Forming Video from frames but getting the error

Hi,

I am trying to made a video using images (30 fps) but I am getting an error which I am failing to understand or correct it. Both code and error shown below.

Thanks for the help in advance!

Code:

%Read the Images
for m=2:10
   images =imread(sprintf('frame%d.jpg',m));%name of files are frame2.jpg till frame190.jpg so on
end
 % create the video writer with 30 fps
 writerObj = VideoWriter('myVideo.avi');
 writerObj.FrameRate = 30;
 % open the video writer
 open(writerObj);
 % write the frames to the video
 for u=1:length(images)
     % convert the image to a frame
     frame = im2frame(images{u});
 end
 % close the writer object
 close(writerObj);

Error:

Brace indexing is not supported for variables of this type.

Error in videowriter (line 16)

frame = im2frame(images{u});

Answer 1

[Walter Roberson]

for m=2:10
   images =imread(sprintf('frame%d.jpg',m));%name of files are frame2.jpg till frame190.jpg so on
end

That loop overwrites all of images each time.

for m=2:10
   images{m-1} =imread(sprintf('frame%d.jpg',m));%name of files are frame2.jpg till frame190.jpg so on
end

[muhammad choudhry]

Hi,

I just encounter further error in the line below.

Error:

Error using im2frame

Indexed movie frame must have a non-empty colormap

Error in videowriter (line 16)

frame = im2frame(images{u});

[Walter Roberson]

writerObj = VideoWriter('myVideo.avi');
writerObj.FrameRate = 30;
open(writerObj);
for m=2:190
   thisimage =imread(sprintf('frame%d.jpg',m));%name of files are frame2.jpg till frame190.jpg so on
   writeVideo(writerObj, thisimage);
end
 close(writerObj);

im2frame() is intended for converting colormapped images into a structure suitable for writing as "frames", but can also be used for RGB images. You are working with .jpg images, so the two ways that you could end up with a frame that would give that particular error message are:

1. One of the images was empty, []; Or
2. One of the images was a true grayscale jpg image. True grayscale jpg images are very uncommon; more than 99% of the time, grayscale jpg images are saved as RGB images that just happen to have the same content for all three color panes. But real grayscale jpg are technically possible. If you happen to have an actual grayscale jpg then chances are that you want the output frame to be grayscale as well. In that situation you should either skip converting to "frame" structure or else you should explicitly pass in a gray colormap when you im2frame()

If you were using an image format such as .png or .tif I would give more weight to the possibility that you have indexed images that you want to write out after being processed through a colormap. However, .jpg is not a suitable file format for images that are indexed.

[muhammad choudhry]

Thanks alot for the explanation!

I actually extracted the frames from the video hence did converted to greyscale images then did the backgroud substraction to see the movement of object in the frames. Your code worked and now I can only see the object moving in the video.

I will try to avoid .jpg format. Thanks alot once again!