Hi, was working on a site and as I always have debug on for each new site I found a few bugs for the plugin.
First one is line 127 for the main file audio-player/audio-player.php
if ($_SERVER["HTTPS"] == "on" || $_SERVER["SERVER_PORT_SECURE"] == "1")
if ( isset( $_SERVER["HTTPS"] ) && strtolower( $_SERVER["HTTPS"] ) == "1")
and the second on is deprecated function.
When adding an options page it a numerical value is no longer valid.
add_options_page('Audio player options', 'Audio Player', 'manage_options', $this->optionsPageName, array(&$this, "outputOptionsSubpanel"));
the change is in bold.
other than those two things, everything is good.