Extraction of images from video: why images are missed?

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INTRODUCTION:
I have a avi-video recorded at 2 frames per second and I used the following commands to extract the images of the video:
obj = VideoReader('C:\Desktop\test.avi');
vid = read(obj,[1 5000]);
for k = 1:1:5000
newname = strcat('C:\Desktop\TEST\',num2str(k),'.png');
imwrite(vid(:,:,:,k), newname);
end;
PROBLEM:
I controlled the extracted images and realized that one image is missed at every sixth image or 20 images per minutes. Instead of counting 120 images per minute I counted only 100.
I wonder if someone knows what is going wrong with the commands and what I can do to solve this problem.
Thank you in advance Emerson

Accepted Answer

Image Analyst
Image Analyst on 13 Mar 2013
Add k to your loop to display it:
for k = 1:5000
k % No semicolon.
newname = strcat('C:\Desktop\TEST\',num2str(k),'.png');
imwrite(vid(:,:,:,k), newname);
end
Now, do you see any missing k in the list printed to the command line?
  10 Comments
AJ
AJ on 13 Jun 2013
Hi Image Analyst, I have a problem , when I am using your code to extract individual frames from a video, I am only able to extract 80 frames from the total number of frames. Kindly help me.

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More Answers (2)

Shaun VanWeelden
Shaun VanWeelden on 13 Mar 2013
Also, I would do obj.FrameRate to see if it really is 2, this seems much more likely than a number not showing up in a vector.
  1 Comment
Emerson De Souza
Emerson De Souza on 13 Mar 2013
Thank you Shaun,
I double checked the frame rate and it is correct 2. I recorded videos with different frame rate and the problem as described above persists. It seems that there is no relationship between frame rate and not writing the image in correct sequence during extraction. Thanks anyways.
Emerson

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Akhilkumar1307
Akhilkumar1307 on 8 Mar 2017
Hi
I am facing similar problem too
My video frame rate is 30 fps, so it should show me a frame every 33(1000/30) millisecond but its not Its showing around a frame every 400 millisecond
please help
  1 Comment
Akhilkumar1307
Akhilkumar1307 on 20 Mar 2017
Problem is solved
Previously am using .avi files, and know its fine with .mp4 files

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