Re: [MMUSIC] [rtcweb] Fwd: New Version Notification for draft-uberti-rtcweb-plan-00.txt

Christer Holmberg <christer.holmberg@ericsson.com> Tue, 07 May 2013 10:12 UTC

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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Harald Alvestrand <harald@alvestrand.no>, Justin Uberti <juberti@google.com>
Thread-Topic: [rtcweb] Fwd: New Version Notification for draft-uberti-rtcweb-plan-00.txt
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Date: Tue, 07 May 2013 10:11:55 +0000
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Subject: Re: [MMUSIC] [rtcweb] Fwd: New Version Notification for draft-uberti-rtcweb-plan-00.txt
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Hi,

A few questions on the draft:

Q1_CODEC/CODEC CONFIGURATION:

The examples only show one PT per m- line, and the draft seem to assume that all PTs (ie codecs and/or codec configurations) apply to all SSRCs within an m- line. I think that is very important to point out, because at least in my opinion it is an important factor that we need to discuss.

Example: I think Cullen often talks about using a camera with built in codec X. But, Plan B does not allow to (or, at least does not describe how to) explicitly offer codec X for the track/ssrc associated with the camera. Codec X is offered for ALL tracks/ssrcs associated with the m- line.


Q2_1_LEGACY:

The text says that things must work with legacy devices, and that an endpoint can choose a single source when communicating with a legacy device. But, there is really no text about how the legacy device will know which source to use, etc.


Q2_2_LEGACY:

The example in section 5.2 (and sub sections) confuses me a little. You indicate that the m- line itself represents "main", while ssrc attributes are used to describe the left/center/right mic sources. Why is there no ssrc attribute for the main flow?


Q3_NUMBER_OF_M_LINES:

The draft does not explicitly forbid the usage of multiple m- lines for a given media type (e.g. audio). It would probably be good to point that out also.


Regards,

Christer



From: rtcweb-bounces@ietf.org<mailto:rtcweb-bounces@ietf.org> [mailto:rtcweb-bounces@ietf.org] On Behalf Of Harald Alvestrand
Sent: 6. toukokuuta 2013 17:20
To: Justin Uberti
Cc: rtcweb@ietf.org<mailto:rtcweb@ietf.org>; mmusic@ietf.org<mailto:mmusic@ietf.org>
Subject: Re: [rtcweb] Fwd: New Version Notification for draft-uberti-rtcweb-plan-00.txt

Note - I regard the Plan A / Plan B conflict as the "long end of the pole" with regards to resolving issues regarding SDP signalling in RTCWEB - and as such, I regard it as very important to get it resolved.

The silence on this issue is disquieting.

           Harald


On 05/03/2013 08:08 AM, Justin Uberti wrote:
Scribbled down the basic concepts of what I have been referring to as "Plan B" - a way to signal multiple MediaStreamTracks in SDP without needing a separate m= line for each.

Hopefully this will make discussion of this topic easier.

---------- Forwarded message ----------
From: <internet-drafts@ietf.org<mailto:internet-drafts@ietf.org>>
Date: Thu, May 2, 2013 at 10:46 PM
Subject: New Version Notification for draft-uberti-rtcweb-plan-00.txt
To: Justin Uberti <justin@uberti.name<mailto:justin@uberti.name>>



A new version of I-D, draft-uberti-rtcweb-plan-00.txt
has been successfully submitted by Justin Uberti and posted to the
IETF repository.

Filename:        draft-uberti-rtcweb-plan
Revision:        00
Title:           Plan B: a proposal for signaling multiple media sources in WebRTC.
Creation date:   2013-05-03
Group:           Individual Submission
Number of pages: 15
URL:             http://www.ietf.org/internet-drafts/draft-uberti-rtcweb-plan-00.txt
Status:          http://datatracker.ietf.org/doc/draft-uberti-rtcweb-plan
Htmlized:        http://tools.ietf.org/html/draft-uberti-rtcweb-plan-00


Abstract:
   This document explains how multiple media sources can be signaled in
   WebRTC using SDP, in a fashion that avoids many common problems and
   provides a simple control surface to the receiver.




The IETF Secretariat






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