[Icecast] how to update stream metadata by source client

[Akos Maroy]

this is an ICE protocol question - how would a source client send an
update of the stream metadata to an icecast 2 server?

as much as I know, the source sends an HTTP-style header at the
beginning, with various metadata fields, than an empty line, then starts
to send the binary audio data to icecast.

but if the metadata for the stream needs to be updated, I guess the
source has to 'stop' the binary data flowing for a second, send the new
metadata, then resume sending the binary data.

but how would this work precisely?