Audio preload problems with Safari (MacOS and iOS)

[amunn]

I'm having problems getting audio tasks to work properly on Safari. They work fine with Firefox and Chrome on MacOS.

Using Safari on MacOS, the first stimulus doesn't play; subsequent ones do.
Using Safari on iOS, the experiment fails to load at all.

Setting use_webaudio to either 'true' or 'false' makes no difference.

Link on cognition.run:

Code:

    var dev_version = "6.3.1";
    var cur_version = jsPsych.version();

		if (cur_version != dev_version)
			{console.log("Warning! Developed version " + dev_version + " doesn't match running version! " + cur_version)};

		var audio = 'P_audio';
		if (CONDITION == 2) {
			audio = 'P_audio';
		};
    if (CONDITION == 3) {
      audio = 'C_audio';
    };

		var timeline = [];
    var audio_list =
    [
      'audio/C_TheDolls.mp3',
      'audio/C_ThreeDolls.mp3',
      'audio/P_TheDolls.mp3',
      'audio/P_ThreeDolls.mp3',
    ];

    var stimuli = [
      {
        "P_audio": "P_TheDolls.mp3",
        "C_audio": "C_TheDolls.mp3",
        "sentence": "The girl fixed the dolls."
      },
      {
        "P_audio": "P_ThreeDolls.mp3",
        "C_audio": "C_ThreeDolls.mp3",
        "sentence": "The girl fixed three dolls."
      }
    ]

    var preload = {
    type: 'preload',
    auto_preload: true,
    audio: audio_list,
    message: "<h2>Preparing your experiment</h2>"
    };

    timeline.push(preload);


		var instructions = {
          type: 'instructions',
          pages: [
                '<p>In this task, you will read a sentence and be asked to judge that sentence on a scale of 1-5.</p>'+
                '<p>1 is a sentence that does not sound like a natural sentence you would say.</p>'+
                '<p>5 is a sentence that sounds like a perfectly natural thing you would say.</p>'+
                '<p>Click the "Next" button to start.</p>'
            ],
          show_clickable_nav: true,
					allow_backward: false,
          post_trial_gap: 1000
        };
		timeline.push(instructions);



		  var judgment_trial = {
				type: 'audio-slider-response',
				stimulus: jsPsych.timelineVariable(audio), // audio varies by CONDITION
				data: {sentence: jsPsych.timelineVariable('sentence'),
						  },
				labels: ['1','','','','5'],
				button_label: 'Next',
				max: 5,
				min: 1,
				slider_start: 3,
				slider_width: 300,
			};


			var judgment_task = {
 			 timeline: [judgment_trial], 
 			 timeline_variables: stimuli,
 			 randomize_order: true,
 		 };


		 timeline.push(judgment_task);



				 var end_task_html = [ '<p>The experiment is over!</p>' +
							'<p>Thank you for your participation.</p>'
							  ];


		 		 var end_task = {
		 			 type: 'instructions',
		 			 pages: end_task_html,
		 			 show_clickable_nav: true,
		 			 button_label_next: 'End',
		 			 allow_backward: false,
		 			 post_trial_gap: 1000
		 		 };

		 timeline.push(end_task);

			jsPsych.init({
				timeline: timeline,
        override_safe_mode: 'true',
        use_webaudio: 'true',
				 on_finish: function(){jsPsych.data.displayData()}// comment this out when running on server
			})