function EyeLink_SimpleVideo(screenNumber)
% Simple video demo with EyeLink integration and animated calibration / drift-check/correction targets.
% In each trial eye movements are recorded while a video stimulus is presented on the screen.
% Each trial ends when the space bar is pressed or the video stops playing. A different drift-check/correction
% animated target is used in each of the 2 trials.
%
% Illustrates how a video file can be added for trial play back in Data Viewer's "Trial Play Back Animation" view. 
%
% Usage:
% Eyelink_SimpleVideo(screenNumber)
% 
% screenNumber is an optional parameter which can be used to pass a specific value to PsychImaging('OpenWindow', ...)
% If screenNumber is not specified, or if isempty(screenNumber) then the default:
% screenNumber = max(Screen('Screens'));
% will be used.

% Bring the Command Window to the front if it is already open
if ~IsOctave; commandwindow; end

PsychDefaultSetup(2);

% Initialize PsychSound for calibration/validation audio feedback
InitializePsychSound();

% Use default screenNumber if none specified
if (nargin < 1)
    screenNumber = [];
end

try
    %% STEP 1: INITIALIZE EYELINK CONNECTION; OPEN EDF FILE; GET EYELINK TRACKER VERSION
    
    % Initialize EyeLink connection (dummymode = 0) or run in "Dummy Mode" without an EyeLink connection (dummymode = 1);
    dummymode = 0;
    EyelinkInit(dummymode); % Initialize EyeLink connection
    status = Eyelink('IsConnected');
    if status < 1 % If EyeLink not connected
        dummymode = 1; 
    end
    
    % Open dialog box for EyeLink Data file name entry. File name up to 8 characters
    prompt = {'Enter EDF file name (up to 8 characters)'};
    dlg_title = 'Create EDF file';
    def = {'demo'}; % Create a default edf file name
    answer = inputdlg(prompt, dlg_title, 1, def); % Prompt for new EDF file name    
    % Print some text in Matlab's Command Window if a file name has not been entered
    if  isempty(answer)
        fprintf('Session cancelled by user\n')
        EyelinkCleanupHelper; % Abort experiment (help EyelinkCleanupHelper function)
        return
    end    
    edfFile = answer{1}; % Save file name to a variable    
    % Print some text in Matlab's Command Window if file name is longer than 8 characters
    if length(edfFile) > 8
        fprintf('Filename needs to be no more than 8 characters long (letters, numbers and underscores only)\n');
        EyelinkCleanupHelper; % Abort experiment
        return
    end
    
    % Open an EDF file and name it
    if Eyelink('IsConnected') == 1 % if we have a live connection to a Host PC
        failOpen = Eyelink('OpenFile', edfFile);
        if failOpen ~= 0 % Abort if it fails to open
            fprintf('Cannot create EDF file %s', edfFile); % Print some text in Matlab's Command Window
            EyelinkCleanupHelper;
            return
        end
    end
    
    % Get EyeLink tracker and software version
    % <ver> returns 0 if not connected
    % <versionstring> returns 'EYELINK I', 'EYELINK II x.xx', 'EYELINK CL x.xx' where 'x.xx' is the software version
    ELsoftwareVersion = 0; % Default EyeLink version in dummy mode
    [ver, versionstring] = Eyelink('GetTrackerVersion');
    if dummymode == 0 % If connected to EyeLink
        % Extract software version number. 
        [~, vnumcell] = regexp(versionstring,'.*?(\d)\.\d*?','Match','Tokens'); % Extract EL version before decimal point
        ELsoftwareVersion = str2double(vnumcell{1}{1}); % Returns 1 for EyeLink I, 2 for EyeLink II, 3/4 for EyeLink 1K, 5 for EyeLink 1KPlus, 6 for Portable Duo           
        % Print some text in Matlab's Command Window
        fprintf('Running experiment on %s version %d\n', versionstring, ver );
    end
    % Add a line of text in the EDF file to identify the current experimemt name and session. This is optional.
    % If your text starts with "RECORDED BY " it will be available in DataViewer's Inspector window by clicking
    % the EDF session node in the top panel and looking for the "Recorded By:" field in the bottom panel of the Inspector.
    preambleText = sprintf('RECORDED BY Psychtoolbox demo %s session name: %s', mfilename, edfFile);
    Eyelink('Command', 'add_file_preamble_text "%s"', preambleText);
    
