opencv with pi5 (or pi4 or..)

[petercwallis]

I came across this page:
https://forums.raspberrypi.com/viewtopic.php?t=361778

Which describes how to name the camera when creating a new opencv VideoCapture object. The opencv demos say use VideoCapture vcFramesIn(0) to get the default device; rpi users need to use gstreamer with some rather esoteric strings.

Is this still current?

And would it be possible to either update rpicam-apps to provide opencv "device 0" or to at least provide an up to date description of what parameter to hand to VideoCapture for the pis and to do that where we don't spend days looking for it.
cheers, P

[naushir]

OpenCV does not have native support for libcamera yet. So unfortunately you cannot use the OpenCV api to capture frames directly from /dev/video0 or similar.

To use OpenCV with rpicam-apps, we have a postprocessing API you can find here: https://github.com/raspberrypi/rpicam-apps/tree/main/post_processing_stages. This uses libcamera to capture frames, and OpenCV APIs for any image processing tasks needed. You can find similar examples with Picamera2 here: https://github.com/raspberrypi/picamera2/tree/main/examples.