How do I extract frames iteratively?

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Daniel Mendoza Hermosillo
评论： Daniel Mendoza Hermosillo 2022-4-7
So far I have been able to trim the video and went from 4007 frames to 1509 frames, from those frames I only want to get every 3rd frame starting from the first. Currently I only know how to trim the video and to check how much frames the video has not much else.
  1 个评论
Daniel Mendoza Hermosillo
Daniel Mendoza Hermosillo 2022-4-7
编辑：Walter Roberson 2022-4-7
% Import video file
obj = VideoReader('D:\Spring 2022\MARS Capstone\Trimmed Videos\Reef 1\GH010063.MP4');
vid = read(obj);
% Read the total number of frames
frames = obj.NumFrames;
% File format of the frames to be saved
ST = ' .jpg';
% Reading and writing the frames
for x = 1 : frames
% Converting integers to string
Sx = num2str(x);
% Concatening 2 string
Strc = strcat(Sx, ST);
vid = vid(:, :, :, x);
% Exporting the frames
imwrite(vid, Strc);
end
this is a code i found online that helps me write the frames into images that I can use later but it stops because it needs 23.2 GB storage to run, so I wanted to reduce the number of frames that I pick up from this code.

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采纳的回答

Walter Roberson
Walter Roberson 2022-4-7
% Import video file
obj = VideoReader('D:\Spring 2022\MARS Capstone\Trimmed Videos\Reef 1\GH010063.MP4');
% File format of the frames to be saved
ST = ' .jpg';
% Reading and writing the frames
i = 1;
while hasframe(obj)
% Converting integers to string
Sx = num2str(x);
% Concatening 2 string
Strc = strcat(Sx, ST);
vid = readframe(obj);
% Exporting the frames
imwrite(vid, Strc);
i = i + 1;
end
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Walter Roberson
Walter Roberson 2022-4-7
% Import video file
obj = VideoReader('D:\Spring 2022\MARS Capstone\Trimmed Videos\Reef 1\GH010063.MP4');
% File format of the frames to be saved
ST = ' .jpg';
% Reading and writing the frames
x = 0;
while hasframe(obj)
vid = readframe(obj);
x = x + 1;
if mod(x, 3) ~= 1; continue; end
% Converting integers to string
Sx = num2str(x);
% Concatening 2 string
Strc = strcat(Sx, ST);
% Exporting the frames
imwrite(vid, Strc);
end
It is also possible to ask to read() a particular frame by frame index, but I suspect this code would be faster.

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