This page covers tracks: the six channels the engine mixes into, and which one your output takes. On a machine that only runs playouts you set this once and forget it. On a machine that does more, this page is the one that prevents an unpleasant surprise.
What a track is
The engine has six audio tracks. Every source is on all six by default, and an output picks one.
A playout is put on the track you choose, automatically. So the setting is not “which sound goes in” but “which track the output listens to”.
The setting
Settings → Outputs → Audio track, per playout.
A DeckLink output carries exactly one track. So does a stream. Two playouts on one machine normally use two different tracks, so that each output carries its own line.
Reserving a track
Reserve this track for the playout takes every other source off that track.
Without it, a source that somebody added to the engine — a microphone, a capture card, a media file — is on all six tracks, and therefore also on the one your SDI feed is carrying. It arrives on air underneath your playout and nobody in the control room hears it, because the desk is monitoring the same output.
With it on, the card carries the playout and nothing else.
On a machine that does nothing but playout, leave it on. It costs nothing and removes a category of surprise.
Leave it off only when something outside the playout genuinely has to reach that output as well — and then know exactly what that something is.
A worked example
Two playouts, two DeckLink ports:
| Playout 1 | Playout 2 | |
|---|---|---|
| Track | 5 | 6 |
| Reserved | yes | yes |
| Result | Port 1 carries line 1 only | Port 2 carries line 2 only |
Anything else on the machine sits on tracks 1–4 and reaches neither port.
Where else the track shows up
Recording and streaming take the same track as that playout’s output, so what you record is what you sent.
A playout used as a source in another scene carries picture only — precisely because its audio is already in the mix through its own track, and would otherwise arrive twice.