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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
There's more seats on the side, but people are walking in late.
0
7
NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, just to make sure you're in CS231N, the deep learning on your network class for visual recognition.
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23
NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Anybody in the wrong class? Good. All right, so welcome and happy new year, happy first day of winter break.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, this class CS231N, this is the second offering of this class when we have literally doubled our enrollment from 180 people last time we offered to about 350 of you signed up.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Just a couple of words to make us all legally covered. We are video recording this class.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, you know, if you're uncomfortable about this, for today just go behind a camera or go to a corner that the camera is not gonna turn.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
But we are going to send out forms for you to fill out in terms of allowing a video recording. So, that's just one bit of housekeeping.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, all right, my name is Fei-Fei Li, I'm a professor at the computer science department.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, this class, I'm co-teaching with two senior graduate students and one of them is here is Andre Kapathy. Andre, can you just say hi to everybody?
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
We have, well, I don't think Andre needs too much introduction. A lot of you probably know his work, follow his blog, his Twitter follower.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Andre has way more followers than I do. He's very popular. And also Justin Johnson, who is still traveling internationally but will be back in a few days.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, Andre and Justin will be picking up the bulk of the lecture teaching. And today I will be giving the first lecture but as you probably can see that I'm expecting a newborn ratio speaking of weeks.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, you'll see more of Andre and Justin in lecture time. We will also introduce a whole team of TAs towards the end of this lecture.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Again, people who are looking for seats, if you go out of that door and come back, there is a whole bunch of seats on this side.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, for this lecture we're going to give an introduction of the kind of problems we work on and the tools we'll be learning.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, again, welcome to CS231 and this is a vision class. It's based on a very specific modeling architecture called Neur Network and even more specifically, mostly on convolutional Neur Network.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And a lot of you hear this term maybe through a popular press article or coverage we tend to call this the Deep Learning Network.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
But, vision is one of the fastest growing field of artificial intelligence. In fact, Cisco has estimated and we are on day four of this by 2016, which we already have arrived, more than 85% of the internet, cyber space data is in the form of pixels.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Or what they call multimedia. So, we basically have entered an age of vision, of images and videos. And why is this so?
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Well, partly, a large extent is because of the explosion of both the internet as a carrier of data, as well as sensors. We have more sensors than the number of people on Earth these days.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Every one of you is carrying some kind of smartphones, digital cameras and cars running on the street with the cameras. So, the sensors have really enabled the explosion of visual data on the internet.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
But, visual data or pixel data is also the hardest data to harness. So, if you have heard my previous talks and some other talks by computer vision professors, we call this the dark matter of the internet.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Why is this the dark matter? Just like the universe is consisted of 85% dark matter, dark energy. It's this matters energy that is very hard to observe. We can infer it by mathematical models in the universe.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
On the internet, these are the matters. Pixel data are the data that we don't know. We have a hard time grasping the contents. Here's one very simple spec for you to consider.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, today, YouTube servers for every 60 seconds, we have more than 150 hours of videos uploaded onto YouTube servers. For every 60 seconds, think about the amount of data.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
There's no way that human eyes can sift through this massive amount of data and make annotations labeling it and describe the contents.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, think from the perspective of the YouTube team or Google company. If they want to help us to search, index, manage, and of course, for their purpose, put an advertisement or whatever, manipulate the content of the data, we're at loss.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Because nobody can hand annotators. The only hope we can do this is through vision technology to be able to label the objects, find the scenes, find the frames, locate where that basketball video where Kobe Bryant is making that awesome shot.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, these are the problems that we are facing today. The massive amount of data and the challenges of the dark matter.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, computer vision is a field that touches upon many other fields of studies. So, I'm sure that even sitting here, sitting here, many of you come from computer science, but many of you come from biology, psychology,
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
are specializing in natural language processing, or graphics, or robotics, or medical imaging, and so on.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, as a field, computer vision is really a truly interdisciplinary field. The problems we work on, the models we use, touches on engineering, physics, biology, psychology, computer science, and mathematics.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, just a little bit of a more personal touch. I am the director of the computer vision lab at Stanford. In our lab, I work with graduate students and postdocs, and even other graduate students on a number of topics, and most dear to our own research, who some of them, you know, the Andre Justin come from my lab, a number of TAs come from my lab.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
We work on machine learning, which is a super set of deep learning. We work a lot on cognitive science, and neuroscience, as well as the intersection between an LPN speech.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, that's the kind of landscape of computer vision research that my lab works in.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, also to put things in a little more perspective, what are the computer vision classes that we offer here at Stanford through the computer science department?
