Movie creation recording incorrect frames

Question

function create_simulation( matrix_all,timesteps,num_agents )
mkdir('movies');
filename_mov='.\movies\vid1';
vidObj = VideoWriter(filename_mov,'Motion JPEG AVI');
set(vidObj,'Quality',100,'FrameRate',2);
%matrix_all='time','id','xcor','ycor'
time=matrix_all(:,1);
id=matrix_all(:,2);
x=matrix_all(:,3);
y=matrix_all(:,4);
colors=jet(num_agents);
min_x=min(x);max_x=max(x);min_y=min(y);max_y=max(y);
f=figure('renderer', 'zbuffer');
a = axes('Parent',f);
axis(a,'tight');
set(a,'nextplot','replacechildren');
open(vidObj);
for t=1:timesteps,
    t_filter=time==t;
    scatter(x(t_filter),y(t_filter),[],colors,'filled');   
    xlim([min_x max_x]);
    ylim([min_y max_y]); 
    xlabel(num2str(t));
    drawnow;
    writeVideo(vidObj, getframe(f));
end
close(vidObj);
end

The above code creates a movie just recording the first frame every time only. I have tried these answers,(as you can see in code) but no success.

Data(some of it):

>>matrix_all
      1 1   680.640000000000    898.650000000000
      1 2   754.610000000000    832.080000000000
      1 3   864.500000000000    935.870000000000
      1 4   752.080000000000    1023
      1 5   728.080000000000    1052.10000000000
      1 6   787.900000000000    1030.60000000000
      2 1   678.170000000000    898.650000000000
      2 2   754.610000000000    832.080000000000
      2 3   864.500000000000    935.870000000000
      2 4   752.080000000000    1023
      2 5   728.080000000000    1052.10000000000
      2 6   787.900000000000    1030.60000000000
      3 1   678.170000000000    898.650000000000
      3 2   754.610000000000    832.080000000000
      3 3   864.500000000000    935.870000000000
      3 4   752.080000000000    1023
      3 5   728.080000000000    1052.10000000000
      3 6   787.900000000000    1030.60000000000
      4 1   678.170000000000    898.650000000000
      4 2   754.610000000000    832.080000000000
      4 3   864.500000000000    935.870000000000
      4 4   752.080000000000    1023
      4 5   728.080000000000    1052.10000000000
      4 6   787.900000000000    1030.60000000000
>> create_simulation( matrix_all,4,6)

Worst case I will have to write all images to disk and create a movie of it.

Can you give us the data where this is reproduced? matrix_all, timespteps,num_agents. — Ander Biguri, Oct 20 '15 at 11:43
@AnderBiguri Thanks for the reply! Please check I have posted some data. I don't think the issue would data specific though. — Abhishek Bhatia, Oct 20 '15 at 22:36
Sorry you didn't understand. We don't want to look at your data, we want a piece of code that works if we try it by copy-pasting. — Ander Biguri, Oct 21 '15 at 07:51
@AnderBiguri Please check now I have added call to the function. — Abhishek Bhatia, Oct 21 '15 at 10:41
@Ander Biguri It not that, actual data is bigger than this so there is a difference. The label remains the same besides! — Abhishek Bhatia, Oct 21 '15 at 11:27
Yes, sorry. Next time try to use data that we can see, easier for all. — Ander Biguri, Oct 21 '15 at 11:37
@Ander Biguri Sorry for bad reproducibility here. As a check please the xlabel changes in video frames or not. Thanks. — Abhishek Bhatia, Oct 21 '15 at 11:49

score 1 · Accepted Answer · answered Oct 21 '15 at 11:54

You are writing the video correctly. The thing is, most of video players will not show all the frames saved in order to improve computational time. This also depedns a lot in the format you are saving the video on.

For example, if you save the video in 'Motion JPEG AVI'you will get big compression, while of you save it in 'MPEG-4' the compression is smaller.

The whole point here is: if you want to be able to see the video as it is, save it in a very little/none compressed file type. Also, never trust what VLC or any other video players plays for you, if you want to check the frames, load the video and check them.

You'll see that if you use vidObj = VideoWriter(filename_mov,'MPEG-4'); and open it in any video player, you will see the changes, but if you save it the way you do ant this way and you load them to MATLAB again, the frames are exactly the same.

Awesome! Thanks so much for the help! Both formats seem to work on `Quicktime`! — Abhishek Bhatia, Oct 21 '15 at 12:04

Movie creation recording incorrect frames

1 Answers1