How to change movie to image per frame

Question

Mr Smart 2012-11-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/54287-how-to-change-movie-to-image-per-frame

回答： Sk Sahariyaz Zaman 2016-4-28

Hello , anyone does know I need to change video to image with each frames.And now my problem was: I can`t read in matlab, mpg or wav file.When I read this short movie with mmreader . But Matlab says - warning: Unable to determine the number of frames in this file.I have short movie. Here my .m file from internet:

% Read and play back the movie file
obj=mmreader('shuttle.wmv'); 
nFrames =obj.numberOfFrames;
vidHeight = obj.Height;
vidWidth = obj.Width;
% Preallocate movie structure.
mov(1:nFrames) = ...
    struct('cdata', zeros(vidHeight, vidWidth, 3, 'uint8'),...
           'colormap', []);
% Read one frame at a time.
for k = 1 : nFrames
    mov(k).cdata = read(obj, k);
end
% Size a figure based on the video's width and height.
hf = figure;
set(hf, 'position', [150 150 vidWidth vidHeight])
% Play back the movie once at the video's frame rate.
movie(hf,mov, 1, obj.FrameRate);

******* And how to make video to image per frame.Thanks

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Answer 1

Walter Roberson 2012-11-20

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https://ww2.mathworks.cn/matlabcentral/answers/54287-how-to-change-movie-to-image-per-frame#answer_65965

编辑：Walter Roberson 2012-11-20

在 MATLAB Online 中打开

Movies that were recorded with variable frame rates cannot have their numberOfFrames determined until they have been read through completely.

You can work around by not preallocating and simply reading everything at once:

mov = read(obj);

Side note: because of MATLAB's copy-on-write behavior, pre-allocating the cdata field does not help; the cdata will be completely overwritten in your assignment, not using the pre-allocated memory.