Psychopy Learning Notes — MovieStim

In the past few days, I need to write a movie playback solution using Psychopy. Although I have used it many times before, Psychopy has been constantly updating, and I am not very satisfied with the previous implementation. Today, I organized it.

The main class used is psychopy.visual.MovieStim, which has several useful methods.

How to check if the movie has finished?#

You can use the MovieStim.isFinished method. Check if this value is True in a while loop to determine if the movie has finished playing. If it has finished, you can proceed to the next task. If it hasn't finished, continue playing.

How to exit the playback screen when testing?#

I tried adding a global exit key, but it didn't work, probably because there was an issue with my code. So I had to find an alternative solution. Currently, I check for key presses during the video playback and stop the playback if a key is pressed.

You can stop the video playback using the mov.stop() method.

Code for playing the video:#

while not mov.isFinished:
    mov.draw()
    win.flip()
    if len(event.getKeys())>0:
        mov.stop()
        break

Automatically adjusting the size of the video#

I prepared two videos, and the frame sizes of these two videos are different. To achieve automatic adjustment, you need to use the cv2 library.

Automatically detecting the frame size of the video#

import cv2
def get_movie_frame_size(movie_path):
    cap = cv2.VideoCapture(movie_path)
    frame_width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
    frame_height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))
    cap.release()
    return frame_width, frame_height

This code was generated by chatGPT. I initially tried to use Psychopy to complete the task with chatGPT, but the outputs were incorrect.

According to the documentation API I read in the afternoon, Psychopy has movie.size, which should output the frame size. However, when I tested it, the output was incorrect. Initially, chatGPT also used Psychopy itself to complete the task, but with similar issues. It is possible that the Psychopy interface has been constantly updating, so chatGPT did not learn it. In the end, I used OpenCV to complete this task.

Final code#

for i in range(2):  # I only have two videos
        video_used = cur_movie_path + video_names[i]
        mov = visual.MovieStim(win, video_used,
                                flipVert=False, flipHoriz=False, loop=False)
        frame_width, frame_height = \ 
            get_movie_frame_size(cur_movie_path+video_names[i])
        mov.size = (frame_width, frame_height)

        while not mov.isFinished:
           mov.draw()
           win.flip()
           if len(event.getKeys())>0:
               mov.stop()
               break

The code was copied, and the indentation is not correct. If you want to use it, you need to adjust the indentation of the code to avoid errors.