Re: [AVT] draft-kerr-avt-vorbis-rtp-04

Hi,

On 4 Jan 2005, at 15:54, Phil Kerr wrote:
> An -04 update of the Vorbis-RTP draft was submitted a few days ago.
>
> http://www.ietf.org/internet-drafts/draft-kerr-avt-vorbis-rtp-04.txt
>
> Major changes include:
>
> Removal of RTCP-based transport for configuration headers, replaced 
> with in-band transport.
> Inclusion of a CRC32 header field used to tie the stream to the 
> associated decoding codebook.

This is an interesting idea. How is the CRC32 calculated? What is the 
chance of collision, and how would that be resolved?

> Simplification of SDP parameters.

These certainly look reasonable. However, we try to avoid mandating SDP 
(since there may be other session description formats). Can you move 
the description of the parameters into the MIME registration, and make 
this section describe how they can be mapped onto SDP (for those 
applications which use SDP). Section 5 of RFC 3557 is a good example of 
what is needed.

> Plus a number of textual changes.
>
> Comments/feedback welcomed.

A few issues to consider:

  - Why is the payload length only an 8 bit field? It seems that this 
might
    force fragmentation when it's not otherwise needed. Could one use a 
16
    bit field instead?

  - Providing a URI for the configuration header is appropriate, but the
    draft needs to define the syntax of that URI (e.g. by referencing an
    appropriate specification, perhaps RFC 2396). It also needs to define
    the legal MIME types for the data referenced, so the format is known.
    Is there an existing MIME type for this?

  - Need to discussion offer/answer considerations when using SDP. See
    section 5 of RFC 3952 for an example.

Cheers,
Colin

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