Ok, I have been able to move this forward a bit thanks to the help of folks over on #icecast.
This command allowed me to test the connection to icecast:
# gst-launch-1.0 audiotestsrc ! audioresample ! lamemp3enc ! shout2send mount=/mopidy ip=127.0.0.1 port=8003 password=********
There were two issues.
Firstly, I had inadvertently placed the section within the comment markers after the examples in the icecast.xml file. Moving the section below the end marker enabled the mount and the fallback /silence.mp3 mount could not be seen.
Secondly, it seems that the password in the output line in the [audio] section must be the password found in in the icecast.xml config file. This information is currently omitted from the instructions. Since this did not initially work, I had assumed that maybe admin level access was required so had used the admin password, although I was not comfortable with it.
The command shown in the instructions assumes the username is ‘source’ hence the username= parameter is not required.
Specifying user admin will not work. Once the username was removed and the source password specified, the login now succeeded. Once that part was sorted, I now had a connection between mopidy and icecast, which could be seen in the log:
127.0.0.1 - - [01/Jun/2018:12:12:01 +0100] “SOURCE /mopidy HTTP/1.0” 200 19 “-” “GStreamer 1.4.4” 172
Now that was working, the mountpoint could be seen in the public home in icecast, but not in the Admin home mountpoint list - yet.
When a track is played, there is no audio in the browser, however, this seems to create a stream and a /mopidy mountpoint is now shown in Admin home mountpoint list. When you click on the M3U button there, and choose ‘open with’, selecting the media player, this appears to open the stream and play it in the said media player. Any tracks that are subsequently selected and played in musicbox webclient will now play in the open media player session.
Ok, this is rather cumbersome, but at least I have a working audio stream. So, why do the tracks not play in musicbox in the browser when they are selected?