function PlayMoviesDemoOSX(moviename, backgroundMaskOut, tolerance)
%
% PlayMoviesDemoOSX(moviename [, backgroundMaskOut][, tolerance])
%
% This demo accepts a pattern for a valid moviename, e.g.,
% moviename='*.mpg', then it plays all movies in the current working
% directory whose names match the provided pattern, e.g., the '*.mpg'
% pattern would play all MPEG files in the current directory.
%
% If you don't specify a moviename, the demo will ask you if it should play
% our standard DualDiscs.mov demo movie, or rather play through a set of
% videos in a playlist which are streamed from the internet. These 'c'ool
% videos may provide you with useful information for your daily work.
%
% This demo uses automatic asynchronous playback for synchronized playback
% of video and sound. Each movie plays until end, then rewinds and plays
% again from the start. Pressing the Cursor-Up/Down key pauses/unpauses the
% movie and increases/decreases playback rate.
% The left- right arrow keys jump in 1 seconds steps. SPACE jumps to the
% next movie in the list. ESC ends the demo.
%
% If the optional RGB color vector backgroundMaskOut is provided, then
% color pixels in the video which are equal or close to backgroundMaskOut will be
% discarded during drawing. E.g., backgroundMaskOut = [255 255 255] would
% discard all white pixels, backgroundMaskOut = [0 0 0] would discard all
% black pixels etc. The optional tolerance parameter allows for some
% lenience, e.g., tolerance = 10 would discard all pixels whose euclidean
% distance in RGB color space is less than 10 units to the backgroundMaskOut
% color. Background color masking requires a graphics card with fragment
% shader support and will fail otherwise.
%

% History:
% 10/30/05  mk  Wrote it.
% 07/17/11  mk  Add support for background pixel color removal via shaders.
%               Code cleanup, dead code removal.
% 04/14/12  mk  Code cleanup, refinements for network video streams.
%               Add useful videos to playlist which are less pathetic than
%               the fairy-tales of the iPhone company.

theanswer = [];

if (nargin < 1) || isempty(moviename) 
    moviename = [];
    theanswer = input('Serious or cool? Type s or c [s/c]? ', 's');
end;

if isempty(moviename)
    moviename = '*.mov';
end

% Switch KbName into unified mode: It will use the names of the OS-X
% platform on all platforms in order to make this script portable:
KbName('UnifyKeyNames');

space=KbName('SPACE');
esc=KbName('ESCAPE');
right=KbName('RightArrow');
left=KbName('LeftArrow');
up=KbName('UpArrow');
down=KbName('DownArrow');
shift=KbName('RightShift');

try
    % Child protection
    AssertOpenGL;
    background=[128, 128, 128];

    % Open onscreen window:
    screen=max(Screen('Screens'));
    win = Screen('OpenWindow', screen, 0);

    shader = [];
    if (nargin > 1) && ~isempty(backgroundMaskOut)
        if nargin < 3
            tolerance = [];
        end
        shader = CreateSinglePassImageProcessingShader(win, 'BackgroundMaskOut', backgroundMaskOut, tolerance);
    end
    
    % Clear screen to background color:
    Screen('FillRect', win, background);
    
    % Initial display and sync to timestamp:
    Screen('Flip',win);
    iteration = 0;    
    abortit = 0;

    % Use blocking wait for new frames by default:
    blocking = 1;

    % Default preload setting:
    preloadsecs = [];

    if isempty(strfind(moviename, 'http'))
        % Return full list of movie files from directory+pattern:
        moviefiles=dir(moviename);
        
        if isempty(moviefiles)
            moviefiles(1).name = [ PsychtoolboxRoot 'PsychDemos/QuicktimeDemos/DualDiscs.mov' ];
        else
            for i=1:size(moviefiles,1)
                moviefiles(i).name = [ pwd filesep moviefiles(i).name ];
            end
        end
        
        moviecount = size(moviefiles,1);
    else
        moviefiles(1).name = moviename;
        moviecount = 1;
    end

    if strcmpi(theanswer, 'c')
        % Cool stuff, streaming from the web ;-)
        moviefiles = [];
        
        % On GStreamer setups we add a few more movies to the playlist, before the pathetic Apple
        % commercials. Can't use them on OS/X yet, as Apple's QT engine does not handle them
        % with the default codec set:
        if IsLinux || (Screen('Preference', 'OverrideMultimediaEngine') == 1)
            % Promotional videos for the best OS for cognitive science and technical/educational
            % videos some users may find of practical use:

            % ELC 2012 talk: Gstreamer-1.0 No-longer-compromise-flexibility-for-performance:
            moviefiles(end+1).name = 'http://d17mmld7179ppq.cloudfront.net/gstreamer-10-no-longer-compromise-flexibility-for-performance_52ca47/hd_ready.webm';

