Re: [rtcweb] Reasons (not?) to multiplex audio with video

Aron Rosenberg <arosenberg@logitech.com> Tue, 26 July 2011 21:58 UTC

Return-Path: <arosenberg@logitech.com>
X-Original-To: rtcweb@ietfa.amsl.com
Delivered-To: rtcweb@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 0B0C811E80B7 for <rtcweb@ietfa.amsl.com>; Tue, 26 Jul 2011 14:58:34 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -5.676
X-Spam-Level:
X-Spam-Status: No, score=-5.676 tagged_above=-999 required=5 tests=[AWL=-0.300, BAYES_00=-2.599, FM_FORGED_GMAIL=0.622, HTML_MESSAGE=0.001, J_CHICKENPOX_15=0.6, RCVD_IN_DNSWL_MED=-4]
Received: from mail.ietf.org ([64.170.98.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id glAQRYiGfFFF for <rtcweb@ietfa.amsl.com>; Tue, 26 Jul 2011 14:58:33 -0700 (PDT)
Received: from na3sys009aog104.obsmtp.com (na3sys009aog104.obsmtp.com [74.125.149.73]) by ietfa.amsl.com (Postfix) with SMTP id B082411E80B3 for <rtcweb@ietf.org>; Tue, 26 Jul 2011 14:58:32 -0700 (PDT)
Received: from mail-gx0-f173.google.com ([209.85.161.173]) (using TLSv1) by na3sys009aob104.postini.com ([74.125.148.12]) with SMTP ID DSNKTi84h2uEpndR5FdIfbOFkuSIPbyT0da2@postini.com; Tue, 26 Jul 2011 14:58:32 PDT
Received: by mail-gx0-f173.google.com with SMTP id 26so900774gxk.18 for <rtcweb@ietf.org>; Tue, 26 Jul 2011 14:58:31 -0700 (PDT)
Received: by 10.236.176.194 with SMTP id b42mr7743439yhm.524.1311717511094; Tue, 26 Jul 2011 14:58:31 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.236.42.196 with HTTP; Tue, 26 Jul 2011 14:58:11 -0700 (PDT)
In-Reply-To: <38DF8F00ABAB77498A75469448CB081B3AE69BF4AA@BE235.mail.lan>
References: <4E123C54.10405@jdrosen.net> <8785C0A3-31E5-44D7-8557-3BEEE4F95E3D@skype.net> <4E2D5C5D.6060402@alvestrand.no> <f06240801ca54cb571321@66.80.62.44> <38DF8F00ABAB77498A75469448CB081B3AE69BF4AA@BE235.mail.lan>
From: Aron Rosenberg <arosenberg@logitech.com>
Date: Tue, 26 Jul 2011 14:58:11 -0700
Message-ID: <CAB+e8F6H1ThgKUnTumfOPPVdHOjDLfh_AH0SWsrkDUUMz99MCQ@mail.gmail.com>
To: "rtcweb@ietf.org" <rtcweb@ietf.org>
Content-Type: multipart/alternative; boundary=20cf305b12824b60bd04a900083f
Subject: Re: [rtcweb] Reasons (not?) to multiplex audio with video
X-BeenThere: rtcweb@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Real-Time Communication in WEB-browsers working group list <rtcweb.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/rtcweb>, <mailto:rtcweb-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/rtcweb>
List-Post: <mailto:rtcweb@ietf.org>
List-Help: <mailto:rtcweb-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/rtcweb>, <mailto:rtcweb-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 26 Jul 2011 21:58:34 -0000

Facetime muxes everything onto the same port using RTP SSRC and signals that
in SDP using an a=rtpID attribute inside each m= line. Each m= line has the
same <port> value.

-Aron

On Tue, Jul 26, 2011 at 2:48 PM, Bala Pitchandi <Bala@vidyo.com> wrote:

> > 1/ Apple's "FaceTime".  OK, this is not browser-based (although with a
> bit of work it probably could have been), but it does use RTP.  Is it using
> separate ports for audio and video (and two more for RTCP)?
> > If so, has NAT traversal been a problem, and would it have been
> beneficial to have been able to reduce the number of ports used?  (Is Dave
> Singer on this mailing list?)
>
> I believe FaceTime multiplexes audio & video on to the same port. In fact,
> it even multiplexes the signaling on to the same port. See:
> http://blog.roychowdhury.org/2010/06/25/facetime-on-iphone-4-vanilla-unencrypted-stun-and-sip/
>
> -- Bala
>
> _______________________________________________
> rtcweb mailing list
> rtcweb@ietf.org
> https://www.ietf.org/mailman/listinfo/rtcweb
>