[Icecast] Add metadata to fallback mount?

Philipp Schafft phschafft at de.loewenfelsen.net
Fri May 29 11:40:20 UTC 2020

Good afternoon,

On Fri, 2020-05-22 at 05:52 -0700, Jack Elliott wrote:
> On 5/21/2020 1:10 AM, Philipp Schafft wrote:
> > On Sat, 2020-05-16 at 12:30 -0700, Jack Elliott wrote:
> >> Hi, I'm pretty sure this isn't going to be possible, but I'll ask. I'd
> >> like to add a <stream-title> to my fallback mount so when the main
> >> stream mount drops and the fallback kicks in, that the connected player
> >> shows a different title.
> >>
> >> Then back again, of course.
> > The metadata data is in the responsibility of the source client. Icecast
> > just relays that information. As soon as the client hits the fallback
> > stream the metadata of the fallback stream is sent to the client.
> >
> > So, best advice would be to check the configuration of the fallback's
> > source client.
> >
> > With best regards,
> >
> Thank you.
> In our case, the fallback is an mp3 file. Is there a specific metadata 
> "tag" I should use for the identifying string?

I think there is some misunderstanding here:
When you set a file as fallback Icecast will just send that file as if
serving it by a direct request. This comes with two effects:
      * Icecast will send it as fast as it can. Sending at "the correct
        speed" is not something Icecast manages. It always forwards data
        as fast as it can. Sending at a real time speed is part of the
        source client's work. And as your disk is normally much faster
        than your network connection Icecast will send it with full
      * For legacy codecs only: Legacy codecs (that is MP3 and AAC) do
        not implement metadata at all. If stored in a file it ID3 is
        used. ID3 however is a container that contains the actual file.
        Exactly like a Zip file contains other files. However ID3 can
        not be streamed. Trying to do so may or may not break listener
        clients. For streaming Nullsoft invented a, also legacy protocol
        called ICY. Icecast uses this for MP3 and AAC if requested by
        the client. This protocol contains (crippled) metadata. However
        as it is a network protocol it can not be used for storage.

Long story short: It is generally recommended to have a local source
client that serves the fallback. Otherwise timing will break.
For legacy codecs it is also important as there can not be metadata
without a proper source client.

I hope that helps. :)

With best regards,

Philipp Schafft (CEO/Geschäftsführer) 
Telephon: +49.3535 490 17 92

Löwenfelsen UG (haftungsbeschränkt)     Registration number:
Bickinger Straße 21                     HRB 12308 CB
04916 Herzberg (Elster)                 VATIN/USt-ID:
Germany                                 DE305133015
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