How to make a video in which every alternate frame is gray?

I have extracted frames from a video(e.g. Rhino.avi). Now I have to convert the alternate images among the extracted frames to grayscale and then write the frames back into a video file. So when the new video is played its every alternate frame would be in grayscale.

[Doug Hull]

What part are you having trouble with?

I think you need to be able to read a given frame, convert a frame to gray, then store it back in the file. What format do you want out, RGB where the RGB just happens to look gray? You need to give details of the specific problem that you are having so we can help you more effectively.

Answer 1

[Image Analyst]

See the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_extract_frames_from_a_video_file.3F Then, at the appropriate place, convert the image to 3D grayscale before saving.

grayImage = rgb2gray(colorFrame);
grayFrame = cat(3, grayImage, grayImage, grayImage);
% Then write out grayFrame.