W3C home > Mailing lists > Public > public-webrtc@w3.org > November 2012

V2 of DTMF - the "Object Oriented" approach

From: Harald Alvestrand <harald@alvestrand.no>
Date: Fri, 16 Nov 2012 12:56:40 +0100
Message-ID: <50A629F8.3010308@alvestrand.no>
To: public-webrtc@w3.org
I realized that I'd forgotten about the callback / event aspect of the 

Feedback so far:
- No need to inherit from MediaStreamTrack
- Name's ugly, but we can live with it

If we don't need to inherit, name can be a little nicer. I like to keep 
the RTC prefix.

Modified version:

On 11/14/2012 03:46 PM, Harald Alvestrand wrote:
> Takeaways from Lyon were that:
> - Executing DTMF needs reference to an audio track (to know where to 
> send the data) and to a PeerConnection (to know that we've 
> successfully negotiated use of the DTMF codec).
> - The WG preferred an "object oriented" model: creating a DTMF handler 
> object, rather than the "fortran" approach of having all functions 
> directly on the PeerConnection.
> Suggested edits, delta from the October 19 version of the spec:
> - In section 8.4, rename AudioMediaStreamTrack to RTCDTMFSender. 
> Remove inheritance.
> Add the following text:
> A RTCDTMFSender is created by calling the createDTMFSender() method on 
> a PeerConnection. This constructs an object that exposes the functions 
> required to send DTMF.

Add to RTCDTMFSender:

    attribute EventHandler ontonechange;

Add text under 8.4.2 "InsertDTMF":

    When InsertDTMF is called, do the following:

    1. If the associated MediaStreamTrack is not connected to the 
associated PeerConnection, return.
    2. If canInsertDTMF is false, return.
    3. Set the value of the tone buffer to the "tones" argument.
        Return, but continue the following steps asynchronously.

    The following steps take place asynchronously.
    4. Start playout of the tone on the associated RTP media stream, 
using the appropriate codec.
    5. Fire a "tonechange" event at the object, with an event parameter 
consisting of the first character
    of the tone buffer. Remove the first character of the tone buffer.
    6. If the tone buffer is empty, fire a "tonechange" event at the 
object, with an empty string as
        its parameter, and stop.
    7. Schedule a task for <duration> milliseconds later, which will 
repeat steps 4-7.

Wordsmithing is of course needed.

> - In section 4.3.2, add the function
> RTCDTMFSendingMediaStreamTrack createDTMFSender(MediaStreamTrack track);
> - In section, add the paragraph
> createDTMFSender
> The createDTMFSender() creates an RTCDTMFSendingMediaStreamTrack that 
> references the given MediaStreamTrack. The MediaStreamTrack MUST be an 
> element of a MediaStream that's currently in the PC's localStreams 
> attribute; if not, throw an Illegal Argument Exception. [NOTE - get 
> correct name for exception before inserting]
Received on Friday, 16 November 2012 11:57:09 UTC

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