What formats does the default stream support?
- HE-AACv1 from 16kbps Mono to 128kbps Stereo at 44.1kHz
- MP3 from 8kbps Mono to 320kbps Stereo at 44.1kHz
- HE-AACv2 from 18kbps Stereo to 64kbps Stereo at 44.1kHz
I see Silver + includes 2 external relays. My question is are they really needed? What extras would that bring to the party?
With every extra relay you can add one streaming server to relay your stream. LoadBalancing, Geobalancing, that kind of stuff.
Also: SAM Cloud streams won't be listed on shoutcast.com or xiph.org, an Icecast or Shoutcast Relay server can be listed on either of these portals.
I assume it will still only be 120 listeners regardless of if via the SAM stream or relay stream
No, the 120 listener limit only applies to the Stream hosting provided by Spacial as part of SAM Cloud.
If you rent a stream server with 1000 slots or put your own 10 GigE Server as a relay, you can add more listeners to your stream. For external Relays, SAM Cloud behaves just like any normal encoder (SAM Broadcaster, Winamp DSP, VLC, etc.) would.