Re: [rtcweb] Low Level Javascript API Proposal avail on the webrtc list

Tim Panton <> Wed, 28 September 2011 18:07 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 04D0E21F8C0F for <>; Wed, 28 Sep 2011 11:07:40 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -2.598
X-Spam-Status: No, score=-2.598 tagged_above=-999 required=5 tests=[BAYES_00=-2.599, HTML_MESSAGE=0.001]
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id v7gLJ54WFA6o for <>; Wed, 28 Sep 2011 11:07:39 -0700 (PDT)
Received: from ( []) by (Postfix) with ESMTP id 7CF5521F8C0C for <>; Wed, 28 Sep 2011 11:07:33 -0700 (PDT)
Received: from [] ( []) by (Postfix) with ESMTP id A800437A902; Wed, 28 Sep 2011 19:23:09 +0100 (BST)
Mime-Version: 1.0 (Apple Message framework v1244.3)
Content-Type: multipart/alternative; boundary="Apple-Mail=_E127057F-3B1C-4B80-A9E4-13756EE4681F"
From: Tim Panton <>
In-Reply-To: <>
Date: Wed, 28 Sep 2011 11:09:25 -0700
Message-Id: <>
References: <> <>
To: Roman Shpount <>
X-Mailer: Apple Mail (2.1244.3)
Subject: Re: [rtcweb] Low Level Javascript API Proposal avail on the webrtc list
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Real-Time Communication in WEB-browsers working group list <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Wed, 28 Sep 2011 18:07:40 -0000

On 28 Sep 2011, at 09:12, Roman Shpount wrote:

> Few questions that I have in regard to this:
(Neil seems to be having trouble posting to this list - so I'm forwarding his reply):

Answers inline:

> 1. How can you get local codec capabilities to implement something like

The local codecs and capabilities can be queried at any time, returned
as a json object to the javascript. This is really just asking the
browser what codecs it supports, which we have separated out from SDP

> 2. Can you specify multiple stun/turn/turns servers? If you do what is
> the candidate generation process? On the same note why do we provide
> both stun and turn relays? Isn't turn server is normally stun server as
> well?

I believe that you should be able to specify multiple servers if you
wanted to and that all candidates would be generated and tested based on
priorities etc. One relay may be in a better physical location for
instance than another for a given pair of users.

There may be cases when you want to specify both a stun and turn relay
even if the turn server can serve both purposes, for example as a backup.

> 3. How do you process multiple answers for the same dialog?
> 4. What do we do with multiple answers from a forked dialog? Is it even
> supported?

The intention is that we leave that to the javascript (library)
developer to decide how best to handle it. Forking presents some
interesting challenges.

> 5. What is the process for synchronizing audio and video streams?

We have the concept of a synchronization group as an attribute that can
be applied to streams, the intention being that those streams in the
same group should be synchronized by the lower layers if possible using
whatever mechanism they can.

> On Wed, Sep 28, 2011 at 11:59 AM, Tim Panton <> wrote:
> I just want to ask folks to take a look at a proposal Neil Stratford wrote for the
> Low Level Javascript API and sent to the webrtc list.
> It  is based on his and my experience of web based audio plugins and on a
> proposal of Cullen's a while back.
> We'd appreciate any feedback either here or on the webrtc list as appropriate.
> Tim.
> _______________________________________________
> rtcweb mailing list