Subject: [MMUSIC] Re: mmusic digest, Vol 1 #376 - 4 msgs

From: John Lazzaro <[email-masked]>
Date: Wed, 26 Mar 2003 09:10:50 -0800

> Magnus Westerlund <[email-masked]> writes
>
> The usage is 
> dependent on application and can be seen as two attributes for 
> controlling how the packetization/encoding work. For ptime the "typical" 
> you imply does exist in my opinion. 

Thanks -- I'm rewriting the media timing section of the MWPP
normative I-D, and wanted to make sure I was interpeting the
semantics correctly.

> when looking at the version 12 draft [...]

Yes, a tangentially related issue is that the value of ptime
and maxptime is neither constrained to be an integral value of
milliseconds, nor expressly permitted to have a fractional 
component. I would normally take that to mean that a fractional
part is permitted (" ... be liberal in what you accept"), except
that the definition of the framerate attribute explicitly allows
<integer>.<fractional> in its text, as if it was an exceptional
condition to an unstated norm ... 

-------------------------------------------------------------------------
John Lazzaro -- Research Specialist -- CS Division -- EECS -- UC Berkeley
lazzaro [at] cs [dot] berkeley [dot] edu     www.cs.berkeley.edu/~lazzaro
-------------------------------------------------------------------------
_______________________________________________
mmusic mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/mmusic

---

From: Magnus Westerlund <[email-masked]>
Date: Thu, 27 Mar 2003 08:52:56 +0100

Hi John,

>condition to an unstated norm ... 

No, I have never seen ptime or maxptime being used with a fractional 
part. I would strongly discourage the use with fractional part as it 
will probably not interoperate. However the attributes seem to be 
lacking any formal notation or language to clarify that it is only 
integer. My intention for maxptime was never to have it fractional as I 
saw no need for AMR. I know that there exist some codecs that could 
result in fractional milli second values. Also I don't see a big 
problem. As maxptime provides a upper boundary when having a codec with 
frame length of 7.7 milli seconds it seems obvious that if you want to 
limit this to three frames one simple uses 24 ms in maxptime. If one at 
the same time want to recommend the usage of one frames ptime is given 
the value of 8.

Colin: why does not the attributes defined in the SDP new draft have 
ABNF definitions? Had ptime and maxptime had it the question would been 
clearly solved.

Best Regards

Magnus Westerlund 

Multimedia Technologies, Ericsson Research ERA/TVA/A
----------------------------------------------------------------------
Ericsson AB                | Phone +46 8 4048287
Torshamsgatan 23           | Fax   +46 8 7575550
S-164 80 Stockholm, Sweden | mailto: [email-masked]

---

From: Colin Perkins <[email-masked]>
Date: Thu, 27 Mar 2003 11:28:31 -0500

>ABNF definitions? Had ptime and maxptime had it the question would been 

History. I have no objection to including ABNF, if you want to suggest the
appropriate form.

Colin