[h323forum] Re: Codec negotiation question

Balasubramanian Pitchandi bs at UTSTAR.COM
Tue Dec 17 16:42:26 EST 2002


You can look at the IETF AVT Working group's draft on TCRTP:

http://www.ietf.org/internet-drafts/draft-ietf-avt-tcrtp-07.txt

It's a mature protocol being implemented (or already implemented) by
handful of vendors.

Thanks,
Bala


-----Original Message-----
From: Mailing list for parties associated with ITU-T Study Group 16
[mailto:ITU-SG16 at echo.jf.INTEL.COM] On Behalf Of Denise Shull
Sent: Tuesday, December 17, 2002 3:56 PM
To: ITU-SG16 at echo.jf.INTEL.COM
Subject: Re: [h323forum] Re: Codec negotiation question

Trying to not 'plug' any company or technology in this arena, however, I
am doing a consulting project for a company that schedules the packets -
versus prioritizing them.  They are in beta mode but their tests reveal
a very effective method for delivering video with greatly reduced
latency and jitter.

It would be useful to be able to have input from this group both on the
idea and on their technology specifically.

Regards,
Denise

Denise K. Shull
SHULL ADVISORS, LLC
Strategic Application of Meeting Technologies
646-498-6403
www.videooverip.biz



-----Original Message-----
From: Paul E. Jones [mailto:paulej at packetizer.com]
Sent: Monday, December 16, 2002 8:04 PM
To: Paul Long; h323forum at mail.imtc.org; ITU-SG16 at echo.jf.INTEL.COM
Subject: [h323forum] Re: Codec negotiation question

Paul,

Do you mean RFC 2508?

In any case, Robert's point is indeed valid.  This is where having a
specialize GW that multiplexes the RTP streams for delivery over the
long-haul is something practical.

Perhaps we could take that up as a work item with SG16? It would be
reasonable to specify how such an Gateway might function in order to
trunk a
large number of active calls over long distance.  Anyone interested in
such
a work item?

Paul

----- Original Message -----
From: "Paul Long" <plong at packetizer.com>
To: <h323forum at mail.imtc.org>
Sent: Monday, December 16, 2002 7:49 PM
Subject: [h323forum] Re: Codec negotiation question


> Robert,
>
> Excellent point. I hadn't thought of that. I wonder what happened to
> cRTP. Anybody know? That would sure help.
>
> Paul
>
> >
> > On Mon, 16 Dec 2002 12:53:34 -0500
> > "Paul Long" <plong at packetizer.com> wrote:
> >
> > > I know lots of folks would like a means of expressing exact
> > > packetization, but isn't the solution trivial? All you need is a
> small
> > > FIFO and a few lines of code to re-packetize according to any
> internal
> > > requirements. Just write incoming frames regardless of size, e.g.,
> > > 30fpp, to the FIFO, and read whatever size frames you want, e.g.,
> 80fpp
> > > from the FIFO (only read if there are at least X fpp in the FIFO).
> >
> > DSP hardware is not the only reason for wanting to have the remote
> > endpoint send larger packets. We have many clients on long haul
> internet
> > links (300ms+ ping times), often with a slow tail circuit (ISDN or
> even
> > modem) and you REALLY want the other end to send more than one
G.723.1
> > frame per packet to reduce the significant overhead that there is in
> the
> > RTP.
> >
> >
> >
> > > > It is unfortunate but true that there is no way of expressing a
> > > minimum
> > > > acceptable number of frames per packet.
> > > >
> > > > Regards,
> > > > Chris
> > > >
> > > > Paul Long wrote:
> > > > > Davide,
> > > > >
> > > > > There is nothing in the standard that requires the acceptance
> of an
> > > OLC
> > > > > or precludes terminating the call for any reason whatsoever so
> both
> > > EPs
> > > > > are technically compliant.
> > > > >
> > > > > Packetization in TCS and OLC expresses the _maximum_ frames
per
> > > packet,
> > > > > but several vendors don't understand this simple concept and
> > > continue
> > > > > to produce products that expect an exact packetization. There
> is a
> > > good
> > > > > chance that that is why EP A is rejecting the OLC. It wants
the
> > > channel
> > > > > opened at exactly 80fpp, although there is no way to express
> this
> > > in
> > > > > H.323. IMO, if this is the reason, that product is broken.
> > > > >
> > > > > Paul
> > > > >
> > > > >
> > > > >>Hi all,
> > > > >>
> > > > >>I have a question about a codec negotiation.
> > > > >>During H.245 negotiation, endpoint A (master) exports
g711A-law
> > > with
> > > > >
> > > > > packetization 80, endpoint B (slave) exports g711A-law with
> > > > > packetization 30. After that, endpoint A opens a channel with
> > > > > packetization = 20 ms. Endpoint B acknoledges the OLC and
tries
> to
> > > open
> > > > > a channel with packetization = 30 ms.
> > > > >
> > > > >>Here Endpoint A rejects the OLC and the call is disengaged.
> > > > >>
> > > > >>Does anybody can tell me which endpoint dosn't behave
according
> to
> > > > >
> > > > > the H323 standard?
> > > > >
> > > > >>Thank you in advance.
> > > > >>
> > > > >>Davide
> > > > >
> > > > >
> > > > > ---
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> >
> > ----------
> > Robert Jongbloed                        Equivalence Pty. Ltd.
> > Architect Open Phone Abstraction Library (OPAL) & OpenH323
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