Tag: video

Fourier Transform

the Fourier transform tells you how much of each ingredient “note” (sine wave or circle) contributes to the overall wave. Here’s why Fourier’s trick is useful. Imagine you were talking to your friend over the phone and you wanted to get them to draw this squarish wave. The tedious way to do this would be to read out a long list of numbers that represent the height of the wave at every instant in time. With all these numbers, your friend could patiently stitch together the original wave. This is essentially how old audio formats like WAV files worked. But if your friend knew Fourier’s trick, you could do something pretty slick: You could just tell them a handful of numbers—the sizes of the different circles in the picture above. They can then use this circle picture to reconstruct the original wave.

2022-11-14: The nuclear origins of Fast Fourier Transforms

And this trick works even if the signal is composed of a bunch of different frequencies. If the sine waves frequency is one of the components of the signal it will correlate with the signal producing a non-0 area. And the size of this area tells you the relative amplitude of that frequency sine wave in the signal. Repeat this process for all frequencies of sine waves and you get the frequency spectrum. Essentially which frequencies are present and in what proportions. If the signal is a cosine wave, then even if you multiply it by a sine wave of the exact same frequency, the area under the curve will be 0. For each frequency, we need to multiply by a sine wave and a cosine wave and find the amplitudes for each. The ratio of these amplitudes indicates the phase of the signal that is how much it’s shifted to the left or to the right. You can use Euler’s formula so you only need to multiply your signal by one exponential term. Then the real part of the sum is the cosine amplitude and the imaginary part is the sine amplitude.

Reading body language

Joe Navarro was a body language expert for the FBI. His job was to catch spies. In this video, he shares some tips. He also busts some myths. For instance, a lot of people think that crossed arms are a blocking behavior. “That’s just nonsense.”

Virtual Angkor

a groundbreaking collaboration between Virtual History Specialists, Archaeologists and Historians designed to bring the Cambodian metropolis of Angkor to life. Built for the classroom, it has been created to take students into a 3D world and to use this simulation to ask questions about Angkor’s place in larger networks of trade and diplomacy, its experience with climate variability and the structure of power and kingship that underpinned the city.

see also

the colossal, densely populated cities would have constituted the largest empire on earth at the time of its peak in the 12th century.

Tactical Driving

Wyatt Knox is a former rally car driver and driving instructor at Team O’Neil Rally School and in this video, he shows us some of the tactical driving techniques that would be in the repertoire of law enforcement or special operations personnel, including running cars off the road, backing up at high speed, and doing a j-turn. (What’s a j-turn? It’s that cool thing they do in the movies where a car in reverse does a 180 and continues driving forwards in the same direction.

Tesla selfdrving

In shadow testing, a car is being driven by a human or a human with autopilot. A new revision of the autopilot software is also present on the vehicle, receiving data from the sensors but not taking control of the car in any way. Rather, it makes decisions about how to drive based on the sensors, and those decisions can be compared to the decisions of a human driver or the older version of the autopilot. If there is a decision — the new software decides to zig where the old one zags, or the new software cruises on when the human hits the brakes, an attempt can be made to figure out how different the decisions were, and how important that difference is. Some portion of those incidents can be given to human beings to examine and learn if the new software is making a mistake. If there is a mistake, it can be marked to be fixed, and the testing continues.

User Input is an error:

Elon Musk views any human user intervention is an error situation for the Tesla Autopilot. Elon means that whenever a human has to take control from the Tesla Autopilot system this is indicating an error that must be fixed for a future fully autonomous car.

Teslas improve with use:

Most of the systems we currently use aren’t built to improve through use. They have locked in performance and capabilities. These systems can only improve through revisions and patches made by technical experts. That approach is on the way out. Systems can now be improved operationally …. Further, for the most complex activities, this will be the only type of system you will be able to buy.

Let me guess, the media won’t be falling over themselves to report on these instances where the tesla autopilot saved lives.

Doctors told Neally later that he’d suffered a pulmonary embolism. They told him he was lucky to have survived. If you ask Neally, however, he’ll tell you he was lucky to be driving a Tesla. As he writhed in the driver’s seat, the vehicle’s software negotiated 30 highway km to a hospital just off an exit ramp. He manually steered it into the parking lot and checked himself into the emergency room, where he was promptly treated. By night’s end he had recovered enough to go home.

Another analysis on the Tesla software disruption:

Tesla’s first bet is that it will solve the vision-only problem before the other sensors get small and cheap, and that it will solve all the rest of the autonomy problems by then as well. This is strongly counter-consensus. It hopes to do it the harder way before anyone else does it the easier way. That is, it’s entirely possible that Waymo, or someone else, gets autonomy to work in 202x with a $1000 or $2000 LIDAR and vision sensor suite and Tesla still doesn’t have it working with vision alone.

The second bet is that Tesla will be able to get autonomy working with enough of a lead to benefit from a strong winner takes all effect – ‘more cars means more data means better autonomy means more cars’. After all, even if Tesla did get the vision-only approach working, it doesn’t necessarily follow that no-one else would. Hence, the bet is that autonomous capability will not be a commodity.

This video from 2014 is what happens when you improve cars at the speed of the software industry. very very impressive.

Being able to update the fleet isn’t just useful for selfdriving

Researchers Hacked a Model S, But Tesla’s Already Released a Patch If you were CEO of a car manufacturer, which of these headlines would you rather were written about you? The first speaks of a tired, old manufacturing model where fixes take months and involve expense and inconvenience. The second speaks of a nimble model more reminiscent of a smartphone than a car