15 December 2016 - Auto alternate source.

<?xml version="1.0"?>
<query>
    <userid><<id>></userid> <!-- required-->
    <userkey><<key>></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]"
        }
    }
}