Lossless compression in Motion JPEG 2000 (.mj2) file. How do I tell?

I found that Matlab's VideoWriter has the capability to write a Motion JPEG 2000 file with the LosslessCompression flag. Is there a way to find out whether images in a Motion JPEG 2000 file has been compressed losslessly?

Answer 1

[Janosch Kunczik]

Hello Spencer,

Yes there is a way:

1. Take an (raw) image sequence or video file and use the VideoWriter to create a .mj2 video.
2. Use the VideoReader to read the video frame by frame
3. Compare both

 %%Write the video
 writer = VideoWriter('test.mj2','Motion JPEG 2000');
 writer.LosslessCompression = true;

 for i=1:length(testData)
    writeVideo(writer,testData(:,:,:,i));
 end

 close(writer);

 vidObj = VideoReader('test.mj2');

 for i=1:length(testData)
   frame = readFrame(vidObj);
   orig_frame = rawObj.Data(i).frame;
   error = frame - orig_frame;
   disp(max(max(abs(error)));
end

This little snippet will let you prove that the result isn't lossless, although the LosslessCompression flag has been set.

I you want to have a lossless Motion JPEG 200 video, you will have to use the 'Archival' profile.

 writer = VideoWriter('test.mj2','Archival');

Kind regards,

Josh