How can I cut every nth frame of a video and save it without those frames?

Hi, I'm trying to save a vídeo without every nth frame. Because I have two vídeos with different frame rates and in order to make the vídeos with the same total number of frames after syncronize them. The code I have now is below. I have some problem in the code because the pc freezes in the end of the vídeo. Could anyone find the problem? Thanks in advance.

Te code is:

 close all; clear all; clc;

      %  file name
         name_vid1='firstvideo.avi';
     %***** read vídeo ***** 
        vid1 = VideoReader(name_vid1);

         name_vid2=secondvideo;
     %***** read vídeo *****
        vid2 = VideoReader(name_vid2);

        frame_vid1=vid1.NumberOfFrames;
        frame_vid2=vid2.NumberOfFrames;
        dif_t=frame_vid1-frame_vid2;

        if dif_t>0
        vid=name_vid1;
        elseif dif_t<0
        vid=name_vid2;
        else 
        disp(' vídeos have the same number of frames.')
        end
        clear vid1;
        clear vid2;
        vid_file= VideoReader(vid);
        Frame_vid = get(vid_file, 'NumberOfFrames');
        n_frame=fix(Frame_vid/abs(dif_t)); % this calculates every nth frame to remove from video

 %***** write a new vídeo *****
 writerObj = VideoWriter([vid '_cutted.avi']);
 %***** change frame rate*****
 writerObj.FrameRate = 240; 
 %***** open new vídeo file
 open(writerObj);
 nFrames = vid_file.NumberOfFrames;
 vidHeight = vid_file.Height;
 vidWidth = vid_file.Width;
 mov(1:nFrames) = struct('cdata', zeros(vidHeight, vidWidth, 3, 'uint8'),'colormap', []);

w=1;

while w<=nFrames;

   last_frames=nFrames-w;

    open(writerObj);

    if last_frames>=1 && last_frames<n_frame

        for k = w : nFrames

        mov(k).cdata = read(vid_file, k);

        writeVideo(writerObj, mov(k).cdata);

        end

   else
        for k = w : w+n_frame-1
        mov(k).cdata = read(vid_file, k);
        writeVideo(writerObj, mov(k).cdata);
        end
    end

   fclose all

    w=w+n_frame+1;
end

close (writerObj);

clear writerObj

Answer 1

[Roberto]

I really don't know whats wrong with your code; but here's what I wrote:

%After your validations and calculations
original = vid ;
output = [vid '_cutted.avi'];
if exist(output,'file');
  delete(output);
end
vidOriginal = VideoReader(original);
N = fix(Frame_vid/abs(dif_t)) ;
writerObj = VideoWriter(output);
writerObj.FrameRate = 240; % CAREFULL!!! 
open(writerObj);
nFrames = vidOriginal.NumberOfFrames;
skipN = 1:N:nFrames ;
vidHeight = vidOriginal.Height;
vidWidth = vidOriginal.Width;
mov(1:nFrames - numel(skipN)) = struct('cdata', zeros(vidHeight, vidWidth, 3, 'uint8'),'colormap', []);
for i =  1:nFrames
  j = find(i== skipN);
  if any(j)
      continue
  end
  mov(i).cdata = read(vidOriginal, i);
  writeVideo(writerObj, mov(i).cdata);
end
close (writerObj);
clear writerObj

[Marco Branco]

hi Roberto, I've tried with a small vídeo and worked fine. Now I'll try with a larger one. Thanks a lot. Best regards, Marco Branco