Subject: Question: packing several frames in a single RTP packet

From: "Guler, Amos" <[email-masked]>
Date: Thu, 7 Sep 2000 10:42:41 +0300

Hello all,

(I hope I am sending this to the correct mailing list. If not, please accept
my apology and advise me of the correct one)

In the new draft "RTP Profile for Audio and Video Conferences with Minimal
Control"
(http://www.ietf.org/internet-drafts/draft-ietf-avt-profile-new-09.txt) that
is supposed to replace RFC-1890, it says (in section 4.4, Guidelines for
Frame-Based Audio Encodings):

"The receiver can tell the number of frames contained in an RTP packet, if
all the frames have the same length, by dividing the RTP payload length by
the audio frame size which is defined as part of the encoding. This does not
work when carrying frames of different sizes unless the frame sizes are
relatively prime."

My question concerns the last statement: suppose, for example, that the
frame sizes are 5 and 7 octets, which are relatively prime, and the receiver
gets a 35-octet packet. How can he/she tell whether the packet contains five
7-octet frames or seven 5-octet frames?

Amos Guler

==================== 
Amos Guler 
Comverse Network Systems Ltd.
[email-masked] 
http://www.comverse.com