Subject: [clue] Concensus call: Text for "Axis of Capture"

From: Mary Barnes <[email-masked]>
Date: Mon, 2 Jul 2012 12:58:08 -0500

Per the design team call last week, we want to do a consensus call for the
text to cover the "Axis of capture".  There were several suggested updates
to Stephan's original text:
http://www.ietf.org/mail-archive/web/clue/current/msg01583.html

Thus, we would like folks to respond as to whether they are okay with the
following text being added to section 6.1.1 (relative to
draft-ietf-clue-framework-05 - after the two paragraphs of "point of
capture" - middle of page 11):

   Axis of Capture Point: {(X, Y, Z)} A field with a single Cartesian

   (X, Y, Z) point value (virtual or physical) which describes a position

   in space of a second point on the axis of capture of the capturing

   device; the first point being the Point of Capture (see above).

   The axis of capture point MUST NOT be specified if the Point of Capture

   is not present for this capture device.

   When the Axis of Capture Point attribute is specified, it must include X,
   Y and Z coordinates.  These coordinates MUST not be identical to the

   Point of Capture coordinates.

   If the Axis of Capture Point is not specified, it
   means the consumer should not assume anything about the axis of

   capture of the capturing device.

So, please respond "Yes" if you think the text if fine, "Maybe" if you
think it needs tweaking (and include the suggested
tweaks). Note, we agreed to add this at the interim meeting, thus if you
answer "No", you must include
a compelling reason why this should not be added in some form.

Regards,
Mary
CLUE WG co-chair

---

From: "Roni Even" <[email-masked]>
Date: Mon, 2 Jul 2012 21:46:37 +0200

Hi,

In general I am OK with the text I am just wondering about

"If the Axis of Capture Point is not specified, it means the consumer should
not assume anything about the axis of capture of the capturing device."
 
Is this the assumption or should the consumer assume that the axis of
capture is perpendicular to the center of the area of capture. If the above
sentence is specified I am wondering what is the value in providing the
point of capture.
Thanks
Roni  

From: [email-masked] [mailto:[email-masked]] On Behalf Of Mary
Barnes
Sent: 02 July, 2012 7:58 PM
To: CLUE
Subject: [clue] Concensus call: Text for "Axis of Capture"

 

 

 

So, please respond "Yes" if you think the text if fine, "Maybe" if you think
it needs tweaking (and include the suggested

Regards,

Mary

CLUE WG co-chair

---

From: "Duckworth, Mark" <[email-masked]>
Date: Mon, 2 Jul 2012 13:32:32 -0700

Yes.

From: [email-masked] [mailto:[email-masked]] On Behalf Of Mary Barnes
Sent: Monday, July 02, 2012 1:58 PM
To: CLUE
Subject: [clue] Concensus call: Text for "Axis of Capture"

Per the design team call last week, we want to do a consensus call for the text to cover the "Axis of capture".  There were several suggested updates to Stephan's original text:
http://www.ietf.org/mail-archive/web/clue/current/msg01583.html

Thus, we would like folks to respond as to whether they are okay with the following text being added to section 6.1.1 (relative to draft-ietf-clue-framework-05 - after the two paragraphs of "point of capture" - middle of page 11):

So, please respond "Yes" if you think the text if fine, "Maybe" if you think it needs tweaking (and include the suggested
tweaks). Note, we agreed to add this at the interim meeting, thus if you answer "No", you must include
a compelling reason why this should not be added in some form.

