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RFC 4733, "RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals", December 2006

Source of RFC: avt (rai)
See Also: RFC 4733 w/ inline errata

Errata ID: 3489
Status: Verified
Type: Technical
Publication Format(s) : TEXT

Reported By: Xavier Marjou
Date Reported: 2013-02-18
Verifier Name: Gonzalo Camarillo
Date Verified: 2013-04-18

Section 2.1 says:

Named telephone events are carried as part of the audio stream and
MUST use the same sequence number and timestamp base as the regular
audio channel to simplify the generation of audio waveforms at a
gateway. 

It should say:

Named telephone events are carried as part of the audio stream and 
if they use the same SSRC (therefore the same timing and sequence 
number space), they MUST use the same timestamp clock rate as the 
regular audio channel.

Notes:

RFC4733 was written in a way to avoid the multiple clock-rate problem by mandating the use of the same SSRC for DTMF and audio. However it's not explicitly written, which brings an ambiguity. It was commented that RFC4733 needs to be updated. (c.f. http://tools.ietf.org/wg/avtext/minutes?item=minutes-85-avtext.html). This errata obsoletes the previous proposed errata (ID: 3451).

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