W3C home > Mailing lists > Public > public-webrtc@w3.org > December 2011

Re: DTMF again

From: Stefan Hakansson LK <stefan.lk.hakansson@ericsson.com>
Date: Fri, 9 Dec 2011 20:07:57 +0100
Message-ID: <4EE25C8D.8030000@ericsson.com>
To: Justin Uberti <juberti@google.com>
CC: "public-webrtc@w3.org" <public-webrtc@w3.org>
On 12/09/2011 07:59 PM, Justin Uberti wrote:
> On Thu, Dec 1, 2011 at 8:20 AM, Stefan HÃ¥kansson LK 
> <stefan.lk.hakansson@ericsson.com 
> <mailto:stefan.lk.hakansson@ericsson.com>> wrote:
>     So, a concrete proposal:
>     we define the operation "insertDTMF" that is available on
>     AudioMediaStreamTrack's (or should that be named AudioStreamTrack?):
>     insertDTMF("1")  // plays tone 1 for 50 ms
>     insertDTMF("2", 200)  // plays tone 2 for 200 ms
>     insertDTMF("123")  // plays tones 1, 2, 3 in succession, each for
>     50 ms
>     insertDTMF("456", 200)  // plays tones 4, 5, 6 in succession, each
>     for 200 ms
>     (I prefer "insert" over "send" as nothing is sent unless the
>     MediaStream that the AudioStreamTrack belongs to is added to a
>     PeerConnection)
> I think the name "sendDTMF" is slightly more intuitive, but I can see 
> your point too. If others prefer sendDTMF I'm fine with that.
>     "insertDTMF" leads to the insertion of the actual tones in the
>     audio, so if the MediaStream in question is attached to an audio
>     element, those tones would be played out. This has the advantage
>     that it is much simpler to locally give audio feedback to the user
>     that dtmf is sent - when I use DTMF on my phone I hear the tones.
> Not sure what you mean here. Do you mean if the local media stream was 
> hooked up to an <audio/>, the tones would be played out? If so, 
> wouldn't that mean that your own voice is being fed back to the audio 
> output (which I'm sure we don't want)?
I meant like this:

Imagine you do "insertDTMF()" on an audio track of an outgoing stream 
(to send DTMF to the other end), if you now want an audio feedback to 
the person sending the DTMF, you could simultaneously do "insertDTMF" on 
the audio track of the incoming MediaStream (assuming a bidirectional 
session). That would lead to that you hear the tones locally as you push 
the dial pad to generate them.

So, you would not hear yourself!
> I agree we want to allow the tones to optionally be played out 
> locally, but I think we need a different mechanism to control this 
> (possibly a flag on the stream or API call).
>     "insertDTMF" also, if the MediaStream in question is attached to
>     an open PeerConnection, leads to RTP packets according to RFC4733
>     being inserted in the RTP stream corresponding to this
>     AudioStreamTrack.
>     (if reception of DTMF is also supported by the browser, I guess
>     that in addition to inserting the tones in the AudioStreamTrack,
>     events informing the application should be dispatched)
Received on Friday, 9 December 2011 19:08:34 UTC

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