MATLAB Answers

How to resize video

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Alessandro Clocchiatti
Alessandro Clocchiatti on 30 Jan 2017
Commented: Image Analyst on 25 Nov 2020
Hi all, I have to create a program that allows me to resize a video by 50%. Does somebody have any tips? How could I set the code?

Answers (4)

Image Analyst
Image Analyst on 31 Jan 2017
See my attached demo. In the loop over frame, just resize the frame just read in and write it out with writeVideo(). If you can't figure it out, let me know what frame size you want your output in.
  4 Comments
Image Analyst
Image Analyst on 15 Oct 2020
Not sure what that means. Image frames have a certain number of pixels across (wide) and high (tall). If you reduce those, you will reduce both the pixel size across and tall, as well as the spatial resolution (meters per pixel) in real world units, meaning the ability to distinguish between two points in meters (or whatever unit you're using). Increasing the number of pixels will give you more pixels across and tall but will not increase the real world spatial resolution, meaning that you'll have more pixels per meter, but how close two points can be and still be resolved will not be changed.

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Takuji Fukumoto
Takuji Fukumoto on 30 Jan 2017
imresize function is fine. Here is the example.
vidobj = vision.VideoFileReader('moviename')
viewer = vision.DeployableVideoPlayer;
while (1)
A = step(vidobj);
viewframe = imresize(A,0.5);
step(viewer, viewframe);
end
release(vidobj);
release(viewer);
  2 Comments
Wenxuan Liang
Wenxuan Liang on 31 Aug 2020
While(1)?~?!!?!?!

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Takuji Fukumoto
Takuji Fukumoto on 31 Jan 2017
I think you can write like this
function myfunc()
%code
end
  4 Comments
Takuji Fukumoto
Takuji Fukumoto on 2 Feb 2017
Not in the loop. When you use system object, you should use step function. This is a sample code to save file.
% Set up the reader and writer objects.
videoFReader = vision.VideoFileReader('viplanedeparture.mp4');
videoFWriter = vision.VideoFileWriter('myFile.avi','FrameRate',...
videoFReader.info.VideoFrameRate);
Write the first 50 frames from original file into a newly created AVI file.
for i=1:50
videoFrame = step(videoFReader);
step(videoFWriter,videoFrame);
end
%%Close the input and output files.
release(videoFReader);
release(videoFWriter);

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Abdullah Amer Mohammed Salih
Thanks for your code, I need to change video in dimentions means the video for example is 100 x 100 it will be 30 x30. that is a liniear transformation.
I also need to change the shape of the video means I change it from rectangle to polygon for example. any clue how I do that?
  10 Comments
Image Analyst
Image Analyst on 25 Nov 2020
Thanks.
You can make whatever list of (x,y) coordinates you want. Or you can just start with a binary image (mask) that you got from thresholding or wherever.
Are you going to be
  1. creating a mask from a list of (x,y) coordinates (in which case you'll use poly2mask), or
  2. creating a mask by some other means, like thresholding or some other image segmentation method?
If you need help, attach either the list of (x,y) coordinates in a .mat file with the paper clip icon, or attach the mask image itself.

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