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Clearly, you're in this class, CS21N, and so, some of you who have never taken computer vision, probably have heard of computer vision for the first time, probably should have already done CS113.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
CS113, that's an intro class of previous quarter we offered, and then next quarter, which normally is offered this quarter, but this year is a little shifted.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
There's an important graduate level computer vision class called CS231A, offered by Professor Sylvia Severese, who works in robotic and 3D vision.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And a lot of you ask us the question that, do these replace each other, this class CS231N versus CS231A, and the answer is no.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And if you're interested in a broader coverage of tools and topics of computer vision, as well as some of the fundamental topics that relates you to 3D vision, robotic vision, and visual recognition, you should consider taking 231A, that is the more general class.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
231N, which will go into starting today more deeply, focuses on a specific angle of both problem and model.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
The model is neural network, and the angle is visual recognition mostly.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Of course, they have a little bit of overlap, but that's the major difference. And next quarter, we also have possibly a couple of advanced seminar level class, but that's still in the formation stage, so you just have to check the syllabus.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So that's the kind of computer vision curriculum we offer this year at Stanford. Anything questions so far? Yes.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Is 131A not a strict requirement for this class, but you'll soon see that if you've never heard of computer vision for the first time, I suggest you find a way to catch up because this class assumes a basic level of understanding of of of computer vision.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
You can browse the notes and so on.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So the rest of today is that I will give a very brief broad stroke history of computer vision, and then we'll talk about 231N a little bit in terms of the organization of the class.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
I actually really care about sharing with you this brief history of computer vision because you know, you might be here primarily because of your interest in this really interesting tool called deep learning, and this is the purpose of this class, while offering you an index looking and just journey through what this deep learning model is.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
But without understanding the problem domain, without thinking deeply about what this problem is, it's very hard for you to go on to be an inventor of the next model that really solves a big problem in vision, or to be developing,
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
making impactful work in solving a hard problem, and also in general problem domain and model, the modeling tools themselves are never, never fully decoupled, they inform each other, and you see through the history of deep learning a little bit, that the convolution on your network architecture come from the need to solve the problem.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And then vision problem helps the deep learning algorithm to evolve and back and forth, so it's really important to, you know, I want you to finish this course and feel proud that your student of computer vision and of deep learning, so you have this both the tool set and the in depth understanding of how to use the tool set to tackle the problem.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So it's a brief history, but doesn't mean it's a short history, so we're going to go all the way back to 240 million years ago.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So why did I pick this, you know, on the scale of the Earth history, this is a fairly specific range of years. Well, so I don't know if you have heard of this, but this is a very, very curious period of the Earth's history.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And biologists call this the big band of evolution. Before 500, 40 million years ago, the Earth is a very peaceful part of water. I mean, it's pretty big part of water.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So we have very simple organisms. These are like animals that just floats in the water and the way they eat and hang out on a daily basis is, you know, they just float and if some kind of food comes by near their mouth or whatever, they just open the mouth and grab it.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And we don't have too many different types of animals, but something really strange happened around 540 million years.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Suddenly, from the fossils we study, there's a huge explosion of species. The biologists call it speciation.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
It's like suddenly, for some reason, something hit the Earth that animals start to diversify and they can get really complex and they start to, you know, to, you start to have predators and prey and then they have all kind of tools to survive.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And what was the triggering force of this was a huge question because people would say, oh, did you know, another set of whatever meteorite hit the Earth or, you know, the environment change.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
It turned out one of the most convincing theory is by this guy called Andrew Parker. He's a modern zoologist in Australia, from Australia. He studied a lot the fossils and his theory is that it was the onset of the ice.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, one of the first trilobites developed an eye and really, really simple light. It's almost like a pinhole camera that just catches light and makes some projections and registers some information from the environment.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Suddenly, life is no longer so mellow because once you have the eye, the first thing you can do is you can go catch food. You actually know where food is. You're not just like blind and floating in the water.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
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And once you can go catch food, guess what? The food better develops and to run away from you. Otherwise, they'll be gone, you know, you're, you're, so the first animal who had, had eyes were like in a, you know,
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CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
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in a limited buffet. It's like working at Google. It's, it's just like it has the best time, you know, eating everything they can. But because of this onset of the ice, what we, what the zoologist realized is the biological arms race began.
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CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
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Every single animal needs to needs to learn to develop things to survive or to, you know, you, you suddenly have praise and predators and, and all this. And the speciation began.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, that's when vision began. 540 million years. And not only vision began, vision was one of the major driving force of the speciation or the big band of evolution.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Alright, so, so we're not going to follow evolution for too much detail. Another big important work that focus on engineering of vision happened around the Renaissance.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And of course, it's attributed to this amazing guy Leonardo da Vinci. So, before Renaissance, you know, throughout human civilization, from Asia to Europe to India to Arabic world, we have seen models of cameras.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, Aristotle has proposed the camera through the leaves. Chinese philosopher Moots have proposed the camera through a box with a hole. But if you look at the first documentation of really a modern looking camera, it's called camera upscrewer, upscrewer.
