Comments on H.245v8 & H.263 Annex X

Dave Lindbergh lindbergh at MEDIAONE.NET
Tue May 15 17:05:09 EDT 2001


Mike/all,

A couple of minor comments on the draft H.245v8 in
GEN-009 for Brazil:

1) We've some concern that, given the complexity of
    the current (pre-v8) H.263 caps, a "new vendor"
    unfamiliar with the history of H.245 and H.263
    will be tempted to signal _only_ the new Annex X/H.263
    Generic Caps (H.263 profiles) instead of the
    existing H.263 caps that all current equipment use.
    If this happens, a video call will fall back all the
    way to H.261.

    To avoid this, I suggest adding the following as a
    "Note" to the H.263 generic cap in Table VIII.1/H.245:

    <begin text>
    Note - Use of this capability to signal H.263 "Profiles
    and Levels" per Annex X/H.263 should always be
    accompanied in parallel by the signaling of the
    same modes in H263VideoCapability.  This is necessary
    to ensure that systems which do not recognize the
    H.263 generic capabilities continue to interwork
    with newer systems.
    <end text>

    I think this is an issue _only_ for H.245, and not
    for Annex X/H.263 in general, since any new use
    of H.263 (not involving H.245) will have no such
    backward-compatibility issue.

2) In the title for Table VIII.1/H.245, the words
    "capability" and "organizations" are misspelled.

If you (as editor) and the list members agree, I suggest
these be included in a "corrections" TD for Brazil.

Regards,

--Dave Lindbergh,
   PictureTel Corp.

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