Trouble in making video from frames, can anyone help?

Hi,

I have around 1000 pictures which is like 30th frame from each second of 30 fps. I am trying to make a video with 1 fps hence I am using the code below but the problem is this code is not compiling the video in a sequence manner like frame30.jpg, frame60. jpg instead frames are messed up in video like starting from middle then finish then add the starting frames at the end. what i want is a it reads a frames from first to last hence made a video. I am not sure where I am making a mistake.

Code:

imgFile =dir('*.jpg');
N = length(imgFile);
% create the video writer with 1 FPS 
writerObj = VideoWriter('compilingFrames.avi');
writeObj.FrameRate = 1;
%Open the video writer
open(writerObj);
%write the frame to the video
for i=1:N
    img = imgFile(i).name;
    I = imread(img);
    writeVideo(writerObj,I);
end
% close the writer object
close(writerObj);

Answer 1

[Walter Roberson]

Use https://www.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort

Or if the frames are named strictly sequentially and have a predictable prefix, then generate the file names instead of reading them from the directory.

videofile = 'compilingFrames.avi';
writerObj = VideoWriter(videofile);
writeObj.FrameRate = 1;
%Open the video writer
open(writerObj);
N = 1;
while true
    filename = sprintf('frame%d.jpg', N);
    if ~exist(filename); break; end
    try
      I = imread(filename);
    catch ME
       fprintf('Failed to read file "%s", giving up', filename);
       break;
    end
    writeVideo(writerObj, I);
    N = N + 1;
end

%to get here we ran out of sequential files, or a file was not readable

% close the writer object
close(writerObj);

if N == 1
   fprintf('No frames were written at all, deleting movie!\n');
   delete(videofile);
elseif N == 2
    fprintf('Only one frame was written to movie, but need at least two for valid movie, deleting movie\n');
    delete(videofile);
else
    fprintf('Wrote %d frames succesfully\n', N-1);
end

[muhammad choudhry]

Hi, thanks for the help and see the error below. I am not understanding why it is not writting the frames as the images name are in sequence like frame30.jpg, frame60.jpg,frame90.jpg,frame120.jpg, and so on!

error:

Warning: No video frames were written to this file. The file may be invalid.

> In VideoWriter/close (line 282)

In compilingframes_2 (line 23)

No frames were written at all, deleting movie!

[Walter Roberson]

videofile = 'compilingFrames.avi';
writerObj = VideoWriter(videofile);
writeObj.FrameRate = 1;
%Open the video writer
open(writerObj);
N = 1;
while true
    filename = sprintf('frame%d.jpg', 30*N);
    if ~exist(filename); break; end
    try
      I = imread(filename);
    catch ME
       fprintf('Failed to read file "%s", giving up', filename);
       break;
    end
    writeVideo(writerObj, I);
    N = N + 1;
end

%to get here we ran out of sequential files, or a file was not readable

% close the writer object
close(writerObj);

if N == 1
   fprintf('No frames were written at all, deleting movie!\n');
   delete(videofile);
elseif N == 2
    fprintf('Only one frame was written to movie, but need at least two for valid movie, deleting movie\n');
    delete(videofile);
else
    fprintf('Wrote %d frames succesfully\n', N-1);
end

[muhammad choudhry]

Thanks, it worked with the frame sequence but still there is one problem which is the frame rate I wanted the frame rate to be 1 fps but it is going like 100 fps, video is too fast, even I mention in the code 1 fps but it did not implement it.

[Walter Roberson]

The line that is already in the code,

writeObj.FrameRate = 1;

should take care of that.

As an experiment, after the above code, try

v = VideoReader(videofile);
if isfield(v, 'FrameRate')
  fprintf('Frame rate stored in file is: %g\n', v.FrameRate);
else
    fprintf('Somehow file does not have any recorded FrameRate??\n');
end
clear v

Answer 2

[Chunru]

If your image file names are well behaved, you can do a simple sorting of the file names:

imgFile =dir('*.jpg');
imgFile = sort({imgFile.name}');            % sort the file name
N = length(imgFile);
% create the video writer with 1 FPS 
writerObj = VideoWriter('compilingFrames.avi');
writeObj.FrameRate = 1;
%Open the video writer
open(writerObj);
%write the frame to the video
for i=1:N
    img = imgFile{i};                       %.name;
    I = imreadimg);
    writeVideo(writerObj,I);
end
% close the writer object
close(writerObj);

[muhammad choudhry]

Error coming as .name has been removed and it is looking character vector or string scaler. Error is below!

Error using imread>parse_inputs (line 501)

The file name or URL argument must be a character vector or string scalar.

Error in imread (line 339)

[source, fmt_s, extraArgs, was_cached_fmt_used] = parse_inputs(cached_fmt, varargin{:});

Error in compilingframes_1 (line 14)

I = imread(img);

[Chunru]

Change to the following line

%img = imgFile(i);  
img = imgFile{i};  

[muhammad choudhry]

it compiled the frames into video same as before, no difference. Is there anyway I can define int he code that start read the frame from frame30.jpg then go to frame60.jpg, then go to frame90.jpg until the last frame ?

[Chunru]

Yes. You can define the frame sequence with the order you want:

imgFile ={'filename1.jpg', 'filename2.jp', ....}