            % FOSDEM 2012 talk about Linux's next generation graphics display server "Wayland":
            moviefiles(end+1).name = 'http://video.fosdem.org/2012/maintracks/k.1.105/Wayland.webm';
        end

        moviefiles(end+1).name = 'http://movies.apple.com/movies/us/apple/getamac/apple_getamac_group_20080512_480x272.mov';
        moviefiles(end+1).name = 'http://movies.apple.com/movies/us/apple/getamac/apple_getamac_sadsong_extended_20080519_480x272.mov';
        moviefiles(end+1).name = 'http://movies.apple.com/movies/us/apple/getamac/apple_getamac_breakthrough_20080401_480x272.mov';
        moviefiles(end+1).name = 'http://movies.apple.com/movies/us/apple/getamac/apple-getamac-fat_480x376.mov';
        moviefiles(end+1).name = 'http://movies.apple.com/movies/us/apple/getamac_ads4/prlady_480x272.mov';

        % Count all movies in our playlist:
        moviecount = size(moviefiles,2);

        % Use polling to wait for new frames when playing movies from the
        % internet. This to make sure we don't time out too early or block
        % for too long if the network connection is slow / high-latency / bad.
        blocking = 0;

        % For network playback we use a higher than default caching time:
        preloadsecs = 10;
    end

    % Playbackrate defaults to 1:
    rate=1;
    
    % Endless loop, runs until ESC key pressed:
    while (abortit<2)
        iteration=iteration + 1;
        fprintf('ITER=%i::', iteration);
        moviename=moviefiles(mod(iteration, moviecount)+1).name;
        
        % Open movie file and retrieve basic info about movie:
        [movie movieduration fps imgw imgh] = Screen('OpenMovie', win, moviename, [], preloadsecs);
        fprintf('Movie: %s  : %f seconds duration, %f fps, w x h = %i x %i...\n', moviename, movieduration, fps, imgw, imgh);
        
        i=0;
        
        % Start playback of movie. This will start
        % the realtime playback clock and playback of audio tracks, if any.
        % Play 'movie', at a playbackrate = 1, with endless loop=1 and
        % 1.0 == 100% audio volume.
        Screen('PlayMovie', movie, rate, 1, 1.0);
    
        t1 = GetSecs;
        
        % Infinite playback loop: Fetch video frames and display them...
        while 1
            % Check for abortion:
            abortit=0;
            [keyIsDown,secs,keyCode]=KbCheck;
            if (keyIsDown==1 && keyCode(esc))
                % Set the abort-demo flag.
                abortit=2;
                break;
            end;

            % Check for skip to next movie:
            if (keyIsDown==1 && keyCode(space))
                % Exit while-loop: This will load the next movie...
                break;
            end;

            % Only perform video image fetch/drawing if playback is active
            % and the movie actually has a video track (imgw and imgh > 0):
            if ((abs(rate)>0) && (imgw>0) && (imgh>0))
                % Return next frame in movie, in sync with current playback
                % time and sound.
                % tex is either the positive texture handle or zero if no
                % new frame is ready yet in non-blocking mode (blocking == 0).
                % It is -1 if something went wrong and playback needs to be stopped:
                tex = Screen('GetMovieImage', win, movie, blocking);

                % Valid texture returned?
                if tex < 0
                    % No, and there won't be any in the future, due to some
                    % error. Abort playback loop:
                    break;
                end

                if tex == 0
                    % No new frame in polling wait (blocking == 0). Just sleep
                    % a bit and then retry.
                    WaitSecs('YieldSecs', 0.005);
                    continue;
                end

                % Draw the new texture immediately to screen:
                Screen('DrawTexture', win, tex, [], [], [], [], [], [], shader);

                % Update display:
                Screen('Flip', win);

                % Release texture:
                Screen('Close', tex);

                % Framecounter:
                i=i+1;
            end;

            % Further keyboard checks...

            if (keyIsDown==1 && keyCode(right))
                % Advance movietime by one second:
                Screen('SetMovieTimeIndex', movie, Screen('GetMovieTimeIndex', movie) + 1);
            end;

            if (keyIsDown==1 && keyCode(left))
                % Rewind movietime by one second:
                Screen('SetMovieTimeIndex', movie, Screen('GetMovieTimeIndex', movie) - 1);
            end;

            if (keyIsDown==1 && keyCode(up))
                % Increase playback rate by 1 unit.
                if (keyCode(shift))
                    rate=rate+0.1;
                else
                    KbReleaseWait;
                    rate=round(rate+1);
                end;
                Screen('PlayMovie', movie, rate, 1, 1.0);
            end;

            if (keyIsDown==1 && keyCode(down))
                % Decrease playback rate by 1 unit.
                if (keyCode(shift))
                    rate=rate-0.1;
                else
                    while KbCheck; WaitSecs(0.01); end;
                    rate=round(rate-1);
                end;
                Screen('PlayMovie', movie, rate, 1, 1.0);
            end;
        end;
    
        telapsed = GetSecs - t1;
        fprintf('Elapsed time %f seconds, for %i frames.\n', telapsed, i);

        Screen('Flip', win);
        KbReleaseWait;
        
        % Done. Stop playback:
        Screen('PlayMovie', movie, 0);

        % Close movie object:
        Screen('CloseMovie', movie);
    end;
    
    % Close screens.
    Screen('CloseAll');

    % Done.
    return;
catch
    % Error handling: Close all windows and movies, release all ressources.
    Screen('CloseAll');
end;