Chroma Subsampling and Quality Factor when writing MJPEG videos.

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Hi, I'm trying to capture videos from a webcam and save them as MJPEG videos, using the OpenCV VideoWriter class. I'm trying to determine the default Chroma Subsampling and Quality Factor values used by OpenCV, and whether there is any way to change these. I'd like to use 4:2:2 subsampling, and, as far as I can tell, OpenCV uses 4:2:0. I'd also like to manually set the quality factor, if possible.

I have looked for answers already in the docs, google and even browsed the repos, to no avail. Any help would be greatly appreciated.

I'm on OpenCV 2.4.5, for reasons of compatibility with older code.