Regards,
Mary
CLUE WG co-chair

---

From: Stephan Wenger <[email-masked]>
Date: Mon, 2 Jul 2012 20:51:32 +0000

Lousy internet connection—let's see whether this gets through…
Roni, without any changes, y reading of the text proposed is that there is no axis of capture knowledge unless both point and axis of capture are specified.  No inference of the axis of capture from the field of capture is implied.
I think I support this proposal.  It is trivial to calculate a point of capture even if point of capture is identical with the center of the field of capture coordinates.   The signaling may be unnecessary if we were  mandating a condition as you implicitly propose it, but bits on this level ought to be cheap.  Suggest we be explicit and say either point of capture is specified, or no one knows.
Stephan

From: Roni Even <[email-masked]<mailto:[email-masked]>>
Date: Monday, 2 July, 2012 12:46
To: 'Mary Barnes' <[email-masked]<mailto:[email-masked]>>, 'CLUE' <[email-masked]<mailto:[email-masked]>>
Subject: Re: [clue] Concensus call: Text for "Axis of Capture"

Hi,

“If the Axis of Capture Point is not specified, it means the consumer should not assume anything about the axis of capture of the capturing device.”

Is this the assumption or should the consumer assume that the axis of capture is perpendicular to the center of the area of capture. If the above sentence is specified I am wondering what is the value in providing the point of capture.

Thanks

Roni

From: [email-masked]<mailto:[email-masked]> [mailto:[email-masked]] On Behalf Of Mary Barnes
Sent: 02 July, 2012 7:58 PM
To: CLUE
Subject: [clue] Concensus call: Text for "Axis of Capture"

Regards,
Mary
CLUE WG co-chair

---

From: Stephan Wenger <[email-masked]>
Date: Mon, 2 Jul 2012 20:53:47 +0000

Not sure this will make it—let's try.  I will not be able to join any call over the next two weeks.  I'm fine with the text proposed re axis of capture.
Stephan

From: Mary Barnes <[email-masked]<mailto:[email-masked]>>
Date: Monday, 2 July, 2012 10:58
To: CLUE <[email-masked]<mailto:[email-masked]>>
Subject: [clue] Concensus call: Text for "Axis of Capture"

Regards,
Mary
CLUE WG co-chair

---

From: "Allyn Romanow (allyn)" <[email-masked]>
Date: Mon, 2 Jul 2012 21:42:11 +0000

yes

From: [email-masked] [mailto:[email-masked]] On Behalf Of Mary Barnes
Sent: Monday, July 02, 2012 10:58 AM
To: CLUE
Subject: [clue] Concensus call: Text for "Axis of Capture"

Regards,
Mary
CLUE WG co-chair

---

From: Christian Groves <[email-masked]>
Date: Tue, 03 Jul 2012 16:48:46 +1000

I'm getting confused.... my understanding is the following:

- If the "point of capture" is included and the "axis of capture point" 
is not included then the axis is assumed to be perpendicular to the 
centre of the capture area.
- if the "point of capture" is included and the "axis of capture point" 
is included it describes a position in space of a second point on the 
axis of capture of the capturing device;***
- If the "point of capture" is not included then "axis of capture point" 
is not used.

Is this the desired behaviour?

With regards to the *** above, an axis (line) travels in two directions. 
I wonder if it is beneficial to specify that the axis of capture point 
must lie between the capture area and the point of capture. Might help 
avoid some confusion if someone defines a point behind the capture point.

I'm also wondering if it is better to call this "line of capture" or 
"optical axis" or similar? Mathematically speaking what we're defining 
by two points is a line or optically speaking its an optical axis.

Regards, Christian

On 3/07/2012 6:51 AM, Stephan Wenger wrote:
> Roni, without any changes, y reading of the text proposed is that 
> there is no axis of capture knowledge unless both point and axis of 
> capture are specified. No inference of the axis of capture from the 
> field of capture is implied.
> I think I support this proposal. It is trivial to calculate a point of 
> capture even if point of capture is identical with the center of the 
> field of capture coordinates. The signaling may be unnecessary if we 
> were mandating a condition as you implicitly propose it, but bits on 
> this level ought to be cheap. Suggest we be explicit and say either 
> point of capture is specified, or no one knows.
> Stephan
>
>
> From: Roni Even <[email-masked] <mailto:[email-masked]>>
> To: 'Mary Barnes' <[email-masked] 
> <mailto:[email-masked]>>, 'CLUE' <[email-masked] 
> <mailto:[email-masked]>>
> *From:[email-masked] <mailto:[email-masked]> 
> [mailto:[email-masked]] *On Behalf Of *Mary Barnes
> *Sent:* 02 July, 2012 7:58 PM
> *To:* CLUE
> *Subject:* [clue] Concensus call: Text for "Axis of Capture"
>
> Per the design team call last week, we want to do a consensus call for 
> the text to cover the "Axis of capture". There were several suggested 
> updates to Stephan's original text:
>
> Thus, we would like folks to respond as to whether they are okay with 
> the following text being added to section 6.1.1(relative to 
> _______________________________________________
> clue mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/clue

