Subject: [clue] Support for information about the spacing between monitors.

From: Roni Even <[email-masked]>
Date: Sat, 24 Sep 2011 10:24:48 +0300

Hi,

During the last Interim meeting I mentioned this requirement and will now
try to explain the use case for it. 

In a conference room when there are three camera and three monitors and when
there is an object that spans between two monitors (for example a person
standing so that his image is divided between two cameras) it will be good
if the image will look continuous even though part of it is missing due to
the gap between the monitors.

It is possible to calibrate the local room capture so that the  local image
will look continuous. In order to have a similar experience on the remote
side when rendering the local system can convey the distance between the
local monitors (including the monitor frame) in pixels (This can be
calculated based on the local monitor size and resolution) allowing the
remote side to have similar compensation.

This will require the local system to send this information, which is an
attribute on the conference room level or the capture scene level.

I think that it will also be good to add this feature to the use case
document

Regards

Roni Even

---

From: Stephen Botzko <[email-masked]>
Date: Sat, 24 Sep 2011 07:39:02 -0400

There is a similar overlap case when projectors are in use.  Some projector
walls overlap the pictures slightly, gradually fading each picture in the
overlap region to keep the overall brightness even. This makes it much
harder to see any mismatch in the various projectors.

In either case (gaps or overlap) the compensation can be done in either the
receiver or the sender.

-The receiving system can crop the original capture (to create the gap) and
stretch the slightly smaller picture to fill the screen.  Creating overlap
is a bit harder, as you need to grab some pixels from the adjacent
capture(s).  Though projector walls that use overlap are already doing this.

-A sending system would most likely use the identical methods.  In
principle, PTZ motors could also be used to shift the capture.  But
pan-tilt-zoom motors are generally not accurate enough to maintain precise
alignment, esp. when you are adjusting multiple cameras. Every time you move
the camera, the positional error builds, which requires fairly frequent
manual re-alignment.

Since a capture can be received by more than one receiver, it is generally
much better if such compensation is done in each receiver.  The bezels in
new displays keep shrinking, so even system models from the same
manufacturer are likely to have different gaps (depending on their
deployment date).  So I am thinking that signaling display arrangements (and
hoping that the sender will compensate) is not a good idea. It is more
robust to use receiver compensation.

I am ok with senders being able to signal that their *captures* (not their
displays) either have small gaps or small overlaps between them.  Though for
the reasons above, I suspect most vendors will go with precisely adjacent
captures.

Regards,
Stephen Botzko

On Sat, Sep 24, 2011 at 3:24 AM, Roni Even <[email-masked]> wrote:

> Hi,****
> try to explain the use case for it. ****
>
> In a conference room when there are three camera and three monitors and
> when there is an object that spans between two monitors (for example a
> person standing so that his image is divided between two cameras) it will be
> good if the image will look continuous even though part of it is missing due
> to the gap between the monitors.****
>
> calculated based on the lo cal moni allowing the remote side to have similar
> compensation.****
>
> attribute on the conference room level or the capture scene level.****
>
> ** **
>
> document****
> ** **
> Regards****
> Roni Even****
> ** **
> _______________________________________________
> clue mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/clue
>
>

---

From: "Duckworth, Mark" <[email-masked]>
Date: Sat, 24 Sep 2011 11:22:41 -0700

Hi Roni,

Let me see if I understand.  Is this what you mean?
The side that receives video can send some information about its physical display placement (size of gap between displays).
The side that sends video might be able to use this information to automatically adjust its cameras (pan and zoom) or video cropping and scaling parameters such that the image rendered on the receiving side looks continuous, taking into account the gap between displays.

Mark Duckworth

From: [email-masked] [mailto:[email-masked]] On Behalf Of Roni Even
Sent: Saturday, September 24, 2011 3:25 AM
To: [email-masked]
Subject: [clue] Support for information about the spacing between monitors.

