Subject: Re: [AVT] Comments on draft-gmassey-avt-rtp-aptx-01

From: "Greg Massey" <[email-masked]>
Date: Thu, 19 Jun 2008 14:10:05 +0100

Hi All,

see attached revised RFC draft.

Thanks

Gregory Massey

Chief Technical Officer
Tel: +442890677200
Fax: +442890677201
Mob: +7841102975

-----Original Message-----
From: Even, Roni [mailto:[email-masked]] 
Sent: 06 May 2008 11:24
To: [email-masked]
Cc: Greg Massey
Subject: Comments on draft-gmassey-avt-rtp-aptx-01

Hi,
I reviewed the draft and have some comments and questions.

1. You specify four different payload subtype types, the introduction
section mentions just three of them. I was wondering if you can specify
just one payload subtype and have parameters that will identify the
separate apt-X modes(?). This may enable you to have a default mode that
must be supported.

2. Section 3 title has apt-x but the text in the first line talks about
apt-X Live.

3. I am not familiar with the apt-X codec but you mention that it
compress 4 16bit words to 1 16 bit word, so I was wondering why the
packetization requires packets that are based on 8-bit and not 16-bits
resolution.

4. Section 3.1 describe the RTP header usage. It should have better
text. Also the PT should discuss dynamic allocation and not static PT
numbers.

5. In 3.1 after the first part of the payload header (end with SN) you
repeat the header but say payload, this is not clear.

6. in 3.1 after the header you discuss only live and enhance apt-X.
afterwards in 1) you have LL/RR but you do not say what is the LL and
RR.

7. The example in the end of 3.1 was not clear to me after reading the
text above it.

8. IANA consideration should be based on RFC 4288 - you can look at an
example in other AVT drafts for example draft-ietf-avt-rfc3047-bis-05.

9. In the rate channel you say that typical rate is 48000. I could not
see any text discussing the rate and there is no explanation about what
are the allowed rates.

10. In section 5.2 you talk about a uri and configurations but there is
no text explaining what these are.

11. In 5.2 a=fmtp you have aux=auxoff which is not specified in the IANA
section.

12. Section 5.3 has uri and talks about delivery method which are not
mentioned before and that makes the text un-clear.

13. Section 6 repeats section 5.3

Thanks
Roni Even

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