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Re: DTMF - the "Object Oriented" approach

From: Harald Alvestrand <harald@alvestrand.no>
Date: Fri, 16 Nov 2012 07:49:13 +0100
Message-ID: <50A5E1E9.6060007@alvestrand.no>
To: Adam Bergkvist <adam.bergkvist@ericsson.com>
CC: "public-webrtc@w3.org" <public-webrtc@w3.org>
On 11/16/2012 07:33 AM, Adam Bergkvist wrote:
> On 2012-11-14 15:46, 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
>> DTMFSendingMediaStreamTrack.
>> Add the following text:
>>
>> A RTCDTMFSendingMediaStreamTrack is created by calling the
>> createDTMFSender() method on a PeerConnection. This constructs an object
>> that decorates a MediaStreamTrack with the functions required to send 
>> DTMF.
>>
>>
>> - In section 4.3.2, add the function
>>
>> RTCDTMFSendingMediaStreamTrack createDTMFSender(MediaStreamTrack track);
>>
>> - In section 4.3.2.2, 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]
>
> The prefix (RTCDTMF) it's pretty nasty, but I guess consistency has 
> precedence in this case.
:-)
The way that I think this will be used, it will never appear in JS code, 
so the only people it will be a pain for are the ones who do the 
implementation. I considered RTCMediaStreamTrackWithDTMFExtensions 
briefly, but decided to suggest this one.

>
> Is the intention that the decorated track needs to be added back into 
> the MediaStream where the original track came from?
No, it's my intention that the created object is only a handle that can 
be used for sending DTMF. The MediaStreamTrack that it was created from 
is already part of the MediaStream it belongs in.

(I think it would be entirely reasonable to create the 
RTCDTMFSendingMediaStreamTrack every time you need to send a DTMF tone, 
and throw it away after use. I see no reason to make it a heavy-weight 
object.)
Received on Friday, 16 November 2012 06:49:51 GMT

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