    
    %% STEP 2: SELECT AVAILABLE SAMPLE/EVENT DATA
    % See EyeLinkProgrammers Guide manual > Useful EyeLink Commands > File Data Control & Link Data Control
    
    % Select which events are saved in the EDF file. Include everything just in case
    Eyelink('Command', 'file_event_filter = LEFT,RIGHT,FIXATION,SACCADE,BLINK,MESSAGE,BUTTON,INPUT');
    % Select which events are available online for gaze-contingent experiments. Include everything just in case
    Eyelink('Command', 'link_event_filter = LEFT,RIGHT,FIXATION,SACCADE,BLINK,BUTTON,FIXUPDATE,INPUT');
    % Select which sample data is saved in EDF file or available online. Include everything just in case
    if ELsoftwareVersion > 3  % Check tracker version and include 'HTARGET' to save head target sticker data for supported eye trackers
        Eyelink('Command', 'file_sample_data  = LEFT,RIGHT,GAZE,HREF,RAW,AREA,HTARGET,GAZERES,BUTTON,STATUS,INPUT');
        Eyelink('Command', 'link_sample_data  = LEFT,RIGHT,GAZE,GAZERES,AREA,HTARGET,STATUS,INPUT');
    else
        Eyelink('Command', 'file_sample_data  = LEFT,RIGHT,GAZE,HREF,RAW,AREA,GAZERES,BUTTON,STATUS,INPUT');
        Eyelink('Command', 'link_sample_data  = LEFT,RIGHT,GAZE,GAZERES,AREA,STATUS,INPUT');
    end
    
    
    %% STEP 3: OPEN GRAPHICS WINDOW
    
    % Open experiment graphics on the specified screen
    if isempty(screenNumber)
        screenNumber = max(Screen('Screens')); % Use default screen if none specified
    end

    window = PsychImaging('OpenWindow', screenNumber, GrayIndex(screenNumber)); % Open graphics window
    Screen('Flip', window);
    
    % Get max color value for rescaling  to RGB for Host PC & Data Viewer integration
    colorMaxVal = Screen('ColorRange', window);
    % Return width and height of the graphics window/screen in pixels
    [width, height] = Screen('WindowSize', window);
    
    
    %% STEP 4: SET CALIBRATION SCREEN COLOURS/SOUNDS; PROVIDE WINDOW SIZE TO EYELINK HOST & DATAVIEWER; SET CALIBRATION PARAMETERS; CALIBRATE
    
    % Provide EyeLink with some defaults, which are returned in the structure "el".
    el = EyelinkInitDefaults(window);
    % set calibration/validation/drift-check(or drift-correct) background color. 
    % It is important that this background colour is similar to that of the stimuli to prevent large luminance-based 
    % pupil size changes (which can cause a drift in the eye movement data)
    el.backgroundcolour = repmat(0.45,1,3); % 0.45 == gray matching video stimuli background in normalized color space units
    % set "Camera Setup" instructions text colour so it is different from background colour
    el.msgfontcolour = repmat(BlackIndex(screenNumber),1,3);
    
    % Set calibration beeps (0 = sound off, 1 = sound on)
    % Setting beeps to off (0) for video targets
    el.targetbeep = 0;  % sound a beep when a target is presented
    el.feedbackbeep = 0;  % sound a beep after calibration or drift check/correction
    
    % Required for macOS Catalina users (/w PTB 3.0.17.11) to disable audio
    % with animated calibration targets and trial video stimuli to
    % avoid freezing in video playback
    spcf1 = 0; % Used both here in el struct for animated target movies, and also below when loading trial-stimulus movies
    if IsOSX
        [~, result] = system('sw_vers');
        if regexp(result,'ProductVersion\D*10\.15')
            spcf1 = 2;
            el.calAnimationOpenSpecialFlags1 = spcf1; % for Screen('OpenMovie', ..., specialFlags1) see http://psychtoolbox.org/docs/Screen-OpenMovie
        end
    end
    % N.B. el.calAnimationOpenSpecialFlags1 = 2 may also be required with certain versions of 
    % GStreamer on Ubuntu Linux. In certain cases on Linux (e.g. when PsychPortAudio('GetOpenDeviceCount') > 0), 
    % disabling the audio is required to avoid a crash, or more generally a brief delay oafter the first 
    % frame of the target video is displayed on screen and the eventual continuation of playback
    
