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

From: Timothy B. Terriberry <tterriberry@mozilla.com>
Date: Thu, 09 Aug 2012 14:03:54 -0700
Message-ID: <502425BA.5000803@mozilla.com>
To: public-webrtc@w3.org
Roman Shpount wrote:
> You should suppress sending audio during the time RFC 4733 is being
> sent. This causes interop problems anyway and would prevent potential
> echo problems. I think this is the IETF group recommendation anyway.

This is true, of course, but if you're rendering it locally, there is 
some lag between when the DTMF event ends and when the last sample makes 
it through the audio output, speakers, room, microphone, and audio 
input. _Someone_ needs to estimate this delay and compensate for it, or 
you may have enough trailing echo to get a double detection (as has been 
noted elsewhere), even if you suppress outgoing audio while sending the 
actual event.

Of the proposals so far, only alternative D (which takes an optional 
MediaStream to play the tone out on) has a hope of making this work, 
since it's the only one that can tie both the RFC 4733 message and the 
audible rendering to a single event.
Received on Thursday, 9 August 2012 21:04:23 GMT

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