Problem: the model_visualization.avi with XVID codec did (silently) not work whereas model_visualization.mp4 with H264 does work.

Proposed solution: make the video codec configurable (defaulting to existing behaviour) and error-log-and-exit if the output video file could not be opened.

Usage example

(The "happy fish" image does not have the 20x20 size of the "profile face" model but it seems nonetheless suitable for smoke test use.)

opencv_build/bin/opencv_visualisation \
--image=opencv/samples/data/HappyFish.jpg \
--model=opencv/data/haarcascades/haarcascade_profileface.xml \
--data=temp_data/ \
--ext=mp4 --fourcc=H264 --fps=42

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
• The PR is proposed to the proper branch
• There is a reference to the original bug report and related work
• There is accuracy test, performance test and test data in opencv_extra repository, if applicable
  Patch to opencv_extra has the same branch name.
• The feature is well documented and sample code can be built with the project CMake