Subject: [clue] Capture Scene Entry question

From: Christian Groves <[email-masked]>
Date: Tue, 24 Jul 2012 09:59:36 +1000

Hello all,

In reading the framework document I'm having trouble understanding 
exactly what a "Capture Scene Entry" is. In the framework it is defined as:
/*Capture Scene Entry: a list of media captures of the same media type
    that together form one way to represent the capture scene./

it also says:
/A media provider arranges media captures in a capture scene to help
    the media consumer choose which captures it wants.  The capture scene
    entries in a capture scene are different alternatives the provider is
    suggesting for representing the capture scene./

I'm wondering how people interpret "one way" and "different alternatives"?
You could interpret this as meaning that each "Capture Scene Entry" 
shows an entire scene, or you could interpret this as meaning that each 
"Capture Scene Entry" could show part of the overall scene.

At least from my reading of the framework both interpretations are 
allowed. Is there a preferred interpretation?
For example: if VC1,VC2,VC3 are three main cameras, VC4 is an camera 
that automatically zooms in on the active speaker. I could construct a 
capture scenes with one or two capture scene entries:
+------------------+
| Capture Scene #1 |
+------------------+
| VC1, VC2, VC3    |
| VC4              |
+------------------+
or
+--------------------+
| Capture Scene #1   |
+--------------------+
| VC1, VC2, VC3, VC4 |
+--------------------+

What are people's thoughts?

Regards, Christian

---

From: Paul Kyzivat <[email-masked]>
Date: Mon, 23 Jul 2012 20:10:46 -0400

[as individual]

> capture scenes with one or two capture scene entries:

As described above, VC4 is functionally similar to a switched capture 
that switches between VC1,VC2,VC3. (But I don't know if it is similar 
*enough* to label it as a switched capture. Without some such label the 
receiver won't realize what sort of thing it is getting.)

As such, this seems a valid way to construct entries.

But suppose the scene represents a classroom situation, with VC1,VC2,VC3 
representing the "students" and VC4 represents the "teacher". In that 
case, I think its necessary to place all four into one entry. Putting 
VC1,VC2,VC3 in one entry, and VC4 in another would mean that each only 
provides a partial view of the scene. And so I would think that was not 
a valid usage.

I went back to the framework to see if it was clear about this. IMO it 
isn't.

	Thanks,
	Paul

---

From: "Duckworth, Mark" <[email-masked]>
Date: Tue, 24 Jul 2012 04:25:36 -0700

Christian,
Your first example capture scene, with two separate entries, is exactly the sort of thing intended by the framework.  The first entry (VC1, VC2, VC3) is one good alternative for representing the scene, and the second entry (VC4) is another good alternative.

But there shouldn't be anything stopping you from advertising your second example, with (VC1, VC2, VC3, VC4) all in the same entry.  But this entry by itself is not helpful for a consumer that doesn't want to (or can't) receive all four captures.

Paul,
Your classroom suggestion makes sense.  But the provider might also want to advertise capture scene entries with fewer captures per entry in order to suggest which captures a more limited consumer might find most useful.
Another possible way to do it is to put the students in one scene and the teacher in another scene.

Mark

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf Of Paul
> Kyzivat
> Sent: Monday, July 23, 2012 8:11 PM
> To: [email-masked]
> Subject: Re: [clue] Capture Scene Entry question
> 
> [as individual]
> 
> > shows an entire scene, or you could interpret this as meaning that
> > each "Capture Scene Entry" could show part of the overall scene.
> >
> As described above, VC4 is functionally similar to a switched capture that
> switches between VC1,VC2,VC3. (But I don't know if it is similar
> *enough* to label it as a switched capture. Without some such label the receiver
> won't realize what sort of thing it is getting.)
> 
> representing the "students" and VC4 represents the "teacher". In that case, I
> think its necessary to place all four into one entry. Putting
> provides a partial view of the scene. And so I would think that was not a valid
> usage.
> 
> I went back to the framework to see if it was clear about this. IMO it isn't.
> 
> 	Thanks,
> 	Paul
> _______________________________________________
> clue mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/clue

---

From: "Espen Berger (espeberg)" <[email-masked]>
Date: Tue, 24 Jul 2012 14:42:05 +0000

Christian, I have ready the capture scene entry as meaning 'choose all capture in a capture scene entry to get a good rendering of a capture scene". So I would model your example as { VC1, VC2, VC3} or { VC4  } . A consumer should request all captures in an entry to have a complete entry,  to discourage endpoints to only request VC2 to get half of a rendering. 

For the classroom example I think it's natural to model speaker and audience with two capture-scenes.  

capture-scene id="1" description="Speaker"
  Entry: VC1  // Available as a single video capture. 

capture-scene id="2" description="Audience"
  Entry: VC1 // A single capture view of the audience 
  Entry2: VC2, VC3, VC4  // A triple capture view of the audience 

For the audience capture scene a consumer must choose between the two rendering alternatives depending on the consumer preference.  

Notes 
 * As a provider the 'speaker' is more important, so its listed first in the advertisement. 
 * If the capture scene with audience does not have a single capture alternative, it will exclude many receivers to do sensible renderings of the room. 

