Can't Set CV_CAP_PROP_BUFFERSIZE

[dactylroot]

Problem

Given an unknown source framerate and unknown frame processing time for each frame, we want to be able to always grab the most recent frame at the time of a read() call. In contrast to traditional process-every-frame stream workflows, which opencv-python seems to have been designed around.

Ideally we could follow cap.set(CV_CAP_PROP_BUFFERSIZE,1) and then always have the most recent frame available. Unfortunately, contrary to this suggestion, we don't appear to be able to set this property in Python:

In : cap.set(cv2.CAP_PROP_BUFFERSIZE,1)                                                                                  
Out: False

It appears everyone tries to manually flush the buffer themselves e.g. 1 2a 2b

Current Workaround

As a workaround, I parameterized the buffer skipping rate. So users of this package still have to be conscious of their source framerate and set a flush rate accordingly.

Possible Solutions

Some options to consider to fix this:

• Find out how to set the CAP_PROP_BUFFERSIZE property for OpenCV.
• Use another thread to spool frames as quickly as possible. This is no ideal as we don't want to force every user into multithreading situations, especially when OpenCV supposedly has this capability already.

[Mauhing]

I have also notice that cv2.CAP_PROP_BUFFERSIZE,1) does not work. What I am doing right now is to constantly cv2.grab() and only retrieve when I need it. However, this is not a good solution.

[bvitaz-ck]

On my Raspberry Pi project, cv2.CAP_PROP_BUFFERSIZE, 1 does actually work, but it means there's still a buffer of 1 that needs to be cleared before reading a live image. cv2.CAP_PROP_BUFFERSIZE, 0 is what I have been trying to get to work, and it does work on my Mac and Windows PCs.

[dactylroot]

Closing as this is an OpenCV issue