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CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
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And that is documented by Leonardo da Vinci. I'm not going to get into the details. But this is, you know, you get the idea that there is some kind of lens or at least a hole to capture lights reflected from the real world.
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CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
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And then there is some kind of projection to capture the information of the real world image. So, that's the beginning of the modern, you know, engineering of vision.
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CS231n Winter 2016: Lecture1: Introduction and Historical Context
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And then it started with wanting to copy the world and wanting to make a copy of the visual world. It hasn't got anywhere close to wanting to engineer the understanding of the visual world. Right now, we're just talking about duplicating the visual world.
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CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, that's one important work to remember. And of course, after a camera upscrewer, we start to see a whole series of successful, you know, some film gets developed, you know, like Kodak was one of the first companies developing commercial cameras and then we start to have cancorders and all this.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Another very important, important piece of work that I want you to be aware of as vision student is actually not an engineering work, but a science, science piece of science work that's starting to ask the question is, how does vision work in our biological brain?
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
You know, we now know that it took 540 million years of evolution to get a really fantastic visual system in mammals and in humans. But what did evolution do during this time?
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And the kind of architecture did it develop from that simple trilobite to today yours and mine? Well, a very important piece of work happened at Harvard by two at that time young, two very young ambitious postdoc, Hugo and the visual.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And the thing that I wanted to do is that they used a wake but anesthetized cats and then there was enough technology to build this little needle called electrode to push the electrode into the, the, the, the, the skull is open into the brain of the cat into an area what we already know,
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
visual cortex primary visual cortex is an area that neurons do a lot of things for, for visual processing.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
But before you were a visual, we don't really know what primary visual cortex is doing. We just know it's one of the earliest stage other than your eyes, of course, but earliest stage for visual processing and there's tons and tons of neurons working on vision.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And then we really ought to know what this is because that's the beginning of vision visual process in the brain.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So they put this electrode into the primary visual cortex and interestingly this is another interesting fact, if I don't drop all my stuff I'll show you.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Primary visual cortex, the first stage or second, depending on where you come from, I'm being very, very rough, rough here.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
First stage of your cortical visual processing stage is in the back of your brain, not near your eye.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Okay, it's very interesting because your old factory cortical processing is right behind your nose, your auditory is right behind your ear, but your primary visual cortex is the furthest from your eye.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And another very interesting fact, in fact, not only the primary, there's a huge area working on vision, almost 50% of your brain is involved in vision.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Vision is the hardest and most important sensory perceptual cognitive system in the brain.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
You know, I'm not saying anything else doesn't, it's not, useful clearly, but you know, it takes nature this long to develop this sensory system and it takes nature this much real estate space to be used for this system.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Why? Because it's so important and it's so damn hard. That's why we need to use this much space.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
Okay, back to human viso, they were really ambitious. They want to know what primary visual cortex is doing, because this is the beginning of our knowledge for deep learning neural network.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, they were showing cats, so they put the cats in this room and they were recording neural activities. And when I say recording neural activity, they're basically trying to see, you know, if I put the neural electrode here, like to the neurons, to the neurons fire when they see something.
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1,459
NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, for example, if they show cats, their ideas, if I show this cat a fish, you know, apparently at that time cats eat fish rather than these beings.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
With the cats, neural, like, you know, they're happy and start sending spikes. And the funny thing here is a story of scientific discovery. A scientific discovery takes both luck and care and thoughtfulness.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
They were showing this cat fish, whatever mouse, flower, it just doesn't work.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
The cats, neural, in the primary visual cortex was silent. There was no spiking, a very little spiking, and they were really frustrated.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
But the good news is that there was no computer at that time. So, what they have to do when they show this cat, these stimuli, is they have to use a slight projector.
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NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
So, they put a slide of a fish and then wait till the neuron spike. If the neuron doesn't spike, they take the slide out and put in another slide.
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1,529
NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
And then they notice, every time they change slide, like this, this, like, you know, this squareish film, I don't even remember if they use glass or film, but whatever.
1,529
1,541
NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
The neuron spikes. That's weird, you know, like the actual mouse and fish and flower didn't drive the neuron, excite the neuron. But the movement of taking the slide out or putting a sliding did excite the neuron.
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1,560
NfnWJUyUJYU
CS231n Winter 2016: Lecture1: Introduction and Historical Context
https://youtu.be/NfnWJUyUJYU
2016-01-04T00:00:00.000000
It can be the cat is thinking, finally, they're changing the new object for me. So, it turned out there's an edge that's created by the slide that they're changing, right?
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