RFC 4733, "RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals", December 2006Source of RFC: avt (rai)
See Also: RFC 4733 w/ inline errata
Errata ID: 3489
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.
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).