WEBVTT

00:00:00.000 --> 00:00:05.550 align:middle line:90%


00:00:05.550 --> 00:00:10.630 align:middle line:84%
So now we're going to talk about
the calibration of the system.

00:00:10.630 --> 00:00:14.460 align:middle line:84%
So what do we actually
do when we calibrate?

00:00:14.460 --> 00:00:18.990 align:middle line:84%
Calibration is a process
of allowing the system

00:00:18.990 --> 00:00:23.400 align:middle line:84%
to get an idea of first, how the
cameras are situated relative

00:00:23.400 --> 00:00:27.240 align:middle line:84%
to each other, and then, how the
cameras are situated relative

00:00:27.240 --> 00:00:29.220 align:middle line:90%
to the floor.

00:00:29.220 --> 00:00:32.700 align:middle line:84%
And so this is done
through kind of a process

00:00:32.700 --> 00:00:35.910 align:middle line:84%
of reverse triangulation
compared to what

00:00:35.910 --> 00:00:39.030 align:middle line:90%
happens during the actual take.

00:00:39.030 --> 00:00:44.100 align:middle line:90%
So we use the calibration wands.

00:00:44.100 --> 00:00:47.730 align:middle line:84%
And the system knows the
distance between these two

00:00:47.730 --> 00:00:52.230 align:middle line:84%
markers, and so it's able to use
its knowledge of that distance

00:00:52.230 --> 00:00:54.210 align:middle line:84%
to triangulate the
position of all

00:00:54.210 --> 00:00:58.120 align:middle line:84%
of the cameras
relative to each other.

00:00:58.120 --> 00:01:01.260 align:middle line:84%
And this ground plane
tells the system

00:01:01.260 --> 00:01:04.379 align:middle line:84%
where the ground is
so it can figure out

00:01:04.379 --> 00:01:08.790 align:middle line:84%
how the cameras are situated
relative to this plane.

00:01:08.790 --> 00:01:12.570 align:middle line:84%
And it also have another
function for the system

00:01:12.570 --> 00:01:17.380 align:middle line:84%
because it's creating the
virtual coordinate system.

00:01:17.380 --> 00:01:20.010 align:middle line:84%
So this is actually
what we are recording

00:01:20.010 --> 00:01:21.570 align:middle line:90%
when we are recording.

00:01:21.570 --> 00:01:22.540 align:middle line:90%
Where is my marker?

00:01:22.540 --> 00:01:27.960 align:middle line:90%


00:01:27.960 --> 00:01:31.290 align:middle line:84%
So when we are doing
recordings, what we actually get

00:01:31.290 --> 00:01:33.780 align:middle line:90%
is numbers for each marker.

00:01:33.780 --> 00:01:37.350 align:middle line:84%
And these numbers, they relate
to this coordinate system

00:01:37.350 --> 00:01:38.950 align:middle line:90%
that we just made.

00:01:38.950 --> 00:01:40.690 align:middle line:90%
So here are the axis.

00:01:40.690 --> 00:01:44.250 align:middle line:84%
So you have like, one
dimension, the first dimension,

00:01:44.250 --> 00:01:48.240 align:middle line:84%
the second dimension, and
the third dimension up here.

00:01:48.240 --> 00:01:51.660 align:middle line:84%
And then the system
measure where

00:01:51.660 --> 00:01:55.290 align:middle line:84%
this marker is
and in millimetres

00:01:55.290 --> 00:01:57.570 align:middle line:90%
relative to this axis.

00:01:57.570 --> 00:01:58.710 align:middle line:90%
Very precisely.

00:01:58.710 --> 00:02:01.500 align:middle line:90%
Yeah, very precisely.

00:02:01.500 --> 00:02:06.750 align:middle line:84%
So to take the process
of calibration,

00:02:06.750 --> 00:02:08.759 align:middle line:84%
the first thing
you want to do is

00:02:08.759 --> 00:02:12.270 align:middle line:84%
to clear the space of any
other possible markers.

00:02:12.270 --> 00:02:18.000 align:middle line:84%
Yes, so I have to
remove this [LAUGHS]

00:02:18.000 --> 00:02:26.370 align:middle line:84%
and hide it so it can't be
seen by any of the cameras.