    
    % Configure animated calibration target path and properties
    el.calTargetType = 'video';
    calMovieName = ('calibVid.mov');
    
    el.calAnimationTargetFilename = [pwd '/' calMovieName];
    el.calAnimationResetOnTargetMove = true; % false by default, set to true to rewind/replay video from start every time target moves
    el.calAnimationAudioVolume = 0.4; % default volume is 1.0, but too loud on some systems. Setting volume lower to 0.4 (minimum is 0.0)
    
    % You must call this function to apply the changes made to the el structure above 
    EyelinkUpdateDefaults(el);
    
    % Set display coordinates for EyeLink data by entering left, top, right and bottom coordinates in screen pixels
    Eyelink('Command','screen_pixel_coords = %ld %ld %ld %ld', 0, 0, width-1, height-1);
    % Write DISPLAY_COORDS message to EDF file: sets display coordinates in DataViewer
    % See DataViewer manual section: Protocol for EyeLink Data to Viewer Integration > Pre-trial Message Commands
    Eyelink('Message', 'DISPLAY_COORDS %ld %ld %ld %ld', 0, 0, width-1, height-1);    
    % Set number of calibration/validation dots and spread: horizontal-only(H) or horizontal-vertical(HV) as H3, HV3, HV5, HV9 or HV13
    Eyelink('Command', 'calibration_type = HV5'); % horizontal-vertical 5-points
    % Allow a supported EyeLink Host PC button box to accept calibration or drift-check/correction targets via button 5
    Eyelink('Command', 'button_function 5 "accept_target_fixation"');
    % Hide mouse cursor
    HideCursor(window);
    % Suppress keypress output to command window.
    ListenChar(-1);
    % Clear Host PC display from any previus drawing
    Eyelink('Command', 'clear_screen 0');
    % Put EyeLink Host PC in Camera Setup mode for participant setup/calibration
    EyelinkDoTrackerSetup(el);
    
    
    %% STEP 5: TRIAL LOOP.
    
    driftVidList = {'dotsGrey.mov' 'wheelGrey.mov'};% Provide drift-check video file list for 2 trials
    vidList = {'expected.mov' 'disappear.mov'};% Provide trial video file list for 2 trials
    
    spaceBar = KbName('space');% Identify keyboard key code for space bar to end each trial later on    
    for i = 1:length(vidList)
           
        % Change animated calibration target path for drift-check/correction
        calMovieName = char(driftVidList(i));
        el.calAnimationTargetFilename = [pwd '/' calMovieName];       
        % You must call this function to apply the changes made to the el structure above
        EyelinkUpdateDefaults(el);
        
        % STEP 5.0 DRIFT-CHECK/CORRECTION
        % Perform a drift check/correction.
        % Optionally provide x y target location, otherwise target is presented on screen centre
        EyelinkDoDriftCorrection(el, round(width/2), round(height/2));
        
        % STEP 5.1: START TRIAL; SHOW TRIAL INFO ON HOST PC; SHOW BACKDROP IMAGE AND/OR DRAW FEEDBACK GRAPHICS ON HOST PC
        % Open movie file:
        movieName = char(vidList(i));
        moviePath = [ pwd '/' movieName ];
        [movie, ~, ~, Movx, Movy] = Screen('OpenMovie', window, moviePath, [], [], spcf1); % spcf1 required to disable audio on macOS Catalina and avoid playback freezing issues

