MPTS output — several channels in one multiplex

An MPTS (multi-programme transport stream) puts several channels into one stream with a constant rate and its own tables, the way a DVB-C or DVB-T modulator, a headend or a hotel / campus network expects it. Castreon builds the multiplex itself — PIDs, PCR, PAT, PMT, SDT, NIT with logical channel numbers (LCN), EIT present / following, TDT and TOT — and sends it over UDP or RTP (unicast or multicast), or straight to an ASI card or a modulator in the server.

Available since Castreon 3.0.0, in the Enterprise edition.

Before you start

Every channel that goes into a multiplex needs its HTTP-TS output enabled (Castreon reads the channel from there, locally). Channels keep their other outputs; the multiplex is one more place where they go.

Plan the rate: the multiplex rate must be larger than the sum of the channels plus the tables. For a DVB-C modulator at 256-QAM / 6.9 MS/s that is about 51 Mb/s; for DVB-T 64-QAM 8 MHz, usually 22–32 Mb/s depending on code rate and guard interval. Use profiles with a constant bitrate for channels that go into a multiplex.

A new multiplex

Multiplexes (MPTS) (menu) → New multiplex:

1. Name and Enabled.
2. Destination: udp://239.10.0.1:1234 or rtp://… (unicast or multicast; TTL for multicast, Local address to choose the network card), or device:///dev/asitx0 for an ASI card or a modulator with a Linux device.
3. Multiplex rate (1–200 Mb/s). If you fill in the Delivery announced in the NIT (DVB-C or DVB-T, with frequency, symbol rate / bandwidth, modulation), for DVB-C the editor offers Use the channel rate — the exact useful rate from the symbol rate and the QAM.
4. TSID, ONID, Network ID, Network name, Provider — the identity of the multiplex in the tables.
5. Country (local time) — for the TOT, so receivers show the right local time.
6. Table texts — UTF-8, or No accents (old receivers).
7. Programme guide (EIT) — present / following for each service, taken from the channels' guide.
8. Delay (200–5000 ms, default 700) — the buffer that smooths the channels' timing; larger = steadier, but later.

Then Add channel, and for each one: SID (unique, 1–65535), LCN (the number on the receiver's remote) and the Name in SDT (empty = the channel name). Order them with Move up / Move down.

While it runs

The multiplex page shows the state (sending, not sending, over capacity), how much of the rate is Used by channels and tables, Dropped packets, and per channel: in the multiplex, waiting for tables, connecting or error, with its bitrate and delay. Over capacity means the channels need more than the multiplex rate — packets are dropped and the picture breaks on the receivers; raise the rate or lower the channels' bitrate.

Restart rebuilds the multiplex; deleting a multiplex stops the stream right away and leaves the channels untouched.

Good to know

• A multiplex is built from channels on the same server; with a cluster, bring a channel from another server first with a channel from the cluster.
• Scrambling, BISS or CA in the multiplex are not done by Castreon; the stream leaves in the clear.
• For a single channel to a modulator, an ordinary UDP output is enough — an MPTS is for several services with their own tables.