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

Re: [Bug 18485] Change DTMF API to be on PeerConnection

From: Stefan Hakansson LK <stefan.lk.hakansson@ericsson.com>
Date: Wed, 8 Aug 2012 14:43:48 +0200
Message-ID: <50225F04.3080604@ericsson.com>
To: public-webrtc@w3.org
On 08/08/2012 12:52 PM, Harald Alvestrand wrote:
> [Continuing discussion on list]
>
> I updated the bug in order to solicit views from the WG - would you
> prefer A, B or C?
>
> On 08/08/2012 12:23 PM, bugzilla@jessica.w3.org wrote:
>> https://www.w3.org/Bugs/Public/show_bug.cgi?id=18485
>>
>> Stefan Hakansson LK<stefan.lk.hakansson@ericsson.com>  changed:
>>
>>              What    |Removed                     |Added
>> ----------------------------------------------------------------------------
>>                    CC|                            |stefan.lk.hakansson@ericsso
>>                      |                            |n.com
>>
>> --- Comment #2 from Stefan Hakansson LK<stefan.lk.hakansson@ericsson.com>  2012-08-08 10:23:07 UTC ---
>> (In reply to comment #1)
>>
>> As for alternatives B and C, I think that the tones should not be inserted in
>> the same MediaStream as the outgoing DTMF. The tones are to be used for local
>> feedback, and you would not like to play the other outgoing audio locally.
>>
>> I think we should go for alternative A initially.
> My thought was that if an app wants ringback of the tones, he does:
>
> incomingStream = pc.remoteStreams[0].audioTracks[0]
> outgoingStream = pc.remoteStreams[0].audioTracks[0]
Guess it should read
outgoingStream = pc.localStreams[0].audioTracks[0]
>
> pc.sendDTMF(outgoingStream, "12345")
> pc.sendDTMF(incomingStream, "12345")
>
> the two should then play out at ~ the same time.
>
> I don't want to force there to be always ringback present - that's app
> dependent.

I agree, and this makes sense. Personally I don't have a strong opinion, 
we could go for A (the web author wanting local feedback could easily 
accomplish that with a audio element and some files with tones), B or C. 
We could even consider an alternative D:

pc.canSendDTMF(MediaStreamTrack)
pc.sendDTMF(MediaStreamTrack, tones, duration, optional MediaStreamTrack)

where tones are inserted in the audio of the second (optional) 
MediaStreamTrack supplied.


>
> In case C, even this is possible:
>
> speakers = <whatever constructor we have for a synthetic media source>
> <add speakers to an audio tag>
> pc.sendDTMF(speakers, "12345")
>
> It means that behind the scenes, the "PC" implementation must be able to
> touch any audio stream in the system, but then again - streams aren't
> real physical items, they're control-surface abstractions anyway.

Agree.

>
>>
>>
>>> based on discussion on the list, there seems to be 3 alternate descriptions of
>>> what sendDTMF actually does.
>>>
>>> I outline them below as text that can be inserted into the description.
>>>
>>> A)
>>> 1) If the track argument to sendDTMF is not an audio track connected to this
>>> PeerConnection on an outgoing SSRC where use of RFC 4733 DTMF has been
>>> negotiated, throw a<IllegalParameter>  exception.
>>> 2) Send the tones using RFC 4733 signalling.
>>>
>>> B)
>>> 1) If the track argument to sendDTMF is not an audio track connected to this
>>> PeerConnection, throw an<illegalParameter>  exception.
>>> 2) If sendDTMF is connected to an outgoing SSRC where use of RFC 4377 is
>>> negotiated, send the tones using RFC 4377 and return.
>>> 3) Insert the corresponding tones into the media stream as if they were coming
>>> from the media source.
>>>
>>> C)
>>> 1) If sendDTMF is connected to an outgoing SSRC on this PeerConnection where
>>> use of RFC 4377 is negotiated, send the tones using RFC 4377 and return.
>>> 2) Insert the corresponding tones into the media stream as if they were coming
>>> from the media source.
>>>
>>> The difference between B) and C) is that B) insists on using the right PC to
>>> generate tones.
>
>
Received on Wednesday, 8 August 2012 12:44:20 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Wednesday, 8 August 2012 12:44:20 GMT