Re: [AVTCORE] [Technical Errata Reported] RFC4733 (3451)

IMNSHO, for this provision to have any impact "same timestamp base" must mean the same clock source as well as the same units.
Use of the same units from a different clock source than the 'regular' audio results in an indeterminate timing relationship for rendered elements.
(would have pruned names but I do not know that all are on the avt list.)

Art Allison 
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National Association of Broadcasters
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-----Original Message-----
From: avt-bounces@ietf.org [mailto:avt-bounces@ietf.org] On Behalf Of Tom Taylor
Sent: Sunday, January 13, 2013 8:09 PM
Cc: schulzrinne@cs.columbia.edu; xavier.marjou@orange.com; even.roni@huawei.com; avt@ietf.org
Subject: Re: [AVTCORE] [Technical Errata Reported] RFC4733 (3451)

Before accepting this report I would want to know the consensus view of the meaning of "same timestamp base". The problem was raised in the discussion of draft-ietf-avtext-multiple-clock-rates. My understanding of "timestamp base" is that it defines the time units in which the timestamp is expressed (usually some small fraction of a second) for all payloads using the same SSRC. The fact that the above-mentioned draft was accepted as a WG document suggests that my understanding is wrong. 
Perhaps someone else can comment.

On 11/01/2013 8:24 AM, RFC Errata System wrote:
>
> The following errata report has been submitted for RFC4733, "RTP 
> Payload for DTMF Digits, Telephony Tones, and Telephony Signals".
>
> --------------------------------------
> You may review the report below and at:
> http://www.rfc-editor.org/errata_search.php?rfc=4733&eid=3451
>
> --------------------------------------
> Type: Technical
> Reported by: Xavier Marjou <xavier.marjou@orange.com>
>
> Section: 2.1
>
> Original Text
> -------------
> 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
> --------------
> Named telephone events are carried as part of the audio stream and 
> MUST use the same SSRC (therefore the same timing and sequence number 
> space) and the same timestamp clock rate as the regular audio channel 
> to simplify the generation of audio waveforms at a gateway.
>
> 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)
>
> Instructions:
> -------------
> This errata is currently posted as "Reported". If necessary, please 
> use "Reply All" to discuss whether it should be verified or rejected. 
> When a decision is reached, the verifying party (IESG) can log in to 
> change the status and edit the report, if necessary.
>
> --------------------------------------
> RFC4733 (draft-ietf-avt-rfc2833bis-15)
> --------------------------------------
> 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
> _______________________________________________
> Audio/Video Transport Core Maintenance avt@ietf.org 
> https://www.ietf.org/mailman/listinfo/avt
>
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