[open] Help recording webcam video to file via OpenCV
Hello,
I am currently trying to implement a background video recording process that would run while a movie was played onscreen. Conceptually, everything is in place and ready, the only problem is when I attempt to save the video being recorded to a file, the file is saved without content. Some investigating shows that the main issue behind this error is codecs, or lack there of.
I was able to record the video to file successfully in PsychoPy, and upon investigation saw that there is a DLL folder holding all the binaries necessary for ffmpeg, is there an equivalent location for the compiled version of OpenSesame?
If that is the case with ffmpeg, what I would like to do is utilize ffmpeg binaries to save the video file to mpeg, but I can't determine how to do this without running OpenSesame from source, which at this point in development is not feasible.
Here is my (simplified) code for testing purposes:
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
# Define the codec and create VideoWriter object
fourcc = cv2.cv.CV_FOURCC(*'MJPG')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
i=0
while(cap.isOpened()):
ret, frame = cap.read()
i += 1
if ret==True:
# write the frame
out.write(frame)
# show frame
cv2.imshow('frame',frame)
# escape after a few seconds of recording
if i > 200:
break
else:
break
# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
As a side note, when I run this script, it doesn't show the image being stored to the frame variable. I assume this is related to the codec issue, but is to some degree irrelevant as we don't want to show the frame during the experiment.
Comments
Not really, but I imagine that just copying the .dll files from PsychoPy to the main OpenSesame folder (i.e. not a subfolder) should do the trick. Does this work for you?
The
cv2.imshow()function shows the frame on the cv2 window, which you have to initialize separately. I guess it fails silently if you haven't done this. In any case, it will not show the image on the OpenSesame window, because cv2 knows nothing about that.Cheers!
Sebastiaan
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Hi,
Maybe the solution here https://forum.cogsci.nl/index.php?p=/discussion/comment/16103 might come in handy. I could use it to successfully record webcam feed while displaying stimuli.