        % Write TRIALID message to EDF file: marks the start of a trial for DataViewer
        % See DataViewer manual section: Protocol for EyeLink Data to Viewer Integration > Defining the Start and End of a Trial
        Eyelink('Message', 'TRIALID %d', i);
        % Write !V CLEAR message to EDF file: creates blank backdrop for DataViewer
        % See DataViewer manual section: Protocol for EyeLink Data to Viewer Integration > Simple Drawing
        Eyelink('Message', '!V CLEAR %d %d %d', round(el.backgroundcolour(1)/colorMaxVal*255), round(el.backgroundcolour(2)/colorMaxVal*255), round(el.backgroundcolour(3)/colorMaxVal*255));
        % Supply the trial number as a line of text on Host PC screen
        Eyelink('Command', 'record_status_message "TRIAL %d %s"', i, movieName);        
        % Draw graphics on the EyeLink Host PC display. See COMMANDS.INI in the Host PC's exe folder for a list of commands
        Eyelink('SetOfflineMode'); % Put tracker in idle/offline mode before drawing Host PC graphics and before recording
        Eyelink('Command', 'clear_screen 0'); % Clear Host PC display from any previus drawing
        % Optional: draw feedback box and lines on Host PC interface
        % See section 25.7 'Drawing Commands' in the EyeLink Programmers Guide manual
        Eyelink('Command', 'draw_box %d %d %d %d 15', round(width/2-Movx/2), round(height/2-Movy/2), round(width/2+Movx/2), round(height/2+Movy/2));
        Eyelink('Command', 'draw_box %d %d %d %d 15', round(width/2-80), round(height/2-70), round(width/2+80), round(height/2+90));
        Eyelink('Command', 'draw_line %d %d %d %d 15', round(width/2-Movx/2), round(height/2)+40, round(width/2+Movx/2), round(height/2)+40);
        
        %STEP 5.2: START RECORDING
        
        % Put tracker in idle/offline mode before recording. Eyelink('SetOfflineMode') is recommended 
        % however if Eyelink('Command', 'set_idle_mode') is used allow 50ms before recording as shown in the commented code:        
        % Eyelink('Command', 'set_idle_mode');% Put tracker in idle/offline mode before recording
        % WaitSecs(0.05); % Allow some time for transition           
        Eyelink('SetOfflineMode');% Put tracker in idle/offline mode before recording
        Eyelink('StartRecording'); % Start tracker recording
        WaitSecs(0.1); % Allow some time to record a few samples before presenting first stimulus
        
        % STEP 5.3: PRESENT VIDEO; CREATE DATAVIEWER BACKDROP AND INTEREST AREA; STOP RECORDING
        
        timeOut = 'yes'; % Variable set to a default value. Changes to 'no' if key pressed to end video early
        % Start playback engine:
        Screen('PlayMovie', movie, 1);
        frameNum = 0;        
        % Wait until user releases keys on keyboard:
        KbReleaseWait;       
        % Playback loop: Runs until end of movie or keypress:
        while 1
            % Check that eye tracker is  still recording. Otherwise close and transfer copy of EDF file to Display PC
            error = Eyelink('CheckRecording');
            if(error ~= 0)
                fprintf('EyeLink Recording stopped!\n');
                % Transfer a copy of the EDF file to Display PC
                Eyelink('SetOfflineMode');% Put tracker in idle/offline mode
                Eyelink('CloseFile'); % Close EDF file on Host PC
                Eyelink('Command', 'clear_screen 0'); % Clear trial image on Host PC at the end of the experiment
                WaitSecs(0.1); % Allow some time for screen drawing
                % Transfer a copy of the EDF file to Display PC
                EyelinkTransferFileHelper(el, edfFile);
                EyelinkCleanupHelper; % Abort experiment
                return
            end
            % Wait for next movie frame, retrieve texture handle to it
            tex = Screen('GetMovieImage', window, movie);
            if tex<=0 % Valid texture returned? A negative value means end of movie reached
                break;
            end
            % Draw the new texture immediately to screen:
            Screen('DrawTexture', window, tex);            
            % Update display:
            Screen('Flip', window);
            frameNum = frameNum + 1;
            if frameNum == 1
                % Write message to EDF file to mark the start time of stimulus presentation.
                Eyelink('Message', 'STIM_ONSET');
                % Write !V IAREA message to EDF file: creates interest areas in DataViewer
                % See DataViewer manual section: Protocol for EyeLink Data to Viewer Integration > Interest Area Commands
                Eyelink('Message', '!V IAREA RECTANGLE %d %d %d %d %d %s', 1, round(width/2-80), round(height/2-70), round(width/2+80), round(height/2+90), 'BOX_IA');
                vidStart = GetSecs;  % Start a timer
            end
            % Write message to EDF file to mark the time of each video frame
            Eyelink('Message', 'Frame to be displayed %d', frameNum);
            % Write a !V VFRAME message to the data file specifying the frame number, location and file name so DataViewer can play back the video
            Eyelink('Message', '%d !V VFRAME %d %d %d %s', 0, frameNum, round(width/2-Movx/2), round(height/2-Movy/2), movieName);
            % End trial if space bar is pressed
            [~, kbSecs, keyCode] = KbCheck;
            if keyCode(spaceBar)
                % Write message to EDF file to mark the space bar press time
                Eyelink('Message', 'KEY_PRESSED');
                timeOut = 'no';
                % Release texture:
                Screen('Close', tex);
                break;
            end
            Screen('Close', tex); % Release texture if no key is pressed
        end  % End while loop
        Screen('PlayMovie', movie, 0); % Stop playback
        Screen('CloseMovie', movie); % Close movie
        
