how to deconstruct a video with audio frame by frame and resemble to a new video only the images?

I have a video which on I do some work for each frame. here's how I read the video and create the output video:

video = VideoReader('in_vid.mp4');
outputVideo = VideoWriter(fullfile('Documents\','vid_out8.avi'));
outputVideo.FrameRate = video.FrameRate;
open(outputVideo)

here's how I read each frame and close the work on the video:

 while hasFrame(video)
img = readFrame(video);
%do some work and construct newimg 
writeVideo(outputVideo,newimg);
end
close(outputVideo);

when my input video has sound I cannot access it ones it finishes cause it writes 'file format not supported', when searching for this issue I saw that it has to do with the fact the video contains audio so I muted it then the program ran just fine and I was able to watch the end result, but the software I used the mute the video lowers its quality. what I seek here is either a way to save properly only the video or for a software that mutes the video without loss in image quality

thanks in advance, :).