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High Speed Video Analysis

26 bytes removed, 21:18, 6 October 2013
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High Speed Video is a great way of analyzing your [[Running Form]]. While high end equipment is extremely expensive, there are a number of options for relatively inexpensive cameras with this ability.
=Cameras with High Speed Video=
{| class="wikitable"
| 120
=Camera Recommendations=
There are pros and cons to the various cameras.
* I've used the Casio cameras a number of times, and they are easy to use and work well. The resolution and quality of the higher frame rates it too poor to be of much use, so don't expect to be able to use the 1000 fps mode.
* You can sometimes get [ used High Speed EXILIM cameras on ebay] for a reasonable cost.
* The Nikon J1 is crippled by its 5 second maximum record time.
* The GoPro a good frame rate and a nice resolution, as well as a WiFi remote control
* There is no LCD screen for replay of the video on the GoPro, so you need to by the [ LCD Screen] for $80.
=Evaluating the video=
The simplest approach is to step through the video frame by frame, which is possible with many software video players. For a more detailed analysis you can extract each frame into a separate photo file using the free open source software [ FFMpeg]. You can use the following command to extract separate images, but you probably want to extract a short relevant clip before you run this command or you will end up with too many image files to handle.
* Input.avi is the name of your input video file
* image-%4d.jpeg is the name of the output files, with %4d replaced by the frame number
=Sample Output=
Below are four consecutive frames from a recording at 120 fps to give a sense of the resolution and timing of the available video from a Casio camera. These pictures look identical on first glance, but there is slight movement visible if you rapidly swap between the images.
=Automated Analysis Software=
I am hoping to write some software that will perform some automated analysis. Here are my current thoughts on the algorithm that could be used.
** For the first contact frame:
*** Measure the angle of the heel/forefoot line to estimate strike angle and therefore strike index. This can be categorized into FFS, MFS, RFS.
*** Find the horizontal distance from the middle of the foot to the hip to check for [[Overstriding|overstriding]].
*** Look at the angle between the hip/knee and the knee/ankle to determine how straight the leg is. A straighter leg may indicate a higher impact force.
** Evaluate the frames between first and last contact:

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