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Won't load video from phone post and replies

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Deleted Post
David Sands
1 Posts

Post removed on September 27, 2016 at 10:03 AM EST.


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Re: I get the error "File cannot be loaded" -
Scott McCullough
4 Posts

This is not a technical help to the loading problem, but I wanted to mention that I was enthusiastic about students using their phones to take video, but that it didn't work out very well.

The main problem is that the phone video uses a virtual "rolling shutter", which means that the image for a frame is not taken all at once, but scanned in a few rows of pixels at a time. This means that moving objects are blurred in the frame.

If you explain this, students can use either the top or bottom of the blurred image in a consistent way to get the best results.

There are some videos 'out there' that were taken with "global shutter" technology, which captures the entire frame at the same instant.

There are a few high speed videos on my webpage. http://spas.cis.indwes.edu/dns-research-faculty/scott-mccullough-phd/. The server is down at the moment (0957 on 27 Sep 2016, EDT) but should be back up soon.



Re: Re: I get the error "File cannot be loaded" -
Paul Nord
26 Posts

We had a good discussion of using student devices to record video at the summer AAPT meeting.  I don't have a reply to your question, but the advice seems relevant to this discussion.

Those who had tried it warned that it just opens a can of worms.  Trying to figure out features of individual devices and file transfer methods is a headache.  Some reported that each and every device required the instructor to spend 5 to 10 minutes figuring out all of the quirks.  If you want to allow just one particular phone model, it's possible that you'll have several in your classroom.  Or it you have a set of iPads or Chromebooks, that's fine.  But trying to do tech support for a dozen different devices is more effort than it is worth.

Paul



Re: Re: Re: I get the error "File cannot be loaded" -
Scott McCullough
4 Posts

Very helpful advice.

The other difficulty I found with using student devices was that the results were often far off of the "expected values".

A colleague from the UK argues that the experiments that don't work offer the best learning opportunities, and generally speaking I agree. However, in video analysis, the issues are numerous, arise from multiple sources and are not simple enough to sort out with good observation and trial and error.

None of this is meant to discourage you from using video analysis. By all means, do! It addresses both conceptual issues and affective concerns. The struggle is in making good videos.



Re: Re: Re: Re: I get the error "File cannot be loaded" -
Scott McCullough
4 Posts

BTW, our server is back up. http://spas.cis.indwes.edu/scott-mccullough/

There are a few high-speed videos taken with a camera that has a global shutter. The frame rate is too high for something like free fall, but you can set Tracker to read every 5th or 10th frame.


The basketball and tennis ball bounce videos offer the possibility of connecting dynamics and kinematics. I slammed them to floor as hard as I could. Masses and dimensions are on the webpage.

I will add videos over the next few months.



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