video processing

I want to split a video into frames ie., jpg/bmp images with a decent frame rate - 100fps, perform contrast enhancement for each frame and rejoin it. How do i go through this procedure? I know im2frame is available, but i don't know how to use it in real time.

Answer 1

[Satwik]

Hi,

To break down a video into individual frames, enhance the contrast of each frame, and then reassemble the frames into a video at a specified frame rate, you can utilize MATLAB's built-in functions. Here's an example of how you can do it:

1. Read the Video and Extract Frames:

% Create a VideoReader object for the sample video file
videoFile = 'video_file.mp4';
videoReader = VideoReader(videoFile);

% Create a directory to save frames if it doesn't exist
outputDir = 'frames';
if ~exist(outputDir, 'dir')
    mkdir(outputDir);
end

frameIdx = 1;
while hasFrame(videoReader)
    % Read each frame from the video
    frame = readFrame(videoReader);
    
    % Save each frame as an image file
    imwrite(frame, fullfile(outputDir, sprintf('frame_%04d.jpg', frameIdx)));
    frameIdx = frameIdx + 1;
end

2. Perform Contrast Enhancement

% Get list of all frame files in the directory
frameFiles = dir(fullfile(outputDir, '*.jpg'));

for k = 1:length(frameFiles)
    % Read the image from file
    framePath = fullfile(outputDir, frameFiles(k).name);
    frame = imread(framePath);
    
    % Enhance the contrast of the image using imadjust
    enhancedFrame = imadjust(frame, stretchlim(frame), []);
    
    % Save the enhanced image, overwriting the original or in a new directory
    imwrite(enhancedFrame, framePath);
end

3. Reassemble the Frames into a Video

% Create a VideoWriter object to write the video
outputVideoFile = 'enhanced_video.mp4';
videoWriter = VideoWriter(outputVideoFile, 'MPEG-4');
videoWriter.FrameRate = 100; % Set the frame rate to 100 fps
open(videoWriter);

% Write each enhanced frame back into the video
for k = 1:length(frameFiles)
    % Read the enhanced image from file
    framePath = fullfile(outputDir, frameFiles(k).name);
    enhancedFrame = imread(framePath);
    
    % Write the frame to the video
    writeVideo(videoWriter, enhancedFrame);
end

% Close the video writer object
close(videoWriter);

Here is some documentation for the functions used in the example above, which you may refer to:

• https://www.mathworks.com/help/matlab/ref/videoreader.html
• https://www.mathworks.com/help/matlab/ref/imwrite.html
• https://www.mathworks.com/help/images/ref/imadjust.html
• https://www.mathworks.com/help/matlab/ref/videowriter.html

I hope this gives you a direction on how you can efficiently process video frames and reassemble them back into a video. Adjust the paths and filenames as necessary for your specific use case.