Subject: RE: [AVT] Re: MPEG-4 BIFS in the packet loss environment

From: [email-masked]
Date: Thu, 28 Mar 2002 17:12:49 +0100

Zvi,

I understand the need for non-MPEG experts to get some additional 
explanation:

MPEG invested a lot of work in the past 10 years
to make sure that scene description could be "broadcasted",
including resistance to network losses.

The results of this is a set of techniques that make BIFS unique
in the scene description landscape.

specifically BIFS has been described as a binary (compressed) version
(actually superset) of VRML for 3D scenes. And it is.

BIFS has also been described as a binary (compressed) version of W3C SMIL
for 2D scenes. And it is.

But BIFS is more and the key competitive advantage of BIFS over
either VRML or SMIL *IS* this ability to be "broadcasted"
i.e. sent over a possibly uni-directional and probably lossy links....

And the way this was implemented is similar to I frames in video.

However some people out there (hello stephan)
have been expressing concerns about that statement.

My understanding for the basis of this concern is that they would say:
"scene description is not like video, either you get it or you dont"

Well the truth is that the "threshold" is not binary ,as I shall 
demonstrate now:

Take for example a scene describing a room with several objects in it.

If you loose the big arm chair in the corner
(but get it ok a few seconds latter i.e. at the next "I" frame)
the scene is still "usable", it is *inexact*, but usable.

If you loose the texture on the wall the wall is still a wall
(and a texture-less wall is so cheap that you can triplicate or heavily 
FEC the packet transporting it).

Of course if you loose the "I buy it" button of your E commerce 
interactive application
you would be in trouble with the guy paying for it.

I believe that judging if you would be in more trouble than if you loose
the split second part of the movie where the hero gets shot is not for us 
to decide.

And to conclude I think the point is to document the fact that :

- yes loosing piece of scene description CAN be bad
- and therefore that users of this payload format should take
the required steps to make sure:
* either that it does not happen
* or that their application is carefully designed to handle those losses

regards,

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

"Zvi Lifshitz" <[email-masked]>
03/26/2002 21:30

        To:     Philippe Gentric/LIM/CE/PHILIPS@EMEA1
"'Vishy Swaminathan'" <[email-masked]>
        cc:     <[email-masked]>
<[email-masked]>
<[email-masked]>
"'Colin Perkins'" <[email-masked]>
"'Lim, Young-Kwon'" <[email-masked]>
        Subject:        RE: [AVT] Re: MPEG-4 BIFS in the packet loss environment
        Classification: 

[[email-masked]:] 
 
> * BIF scene and MPEG-J are more sensitive i.e. the usual 
> techniques (including RTP/RTSP/TCP, but this is 
> acutzally out of scope for a RTP payload format, right ?) 
> should be used to make sure the content actually arrived. 

[Reply:]
 
BIFS scenes are like video I-frames.
 
z
soon the whole world will STREAM
==================================================================
Zvi Lifshitz                      Phone +972-2-679-4788
[email-masked]         Fax +972-9-958-6099
Optibase Ltd.                 GSM: +972-54-461-787  (+972-LI-IM1-RTP)
http://www.optibase.com   US voice mail/fax  +1(206)888-4149
==================================================================
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Las Vegas, Nevada USA,  April 8 - 11, 2002

---

From: Marshall Eubanks <[email-masked]>
Date: Thu, 28 Mar 2002 12:29:16 -0500

Bonjour Phillippe;

    Is there a document that describes the FEC for the BIFS ? Or is this
up to the implementor ?

                                Regards
                                Marshall

[email-masked] wrote:

> the split second part of the movie where the hero gets shot is not for 
> us to decide.
> 

T.M. Eubanks
Multicast Technologies, Inc
10301 Democracy Lane, Suite 410
Fairfax, Virginia 22030
Phone : 703-293-9624       Fax     : 703-293-9609
e-mail : [email-masked]
http://www.multicasttech.com

Test your network for multicast :
http://www.multicasttech.com/mt/
  Status of Multicast on the Web  :
  http://www.multicasttech.com/status/index.html

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

---

From: "Zvi Lifshitz" <[email-masked]>
Date: Sun, 31 Mar 2002 01:07:35 +0300

Philippe,

I basically agree with your description of the issue. I just want to add few
words for further clarification.

Essentially BIFS (and OD) stream _are_ like video in the sense that they are
made up of Intra (or Key) frames (scenes) and delta frames (BIFS updates).
They are, however, two differences:

1.	Users may interact with BIFS scenes locally. This means that reverting to
an I frame after losing delta frames might incur the penalty of the user
losing his/her local manipulation of the scene. For instance, you have a
movie with translation sub-titles at the bottom, and you drag the titles to
the top. If you loose one title and wait to refresh your screen at the next
"replace scene" command, the titles will go down again.

2.	In video the deltas are usually accumulative. I.e. each delta refers to
the immediately preceding frame. This is not always the case with BIFS.
Using again the sub-titles example, the position, size and font of the
titles will be set at the initial scene description, while the content of
each title is a BIFS-update frame. Loosing one update has no effect on
subsequent updates.

The "scene carousel" mechanism introduced in MPEG-4 Systems addresses those
points, by featuring the following:

1.	The I-frames are interspersed in the stream as _optional alternatives_ to
the sequence of updates. They come to rescue only when loss of indispensable
data occurs.

2.	There is a mechanism to differentiate between "indispensable" update
commands and commands whose loss may be ignored without severely affecting
the presentation.

Regards,

z
soon the whole world will STREAM
==================================================================
Zvi Lifshitz                      Phone +972-2-679-4788
[email-masked]         Fax +972-9-958-6099
Optibase Ltd.                 GSM: +972-54-461-787  (+972-LI-IM1-RTP)
http://www.optibase.com   US voice mail/fax  +1(206)888-4149
==================================================================
Come see us at:
NAB 2002 (National Association of Broadcasters), The Sands Expo Center, Las
Vegas, Nevada USA,  April 8 - 11, 2002

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
Sent: Thursday, March 28, 2002 7:13 PM
To: Zvi Lifshitz
Cc: [email-masked]; [email-masked]; [email-masked];
'Colin Perkins'; 'Vishy Swaminathan'; 'Lim, Young-Kwon'
Subject: RE: [AVT] Re: MPEG-4 BIFS in the packet loss environment

Zvi,

Well the truth is that the "threshold" is not binary ,as I shall demonstrate
now:

If you loose the texture on the wall the wall is still a wall
(and a texture-less wall is so cheap that you can triplicate or heavily FEC
the packet transporting it).

Of course if you loose the "I buy it" button of your E commerce interactive
application
you would be in trouble with the guy paying for it.

I believe that judging if you would be in more trouble than if you loose
the split second part of the movie where the hero gets shot is not for us to
decide.

regards,

Philippe Gentric
Software Architect
Philips MP4Net

        Subject:        RE: [AVT] Re: MPEG-4 BIFS in the packet loss
environment
        Classification:

[Reply:]

z
soon the whole world will STREAM
==================================================================
Zvi Lifshitz                      Phone +972-2-679-4788
[email-masked]         Fax +972-9-958-6099
Optibase Ltd.                 GSM: +972-54-461-787  (+972-LI-IM1-RTP)
http://www.optibase.com   US voice mail/fax  +1(206)888-4149
==================================================================
Come see us at:
NAB 2002 (National Association of Broadcasters), The Sands Expo Center, Las
Vegas, Nevada USA,  April 8 - 11, 2002