00:02:26.370 --> 00:02:31.930 align:middle line:90%


00:02:31.930 --> 00:02:36.900 align:middle line:84%
The reason for this is that
any other markers or reflective

00:02:36.900 --> 00:02:40.920 align:middle line:84%
spots that are visible during
the calibration process

00:02:40.920 --> 00:02:44.280 align:middle line:84%
will cause an interference,
and usually the system

00:02:44.280 --> 00:02:46.080 align:middle line:84%
will complain that it
can see other markers

00:02:46.080 --> 00:02:49.252 align:middle line:84%
and you need to move them
before you can calibrate.

00:02:49.252 --> 00:02:50.550 align:middle line:90%
[MUSIC PLAYING]

00:02:50.550 --> 00:02:52.902 align:middle line:84%
Do you want to demonstrate
your technique?

00:02:52.902 --> 00:02:57.060 align:middle line:90%
[LAUGHTER]

00:02:57.060 --> 00:03:01.650 align:middle line:84%
So we also set the
calibration space.

00:03:01.650 --> 00:03:06.210 align:middle line:84%
So it's important
that you move about

00:03:06.210 --> 00:03:10.800 align:middle line:84%
because if I just stand
here, then I will actually

00:03:10.800 --> 00:03:13.620 align:middle line:90%
occlude these markers--

00:03:13.620 --> 00:03:16.200 align:middle line:90%
or I mean, occlude that camera.

00:03:16.200 --> 00:03:18.825 align:middle line:84%
So it's important
that I move around.

00:03:18.825 --> 00:03:21.690 align:middle line:90%


00:03:21.690 --> 00:03:25.560 align:middle line:84%
And also make sure
if the recording

00:03:25.560 --> 00:03:29.770 align:middle line:84%
will also happen quite
high up, that's important.

00:03:29.770 --> 00:03:34.020 align:middle line:84%
The floor, you can make
a dance if you want.

00:03:34.020 --> 00:03:50.600 align:middle line:90%
[MUSIC PLAYING]

00:03:50.600 --> 00:03:53.030 align:middle line:84%
And so as she's doing
this, the cameras

00:03:53.030 --> 00:03:55.400 align:middle line:84%
are constantly
collecting samples

00:03:55.400 --> 00:03:56.960 align:middle line:84%
at a very-- well,
at the frame rate

00:03:56.960 --> 00:04:00.410 align:middle line:84%
that you're intending
to capture at.

00:04:00.410 --> 00:04:04.100 align:middle line:84%
And so she's moving
around and trying

00:04:04.100 --> 00:04:07.790 align:middle line:84%
to show the wand to all
of the cameras in as much

00:04:07.790 --> 00:04:09.890 align:middle line:84%
of their visual
field as she can.

00:04:09.890 --> 00:04:16.430 align:middle line:90%
[MUSIC PLAYING]

00:04:16.430 --> 00:04:18.529 align:middle line:84%
And if you need a
large space, you

00:04:18.529 --> 00:04:22.310 align:middle line:84%
can also set the
calibration time.

00:04:22.310 --> 00:04:26.110 align:middle line:84%
It can have a longer
calibration time.

00:04:26.110 --> 00:04:34.120 align:middle line:90%
[VOCALISING] [LAUGHS]

00:04:34.120 --> 00:04:37.720 align:middle line:10%
When I'm capturing
musicians, usually I'm

00:04:37.720 --> 00:04:39.640 align:middle line:10%
quite careful about
the orientation

00:04:39.640 --> 00:04:41.350 align:middle line:10%
that I use when I place this.

00:04:41.350 --> 00:04:44.710 align:middle line:10%
For instance, if I'm
capturing pianists

00:04:44.710 --> 00:04:47.560 align:middle line:10%
who are moving quite
a lot back and forth

00:04:47.560 --> 00:04:49.810 align:middle line:10%
and forwards and
backwards, then I

00:04:49.810 --> 00:04:53.050 align:middle line:10%
would set this axis so that
it's parallel to the direction

00:04:53.050 --> 00:04:57.400 align:middle line:10%
where I expect them to move
so that it's easy to isolate

00:04:57.400 --> 00:04:59.560 align:middle line:10%
that movement afterwards.

