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

It seems to me that the conditional mandatory sentence is clearer if the (informative) reason is separated to prevent any misread of the 'MUST' as appling only to streams that pass through a gateway.
As in RTR:
" 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.  Note: One benefit of this requirement is simplification of the generation of audio waveforms at a gateway." 

Regards, 
Art
Art Allison 
Senior Director Advanced Engineering, Technology 
National Association of Broadcasters
1771 N Street NW
Washington, DC 20036
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Fax  202 775 4981 
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Advocacy  Education  Innovation 

-----Original Message-----
From: avt-bounces@ietf.org [mailto:avt-bounces@ietf.org] On Behalf Of Marc Petit-Huguenin
Sent: Wednesday, January 16, 2013 11:45 AM
To: Magnus Westerlund
Cc: avt@ietf.org
Subject: Re: [AVTCORE] [Technical Errata Reported] RFC4733 (3451)

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On 01/15/2013 08:54 AM, Magnus Westerlund wrote:
> Hi,
> 
> (As Individual)
> 
> Are we certain that the RTP payload format will never be sent over two 
> different but linked SSRCs to the original audio. There is such a use 
> case (See RFC 3388) where DTMF and original audio are sent in two 
> different RTP sessions and thus with different SSRCs (although, they 
> could have the same number for binding reasons). I fear the proposed 
> corrected text is to restrictive.

Right.  I propose this:

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 to simplify the generation of audio waveforms at a gateway.

> 
> Cheers
> 
> Magnus
> 
> On 2013-01-11 14:24, 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
>> 
> 
> 

- --
Marc Petit-Huguenin
Email: marc@petit-huguenin.org
Blog: http://blog.marc.petit-huguenin.org
Profile: http://www.linkedin.com/in/petithug
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