---

From: John Leslie <[email-masked]>
Date: Tue, 3 Jul 2012 13:50:54 -0400

>   centre of the capture area.

   That's enough to confuse me!

   I went back to the text of draft-ietf-clue-framework-05, section 6.1.1:
]...
] Point of Capture: {(X, Y, Z)} A field with a single Cartesian (X, Y,
] Z) point value which describes the spatial location, virtual or
] physical, of the capturing device (such as camera).
] 
] When the Point of Capture attribute is specified, it must include X,
] Y and Z coordinates.  If the point of capture is not specified, it
] means the consumer should not assume anything about the spatial
] location of the capturing device.  Even if the provider specifies an
] area of capture attribute, it does not need to specify the point of
] capture.

   That last sentence is enough to confuse anybody, IMHO. :^(

   But I don't see how you're entitled to assume "perpendicular" to the
plane of the Area of Capture. IMHO, failure to include Point of Capture
is distinctly not-nice, and leaves you no good way to associate pixel
positions with physical positions.

   It's certainly possible that the provider would fail to include Point
of Capture because s/he's providing a processed piece, possibly stiched
together from parts of different cameras. (I don't consider that nice
either!)

>   axis of capture of the capturing device;***

   Refer to the proposed text:
] 
] Axis of Capture Point: {(X, Y, Z)} A field with a single Cartesian 
] (X, Y, Z) point value (virtual or physical) which describes a position 
] in space of a second point on the axis of capture of the capturing 
] device; the first point being the Point of Capture (see above).
]
] The axis of capture point MUST NOT be specified if the Capture Point 
] is not present for this capture device.
]
] When the Axis of Capture Point attribute is specified, it must include X,
] Y and Z coordinates.  If the Axis of Capture point is not specified, it
] means the consumer should not assume anything about the axis of
] Capture of the capturing device.

   Your statement seems correct, though not 100% implied. I wonder why
we don't specify that the Axis of Capture Point is a point within the
plane of the Area of Capture (when possible).

> - If the "point of capture" is not included then "axis of capture point" 

   That much is clear.

> With regards to the *** above, an axis (line) travels in two directions. 

   Quite correct.

> must lie between the capture area and the point of capture.

   You mean Area of Capture, no doubt?

> Might help avoid some confusion if someone defines a point behind the
> capture point.

   If someone can't handle that, we have worse problems!

   Nonetheless, ISTM that one will need to calculate the intersection
of that line with the Area of Capture (unless the Axis of Capture Point
is defined to be that intersection already). This introduces rounding
errors which could possibly be significant.

> by two points is a line or optically speaking its an optical axis.

   It might indeed be easier to understand (though I must admit the
_value_ is a single XYZ point)...

--
John Leslie <[email-masked]>

---

From: Paul Kyzivat <[email-masked]>
Date: Tue, 03 Jul 2012 14:40:28 -0400

Interesting discussion.

I'm known for probing corner cases, and I'm going to do some of that here.

On 7/3/12 1:50 PM, John Leslie wrote:
> Christian Groves<[email-masked]>  wrote:
>>

What is confusing?

> positions with physical positions.

Is there any requirement that the point of capture be *in front* of the 
area of capture? Couldn't it be behind? If so, wouldn't that have great 
impact on how you interpret the video?

> together from parts of different cameras. (I don't consider that nice

Again, without a point of capture, how do you know the orientation of 
the display?

> plane of the Area of Capture (when possible).