00:04:59.560 --> 00:05:03.460 align:middle line:10%
And also because I sometimes
need quite large volume,

00:05:03.460 --> 00:05:05.140 align:middle line:10%
I sometimes extend--

00:05:05.140 --> 00:05:09.880 align:middle line:10%
so it's often like a
default setting or duration

00:05:09.880 --> 00:05:12.160 align:middle line:10%
of a calibration,
and I quite often

00:05:12.160 --> 00:05:14.650 align:middle line:10%
extend that a bit so
I have some more time

00:05:14.650 --> 00:05:19.770 align:middle line:10%
to get a really good calibration
and to get the whole volume

00:05:19.770 --> 00:05:22.090 align:middle line:10%
good calibrated.

00:05:22.090 --> 00:05:25.120 align:middle line:10%
And I guess for the
things that I do,

00:05:25.120 --> 00:05:28.930 align:middle line:10%
I also find it very important
to calibrate a much larger area

00:05:28.930 --> 00:05:31.570 align:middle line:10%
than I anticipate using.

00:05:31.570 --> 00:05:35.440 align:middle line:84%
In the past, I've had
difficult situations when

00:05:35.440 --> 00:05:36.730 align:middle line:90%
there was a lot of musicians.

00:05:36.730 --> 00:05:38.560 align:middle line:10%
For instance, with
a string quartet

00:05:38.560 --> 00:05:40.690 align:middle line:10%
where we had a kind
of concert situation

00:05:40.690 --> 00:05:44.270 align:middle line:10%
and there was not a whole
lot of space around them,

00:05:44.270 --> 00:05:46.330 align:middle line:10%
we had a bit of an
issue where some of them

00:05:46.330 --> 00:05:48.460 align:middle line:10%
were very much at the
edge of the capture

00:05:48.460 --> 00:05:50.350 align:middle line:10%
space of the calibrated area.

00:05:50.350 --> 00:05:52.390 align:middle line:10%
And then you end up
getting a lot of noise

00:05:52.390 --> 00:05:54.820 align:middle line:10%
and losing some of
the markers so--

00:05:54.820 --> 00:05:57.100 align:middle line:10%
Yeah, because there's
more noise like in the--

00:05:57.100 --> 00:05:59.470 align:middle line:10%
--towards the edge of
the calibrated area.

00:05:59.470 --> 00:06:03.370 align:middle line:84%
But what do you do when
you-- when you are recording

00:06:03.370 --> 00:06:04.050 align:middle line:90%
pianists?

00:06:04.050 --> 00:06:08.440 align:middle line:84%
So do you remove the
instrument before calibrating?

00:06:08.440 --> 00:06:08.980 align:middle line:90%
Yeah.

00:06:08.980 --> 00:06:13.670 align:middle line:10%
I would take everything
out of the area.

00:06:13.670 --> 00:06:15.640 align:middle line:84%
If you have the piano,
that's if you're--

00:06:15.640 --> 00:06:18.182 align:middle line:84%
people are going to play piano
and you have the piano sitting

00:06:18.182 --> 00:06:21.010 align:middle line:84%
here, then that's space
that you cannot calibrate.

00:06:21.010 --> 00:06:23.405 align:middle line:10%
And it's especially
important if you

00:06:23.405 --> 00:06:25.030 align:middle line:10%
are expecting that
the people are going

00:06:25.030 --> 00:06:26.740 align:middle line:10%
to be very near to that space.

00:06:26.740 --> 00:06:28.720 align:middle line:84%
For instance if you're
tracking their hands,

00:06:28.720 --> 00:06:31.030 align:middle line:84%
and then you're not going
to calibrate the space where

00:06:31.030 --> 00:06:33.470 align:middle line:84%
their hands are going to be,
then that's pretty dangerous.

00:06:33.470 --> 00:06:37.060 align:middle line:84%
So I would take everything
away and bring them back

00:06:37.060 --> 00:06:38.590 align:middle line:90%
after everything's calibrated.

00:06:38.590 --> 00:06:39.910 align:middle line:10%
Yeah.

