[Icecast] Change bitrate

[José Luis Artuch]

Hello, good morning !
Running Icecast2 and Ices2 with live audio from Line IN, what is the
correct way to change the bitrate ?.
In the Icecast2 configuration file I set:

<mount type="normal">
    <mount-name>/entzun.opus</mount-name>
    <bitrate>128</bitrate>
</mount>

But it seems that is not enough since the bitrate does not change.
Receiving the stream with Rhythmbox, after restart the server the
bitrate is not 128 kbps.
If required, how should I set the Ices2 configuration file ?.
Thanks !.
José Luis