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Multicast source

The typical cable-operator picture: a headend or an encoder distributes channels as MPEG-TS transport streams into multicast groups on the local network — one group per channel. This page attaches such a group to a Catena channel.

Attach the group

Create a channel and press + Add Source on the Sources tab. Pick the MPEG-TS/UDP protocol and fill in:

  • Host — the multicast group address, 239.255.1.77 for example.
  • Port — the group's port, 5500 for example.
  • Peer timeout (ms) — how much silence in the group to tolerate before restarting the ingest. An empty field is a sensible default.

Press Save. The streamer joins the group, locks the stream, and the channel's status turns green; the health card shows the bitrate and the tracks.

The multicast source attached and working

What must be true of the network

  • Multicast does not travel the internet. The streamer receiving the group must sit in the same network segment as its source — or the network in between must route multicast.
  • The subscription is the streamer's doing. It sends an IGMP join; switches with IGMP snooping deliver the stream to subscribers only. Nothing needs configuring on the streamer for that — what matters is that the network lets the join through.
  • One input — one group and port. Every channel gets its own group: that is how the headend distributes them too.

Onward by task

  • The stream in the group is usually compressed already (H.264 or MPEG-2). H.264/AAC plays as is; if the headend sends MPEG-2 — add a transcoder, or browser players will not read the stream.
  • TS inputs carry a continuity-error counter: the CC errors limit threshold turns the source "degraded" on packet loss — see Input failover.
  • A multicast group can also be a standby: a second input with a priority below the primary.

If the group did not lock

  • The card says Dead, no bitrate. Packets do not reach the streamer: wrong group or port, a different VLAN, the IGMP join not passed by a switch, a firewall cutting UDP. Check from the streamer's machine — it is the one subscribing.
  • There is bitrate but the channel is not green. The stream arrives but the expected tracks are not found in it — look at the health card: what the streamer parsed out of the stream.
  • The source flaps: working — degraded. Packet loss in the network; the CC-error counter in the card grows. That is a network problem, not a channel problem.