Downsample and Upsample videos in matlab

Question

Ala baccar 2022-7-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1761560-downsample-and-upsample-videos-in-matlab

评论： Image Analyst 2022-7-18

I am working with videos in matlab and the code is taking so much time to give me results, that's why i thought downsampling and upsmaling the video could be the best solution, can anyone help me with that.

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Star Strider 2022-7-16

What do you intend by ‘upsampling’ and ‘downsampling’?

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Answer 1

KSSV 2022-7-16

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1761560-downsample-and-upsample-videos-in-matlab#answer_1008910

Read video frame by frame, and use imresize on each frame.

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Ala baccar 2022-7-16

编辑：Ala baccar 2022-7-16

在 MATLAB Online 中打开

v1 = VideoReader('C:\Users\alaba\Desktop\skeleton\compressed.mp4');
set(gca,'xtick',[],'ytick',[])
set(gca,'LooseInset',get(gca,'TightInset'))
i1 = 0;
i2 = 0;
i3 = 0;
i4 = 0;
%matlab.video.read.UseHardwareAcceleration('on');
while i1 < v1.NumberOfFrames && i2 < v1.NumberOfFrames && i3< v1.NumberOfFrames && i4 < v1.NumberOfFrames
    
    if i1 < v1.NumberOfFrames
        i1 = i1+1;
        im = v1.read(i1);
        im = imresize(im, [300 300]);
        im = imrotate(im,90);
        iim1 = image(im,'XData',[0 0],'YData',[height1/2 - 300/2 height1/2 - 300/2]);
    end
   if i2 < v1.NumberOfFrames
        i2 = i2+1;
        im = v2.read(i2);
        im = imresize(im, [300 300]);
        
        iim2 = image(im,'XData',[width1/2-300/2 width1/2-300/2],'YData',[0 0]);
   end
   
   if i3 < v1.NumberOfFrames
        i3 = i3+1;
        im = v3.read(i1);
        im = imresize(im, [300 300]);
        im = imrotate(im,-90);
        iim3 = image(im,'XData',[width1-300 width1-300],'YData',[height1/2 - 300/2 height1/2 - 300/2]);
    end
   if i4 < v1.NumberOfFrames
        i4 = i4+1;
        im = v4.read(i4);
        im = imresize(im, [300 300]);
        im = imrotate(im,180);
        iim4 = image(im,'XData',[width1/2-300/2 width1/2-300/2],'YData',[height1 - 300 height1 - 300]);
   
        
   end
   %frame=im2frame(gcf);
   frame=getframe(gcf);
   writeVideo(writerObj,frame);
    
    drawnow
   
end
close(writerObj)

Well this is the useful part

Ala baccar 2022-7-16

在 MATLAB Online 中打开

Even when i changed the path out from "C:\Program Files" it gave me this eror Unable to find file. Ensure file exists and path is valid.

% Create a VideoWriter object to write the video out to a new, different file.
outputFullFileName = fullfile(pwd, 'C:\resize\NewRhinos.avi');
outputVideoWriterObject = VideoWriter(outputFullFileName);

Image Analyst 2022-7-18

在 MATLAB Online 中打开

When using VideoWriter, it creates a new file. So all you need to do is to make sure the folder exists:

You can't append c:\resize onto your current folder because then you'd have two drive letters and two colons in the filename. Just leave off the colon off

outputFullFileName = fullfile(pwd, 'C:\resize\NewRhinos.avi')

to see.

>> fullfile(pwd, 'C:\resize\NewRhinos.avi')

ans =

'C:\Users\alabaccar\Documents\MATLAB\work\Tests\C:\resize\NewRhinos.avi'

See - that's not a proper filename.

So do this:

% Create a VideoWriter object to write the video out to a new, different file.
outputFolder = 'C:\resize';
outputFullFileName = fullfile(outputFolder, 'NewRhinos.avi');
fprintf('Creating new output file : "%s".\n', outputFullFileName)
outputVideoWriterObject = VideoWriter(outputFullFileName);

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Answer 2

Image Analyst 2022-7-16

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1761560-downsample-and-upsample-videos-in-matlab#answer_1008935

movie_resize.m

I already have a demo for resizing a video. See attached.

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Image Analyst 2022-7-16

If you say that it takes too long, how long does it take and what is the maximum time you will allow? Perhaps you can use parfor and the Parallel Processing Toolbox, and a faster computer, to speed it up.

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