Can't get movie timestamps due to TypeError: object of type 'cv2.VideoCapture' has no len()

[johnmbarrett]

It is impossible to retrieve movie timestamps due to dlc2nwb.utils.get_movietimestamps throwing TypeError: object of type 'cv2.VideoCapture' has no len()

Steps to reproduce:

• Download this video: https://photos.app.goo.gl/ddFTw11QWRjVPUmXA
• Navigate to the folder where you downloaded the video in the terminal of your choice
• Open a python interpreter
• Run the following code:

  from dlc2nwb.utils import get_movie_timestamps
  get_movie_timestamps('VID_20240117_165651.mp4')

Expected behaviour:

The timestamps are returned

Actual behaviour:

TypeError: object of type 'cv2.VideoCapture' has no len()

Environment info:

OS: Windows 10 x64 Conda version: 23.3.1 Python version: 3.9.0 opencv-python version: 4.7.0.72 dlc2nwb version: 0.3

Additional info:

This error might depend on the opencv-python version, in which case pinning the DLC2NWB package to whichever version added the ability to get the len() of a cv.VideoReader (or the one before they took it away if it's an old feature) is the simplest solution.

Alternatively, the first return value of reader.read() is a boolean indicating whether a frame was successfully reader, so using this to change the for loop to a while loop, like so:

success, _ = reader.read()
while success:
    timestamps.append(reader.get(cv2.CAP_PROP_POS_MSEC))
    success, _ = reader.read()

fixes the issue. However, (again, possibly depending on your opencv-python version) you then run into an AttributeError on line 83, since a cv2.VideoReader has no attribute fps. This can be fixed by replacing reader.fps on that line with reader.get(cv2.CAP_PROP_FPS)

[AlexEMG]

Agree, feel free to submit a PR!