Subject: [MMUSIC] Question on draft-ietf-mmusic-decoding-dependency-00, using more than one a=group:DDP lines

From: "LEPROVOST YANN" <[email-masked]>
Date: Tue, 8 Jan 2008 16:21:47 +0100

Dear Thomas Schierl and Stephan Wenger,

I have a question on behalf of peoples (CC) involved in a french project
(called Scalim@ges) around transport and description of SVC.
In a specific use case, we defined a SVC service with different
dependancy paths: 
	- mid:1 base layer
	- mid:2 quality layer depending on mid:1
	- mid:3 spatial and temporal enhancement layer depending on
mid:1
	- mid:4 quality layer depending on mid:3
	- mid:5 spatial enhancement depending on mid:3

Thus, different dependancy paths exist:
- mid:1 --> mid:2
- mid:1 --> mid:3 --> mid:4
- mid:1 --> mid:3 --> mid:5

We would like to define the different available paths by registering
different "a=group:DDP" lines at the top of the SDP, and possibly by
adding "i=" lines after each group lines. Here is an example of such
description:

a=group:DDP 1 2
i= 576p25, up to 4mbps
a=group:DDP 1 3 4
i=  720p60, up to 8mbps
a=group:DDP 1 3 5
i= 1080p50, up to 12mbps

The idea is provide a simple way for receivers to analyse the different
dependancy paths and to retrieve mid values. 
With theses different "a=group:DDP" lines, receivers do not have to
parse each media line and reconstruct the dependancy tree according to
"a=depend:" lines.

I try to find a restriction on the number of "a=group:DDP" lines in SDP,
in the current draft (00). 
>From my view, there is no restriction, and the proposed description
seems to be compliant ?

I would like to know your opinion regarding such scheme and the
compliancy with current draft ?

Regards

Yann Leprovost
_______________________________________________
mmusic mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/mmusic

---

From: "Thomas Schierl" <[email-masked]>
Date: Wed, 9 Jan 2008 17:48:54 +0100

Dear Yann,

Thanks for your question. 

Following section 5. of RFC 3388  >> An "m" line identified by its "mid"
attribute MUST NOT appear in more than one "a=group" line using the same
semantics. <<, the construction you described is not possible.

Following the  decoding-dependency draft, you would signal one group: DDP 1
2 3 4 5 with the following dependencies:

(For simplicity, I leave out the payload types and show mids only)

m=.

..mid 1

m=.

..mid 2

..depend: 1

m=.

..mid 3

..depend: 1

m=.

..mid 4

..depend: 1 , 3 

m=.

..mid 5

..depend: 1 , 3  

Kind regards,

Thomas

From: LEPROVOST YANN [mailto:[email-masked]] 
Sent: Tuesday, January 08, 2008 4:22 PM
To: [email-masked]; [email-masked]; MMUSIC mailing list
Cc: BABONNEAU Gerard RD-MAPS-REN; [email-masked];
Bordes Philippe; Philippe Courboulay
Subject: Question on draft-ietf-mmusic-decoding-dependency-00, using more
than one a=group:DDP lines

In a specific use case, we defined a SVC service with different dependancy
paths: 
        - mid:1 base layer 
        - mid:2 quality layer depending on mid:1 
        - mid:3 spatial and temporal enhancement layer depending on mid:1 
        - mid:4 quality layer depending on mid:3 
        - mid:5 spatial enhancement depending on mid:3 

We would like to define the different available paths by registering
different "a=group:DDP" lines at the top of the SDP, and possibly by adding
"i=" lines after each group lines. Here is an example of such description:

a=group:DDP 1 2 
i= 576p25, up to 4mbps 
a=group:DDP 1 3 4 
i=  720p60, up to 8mbps 
a=group:DDP 1 3 5 
i= 1080p50, up to 12mbps 

The idea is provide a simple way for receivers to analyse the different
dependancy paths and to retrieve mid values. 
With theses different "a=group:DDP" lines, receivers do not have to parse
each media line and reconstruct the dependancy tree according to "a=depend:"
lines.

I try to find a restriction on the number of "a=group:DDP" lines in SDP, in
the current draft (00). 
>From my view, there is no restriction, and the proposed description seems to
be compliant ? 

I would like to know your opinion regarding such scheme and the compliancy
with current draft ? 

Regards 

Yann Leprovost 

----
Visit us at

FOE 2008 (8th Fiber Optics Expo) / Tokio Big Sight, Japan / 16 - 18 January 2008 / Booth 2 - 50
http://www.foe.jp/english 
GSMA Mobile World Congress / Barcelona, Spain / 11 - 14 February 2008 / Broadcast Mobile Convergence Forum / Booth 2B82
http://www.mobileworldcongress.com/homepage.htm
_______________________________________________
mmusic mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/mmusic

---

From: "Even, Roni" <[email-masked]>
Date: Wed, 9 Jan 2008 23:37:34 +0200

Hi,

Just one more comment about i=.

You should note that it is intended to be presented to human and not
parsed by automata. So it should not be used for giving semantics to a
stream. If you want to specify semantics you should use something like
the content attribute

Roni Even

________________________________

From: Thomas Schierl [mailto:[email-masked]] 
Sent: Wednesday, January 09, 2008 6:49 PM
To: 'LEPROVOST YANN'
Cc: 'MMUSIC mailing list'; 'BABONNEAU Gerard RD-MAPS-REN'; 'Bordes
Philippe'; 'Philippe Courboulay'; [email-masked]
Subject: [MMUSIC] RE: Question on
draft-ietf-mmusic-decoding-dependency-00,using more than one a=group:DDP
lines

Dear Yann,

Following the  decoding-dependency draft, you would signal one group:
DDP 1 2 3 4 5 with the following dependencies:

m=...

..mid 1

m=...

..mid 2

..depend: 1

m=...

..mid 3

..depend: 1

m=...

..mid 4

..depend: 1 , 3 

m=...

..mid 5

..depend: 1 , 3  

Kind regards,

Thomas

From: LEPROVOST YANN [mailto:[email-masked]] 
Sent: Tuesday, January 08, 2008 4:22 PM
To: [email-masked]; [email-masked]; MMUSIC mailing list
Cc: BABONNEAU Gerard RD-MAPS-REN; [email-masked];
Bordes Philippe; Philippe Courboulay
Subject: Question on draft-ietf-mmusic-decoding-dependency-00, using
more than one a=group:DDP lines

a=group:DDP 1 2 
i= 576p25, up to 4mbps 
a=group:DDP 1 3 4 
i=  720p60, up to 8mbps 
a=group:DDP 1 3 5 
i= 1080p50, up to 12mbps 

seems to be compliant ? 

Regards 

Yann Leprovost 

----
Visit us at

FOE 2008 (8th Fiber Optics Expo) / Tokio Big Sight, Japan / 16 - 18
January 2008 / Booth 2 - 50
http://www.foe.jp/english <ttp://www.foe.jp/english> 
GSMA Mobile World Congress / Barcelona, Spain / 11-14 February 2008 /
Broadcast Mobile Convergence Forum / Booth 2B82
http://www.mobileworldcongress.com/homepage.htm
<ttp://www.mobileworldcongress.com/homepage.htm>