7 ‐ The Effects of Filtering

When working with the motion method, there is an option to filter the video frames after calculating the absolute difference between subsequent frames. Finding the right threshold value is crucial for accurate motion extraction. Let's see a few examples.

Example 1 | thresh=0

Here is an example of extracting the motion without any threshold. This will result in a result in which much of the background noise will be visible, including traces of keyframes if the video file has been compressed.

source = musicalgestures.MgObject('/path/to/source/video.avi', starttime=5, endtime=10, skip=0, contrast=100, brightness=20)
motiongrams = source.motiongrams(thresh=0.0)

Vertical (upper) and horizontal (lower) motiongrams, no threshold filter

Example 2 | thresh=0.02

Adding just a little bit of thresholding (0.02 here) will drastically improve the final result.

Vertical (upper) and horizontal (lower) motiongrams, 2% threshold filter