jsPsych/plugins/jspsych-single-audio.js

/**
 * jspsych-single-audio
 * Josh de Leeuw
 *
 * plugin for playing an audio file and getting a keyboard response
 *
 * documentation: docs.jspsych.org
 *
 **/

jsPsych.plugins["single-audio"] = (function() {

  var plugin = {};

  jsPsych.pluginAPI.registerPreload('single-audio', 'stimulus', 'audio');

  plugin.info = {
    name: 'single-audio',
    description: '',
    parameters: {
      stimulus: {
        type: [jsPsych.plugins.parameterType.STRING],
        default: undefined,
        no_function: false,
        description: ''
      },
      choices: {
        type: [jsPsych.plugins.parameterType.KEYCODE],
        array: true,
        default: jsPsych.ALL_KEYS,
        no_function: false,
        description: ''
      },
      prompt: {
        type: [jsPsych.plugins.parameterType.STRING],
        default: '',
        no_function: false,
        description: ''
      },
      timing_response: {
        type: [jsPsych.plugins.parameterType.INT],
        default: -1,
        no_function: false,
        description: ''
      },
      response_ends_trial: {
        type: [jsPsych.plugins.parameterType.BOOL],
        default: true,
        no_function: false,
        description: ''
      },
      trial_ends_after_audio: {
        type: [jsPsych.plugins.parameterType.BOOL],
        default: false,
        no_function: false,
        description: ''
      },
    }
  }

  plugin.trial = function(display_element, trial) {

    // default parameters
    trial.choices = trial.choices || jsPsych.ALL_KEYS;
    trial.response_ends_trial = (typeof trial.response_ends_trial === 'undefined') ? true : trial.response_ends_trial;
    trial.trial_ends_after_audio = (typeof trial.trial_ends_after_audio === 'undefined') ? false : trial.trial_ends_after_audio;
    trial.timing_response = trial.timing_response || -1; // if -1, then wait for response forever
    trial.prompt = (typeof trial.prompt === 'undefined') ? "" : trial.prompt;

    // if any trial variables are functions
    // this evaluates the function and replaces
    // it with the output of the function
    trial = jsPsych.pluginAPI.evaluateFunctionParameters(trial);

    // setup stimulus
    var context = jsPsych.pluginAPI.audioContext();
    if(context !== null){
      var source = context.createBufferSource();
      source.buffer = jsPsych.pluginAPI.getAudioBuffer(trial.stimulus);
      source.connect(context.destination);
    } else {
      var audio = jsPsych.pluginAPI.getAudioBuffer(trial.stimulus);
      audio.currentTime = 0;
    }

    // set up end event if trial needs it
    if(trial.trial_ends_after_audio){
      if(context !== null){
        source.onended = function() {
          end_trial();
        }
      } else {
        audio.addEventListener('ended', function(){ end_trial(); });
      }
    }

    // show prompt if there is one
    if (trial.prompt !== "") {
      display_element.innerHTML = trial.prompt;
    }

    // store response
    var response = {
      rt: -1,
      key: -1
    };

    // function to end trial when it is time
    var end_trial = function() {

      // kill any remaining setTimeout handlers
      jsPsych.pluginAPI.clearAllTimeouts();

      // stop the audio file if it is playing
      // remove end event listeners if they exist
      if(context !== null){
        source.stop();
        source.onended = function() { }
      } else {
        audio.pause();
        audio.removeEventListener('ended', end_trial);
      }

      // kill keyboard listeners
      jsPsych.pluginAPI.cancelKeyboardResponse(keyboardListener);

      // gather the data to store for the trial
      var trial_data = {
        "rt": context !== null ? response.rt * 1000 : response.rt,
        "stimulus": trial.stimulus,
        "key_press": response.key
      };

      // clear the display
      display_element.innerHTML = '';

      // move on to the next trial
      jsPsych.finishTrial(trial_data);
    };

    // function to handle responses by the subject
    var after_response = function(info) {

      // only record the first response
      if (response.key == -1) {
        response = info;
      }

      if (trial.response_ends_trial) {
        end_trial();
      }
    };

    // start audio
    if(context !== null){
      startTime = context.currentTime + 0.1;
      source.start(startTime);
    } else {
      audio.play();
    }

    // start the response listener
    if(context !== null) {
      var keyboardListener = jsPsych.pluginAPI.getKeyboardResponse({
        callback_function: after_response,
        valid_responses: trial.choices,
        rt_method: 'audio',
        persist: false,
        allow_held_key: false,
        audio_context: context,
        audio_context_start_time: startTime
      });
    } else {
      var keyboardListener = jsPsych.pluginAPI.getKeyboardResponse({
        callback_function: after_response,
        valid_responses: trial.choices,
        rt_method: 'date',
        persist: false,
        allow_held_key: false
      });
    }

    // end trial if time limit is set
    if (trial.timing_response > 0) {
      jsPsych.pluginAPI.setTimeout(function() {
        end_trial();
      }, trial.timing_response);
    }

  };

  return plugin;
})();