Why does MPEG-4 video generated by VideoWriter have flickered frames?

I create an animation which uses "xline" command.

When I generated the video(.mp4), the "xline" line flickered in Window Media Player.

figure
t = linspace(0,10,1000);
y = randn(size(t));
plot(t,y)

hold on
h_x = xline(t(1),'--r');

v = VideoWriter('newfile.mp4','MPEG-4');
v.Quality = 100;
v.FrameRate = 10;

open(v)

for n = 1:length(t)
     h_x.Value = t(n);
     drawnow limitrate
     frame = getframe(gcf);
     writeVideo(v,frame);
end

close(v)

Answer 1

[MathWorks Support Team]

The issue was with the resolution of the generated image. As the compression increases from AVI to MPEG-4, the quality drops.

You can see the AVI has better quality than MPEG-4.

v = VideoWriter('newfile.avi','Uncompressed AVI');
% v = VideoWriter('newfile.mp4','MPEG-4');
% v.Quality = 100;
% v.FrameRate = 10;

This drop in quality due to increased compression needs to be compensated by increasing the resolution of the generated figures (or frames).\n

close all, clear all

figure('units','pixels','position',[0 0 1000 800]) % set figure's size


t = linspace(0,10,1000);
y = randn(size(t));
plot(t,y)

hold on
h_x = xline(t(1),'--r');


v = VideoWriter('newfile.mp4', 'MPEG-4');
v.Quality = 100;
v.FrameRate = 10;


open(v)

for n = 1:length(t)
  h_x.Value = t(n);
  drawnow limitrate
  frame = getframe(gcf);
  f = imresize(frame.cdata,4); % resize the image
   writeVideo(v,f);
end

close(v)