Cheers 

-Espen 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Duckworth, Mark
Sent: 24. juli 2012 13:26
To: [email-masked]
Subject: Re: [clue] Capture Scene Entry question

Christian,

Paul,

Mark

> From: [email-masked] [mailto:[email-masked]] On Behalf 
> Of Paul Kyzivat
> > /*Capture Scene Entry: a list of media captures of the same media 
> > type that together form one way to represent the capture scene./
> >
> > it also says:
> > entries in a capture scene are different alternatives the provider 
> > is suggesting for representing the capture scene./
> >
> > that automatically zooms in on the active speaker. I could construct 
> > a capture scenes with one or two capture scene entries:
> > +------------------+
> > | Capture Scene #1 |
> > +------------------+
> > | VC1, VC2, VC3 |
> > | VC4 |
> > +------------------+
> > or
> > +--------------------+
> > | Capture Scene #1 |
> > +--------------------+
> > | VC1, VC2, VC3, VC4 |
> > +--------------------+
> >
> *enough* to label it as a switched capture. Without some such label 
> the receiver won't realize what sort of thing it is getting.)
> 
> But suppose the scene represents a classroom situation, with 
> VC1,VC2,VC3 representing the "students" and VC4 represents the 
> "teacher". In that case, I think its necessary to place all four into 
> one entry. Putting
> provides a partial view of the scene. And so I would think that was 
> not a valid usage.
>

---

From: Christian Groves <[email-masked]>
Date: Wed, 25 Jul 2012 09:43:39 +1000

Hello Espen, Mark and Paul,

My initial preference was to use multiple capture scene entries to for 
the scenario I proposed. However in looking at the draft I couldn't see 
anything that offered guidance of what the grouping of capture into a 
capture set entry actually implies.

For example, Espen indicates that it has the meaning of "choose all 
captures in a capture scene entry to get a good rendering". I would 
agree with this statement but I didn't see anywhere is the draft that 
describes the decision process as to how captures are grouped. The 
framework draft actually says that a consumer may chose a subset of the 
captures in a scene entry but doesn't say what the effect may be.

Another example is the presumed priority in the listing of entries. I 
think having some mechanism to indicate the priority between captures is 
worthwhile but I don't think that its currently specified in the 
framework draft.

Espen: in your example below I would have thought that this would be a 
single Capture scene? I say this because being in the same room there is 
a spatial relationship between all the captures. The draft says that 
"there is no spatial relationship between media captures that are in 
different capture scenes."

Also related to this is the use of "description". Again I think that 
having some keyword to describe what the capture is related to is good. 
I've also been looking at the "Content" attribute and I don't think its 
sufficient for CLUE.  Paul and I are working on some text to describe 
the issues and describe the alternatives.

Regards, Christian

---

From: Paul Kyzivat <[email-masked]>
Date: Tue, 24 Jul 2012 20:25:50 -0400

[as individual]

This discussion leads me to believe that the framework is not yet 
explicit enough about this stuff. More words are needed to make it clear.

Regarding the classroom case: Christian made the point that I intended 
to: If indeed the speaker and the students are in the same room then 
they share a common coordinate space. While it would be *possible* to 
represent this as two scenes, doing so throws away information about the 
relationship between the speaker and the students. For instance, the 
direction of gaze of the speaker is consistent with the location of the 
capture containing the student he is looking at. So I question *why* one 
might prefer to make these two scenes.

	Thanks,
	Paul

On 7/24/12 7:43 PM, Christian Groves wrote:
> sufficient for CLUE. Paul and I are working on some text to describe the
> issues and describe the alternatives.
>
> Regards, Christian
>
>> Christian, I have ready the capture scene entry as meaning 'choose all
>> capture in a capture scene entry to get a good rendering of a capture
>> scene". So I would model your example as { VC1, VC2, VC3} or { VC4 } .
>> A consumer should request all captures in an entry to have a complete
>> entry, to discourage endpoints to only request VC2 to get half of a
>> rendering.
>>
>> For the audience capture scene a consumer must choose between the two
>> rendering alternatives depending on the consumer preference.
>>
>> Notes
>> * If the capture scene with audience does not have a single capture
>> alternative, it will exclude many receivers to do sensible renderings
>> of the room.
>>
>> Cheers
>>
>> -Espen
>>
>>
>> Of Duckworth, Mark
>> Your first example capture scene, with two separate entries, is
>> exactly the sort of thing intended by the framework. The first entry
>> (VC1, VC2, VC3) is one good alternative for representing the scene,
>> and the second entry (VC4) is another good alternative.
>>
>> But there shouldn't be anything stopping you from advertising your
>> second example, with (VC1, VC2, VC3, VC4) all in the same entry. But
>> this entry by itself is not helpful for a consumer that doesn't want
>> to (or can't) receive all four captures.
>>
>> Paul,
>> Your classroom suggestion makes sense. But the provider might also
>> want to advertise capture scene entries with fewer captures per entry
>> in order to suggest which captures a more limited consumer might find
>> most useful.

---

From: Paul Kyzivat <[email-masked]>
Date: Thu, 26 Jul 2012 14:25:22 -0400

> Another possible way to do it is to put the students in one scene and the teacher in another scene.

I see that the provider could provide entries with fewer captures, if it 
is capable of doing so. It could use composition and/or switching to 
cover the entire scene with fewer captures.

But what if it is not capable/willing to do that?
Is it valid for it to offer entries with fewer captures simply by 
dropping what it decides are less important captures? Can that be viewed 
as still representing the full scene?

Suppose that is ok. Then maybe it is ok to provide one entry that only 
shows part of the scene, using static captures, and another entry that 
shows the entire scene using switched captures. If so, how would the 
receiver realize the tradeoffs between the two?

	Thanks,
	Paul