downsample from image 360*640 to 180*320

hi to everyone , I would to ask two question . the first is place in the title , and i know that i'm going to lose data , but i need to. the image in question i frame in the code under

. the second is that i'm trying to execute this code , but somthing wrong append .

video1=VideoReader('Francesca-Michielin---No-Degree-Of-Separation-Italy-Live-at-Semi-Final-2.mp4');

video2=VideoReader('Jamala---1944-Ukraine-Live-at-Semi-Final-2-of-the-2016-Eurovision-Song-Contest.mp4');

videoOut=VideoWriter('provaMix.avi');

videoOut.FrameRate=video1.FrameRate;

open(videoOut)

frames=read(video1,[1 2316]);

for frame=frames

% eventualmente resize (downsampling) del frame

writeVideo(videoOut,frame);

end

thank so much

Answer 1

[Ameer Hamza]

See imresize(): https://www.mathworks.com/help/releases/R2020a/matlab/ref/imresize.html. Use it with a scaling factor of 0.5;

frame_small = imresize(frame, 0.5)

For videoReader object, use readFrame() function to read a frame at a time, as shown in this example:: https://www.mathworks.com/help/releases/R2020a/matlab/ref/videoreader.html#busqe2j-1_1

Answer 2

[Andrea Gusmara]

Thanks you for your answer. For the second question, is there any function that permits to read more frames? I have seen the functions readFrame and read. I have read the documentation about the latter function but I couldn't use it very well. The documentation said that a frame range could be recovered

[Ameer Hamza]

You can use a for-loop to read multiple frames using readFrame(). However, I don't think there is a direct way to use readFrame to read multiple frames. Also, what error you get if you use read() function to read multiple frames?

[Andrea Gusmara]

No errors, the function returned only a value

[Ameer Hamza]

Your for loop is wrong. Write it like this

frames=read(video1,[1 2316]);
for idx=1:2316
    % eventualmente resize (downsampling) del frame
    
    writeVideo(videoOut,frames(:,:,:,i));
end