The only way to process videos in MATLAB is to read frames and process the frames. There is no way in MATLAB to process a video "directly" -- only frames that you read in from the video. The frames that you read from the video are just images.
Therefore you split the work:
- read a frame into an array -- a step that is independent of what you are going to do with the array
- process the array -- a step that is independent of how you input the array
- display or save the processed array -- a step that is independent of how you processed the array