Hi,
During the last Interim meeting I mentioned this requirement and will now try to explain the use case for it.
In a conference room when there are three camera and three monitors and when there is an object that spans between two monitors (for example a person standing so that his image is divided between two cameras) it will be good if the image will look continuous even though part of it is missing due to the gap between the monitors.
It is possible to calibrate the local room capture so that the  local image will look continuous. In order to have a similar experience on the remote side when rendering the local system can convey the distance between the local monitors (including the monitor frame) in pixels (This can be calculated based on the lo cal moni allowing the remote side to have similar compensation.
This will require the local system to send this information, which is an attribute on the conference room level or the capture scene level.

I think that it will also be good to add this feature to the use case document

Regards
Roni Even

---

From: Marshall Eubanks <[email-masked]>
Date: Sat, 24 Sep 2011 15:00:24 -0400

On Sat, Sep 24, 2011 at 2:22 PM, Duckworth, Mark <[email-masked]
> wrote:

> Hi Roni,****
>
> ** **
>
> Let me see if I understand.  Is this what you mean?****
>
> The side that receives video can send some information about its physical
> display placement (size of gap between displays).
>

There is really both a physical gap, and an angular gap.

I would argue that the appropriate metaphor here is a window frame (to be
specific, picture a double hung casement window with vertical sight blockage
between the two sashes -
http://en.wikipedia.org/wiki/File:Gordijnen_aan_venster.JPG ). If I look out
the window right now where I am, I see people crossing behind the join
between the sashes. I will call this a vertical obstruction, again just to
be specific.

There are several things I would want if I was going to replace this view
with a telepresence view, with one screen per sash.

1.) That there be no glitch in time or space as someone passes from one
screen to the next.  Even if the monitors are perfectly synced, if the
vertical obstruction is wider or narrower in the remote room than it is in
the video capture side, that will come across as a glitch in time (i.e.,
your mind will predict that the face or whatever should appear before or
after it actually does). It produces a stutter in what should be a smooth
motion.

This is highly noticeable.

Similar things could be said about differences in scale or orientation, but
is less common that different screen formats abut each other.

2.) That someone who is standing behind the vertical obstruction appears
normal (for example, that we never see more than the usual number of eyes,
and that the face appears to be the right width). This will be tough in some
units (it was a weakness in the old projected Telepresence units).

Now, here is a further complication :

There also can be barrel distortions in the vertical obstruction (in other
words, the actual gap or overlap may not be a vertical line, but a curve).
Typically, this would be smallest mid-level, and would increase going up and
down.  Notice that this means that you could have both a gap and an overlap,
depending on where you are vertically.

These complications are, of course, why typical units try really hard to
keep people from sitting behind a gap.

> ****
>
> The side that sends video might be able to use this information to
> automatically adjust its cameras (pan and zoom) or video cropping and
> scaling parameters such that the image rendered on the receiving side looks
> continuous, taking into account the gap between displays.****
>
> **
>

This is a case where adjustment might be done on both sides. Suppose my unit
has a continuous capture, with no vertical obstruction. If the receive side
knows this, and it has a vertical obstruction, it might usefully crop the
received video to impose the right gap.

Regards
Marshall

> **
>
> Mark Duckworth****
>
> ** **
>
> *From:* [email-masked] [mailto:[email-masked]] *On Behalf Of
> *Roni Even
> *Sent:* Saturday, September 24, 2011 3:25 AM
> *To:* [email-masked]
> *Subject:* [clue] Support for information about the spacing between
> monitors.****
>
> ** **
>
> Hi,****
>

---

From: Roni Even <[email-masked]>
Date: Sat, 24 Sep 2011 22:46:43 +0300

Hi Mark,

It is the other way. The side that send the video calibrated the local
capture, so it provides the information about what is the gap in the
capture.

This allow multiple receiver to get the same capture and crop or scale to
adjust for their gap.

Roni

From: [email-masked] [mailto:[email-masked]] On Behalf Of
Duckworth, Mark
Sent: Saturday, September 24, 2011 9:23 PM
To: [email-masked]
Subject: Re: [clue] Support for information about the spacing between
monitors.

