how can i read all the frames/images from a .rec file?

Hello. I am trying to read all the images/frames from a video. I built up the following code:

 fid = fopen('C:\HiSpecAutoSave\Autosave4.rec');
fseek(fid, 1310720, -1);%move file pointer to first frame of data
img=fread(fid, [1280, 256], 'uint8=>uint8');
fclose(fid);
img2 = fliplr(img);%we need to flip it left/right for some wierd reason
img3 = imrotate(img2, 90);%and rotate, unsure why it's stored this way

My problem is that this code reads only the first image/frame. What should i do to read all the images? Thanks in advance

Answer 1

[Geoff Hayes]

Nikolaos - if we know the number of frames in the video and we assume that all frames follow each other (in the rec file) then we could do something like the following

 % open the file for reading
 fid = fopen('C:\HiSpecAutoSave\Autosave4.rec');

 % if the file descriptor is valid
 if fid>0

     % assume 100 frames
     numFrames = 100;

     % pre-allocate memory for each frame
     allFrames = uint8(zeros(256,1280,numFrames));

     % move file pointer to first frame of data
     fseek(fid, 1310720, -1);

     % read each frame
     for k=1:numFrames

         % read the kth frame
         img=fread(fid, [1280, 256], 'uint8=>uint8');

         % flip it
         img = fliplr(img);

         % rotate it and save to array
         allFrames(:,:,k) = imrotate(img, 90);
     end

     fclose(fid);
 end

The above will read each frame into the allFrames array. Try it and see what happens!

[Nikolaos]

This is almost what i need. In the code above we set the variable "numFrames". Is there any way to "extract" this variable from the file? In the case we don't know the number of the frames, how can we find it?

[Geoff Hayes]

What else do you know about the format of the file? You obviously know where the first frame begins, but do you know anything about what comes before that? There probably is information there for number of frames, frame dimension, etc.

If you don't know that, then you could just store each frame as an element in a cell array, and then rather than looping for a fixed number of frames, just use a while loop and continue looping until the number of elements read in from file is less than the expected amount. Something like

 [img, ctr] = fread(fid, [1280, 256], 'uint8=>uint8');

 if ctr<(1280*256)
    % incomplete frame so exit
    break;
 end

[Nikolaos]

Thank you very very much. Your advice helped me a lot. It made me look at the right direction. Below i send you the final code.

% open the file for reading

        fid = fopen('C:\HiSpecAutoSave\Autosave4.rec');

 % if the file descriptor is valid
 if fid>0
     % move file pointer to first frame of data
     fseek(fid, 1310720, -1);

    k = 0;
    while ~feof(fid)
      [img,ctr] = fread(fid,[1280,256],'uint8=>uint8');
    if ctr < (1280*256)
        break;  %incomplete frame so exit
    else
        k = k + 1;
        % flip it
         img = fliplr(img);
%          % rotate it and save to array
         allFrames(:,:,k) = imrotate(img, 90);
    end
end
 end

[Geoff Hayes]

Glad to have been able to help, Nikolaos!

Answer 2

[Srimathy K SOC IT]

sir how to embed secret data in video????

i had used interframe motion prediction

function [motion,pred_err]=inter_cons(im_old,im_new,i,j,N)

for i=1:100
 rows=i+N-1;cols=j+N-1; 


    SAD = 1.0e+10;
    for u = -N:N
        for v = -N:N
            sad = im_new(rows+1:rows+N,cols+1:cols+N)-im_old(rows+u+1:rows+u+N,cols+v+1:cols+v+N); %difference
            sad = sum(abs(sad(:)));
            if sad < SAD          
                SAD=sad;
                
                x= v; y = u; 
            end
        end
    end

    motion=[x y];

    pred_im(1:N,1:N)=im_old(rows+y+1:rows+y+N,cols+x+1:cols+x+N);
    
   
    pred_err(1:N,1:N) = im_new(rows:rows+N-1,cols:cols+N-1)-pred_im(1:N,1:N);
end
    
end

but the code only giving result for first frame in 8*8 matrix

i need your help sir

[Geoff Hayes]

Srimathy - please post this a new question rather than as an answer to this one.