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Re: DTMF v4

From: Harald Alvestrand <harald@alvestrand.no>
Date: Sat, 15 Dec 2012 14:30:54 +0100
Message-ID: <50CC7B8E.8060305@alvestrand.no>
To: Roman Shpount <roman@telurix.com>
CC: Martin Thomson <martin.thomson@gmail.com>, "public-webrtc@w3.org" <public-webrtc@w3.org>
On 12/14/2012 10:10 PM, Roman Shpount wrote:
> WebRTC-SIP Interworking Requirements Draft states that:
> A3-4 WebRTC MUST provide a means for the Javascript application to 
> invoke [RFC4733] DTMF events to be generated, and their duration, with 
> a default duration of 100ms.
> A3-6 WebRTC MUST NOT generate [RFC4733] events closer than 50ms 
> back-to-back.  In other words, even if                      the 
> Javascript calls the API repeatedly or provides a string of digits to 
> send, the browser must enforce a minimum of 50ms inter-event gap.
> There are several fairly old recommendations, such as ITU-T V.18, on 
> which these values are based, but the bottom line that these values 
> are usually considered safe.
Sounds like defaults of 100 ms duration and 50 ms inter-event gap, and 
enforcing a minimum of 50 ms inter-event gap, will work, then!
> _____________
> Roman Shpount
> On Fri, Dec 14, 2012 at 3:53 PM, Martin Thomson 
> <martin.thomson@gmail.com <mailto:martin.thomson@gmail.com>> wrote:
>     On 14 December 2012 12:40, Harald Alvestrand <harald@alvestrand.no
>     <mailto:harald@alvestrand.no>> wrote:
>     > Bernard mentioned a minimum gap (I think he said 50 ms), but I'm
>     not sure
>     > where that came from.
>     Minimum values come from experience with IVR interoperation for cases
>     where the tone is subsequently mixed into the audio.  Too short a tone
>     (or gap) and some IVRs fail to detect the tone.  I've seen minimum
>     tone duration of 100ms and gap of 50ms in some cases, though more
>     conservative values might be appropriate.  I have no good data to back
>     any specific choice.  I expect fluffy has more data than I.
Received on Saturday, 15 December 2012 13:31:24 UTC

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