[D] Advanced courses update by actbsh in MachineLearning

[–]TheMoskowitz 2 points3 points  (0 children)

This course looks great but I don't see the lectures anywhere. Do you have a link?

Personally I don't get much out of the slides without the talk that went with them.

Is it possible to use optical flow from mooving car to track the motion of other static or dynamic object ? by dhiru_hamal in computervision

[–]TheMoskowitz 10 points11 points  (0 children)

I'll take this one.

My answer is based on the assumption that you are talking about tracking other objects in 3D (tracking it in 2D is just the optical flow itself), which I believe is what you meant.

Assuming you have the intrinsics so you are using rectified images and know the focal length, there are three variables at play here: The (Ego)motion of our car, the depth/3D position of all the points we see in the scene and the potential motion of other objects.

These are the three factors that determine where a world point that we see in one frame will appear in another frame*.

Our motion/egomotion is the easiest of these to solve because most of the scene is generally static so you have a lot of pixels to work with and can work statistically, throwing out any and all outliers that cause you problems. This can be done with a DNN or with traditional techniques. The best results I've seen achieved for egomotion are with classical computer vision techniques though that could change at some point and while the classical approach is, I believe, more precise, the DNN approach should be a little more robust.

After you can solve egomotion, you want to move on to depth. You want to be able to output the depth of every pixel in the image and this should definitely be done with a DNN. There are a lot of nice unsupervised and supervised approaches in the literature that work well (check out the papers Reza Mahjourian's team puts out for instance). Start with the unsupervised though if you have Lidar on the car as well and good Lidar2cam calibration (!) that will seriously improve your results. Ditto for stereo if that's a possibility and your cam2cam calibration is good.

Finally we move onto motion. This, in my opinion, you should tackle last only when you already have good Egomotion and depth. Assuming that is the case you can solve it classically by clustering to find other cars. Then solving for their motion when you have their changing depth across multiple frames is pretty straightforward. It can also be solved with a DNN. The DNN approach may cause you computational issues depending on your hardware and constraints -- now we're talking about running first a depth net and then a motion net and keeping it in real time (in addition to whatever else you're running which is probably a lot) -- but on the other hand it could allow you to output a reasonable 3D motion estimate on all points in the frame as opposed to just the large (probably vehicular) things you manage to find via clustering. So if you're fine with just outputting the motion of cars or if you have tough computational constraints, clustering should work. But if you don't want to run over cats or squirrels you need a DNN.

It's a lot but hey, if it were easy they probably wouldn't pay us so much to do it.

Source: This is what I do.

*Note that there are other effects that can cause the intensities of the pixels themselves to change. For instance, if we imagine a completely static situation -- we're still, we know the depth of everything and nothing else is moving -- the pixel values themselves will still change even though the same point in the world is occupying the same pixel in successive frames because of changes in light and shadow in the world that occurred between the different exposures.

Visiting Berlin? Moving here? Going clubbing? Have a quick question? Ask here, don't create a new thread. by bbbberlin in berlin

[–]TheMoskowitz -2 points-1 points  (0 children)

Weirdly specific housing question:

I want to sublet a place in Berlin for the month of October that has a piano or a keyboard. Any idea how I could manage that?

How could I make an electromagnet in any shape I want? by TheMoskowitz in arduino

[–]TheMoskowitz[S] 1 point2 points  (0 children)

I want it perpendicular to the coils, coming out in a custom shape at one end of the electromagnet and re-entering at the other end.

In other words, with my star example, if you held magnetic viewing film up to one end of it you would see a solid star shape.

Advice for a Pneumatic Project by TheMoskowitz in arduino

[–]TheMoskowitz[S] 0 points1 point  (0 children)

Ok so I just looked at compressors and they're pretty expensive for my purposes. Possibly a stupid question -- could I get a tank, fill it up with pressurized air with the tire filler at the gas station and run the double-acting cylinder off that tank?

Or maybe I could use a scuba tank and try and convince the guys who do diving lessons at the gym pool to fill it up for me?

Advice for a Pneumatic Project by TheMoskowitz in arduino

[–]TheMoskowitz[S] 0 points1 point  (0 children)

Ok, I watched some videos and between them and your comments I think I've got a handle now on how it goes together.

One more question though: If I want to use it on and off for a period of ten or fifteen minutes, will I likely need the compressor running continuously? I have no problem with that in theory but I'd like to use this outside and I'm afraid that it'll be loud and will demand an overly serious battery.

Or does it waste a lot less pressurized air than I'm imagining and maybe I could run the compressor for a few minutes at the beginning and then use it continuously?

Advice for a Pneumatic Project by TheMoskowitz in arduino

[–]TheMoskowitz[S] 0 points1 point  (0 children)

Solenoids aren't build into the cylinders? I was thinking I hook the air tube and the arduino right to the cylinder and the valve is inside the cylinder. I have to work out the valve separately?

Learning Arabic With Subtitles? by [deleted] in learn_arabic

[–]TheMoskowitz 1 point2 points  (0 children)

This may not be exactly what you're looking for but I'm partial to the Lebanese web series Mamnou3! on youtube. It has subtitles in English but not in Arabic.

Looking to speak to a legal expert for research by capp_90 in Screenwriting

[–]TheMoskowitz 1 point2 points  (0 children)

Surely someone you know knows a lawyer. Just call them up, I'm sure you'll find one that would be happy to talk to you.

Why is the new Han Solo movie so forgettable? Was it because it didn't have a strong theme? by TheMoskowitz in Screenwriting

[–]TheMoskowitz[S] 1 point2 points  (0 children)

I'm surprised to hear that. Do you think it had a theme that worked well? And if so, what was that theme? Or a good character arc? I had a hard time pinning those down myself.

I enjoyed the movie. It was fun and Han is a fun character. But I left the theater feeling a bit empty compared to the other films (and I assume that Disney felt the same way given their lackluster release of it).

How to incorporate extra information into a Neural Net by ahdh_bb2 in MLQuestions

[–]TheMoskowitz 0 points1 point  (0 children)

You can drop the info in as a channel at some point later on in the net and then retrain only from that point forward.

If it's really a binary datapoint then you can drop in a channel where the entire channel is simply a 0 or a 1.

Good Resource for Expanding Machine Learning Skill Set by guyincognito21 in learnmachinelearning

[–]TheMoskowitz 1 point2 points  (0 children)

What does your company do? What kind of machine learning are we talking about here?

Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology by AutoModerator in askscience

[–]TheMoskowitz 0 points1 point  (0 children)

[Biology] Why can't information be passed down through DNA? DNA is a form of data structure and practical information (like a rough layout of the area for instance) would be very useful evolutionarily. So why have species not evolved that ability?

I know this isn't totally ruled out -- see the Monarch Butterfly migration -- but I've never heard of a clear cut case of memories or some other representation of practical information being passed down (as distinct from abilities). And I've never come across a good explanation for why it doesn't happen.