Subject: Re: [AVT] Request comments on draft-legrand-rtp-isac-00.txt

From: Tina le Grand <[email-masked]>
Date: Mon, 5 Jan 2009 03:31:04 -0800

Thanks for all the replies on the subject. I have double checked RFC 4855, and as pointed out by others a reference to a description of the data compression format is only required if available. As far as I understand this means there are no formal requirement on an open codec specification. However, I see there are different opinions on the matter, and that a more detailed description is desirable. It is still unclear to me what depth is needed of such description. Besides producing a better description we can provide API information under NDA if that would help in the process.

I agree that using audio/isac without approval is not the right way. Nevertheless, this is the way our customer are using it. It is our desire to facilitate interoperability, and knowing audio/isac is widely used we decided to draft this document and submit it for consideration.

Regards,
Tina le Grand.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Magnus Westerlund
Sent: Monday, December 15, 2008 4:53 PM
To: Tom Taylor
Cc: Ingemar Johansson S; [email-masked]
Subject: Re: [AVT] Request comments on draft-legrand-rtp-isac-00.txt

Tom Taylor skrev:
> We have been going through a similar discussion for other codecs lately:
> SPEEX and UEMCLIP. RFC 4855 requires a description of the media encoding
> and a specification of the payload format. However, the part about
> "description of the media encoding" is qualified by the following sentence:
>
> "A reference to a further description of the data compression format
> itself should be provided, if available."
>
> I interpret this pragmatically to mean that the encoding has to be
> sufficiently well described that the payload description makes sense,
> but no more. Unfortunately I'm not the final arbiter -- the IESG is, and
> Roni may have a slightly different view. (Please cut in if you do, Roni.)

Hi,

As former AVT chair I would like to point to two cases:

Vorbis, which is an open source codec. They have a codec specification
that provide a description that is almost possible to implement from.
However, they also have source code for the codec which in their minds
is the normative description. That is why we previously have accepted
that as reference. But this did result in some discussion at IESG level
before being approved.

ATRAC, the codec is proprietary but Sony does offer to license it and do
have codec specification that to my understanding is possible to
implement from.

Getting more into my personal view and without any IETF formal hats on:

My view is that the codec reference for RTP payload formats that are
requesting media types on the standards tree is well specified. That you
have some possibility to implement based on that reference. Please note
that the reference does not need to be freely available, but if only
released after licensing then it should be released to at least a few
key persons that can review this and say that the payload format and the
codec data format isn't clashing in some way.

I also would like to point out that the argument that you like
audio/isac registered because you are using it, is confrontational. By
starting to use this name prior to haven formally been assigned it you
are basically squatting on an IETF resource. Where audio/vnd.gips.isac
is completely fine because that would be within your domain and within
your right to assign it. And by submitting that to the IANA you will
have ensured that you where the controller of the media type for certain.

In addition I see little gain in having IETF publish RTP payload formats
in RFCs that doesn't have a publicly available and stable specification.
If the codec is proprietary the vendor itself can publish the codec and
its payload format in any venue it choses and use the vendor tree for
identifying the format.

Cheers

Magnus Westerlund

IETF Transport Area Director & TSVWG Chair
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