Hi Roni,

The side that sends video might be able to use this information to
automatically adjust its cameras (pan and zoom) or video cropping and
scaling parameters such that the image rendered on the receiving side looks
continuous, taking into account the gap between displays.

Mark Duckworth

From: [email-masked] [mailto:[email-masked]] On Behalf Of Roni
Even
Sent: Saturday, September 24, 2011 3:25 AM
To: [email-masked]
Subject: [clue] Support for information about the spacing between monitors.

Hi,

compensation.

Regards

Roni Even

---

From: Stephen Botzko <[email-masked]>
Date: Sat, 24 Sep 2011 16:34:46 -0400

Ok.  So you are suggesting that we should support signaling gaps between
captures, not that we should be signaling gaps between monitors???

Regards
Stephen Botzko

On Sat, Sep 24, 2011 at 3:46 PM, Roni Even <[email-masked]> wrote:

> Hi Mark,****
> capture.****
> adjust for their gap.****
>
> Roni****
>
> ** **
>
> *Duckworth, Mark
> *Sent:* Saturday, September 24, 2011 9:23 PM
> *To:* [email-masked]
> *Subject:* Re: [clue] Support for information about the spacing between
> monitors.****
>
> ** **
>
> Hi Roni,****
>
> ** **
>
> display placement (size of gap between displays).****
>

---

From: Roni Even <[email-masked]>
Date: Sun, 25 Sep 2011 00:29:47 +0300

Hi Steve,

I suggest gap between monitors but on the sender size. The sender calibrates
the local view based on the local gap. By providing this gap in pixels the
receiver side can crop or scale.

Roni

From: Stephen Botzko [mailto:[email-masked]] 
Sent: Saturday, September 24, 2011 11:35 PM
To: Roni Even
Cc: Duckworth, Mark; [email-masked]
Subject: Re: [clue] Support for information about the spacing between
monitors.

Regards
Stephen Botzko

Hi Mark,

Roni

Hi Roni,

Mark Duckworth

Hi,

Regards

Roni Even

---

From: Stephen Botzko <[email-masked]>
Date: Sat, 24 Sep 2011 21:20:53 -0400

I don't think I understand what you mean by "calibrate the local view based
on the local gap".

Steve

On Sat, Sep 24, 2011 at 5:29 PM, Roni Even <[email-masked]> wrote:

> Hi Steve,****
>
> I suggest gap between monitors but on the sender size. The sender
> calibrates the local view based on the local gap. By providing this gap in
> pixels the receiver side can crop or scale.****
>
> ** **
>
> Roni****
>
> ** **
>
> *From:* Stephen Botzko [mailto:[email-masked]]
> *Sent:* Saturday, September 24, 2011 11:35 PM
> *To:* Roni Even
> *Cc:* Duckworth, Mark; [email-masked]
>
> Stephen Botzko****
> On Sat, Sep 24, 2011 at 3:46 PM, Roni Even <[email-masked]> wrote:**
> **
>
> Hi Mark,****
>
> https://www.ietf.org/mailman/listinfo/clue****
>
> ** **
>

---

From: Roni Even <[email-masked]>
Date: Sun, 25 Sep 2011 15:41:37 +0300

Hi,

What I mean is that the local capture is fixed based on the gap between the
local monitors such that a person that stands between two cameras will look
correct on the local two displays, There will be a missing part that is
proportional  to the gap. This is based on the gaps between the local
monitors.

Now if the remote monitors will have the same gap (In pixels) the rendering
on the receiver will look the same as the local display, otherwise the
renderer will need to adjust.

Roni

From: Stephen Botzko [mailto:[email-masked]] 
Sent: Sunday, September 25, 2011 4:21 AM
To: Roni Even
Cc: Duckworth, Mark; [email-masked]
Subject: Re: [clue] Support for information about the spacing between
monitors.

Steve

Hi Steve,

Roni

Regards
Stephen Botzko

Hi Mark,

Roni

Hi Roni,

Mark Duckworth

Hi,

Regards

Roni Even