Maksim Shabunin

> I guess `defined(__ARM_NEON) || defined(__aarch64__)` could be simplified into `defined(__ARM_NEON)` but is there a platform where `__aarch64__` is defined and not `__ARM_NEON` ? I don't know if there is...

Try to set environment variable `OPENCV_LOG_LEVEL=0`

Please add more information: camera model, OpenCV installation source, what are `cap` and `cap.isOpened()` after `VideoCapture` construction.

Try to open camera `0`. Try to collect more logs: set environment variables `OPENCV_LOG_LEVEL=debug` and `OPENCV_VIDEOIO_DEBUG=1`. Print contents of `cap` and `cap.isOpened()`

You should set environment variables before importing the library, otherwise they will not work. E.g. ```.bat SET OPENCV_LOG_LEVEL=debug SET OPENCV_VIDEOIO_DEBUG=1 python3 myscript.py ```

We will need to keep backward compatibility at cmake-level for some time and have two sets of targets - namespaced and old. I remember I saw one library that had...

@Ryanf55 , perhaps you should create a PR to 5.x with your changes, so that they could be reviewed and discussed in details.

To elaborate on the _binary size_ point a little bit: * build static OpenCV with reduced dependencies: ``` cmake \ -DBUILD_JAVA=OFF \ -DBUILD_opencv_python3=OFF \ -DBUILD_SHARED_LIBS=OFF \ -DCPU_DISPATCH= \ -DWITH_OPENCL=OFF \...

Preliminary analysis has shown that expressions are widely used in OpenCV source code: * core - 18 matches * imgproc - 52 matches * calib3d - 652 matches * objdetect...

I've found one border case where current expression implementation works slightly different than might be expected - https://github.com/opencv/opencv/blob/76548e29bd62f299386cb919824b34ce4baf73cb/modules/core/test/test_operations.cpp#L249-L250 these cases can be boiled down to: ```.cpp Mat fours(3, 3, CV_16SC1,...