Subject: [AVT] EVRC, SMV and Common Draft

From: "Adam Li" <[email-masked]>
Date: Wed, 10 Oct 2001 10:40:08 -0700

Hi,

We just submitted the latest version 08 of the RTP/EVRC draft, incorporating
all the comments received during the WG Last Call. It should be announced
soon. The text can be obtained at
ftp://ftp.icsl.ucla.edu/pub/EVRC/draft-ietf-avt-evrc-08.txt before it is
available on the IETF site.

Recently, there are two more related draft submitted to AVT. One for "SMV
codec" http://search.ietf.org/internet-drafts/draft-mathai-avt-smv-00.txt.
Another one for "common vocoder"
http://search.ietf.org/internet-drafts/draft-espelien-avt-common-01.txt.

There may be nice to combine some of the drafts.

The SMV codec is very similar to EVRC codec. Even the codec frames are of
exactly the same number of bits between them. The SMV does have one more
mode at 1/4 rate, in additional to the full, 1/2, and 1/8 rate which both of
them have. There should take minimum effort to incorporate SMV into the
current EVRC draft.

The "common vocoder" draft is attempting to design an unified format for all
PureVoice, EVRC and SMV codec. However, the PureVoice codec has data frames
of different size from those of EVRC/SMV. It seems needed more effort to put
those together. Even so, it still just covers 3 of the vocoders, and does
not work for others, such as AMR, etc. Besides, PureVoice already have an
RTP payload defined in RFC 2658.

Maybe it would be more efficient to simply combine EVRC and SMV which have
great parallelism in between and advance that draft?

Your comments and suggestions are very appreciated.

Adam

----------
Adam H. Li
Image Communication Lab                    (310) 825-5178 (Lab)
University of California, Los Angeles      (310) 825-7928 (Fax)

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
http://www1.ietf.org/mailman/listinfo/avt

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From: Randall Gellens <[email-masked]>
Date: Thu, 11 Oct 2001 15:26:11 -0700

>Your comments and suggestions are very appreciated.

I think there are two key questions:

1.  Are there likely to be implementations which need to support multiple 
vocoders?

2.  Would a common format make the implementation easier?

---

From: "Adam Li" <[email-masked]>
Date: Thu, 11 Oct 2001 18:17:21 -0700

>
> 1.  Are there likely to be implementations which need to
> support multiple vocoders?
>

From standardization point of view, simplicity and consistency between
standards and revisions are always nice things to have. People who make the
devices probably will give a better suggestion on advantages on
implementation.

One more issues on the EVRC draft: with one small change, we can make the
current EVRC in exactly the same format at PureVoice in RFC 2658. The only
small change we will need to make is to take the current ToC byte and put
them in front of each data frame, instead of collecting the ToC in the
beginning of the packet.

Actually the EVRC draft was like that before. There is really not much
difference technically. The ToC collected at the beginning of the packet was
chosen simply because that is the trend in contemporary design used in other
newer formats (such as AMR).

Maybe we should reverse that choice. And by doing that we can get rid of the
F bits. Also, if Peter thinks D bits can be packet based instead of frame
base, we can use one of the R bits in the Interleave Byte.

In this way, we can have a new format for EVRC/SMV (Type 1) totally
compatible with RFC 2658. PV/EVRC/SMV will have exactly the same format for
a nice consistency. And there is no need to retire RFC 2658 with a
imcompatible duplicate format for PureVoice. Everything fits perfectly in
place.

We should do that. What do you think? Editing that in should be very easy.

Adam

----------
Adam H. Li

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From: Nikolai Leung <[email-masked]>
Date: Tue, 16 Oct 2001 17:04:01 -0400

Adam, authors, contributors, and AVT members,

On Sept 27, QUALCOMM submitted a "common RTP format" draft.  On October 
9th, the QUALCOMM contributors to the first EVRC draft, found out about 
this common draft submission via the AVT mail list.  Due to the lack of 
internal coordination at QUALCOMM, neither group of authors knew of each 
other.  As a result, we have two different proposals from QUALCOMM which 
define a payload format for EVRC.

This was a mistake on our part.  On behalf of QUALCOMM I send you my 
apologies for any confusion or feelings of resentment caused by this.  We 
have introduced internal procedures to prevent this from happening in the 
future.

We recognize that open disagreement and discussion between individuals from 
the same company are useful and are encouraged in the IETF.  After all, 
independent thinking is what makes the IETF process work so well.  But such 
discussions need to take place in a timely manner and need to be respectful 
of the IETF process in order for work to progress.  Submitting our second 
draft is not in-line with this.

Going forward, we are investigating ways to include three features of the 
common draft proposal into the original EVRC proposal.  We would appreciate 
your continued participation and cooperation in developing an EVRC (and 
other vocoders) format that meets all our needs.

Sincerely,

-Nikolai