Re:

[Leo Butler]

On Tue, 8 Dec 2009, address@hidden wrote:

< I saved this posting from Francesco, watch out for line wrap
< 
< 
< =-=-=
< Subject:      Re: avifile (and all that jazz)
< From:         "Francesco Potorti`" <address@hidden>
< Date:         Wed, September 16, 2009 5:43 am
< 
< >You can do this by generating a series of, for example, png-images and then
< >let mencoder put them together to an avi-file.
< 
< Or else use this function of mine.  By the way, wahat people think:
< would it be reasonable to add it to the video package?
< 
< function movie (action, mmov="octave_movie.mp4")
<   ## Create a movie from plots
<   ##
<   ## Example usage:
<   ##   figure("visible","off"); movie("init")
<   ##   a=zeros(100,100); a(1:20,41:60)=1;
<   ##   for i=1:100; a=shift(a,1); imshow(a); movie("add"); endfor
<   ##   movie("close"); close; system("totem octave_movie.mp4")
<   ##
<   ## There are three commands used as first argment: "init", "add",
<   ## "close". By default, a movie named "octave_movie.mp4" is created
<   ## using ffmpeg.  An optional second argument allows one changing both
<   ## the name and the type of movie.  The type ".dir" creates a
<   ## directory containing a png file per frame.  The type ".zip"
<   ## archives it using zip.  Types ".mp4", ".ogg", ".mov", ".mjpeg",
<   ## ".avi", ".flv" are created using ffmpeg; types ".mng", ".gif" are
<   ## created using convert; type ".swf" is created using png2swf.  You
<   ## must have the relevant program installed to create a movie with the
<   ## corresponding extension; no program is required for ".dir".
< 
<   ## Francesco Potortì, 2008
<   ## Revision 1.10
<   ## License: GPL version 3 or later
< 
<   verbose = false;
<   rate = 5;                        # frames per second
< 
<   actions = {"init" "add" "close"};
<   # gif swf
<   types = {".mp4" ".mng" ".gif" ".zip" ".ogg" ".swf" ".mov" ...
<            ".mjpeg" ".avi" ".flv" ".dir"};
<   if (nargin < 1 || !ischar(action) || !any(strcmp(action, actions)))
<     error("first argument must be one of:%s", sprintf(" %s",actions{:}));
<   endif
<   if (nargin != 2 || !ischar(mmov))

This should be:
if (nargin >= 2 && !ischar(mmov))
The example in the  comments won't work unless the above line is changed.

