mmread getting frames of video

N = 3;

video = mmread('sample.avi', 10, [0 N]);

I = video.frames.cdata(:,:,:,1);

imshow(I);

I need to open video and grab frames of it -frames in 0 to N seconds and 10 frame each second-. Above code gives just first frame of video and when I do the following, error thrown.

I = video.frames.cdata(:,:,:,2);

with the error "Index in position 4 exceeds array bounds (must not exceed 1)." How can I get frame array of first n seconds properly.

Answer 1

[Turlough Hughes]

To get your 10 frames each second from 0 to N seconds you can do the following (Note though that if you are converting from a standard such as 24 fps to 10 fps you will end up sampling frames 1, 3, 6, 8, 11, 13, 16, etc....the spacing is not consistent because 24/10 is not an integer value)

N=3
samples=10*N; % New FPS multiplied by overall time N = new number of frames

[~,inda]=min(abs(video.times-N)) % idx is frame closest too time N
indb=round(linspace(1,inda,samples)) % index for "evenly" spaced frames of original video

To show an individual frame it is just:

I=video.frames(indb(1)).cdata;
imshow(I)

[Turlough Hughes]

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