I suppose it should always be possible. But by requiring it you open up 
issues when rounding errors cause it to be "not quite" in the plane. We 
don't want to have errors just because people use differing precision 
for their arithmetic.

	Thanks,
	Paul

> John Leslie<[email-masked]>

---

From: John Leslie <[email-masked]>
Date: Tue, 3 Jul 2012 20:34:36 -0400

Paul Kyzivat <[email-masked]> wrote:
>>>...
>>] Even if the provider specifies an

   "does not need"

   (It's hard to come up with a fully legitimate case where the point of
capture could reasonably be omitted. Until you do, this sentence only
confuses the reader.)

>> together from parts of different cameras. (I don't consider that nice

   (That's my "fully legitimate" case...)

> Again, without a point of capture, how do you know the orientation of 

   You don't. (But someone could look at it and guess. ;^)

>>... I wonder why

   The rounding error is "nicer" here than different rounding by the
receivers. (Besides, I did say "if possible"...)

---

From: Christian Groves <[email-masked]>
Date: Wed, 04 Jul 2012 11:49:26 +1000

Hello John,

Please see my responses below marked [CNG].

Regards, Christian

>     That's enough to confuse me!
[CNG] Good to know I'm in company :-).
> positions with physical positions.
[CNG] I was trying to clarify what Roni was getting at in his original 
reply on this thread where he mentioned this perpendicular aspect. 
Previous to this discussion there was no concept of a second point to 
define an "axis of capture". Therefore there must have been an 
assumption about the axis...

> plane of the Area of Capture (when possible).
[CNG] We could do that. I think that at least the axis of capture point 
should be in the direction of the capture point to the area of capture. 
The point could lie before or beyond the area of capture plane.
>     You mean Area of Capture, no doubt?
[CNG] Yes, area of capture
>     If someone can't handle that, we have worse problems!
[CNG] I think you've been around on these lists long enough to know that 
it will be a problem for someone :-).

> _value_ is a single XYZ point)...
[CNG] WRT to single XYZ point I agree its inconsistent, however "Second 
point defining the optical axis" whilst precise is a little long winded.

---

From: Mary Barnes <[email-masked]>
Date: Fri, 6 Jul 2012 10:15:57 -0500

There's been a lot of discussion around Roni's point, but I haven't seen an
explicit suggestion for additional text or changes to the proposed text.
 Barring that, Mark will be updating the framework to include the proposed
text (note, he will be on vacation, thus this will be the final update
before the meeting).

Mary.

---

From: John Leslie <[email-masked]>
Date: Fri, 6 Jul 2012 11:55:05 -0400

Mary Barnes <[email-masked]> wrote:
>> think it needs tweaking (and include the suggested tweaks)...

   Maybe...

   The name "Axis of Capture Point" is confusing; "Point on Axis of
Capture" would be easier to understand. (I'm not partial to that name:
I can think of better ones, but I'm not sure exactly what meaning we
agree to for this value.

   "MUST not be specified" deserves wordsmithing; I'd prefer "SHOULD NOT
be specified" or "MUST be ignored". We can't encourage crashing if this
value is included in error.

   "MUST not be identical" is perhaps under-specifying; I'd prefer
"SHOULD be at or near the intersection with the plane of capture" or
something to that effect.

   "Consumer should not assume anything" could use wordsmithing. The
end-user (person) can and will do whatever s/he wants: it's the
receiving system we mean here. And I'd prefer "receiving system MUST NOT
assume anything".

   Other than those, I think it's fine.

---

From: Paul Kyzivat <[email-masked]>
Date: Fri, 06 Jul 2012 12:09:07 -0400

On 7/6/12 11:55 AM, John Leslie wrote:
> Mary Barnes<[email-masked]>  wrote:
>>>

A way to avoid the terminology confusion would be to replace the "point 
of capture" attribute, with an "axis of capture" attribute containing 
two points, with the first specified to be the point of capture. If 
desired, it would still be possible to make the 2nd point optional.

	Thanks,
	Paul