[AVT] question: mapping dynamic RTP formats using SDP

["Hager, Todd" <[e-mail]>]

--- Begin Message ---

Hi all,
 
What is the best method to define a valid encoding name for a new
encoding format?
 
Regarding <draft-flaks-avt-rtp-ac3-03.txt>, I'm trying to determine the
best method of choosing a value for the payload type for AC-3 in the RTP
header.
 
I am proceeding under the assumption that the best course is to randomly
choose a value from the dynamic range (96-127) described in <RTP Profile
for Audio and Video Conferences with Minimal Control.txt> (RFC 1890),
and use SDP to somehow map this value to the AC-3 encoding type. I have
questions regarding the SDP mapping process.
 
 
Pages 21 and 22 in the SDP specification (RFC 2327) indicate the
following mechanism to map a dynamic format ID :
 
m=<media> <port>/<number of ports> <transport> <fmt list>
 
and 
 
a=rtpmap:<payload type> <encoding name>/<clock rate>[/<encoding
parameters>]
 
 
Therefore,  an SDP description ought to be able to incorporate the
following two lines:
 
m=audio 49232 RTP/AVP 98
a=rtpmap:98 <AC3_ENCODING_NAME>/48000
 
How does the AVT group suggest I define <AC3_ENCODING_NAME>? Should I
submit a new Internet Draft describing a full profile specifically for
this format, or can I simply use the AC-3 RTP Payload document itself as
the vehicle that registers a valid AV Profile encoding name?
 
Alternatively, though the current AC-3 RTP Payload draft document does
not currrently define an AV RTP Profile encoding name, it does define a
MIME type description for AC-3. The SDP spec allows MIME types to
describe media encodings, but the wording of the SDP spec (page 22)
implies that this is only intended to be used for non-RTP streams. 
 
Which is the most appropriate course of action:
 
1) Define a new RTP profile, 
2) Use the AC-3 RTP payload document to define a valid encoding name for
the AC-3 format, or
3) Use the defined MIME type to map a dynamic AV Profile payload type to
AC-3?
 
 
Thanks in advance,
Todd Hager 
Dolby Laboratories

--- End Message ---

This message (including any attachments) may contain confidential information intended for a specific individual and purpose. If you are not the intended recipient, delete this message. If you are not the intended recipient, disclosing, copying, distributing, or taking any action based on this message is strictly prohibited.