OpenCV: FFMPEG: tag 0x34363268/'h264' is not supported with codec

You should change:

fourcc = cv2.VideoWriter_fourcc('h', '2', '6', '4')

to:

fourcc = cv2.VideoWriter_fourcc(*'avc1')

The codecs are platform dependent, that could be the problem. Try using this combination:

• extension of file = test.mkv
• codec . = CV_FOURCC(*'X264)

Here is the reference link

FourCC is a 4-byte code used to specify the video codec. The list of available codes can be found in fourcc.org. It is platform dependent. The following codecs work fine for me.

• In Fedora: DIVX, XVID, MJPG, X264, WMV1, WMV2. (XVID is more preferable. MJPG results in high size video. X264 gives very small size video)
• In Windows: DIVX (More to be tested and added)
• In OSX: MJPG (.mp4), DIVX (.avi), X264 (.mkv).

Source

First like some answers pointed out, we should use "AVC1" instead of "h264". Secondly, when we are using opencv-python, there are some licence issues : https://github.com/opencv/opencv-python/issues/207 , we may need to compile on our own.