Admin at 16:25, 28 May 2011

2011-05-28T16:25:55Z

← Older revision		Revision as of 16:25, 28 May 2011
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	For more options besides <code>qscale</code>, see [[Ffmpeg#Images_to_video]].		For more options besides <code>qscale</code>, see [[Ffmpeg#Images_to_video]].

			{{Programs}}
			{{Math Programs}}

Admin: /* Step 4: Assemble Image Series into Video */

2011-04-24T10:52:27Z

Step 4: Assemble Image Series into Video

← Older revision		Revision as of 10:52, 24 April 2011
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	$ ffmpeg -i image_%04d.png -qscale 1 movie.mpg		$ ffmpeg -i image_%04d.png -qscale 1 movie.mpg
	</code>		</code>

			'''Link to the final movie: click image below'''

	[[Image:MatlabVideoExample.png\|350px\|link=http://files.charlesmartinreid.com/matlab_video_example.mpg]]		[[Image:MatlabVideoExample.png\|350px\|link=http://files.charlesmartinreid.com/matlab_video_example.mpg]]

			For more options besides <code>qscale</code>, see [[Ffmpeg#Images_to_video]].

Admin: /* Step 4: Assemble Image Series into Video */

2011-04-24T10:50:35Z

Step 4: Assemble Image Series into Video

← Older revision		Revision as of 10:50, 24 April 2011
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	</code>		</code>

	[[Image:MatlabVideoExample.png\|link=http://files.charlesmartinreid.com/matlab_video_example.mpg]]		[[Image:MatlabVideoExample.png\|350px\|link=http://files.charlesmartinreid.com/matlab_video_example.mpg]]

Admin: Created page with "This page will demonstrate how to create a movie from a set of Matlab plots. This will allow you to make some nice videos from Matlab plots. =Step 1: Generate Matlab Plots= Obv..."

2011-04-24T10:48:38Z

Created page with "This page will demonstrate how to create a movie from a set of Matlab plots. This will allow you to make some nice videos from Matlab plots. =Step 1: Generate Matlab Plots= Obv..."

New page

This page will demonstrate how to create a movie from a set of Matlab plots. This will allow you to make some nice videos from Matlab plots.

=Step 1: Generate Matlab Plots=

Obviously you will have your own particular Matlab script generating your own plots. However, for the sake of illustration, I will use a sample script to illustrate the steps involved in creaing a Matlab video.

==Sample Script==

My sample script plots a sine wave <math>y(x) = sin(x)</math> for the domain <math>0.0 \leq x \leq 2 \pi</math> with a time-varying phase shift.

[[Image:MatlabVideoExample.png|350px]]

The following Matlab script will generate the plot being visualized:

<source lang="matlab">
close all;

x=[0:(pi/16):2*pi];

y_0 = sin(x);

z=0;

for i=0:(pi/32):2*pi
y_1 = sin(x-i);

plot(x,y_0,'k-',x,y_1,'r--')

xlabel('x ');
ylabel('y(x)');
axis([0 2*pi -1 1]);

% Matlab commands to save plots
% to image files go here

z = z + 1;
pause(0.1);
end
</source>

The set of images of plots generated by this Matlab script can be downloaded here: http://files.charlesmartinreid.com/matlab_video_example.tar.gz

Unzip this to anywhere on your computer.

=Step 2: Save Matlab Plots to Image Files=

Once you have a script that will create the Matlab plots you want to make into a video, the next step is to tell Matlab to save each plot to an external image file. This can be accomplished using Matlab's <code>saveas</code> command (try <code>help saveas</code>).

In the above example, the following lines would be added:

<source lang="matlab">
filename = sprintf('image_%0.4d.png',z);
saveas(gcf,filename,'png');
</source>

which will create a set of 65 image files named <code>file_0001.png</code> through <code>file_0064.png</code>.

The <code>sprintf</code> command uses the syntax of <code>printf</code> (a C function, see [http://www.cplusplus.com/reference/clibrary/cstdio/printf/]), but it prints the result to a string, rather than to output. The symbol <code>%0.4d</code> means "print a digit number, with a width of 4, and fill the width with zeros (so that 1 becomes 0001, 50 becomes 0050, etc.)

The <code>saveas</code> command is telling Matlab to save the plot to the file in png format.

=Step 3: Postprocess Images=

I don't have any specific examples here, but sometimes you need to postprocess your images, so this step would go here.

=Step 4: Assemble Image Series into Video=

This step requires [[Ffmpeg]]. The [[Ffmpeg]] page contains a section on [[Ffmpeg#Images_to_video|converting images to video]]. This is the process that must be used to assemble the series of images into a video.

In the Matlab file, we gave <code>sprintf</code> the syntax <code>%0.4f</code>. This can also be used in calling ffmpeg (but without the dot between 0 and 4):

<code>
$ ffmpeg -i image_%04d.png -qscale 1 movie.mpg
</code>

[[Image:MatlabVideoExample.png|link=http://files.charlesmartinreid.com/matlab_video_example.mpg]]

Making Matlab Videos - Revision history

Admin at 16:25, 28 May 2011

Admin: /* Step 4: Assemble Image Series into Video */

Admin: /* Step 4: Assemble Image Series into Video */

Admin: Created page with "This page will demonstrate how to create a movie from a set of Matlab plots. This will allow you to make some nice videos from Matlab plots. =Step 1: Generate Matlab Plots= Obv..."