I am using OpenCV 3.1 with Windows 7 64 bit. When I try to write a move with VideoWriter using MJPG compression, the movies will play back correctly in FFMPEG but will not play using Windows Media Player. If I rebuild OpenCV so that it doesn't use the new built-in MJPEG encoder, then the files that are created (by FFMPEG, I assume) work fine in FFMPEG player and Windows Media Player.
Has anyone else experimented with this?