15 December 2016 - Auto alternate source.

<?xml version="1.0"?>
<query>
    <userid>&lt;&lt;id&gt;&gt;</userid> {/* required*/}
    <userkey>&lt;&lt;key&gt;&gt;</userkey> {/* required*/}
    <action>[Action]</action> {/* required*/}
    <format>
        <output>[advanced_hls|advanced_dash|advanced_mss]</output>
        {/* Main/alternate source fields */}
        <main_source>
            {/* main_sources params */}
        </main_source>
        {/* multiple alternate_sources may be included */}
        <alternate_source>
            <type>[video_audio|video|audio]</type>
            <auto>[yes|no]</auto>
        </alternate_source>
        <destination>[DestFile]</destination> {/* required*/}
    </format>
</query>

{
    "query": {
        "userid": "<<id>>",
        "userkey": "<<key>>",
        "action": "[Action]",
        "format": {
            "output": "[advanced_hls|advanced_dash|advanced_mss]",
            "main_source": "  ",
            "alternate_source": {
                "type": "[video_audio|video|audio]",
                "auto": "[yes|no]"
            },
            "destination": "[DestFile]"
        }
    }
}