<     error("second arg must be a string");
<   endif
<   [mpath mname mtype] = fileparts(mmov);
< 
<   mdir = fullfile(mpath, [mname ".d"]);
<   ppat =  "%06d.png";
<   mpat = fullfile(mdir, ppat);
<   mglob = fullfile(mdir, strrep(sprintf(ppat,0),"0","[0-9]"));
<   fnof = fullfile(mdir, "+frame-number+");
< 
<   switch (action)
<     case actions{1}                # init a movie
<       if (isdir(mmov))
<         cleandir(mmov, verbose)
<       else
<         unlink(mmov);
<       endif
<       while (!([allgood msg] = mkdir(mdir)))
<         if (stat(fnof) && load(fnof).frameno == 0)
<           error("while creating dir '%s': %s", mdir, msg);
<         else
<           cleandir(mdir, verbose);
<         endif
<       endwhile
<       frameno = 0; save("-text",fnof,"frameno");
<       if (verbose) printf("Directory '%s' created.\n", mdir); endif
<     case actions{2}                # add a frame
<       load(fnof);
<       mfile = sprintf(mpat, ++frameno);
<       drawnow("png", mfile);
<       save("-text",fnof,"frameno");
<       if (verbose) printf("Frame '%s' added.\n", mfile); endif
<     case actions{3}                # close the movie
<       switch (mtype)
<         case {types{[1 5 7 8 9 10]}} # mp4, ogg, mov, mjpeg, avi, flv
<           cmd = sprintf("ffmpeg -y -r %d -sameq -i %s %s 2>&1", rate,
< mpat, mmov);
<         case {types{[2 3]}}        # mng, gif
<           cmd = sprintf("convert %s -adjoin %s 2>&1", mglob, mpat);
<         case types{4}                # zip
<           cmd = sprintf("zip -qr9 %s %s 2>&1", mmov, mglob);
<         case types{6}                # swf
<           cmd = sprintf("png2swf -z -r %d -o %s %s", rate, mmov, mglob);
<         case types{end}                # dir
<           rename(mdir, mmov); return
<         otherwise
<           error("second arg must end with one of:%s", sprintf("
< %s",types{:}));
<       endswitch
<       [status output] = system(cmd);
<       if (status != 0)
<         load(fnof);
<         error("Creation of movie '%s' containing %d frames failed:\n%s",
<               mmov, frameno, output);
<       endif
<       if (verbose) printf("Movie '%s' contains %d frames:\n%s",
<                           mmov, frameno, output); endif
<       cleandir(mdir, verbose);
<   endswitch
< endfunction
< 
< 
< function cleandir(mdir, verbose)
<   unwind_protect
<     save_crr = confirm_recursive_rmdir(false);
<     [allgood msg] = rmdir(mdir,"s");
<     if (!allgood)
<       error("while removing dir '%s': %s", mdir, msg); endif
<   unwind_protect_cleanup
<     confirm_recursive_rmdir(save_crr);
<   end_unwind_protect
<   if (verbose) printf("Directory '%s' removed\n", mdir); endif
< endfunction
< 
< -- 
< Francesco Potortì (ricercatore)        Voice: +39 050 315 3058 (op.2111)
< ISTI - Area della ricerca CNR          Fax:   +39 050 315 2040
< via G. Moruzzi 1, I-56124 Pisa         Email: address@hidden
< (entrance 20, 1st floor, room C71)     Web:   http://fly.isti.cnr.it/
< 
< =-=-=
< > Hello list,
< >
< > For an assignment, my students are using finite differences to compute a
< > solution of the 1D wave equation.  Because I only want them to bother with
< > the numerics, not with practical plotting stuff, I've made available the
< > following script which they can use to animate their solution:
< >
< > --------------------------- begin script ---------------------------
< >
< > function generate_movie1d(f, g, Nx, t_max, L, c, lambda)
< >
< > [u dt] = wave1d(f, g, Nx, t_max, L, c, lambda);
< >
< > mymax = max(max(u));
< > mymin = min(min(u));
< >
< > x = linspace(0, L, Nx+1);
< > for i=1:size(u,2)
< >
< >   plot(x, u(:,i), '*r')
< >   axis([0 L mymin mymax])
< >   title(sprintf('Solution of the one-dimensional wave equation at t = %f',
< > (i-1)*dt))
< >   drawnow
< >   hold off
< >
< > end
< >
< > ------------------------------ end script
< > ----------------------------------
< >
< > This all worked fine on my (fast) Ubuntu desktop PC, but one of my
< > students (working on a quite fast Windows Vista laptop) reported
< > 'flickering' graphics... the updating of the animation is very bad and
< > makes the animation very unfluent.  I assume this is not due to a slow
< > computer (his laptop is quite fast), but rather due to the fact that I use
< > the drawnow command to update the graphics...  maybe also due to the fact
< > that he works on Windows Vista?  Unfortunately, I don't know how I would
< > have to change my code so that the updating is more 'fluent'.
< >
< > Can anybody help me out here, so that I can give my students a script that
< > also gives fluent animations, even on Windows?  What is the general
< > technique to do this?  Am i doing it the right way?
< >
< > Kind regards,
< > Bart
 
The example provided in the comments to the script does not work on an 
out-of-the-box
debian ffmpeg, because the mp4 codec is not available. Try .ogg in place of 
.mp4.

Leo
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