00:06:39.910 --> 00:06:44.110 align:middle line:10%
And then I guess you
also get not so many--

00:06:44.110 --> 00:06:46.750 align:middle line:10%
that you don't have to mask
so much because there's not

00:06:46.750 --> 00:06:48.460 align:middle line:10%
so many things that--

00:06:48.460 --> 00:06:51.960 align:middle line:10%
Yeah, actually pianos are really
shiny, especially grand pianos.

00:06:51.960 --> 00:06:54.670 align:middle line:10%
And so you would
end up marking--

00:06:54.670 --> 00:06:56.680 align:middle line:10%
actually masking
a lot of the space

00:06:56.680 --> 00:06:59.920 align:middle line:10%
where the people are expected
to move, especially on the keys.

00:06:59.920 --> 00:07:02.360 align:middle line:90%
The keys are very shiny.

00:07:02.360 --> 00:07:05.560 align:middle line:84%
So then you would be
disqualifying some of the space

00:07:05.560 --> 00:07:06.852 align:middle line:90%
that you want to capture in.

00:07:06.852 --> 00:07:08.330 align:middle line:90%
Yeah.

00:07:08.330 --> 00:07:12.100 align:middle line:84%
And do you have these problems
as well with the dancers

00:07:12.100 --> 00:07:13.600 align:middle line:90%
and the violinists

00:07:13.600 --> 00:07:18.560 align:middle line:84%
Not so much with the dancers but
sometimes with the instruments.

00:07:18.560 --> 00:07:23.320 align:middle line:84%
But yeah, I also get rid of
everything before I calibrate.

00:07:23.320 --> 00:07:27.100 align:middle line:90%
And chairs and-- yeah.

00:07:27.100 --> 00:07:29.560 align:middle line:10%
And do you have any
problems with calibrating

00:07:29.560 --> 00:07:32.950 align:middle line:10%
when you have these kind of
setups where the cameras are

00:07:32.950 --> 00:07:35.770 align:middle line:10%
focused on different locations?

00:07:35.770 --> 00:07:36.400 align:middle line:10%
No.

00:07:36.400 --> 00:07:38.710 align:middle line:10%
I just have to-- you have
to remember that when

00:07:38.710 --> 00:07:42.850 align:middle line:10%
you calibrate so you really get
a good calibration of the space

00:07:42.850 --> 00:07:45.160 align:middle line:10%
that you were going to use.

00:07:45.160 --> 00:07:45.880 align:middle line:10%
Yeah.

00:07:45.880 --> 00:07:50.230 align:middle line:10%
I found it very good with
the OptiTrack system.

00:07:50.230 --> 00:07:52.720 align:middle line:10%
Because while
you're calibrating,

00:07:52.720 --> 00:07:55.420 align:middle line:10%
then you can see for
each camera individually

00:07:55.420 --> 00:07:57.460 align:middle line:10%
how many samples have
been taken and which

00:07:57.460 --> 00:08:00.100 align:middle line:10%
part of the visible
space for each camera

00:08:00.100 --> 00:08:01.420 align:middle line:10%
has been calibrated.

00:08:01.420 --> 00:08:03.430 align:middle line:10%
But not all systems
give you this kind

00:08:03.430 --> 00:08:05.810 align:middle line:10%
of real-time feedback.

00:08:05.810 --> 00:08:06.535 align:middle line:10%
Yeah, true.

00:08:06.535 --> 00:08:08.722 align:middle line:10%
Yeah, you're really painting
with a-- with a wand.

00:08:08.722 --> 00:08:09.222 align:middle line:90%
Yeah.

00:08:09.222 --> 00:08:12.386 align:middle line:90%


00:08:12.386 --> 00:08:13.090 align:middle line:90%
That's good.

00:08:13.090 --> 00:08:13.590 align:middle line:90%
That's it.

00:08:13.590 --> 00:08:13.890 align:middle line:90%
Right?

00:08:13.890 --> 00:08:14.390 align:middle line:90%
[LAUGHTER]

00:08:14.390 --> 00:08:16.590 align:middle line:84%
That's all we need
to say about that.

00:08:16.590 --> 00:08:19.940 align:middle line:10%
[MUSIC PLAYING]

00:08:19.940 --> 00:08:24.000 align:middle line:90%