Subject: [AVTCORE] [Technical Errata Reported] RFC4733 (3489)

From: RFC Errata System <[email-masked]>
Date: Mon, 18 Feb 2013 23:42:01 -0800 (PST)

The following errata report has been submitted for RFC4733,
"RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals".

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You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=4733&eid=3489

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Type: Technical
Reported by: Xavier Marjou <[email-masked]>

Section: 2.1

Original Text
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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.

Corrected Text
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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
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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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RFC4733 (draft-ietf-avt-rfc2833bis-15)
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Title               : RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals
Publication Date    : December 2006
Author(s)           : H. Schulzrinne, T. Taylor
Category            : PROPOSED STANDARD
Source              : Audio/Video Transport
Area                : Real-time Applications and Infrastructure
Stream              : IETF
Verifying Party     : IESG