a stream_type does not appear
to me to result in a strictly MPEG-2 conformant bit stream; and practically
could result in the PIDs being dropped by a remultiplexer.   If the means
for binding the inserted element into a multiplex and subsequent discovery
is to be covered in another document, a pointer to that document would be
more helpful than this warning. It seems at least a warning is needed and
preferably a pointer to where this next level of TS construction is defined.

Art Allison
Director, Advanced Engineering
NAB Science & Technology
1771 N St NW, Washington Dc 20036
202 429 5418