Subject: RE: [AVT] one question about the MPEG-4 generic RTP payload format(multiSL)

From: Franceschini Guido <[email-masked]>
Date: Thu, 31 Jan 2002 18:53:02 +0100

Philippe, all,
 
The "SHOULD NOT" was introduced for enabling synchronization of MPEG-4
content delivered with RTP and MPEG-4 content delivered somehow
differently.
 
I understand that this rule represents an ugly exception within RTP
I am less convinced that this rule represents as well a real security
hole, since in MPEG-4 timestamps as well as sequence numbers are allowed
to have any starting value.
 
If (but only if !!! ) an alternative solution is found that fulfills the
requirement, then I would obviously not object to cancel that rule. But
please show an alternative solution first!
 
Best regards
 
Guido Franceschini
TILAB - Multimedia Division
Via G.Reiss Romoli 274
I-10148 Torino, Italy
tel + 39 011 228 6137
fax + 39 011 228 6299
 
-----Original Message-----
From: [email-masked] [mailto:[email-masked]]

Sent: Thursday, January 31, 2002 5:43 PM
To: [email-masked]
Subject: [AVT] one question about the MPEG-4 generic RTP payload
format(multiSL)

hi all, 

There has been a lot of oral traffic and email traffic on other
reflectors 
(and recently about the emmerging H26L work !) about the issue that the
draft 
currently recommends that RTP time stamps SHOULD NOT 
have random offsets, which is contradictory to the SHOULD in the RTP
spec 

Originally the "should not" was introduced because there was a concern
that random offsets 
would make it difficult to synchronize one RTP source with another
non-RTP 
(say downloaded .mp4 file) source. 

Recent discussions indicated that this issue could rather be delegated
to an application 
integration stage (or to another "hat" specification such as the ones
issued 
by other bodies, 3GPP, ISMA, whatever) 

 I want to ask on this reflector: 

**************** 
would anybody object if this "should not " is simply removed i.e. 
the "classical" RTP time stamp offset is always assumed ? 
***************** 

NB: Assuming that nobody objects I dont plan to add any explanatory
comments 
in the draft itself (that non-RTP source sync is out of scope). 

Regards, 

Philippe Gentric
Software Architect
Philips MP4Net
[email-masked]
http://www.mpeg-4.philips.com