ISSUE 53 Expert Witness Journal - Journal - Page 27
Introduction to Computer
Vision and the Role it Plays in
Forensic Investigations
Technological Advancements in Media and the Limitations of Human Intelligence
Rapid technological advancements in the field of
digital photography have meant that the consumption of digital media has become accessible to everyone. Thanks to constant improvements in resolution,
and encrypted cloud storage offering almost-infinite
storage spaces, many companies can safely analyse a
huge library of high-quality media in the order of gigabytes, or even terabytes at a time depending on
computer processing power.
been investigating this since the 1950s and it is this research that gave rise to what we presently call Artificial
Intelligence (AI).
In the context of images and videos, this research
resulted in a unique field called Computer Vision
(CV), which is the study of programming computers
and systems to automatically obtain, interpret, and
analyse digital imagery. AI is used to program the
computer so that it can mimic how human beings
analyse digital media.
These technological advancements also come with
new challenges in the field of forensics. Higher quality images and videos with higher frame rates mean
that we have exponentially more data to analyse.
Since business time is already a scarce commodity, it is
critically important that we develop workflows that enable us to make sense of this increased volume of data
more quickly.
Examples of CV Techniques
Optical Flow Tracking
The concept of ‘tracking’ is a simple one: pick a
feature point and then track its trajectory as seen on
the screen. As a result of millions of years of evolution, we humans perform this action instinctively. A
natural question is whether it is possible for a computer to track a specific part of a moving object. The
answer is ‘yes’, and the technique used is called
Optical Flow.
Despite humans having the capability to think
creatively and logically, our brains can only work with
a limited amount of data at a time. On the other hand,
computers have the advantage of being able to store
more data and perform calculations faster than an
average human being can. One question which arises
is whether it is possible to have the best of both worlds:
a computer that can mimic the beneficial
behaviours of human beings while exploiting the
superior speeds in which they handle data and memory. Computer scientists and mathematicians have
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The standard algorithm used for tracking features is
called the ‘Lucas-Kanade Optical Flow Method’. This
algorithm calculates the relative displacement vector
of a feature between two consecutive images. The algorithm assumes that the relative motion of the
feature is small and is not affected by sudden changes
in colour and contrast.
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