Webcam Synopsis: Peeking Around the World
School of Computer Science and Engineering
The Hebrew University of Jerusalem
91904 Jerusalem, Israel
The world is covered with millions of webcams, many
transmit everything in their
eld of view over the Internet
24 hours a day. A web search
nds public webcams in air-
ports, intersections, classrooms, parks, shops, ski resorts,
and more. Even more private surveillance cameras cover
many private and public facilities. Webcams are an endless
resource, but most of the video broadcast will be of little
interest due to lack of activity.
We propose to generate a short video that will be a syn-
opsis of an endless video streams, generated by webcams
or surveillance cameras. We would like to address queries
like “I would like to watch in one minute the highlights
of this camera broadcast during the past day”. The pro-
cess includes two major phases: (i) An online conversion
of the video stream into a database of objects and activities
(rather than frames). (ii) A response phase, generating the
video synopsis as a response to the user’s query.
To include maximum information in a short synopsis we
simultaneously show activities that may have happened at
different times. The synopsis video can also be used as an
index into the original video stream.
Millions of webcams and surveillance cameras are cov-
ering the world, capturing their
eld of view 24 hours a day.
It is reported that in the UK alone there are 4.2 million se-
curity cameras covering city streets. Many webcams even
transmit their video publicly over the Internet for everyone
to watch. Several web sites try to index webcams by loca-
tion or by functionality, and there is still much to be done in
order to better organize this endless resource.
One of the problems in utilizing webcams is that they
provide unedited raw data. A two hours feature
lm, for ex-
ample, is usually created from hundreds or even thousands
This research was supported (in part) by grants from the Israeli Min-
istry of Science and from Google.
of hours of raw video footage. Without editing, most of the
webcam data is irrelevant. Also, a viewer in one continent is
likely to reach a webcam in another continent during hours
of non-activity because of time-zone differences.
Our work tries to make the webcam resource more use-
ful by giving the viewer the ability to view summaries of
the endless video, in addition to the live video stream pro-
vided by the camera. To enable this, a server can view the
live video feed, analyze the video for interesting events, and
record an object-based description of the video. This de-
scription lists for each webcam the interesting objects, their
duration, location, and their appearance. In a 3D space-
time description of the video, each object is a “tube”. In
this paper we assume that moving objects are interesting, as
well as phase transitions when a moving object turns into
background and vice versa. Other criteria, e.g. using object