The Interface
The top half of the basic GrabboCam interface is the menu bar
and the current video input feed; the bottom half contains most
of the application's controls. The controls are organized in several
categories: recording, ftp, detection, and notices. Between the
controls and the video image there is a status display for messages.
From the File menu you can access the Video Preferences,
where you can set your prefered default video input device. This
setting can also be done from the Media Preferences, but for the
changes to take effect, you will have to restart GrabboCam (that
is if it is running). As with the other video recording / capturing
programs under Zeta, GrabboCam will also always open the device
at 320x240.
Recording
If you are to start using GrabboCam regularly, with high framerates,
the recordings will occupy a significant amount of space. A small
security is therefore built in to GrabboCam, and it will not be
able to fill up more then 98 % of your hard drive's capacity! When
the limit is reached, old recordings are deleted until the drive
is 95% full. If you have purcased Zeta for mainly doing video related
work, we strongly recommend that you get your self a separate partition
for these files, or even an extra internal/external hard drive.
GrabboCam lets you set the application's local directory, which
is the local folder that it will save the recordings to. By clicking
the browse button you will be able to select a different
local folder. We strongly recommend that you keep your video files
in on place (folder), as it would make it far easier for you to
back up these files.
GrabboCam can be your "SpyCam" as you can set timestamps
in your recordings. When this option is selected, each still and
movie frame recorded will be timestamped with the current date and
time. That will be good enough evidence when somebody is stealing
food from your fridge during the night!
The Movies controls how your movies are created. If you
are running a Pentium 3 or faster, you will easily be able to get
30fps using the Indeo5 Realtime Video codec. Another fast codec
is the Photo JPEG, but your mileage may vary.
Movies are created with a filename based on the date and time of
the recording: YYYYMMDDHHmmss.ext, where YYYY=year, MM=month, DD=day,
HH=hour, mm=minutes, ss=seconds, and ext=avi or mov (the two file
formats you can save the videos to).
The option record movie at motion start will create a new
movie whenever GrabboCam detects motion (again think of the SpyCam).
To avoid missing the onset of motion, the movie will actually start
several frames before the motion was detected and the recording
will stop automatically several frames after the motion stops.
From the Format option you can select the file format you
want to use for your movie.
GrabboCam lets you use various codecs (compression schemes) for
your recordings, and you can select the frame rate which GrabboCam
is to run. GrabboCam also lets you take pictures (stills) using
the JPEG codec, and also for pictures you have the option make the
application start recording at motion start. Filenames are of a
form similar to that used for movies: YYYYMMDDHHmmss.jpg. Another
option is to record pictures periodically (stills recorded at a
regular intervals). When you are setting your system to take periodical
recordings, once again disk space becomes an important issue. GrabboCam
therefore lets you control the rate at which the pictures are periodically
recorded. For you to easily keep track of your recordings, you can
use
fixed filename.
FTP
As CodyCam, GrabboCam
lets you publish your recordings to a FTP
server. If you are to run a webserver like PoorMan,
RobinHood, or Apache on the same system as GrabboCam, or don't care
about web access to your recordings, you can forget this tab. It's
possible that you can be making recordings faster than they can
be uploaded (esp. at high framerates). You can adjust the framerate,
the still recording period or the detection sensitivity to help
in these situations. Uploads are queued by GrabboCam, and only one
can be underway at any time. The queue does not survive reboots.
You can publish both movies and pictures. When it comes to movies,
they will first be published after the recording has ended.
For you to publish the recordings, you would need to now the hostname
of the FTP server (or it's IP address), and you would in most cases
need both an account and a password. In some cases you would also
only be able to publish the recordings to a specific directory,
and in those cases you will also have to add the path in these settings.
Detection
A few words about how GrabboCam detects motions. The application
uses an "adaptive background subtraction" algorithm to
detect motion, as it assumes that incoming video is of a static
scene. When motion occasionally occurs, such as a stationary camera
on an indoor scene, the background is "learned" in the
first few seconds after starting GrabboCam. Small, gradual changes,
such as those due to the passing of the sun, are used to update
the background model. Large or sudden changes, when present for
several frames, trigger a motion event, and recordings are then
made if enabled. This technique works relatively well on outdoor
scenes as well, but can be triggered by clouds transiting the sun,
or when leaves or branches (or their shadows) are moved by the wind.
You can mask out regions you want the motion detector to ignore,
such as trees or passing traffic, by using the edit mask
feature. The option brings up a window with a low-resolution image
of the scene. By using the left mouse button, you can draw a blob
over the areas that you want the detector to ignore. You use the
right mouse button to clear the mask. The mask will be saved when
you exit GrabboCam, and automatically reloaded the next time you
start GrabboCam.
You can even adjust the application's sensitivity, from 1 (least
sensitive) to 10 (most sensitive). An option is to enable crosshair,
which will draw a line at the center of the largest moving object
detected.
Notices
When motion is detected, you can get an alert to an email notice,
or set the system to play a selected audio file.
When you are selecting that you want the alerts in form of emails,
you will have to add your address and the link to put in the email
(an URL that will be included in the email), to make it easy for
you or other recipients to launch a browser to the webcam page.
When choosing a sound as your alert, choosing the right sound is
important. GrabboCam supports the following file formats: .wav,
.au, and .aif . Note that there is no support for MP3. In general
most people would like to use a short, attention-grabbing sound,
that will cut through any audio you happen to be listening to. The
sound will be kept in RAM for low-latency response. Use the "browse"
button to pick your own sound file.
MIDI
GrabboCam will create a MIDI endpoint called "MotionTracker"
that you can connect to any MIDI synth, internal or external. For
example, after starting GrabboCam, you can launch the MidiPlayer
application, and select MotionTracker in MidiPlayer's Live input
menu. Use the PatchBay application to connect MotionTracker to an
external connector.
Note messages are sent, based on the center of the largest moving
object (crosshair position): Low notes on the left of the image,
high notes on the right. Velocity is based on the y-value of the
motion center: large velocities at the bottom of the image, low
velocities at the top. In typical camera setups, where the camera
is looking out and slightly down at the ground, this corresponds
to distant objects causing quieter notes than close objects. It's
possible to learn to tell in which direction objects are moving
based the musical phrase produced, and even tell if they were passing
cars, pedestrians, or birds based on the rate notes change, etc.
You also just point the camera at yourself, in front of any static
background, and have fun waving your hand around, if you're easily
amused.
Usage
GrabboCam is meant to be used with a stationary camera, looking
on a scene where motion is relatively rare. If a portion of the
scene has motion you want to ignore (such as passing traffic), you
can mask out that portion using the mask editor (on the "detection"
tab).
Using television as source of video is not usually a good idea,
since things are constantly in motion on TV. Beware that anytime
you use television as a source of video you can expect GrabboCam
to be recording almost continuously, which can rapidly eat up disk
space (GrabboCam's disk space recycler will avoid the disk from
overflowing, of course).
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