Retaining Bit depth when creating a video from Grayscale Images

Hello, I am trying to create a video (MP4 file) from a stack of 16 bit Grayscale images. My code is below. I see that using the VideoWriter with the MPEG-4 codec, 16 bit resolution isn't possible and the images need to be down sampled to 8 bit. Is there anyway at all to create a video file and retain the original resolution?

Thanks

Jason

       dt = datestr(now,'dd-mmm-yyyy HH-MM-SS');   %get current dateTime 
            filepath=app.SaveVidEditField.Value;
            filename=fullfile(filepath,[dt,'- VidMatlab.mp4']);
            diskLogger=VideoWriter(filename,'MPEG-4');   % Use the MPEG-4 Codec
            diskLogger.FrameRate=app.FrameRateEditField.Value;
            open(diskLogger);
            ReportMessage(app,'..Disklogger Opened');    %Report message is my own function
            
            
            numFrames=size(data,2);
            ReportMessage(app,['..Recording To Disk Started  (', num2str(numFrames),' images)']);
            b=0;   %Holder if want to add background to change contrast in 8 bit video
            for x=1:numFrames
                 writeVideo(diskLogger, uint8((data{x}+b)/ 256));     %Annoyingly, Need to convert images to 8bit
            end
            ReportMessage(app,'DiskLogger Stopped');    
            close(diskLogger);
            
            disp('Finished Saving Video')
            %check
            disp('checking file')
            v = VideoReader(filename);
            fr=v.FrameRate;   %double
            dur=v.Duration;
            ReportMessage(app,['Video Saved as: ',filename, ' @',num2str(fr),'fps  (',num2str(dur,'%.1f'),' s)']);   

Answer 1

[Nandini]

I see that you're using MATLAB to create a video from a stack of 16-bit grayscale images. As you mentioned, the VideoWriter in MATLAB with the MPEG-4 codec does not directly support 16-bit resolution. The images need to be downsampled to 8-bit before creating the video.

In your code, you are converting the images to 8-bit by dividing them by 256 (uint8((data{x}+b)/256)), which effectively scales the pixel values from the original 16-bit range to the 8-bit range (0-255).

Unfortunately, there is no way to create a video file with the MPEG-4 codec and retain the original 16-bit resolution. The MPEG-4 codec is specifically designed for 8-bit color or grayscale images. If you want to preserve the full 16-bit resolution, you would need to use a different codec or file format that supports higher bit depths, such as a lossless format like TIFF or PNG.

Here's an example of how you can modify your code to save the images as a TIFF sequence instead of an MP4 video file:

dt = datestr(now, 'dd-mmm-yyyy HH-MM-SS'); % Get current dateTime
filepath = app.SaveVidEditField.Value;
filename = fullfile(filepath, [dt, '- VidMatlab.tif']); % Save as TIFF file
numFrames = size(data, 2);

ReportMessage(app, ['..Recording To Disk Started  (', num2str(numFrames), ' images)']);

for x = 1:numFrames
    imwrite(data{x}, filename, 'WriteMode', 'append', 'Compression', 'none');
end

ReportMessage(app, 'DiskLogger Stopped');
disp('Finished Saving Video');

% Check TIFF sequence properties
info = imfinfo(filename);
numFramesSaved = numel(info);
fr = app.FrameRateEditField.Value;
dur = numFramesSaved / fr;
ReportMessage(app, ['Video Saved as: ', filename, ' @', num2str(fr), 'fps  (', num2str(dur, '%.1f'), ' s)']);

In this modified code, each image in the data array is saved as a separate frame in a TIFF file using the imwrite function. The Compression option is set to 'none' to ensure lossless saving. Please note that saving each frame as a separate TIFF image will result in a sequence of individual images rather than a single video file. However, this allows you to retain the original 16-bit resolution of the images.

[Jason]

Thankyou. I actually already have the images as individual tiffs - I then load them into a cell array to make the video!

Is there anyother non MP4 way of retaining the resolution as a video

Thanks