        % Draw blank screen at end of trial
        Screen('FillRect', window, el.backgroundcolour);
        [~, vidEnd] = Screen('Flip', window); % Present blank screen
        % Write message to EDF file to mark time when blank screen is presented
        Eyelink('Message', 'BLANK_SCREEN');
        
        % Calculate video duration
        if strcmp(timeOut, 'yes') % If no key pressed during video
            vidDur = round((vidEnd-vidStart)*1000); % Duration of video until BLANK_SCREEN
        else % If key pressed during video
            vidDur = round((kbSecs-vidStart)*1000); % Duration of video until key is pressed
        end
        
        % Write !V CLEAR message to EDF file: creates blank backdrop for DataViewer
        % See DataViewer manual section: Protocol for EyeLink Data to Viewer Integration > Simple Drawing
        Eyelink('Message', '!V CLEAR %d %d %d', round(el.backgroundcolour(1)/colorMaxVal*255), round(el.backgroundcolour(2)/colorMaxVal*255), round(el.backgroundcolour(3)/colorMaxVal*255));
        
        % Stop recording eye movements at the end of each trial
        WaitSecs(0.1); % Add 100 msec of data to catch final events before stopping
        Eyelink('StopRecording'); % Stop tracker recording
        
        % STEP 5.4: CREATE VARIABLES FOR DATAVIEWER; END TRIAL
        
        % Write !V TRIAL_VAR messages to EDF file: creates trial variables in DataViewer
        % See DataViewer manual section: Protocol for EyeLink Data to Viewer Integration > Trial Message Commands
        Eyelink('Message', '!V TRIAL_VAR iteration %d', i); % Trial iteration
        Eyelink('Message', '!V TRIAL_VAR video_file %s', movieName); % Video name
        Eyelink('Message', '!V TRIAL_VAR video_duration %d', vidDur); % Video duration until key press or end of video
        Eyelink('Message', '!V TRIAL_VAR timeout %s', timeOut); % Key pressed to end trial early? 'yes' or 'no'        
        % Write TRIAL_RESULT message to EDF file: marks the end of a trial for DataViewer
        % See DataViewer manual section: Protocol for EyeLink Data to Viewer Integration > Defining the Start and End of a Trial
        Eyelink('Message', 'TRIAL_RESULT 0');
        WaitSecs(0.01); % Allow some time before ending the trial
    end % End trial loop
    
    
    %% STEP 6: CLOSE EDF FILE. TRANSFER EDF COPY TO DISPLAY PC. CLOSE EYELINK CONNECTION. FINISH UP
    
    % Put tracker in idle/offline mode before closing file. Eyelink('SetOfflineMode') is recommended.
    % However if Eyelink('Command', 'set_idle_mode') is used, allow 50ms before closing the file as shown in the commented code:
    % Eyelink('Command', 'set_idle_mode');% Put tracker in idle/offline mode
    % WaitSecs(0.05); % Allow some time for transition  
    Eyelink('SetOfflineMode'); % Put tracker in idle/offline mode
    Eyelink('Command', 'clear_screen 0'); % Clear Host PC backdrop graphics at the end of the experiment
    WaitSecs(0.5); % Allow some time before closing and transferring file    
    Eyelink('CloseFile'); % Close EDF file on Host PC       
    % Transfer a copy of the EDF file to Display PC
    EyelinkTransferFileHelper(el, edfFile);
    EyelinkCleanupHelper;
catch % If syntax error is detected
    EyelinkCleanupHelper;
    % Print error message and line number in Matlab's Command Window
    psychrethrow(psychlasterror);
end
