How does TV Transmission/Playout Work?

I don't know if this is the right place to put this but, I question that I have allways wanted to know how TV Transmission/Playout work.

Do TV channels such as BBC, ITV, Sky ect all have automated playout software which can play out out all of the Programmes, Ads, Idents ect?, And what kind of software do they use?

At its simplest level, yes, it's a bit of software.
But it's a bit of software that has to talk to lots of other systems - software and hardware - and needs some human interaction to play out a channel successfully.

As with many bits of TV, if you were designing it from scratch, you probably wouldn't end up with the way things are today. But it's probably easiest to explain how things were to start with: a vision mixer, a sound mixer, and a number of live and prerecorded (film, tape, etc) sources.

Then basic forms of automation came in; which would take the prepared schedule, and with a bit of tweaking by the director, would automatically select the right source on the vision mixer; press play on the tape deck at the the right time, and so on.

And then tapes were replaced by video servers - so the automation system would be able to get the right clip from the server, copy it to the right place, and turn the data file into a video stream, that then gets switched to air.

For a channel that's largely prerecorded material (the UKTV network, say), one playout director can supervise a number of channels. They need to make sure that the channels largely keep to time, and look out for things failing, and so on.

Channels with more live material - BBC One, for example - will have just one director, and an announcer too. While some parts of the day will be prerecorded material, they also have to liaise with the directors of live programmes, and try to keep the schedule largely on track if things over- or under-run.
In these cases, the automation system won't be left to its own devices, and rather than using fixed points in the schedule, they'll have a handy 'take next' button which will trigger the next event.

A well-known brand of playout system in the UK is Omnibus, which appears to have recently bought by Miranda - there's a little about it here.

That's a basic overview of how it works - I'm sure others here will be able to expand things or answer any more questions you've got.

And if you happen to be working at, oh I dunno, Technicolor during an England World Cup game its a button you want to be very very careful of

thegeek - thanks for that; it's an interesting overview. I have a question for you - when the move from tapes to video server was made, would someone at the BBC have had to copy all the tapes in real time? Take a long-running pre-recorded BBC One programme for instance - say, Murder, She Wrote - would someone have had to sit there and transfer every episode in real time? Or is that job done by the studio that originally produced it in the USA and the BBC just requested electronic copies of episodes?

The way things were done five years ago (and possibly still today), tapes would arrive in the Broadcast Centre three days before transmission. The schedules would be loaded into the automation system along with the tape number & timecodes that it could find the programme on. Then a Media Management Operator (known as a Pres Op in the olden days) would load the tapes into a Flexicart.

A Flexicart is a bit of Sony automation kit which has lots of shelves for tapes in it, and a robotic arm which would scan the barcode labels on the tapes' spines, and pick up and insert the correct tapes into one of a number of VTRs sitting at the bottom of the cabinet. You can see some here.

I think, in pre-server days, the automation system would play stuff straight off tape inside a Flexicart (or similar) - but laterally, the Omnibus system would stick the appropriate clips on a video server, in advance.

For some channels (eg those that repeat programmes often), the video file would then be stored away on a big tape data vault, of the kind you get in big datacentres - the advantage here is that you can fit a lot more on one of those tapes than you can on a DigiBeta, and then don't need a librarian to bring you a tape when the programme gets repeated a few days later. When Flextech moved into the BC, they wanted their entire archive of programmes (both distribution masters and transmission copies) archived to server, then sent off the tapes to a big warehouse somewhere in Wales, because it was cheaper to store them there.

Technology might be more reliable now, so things may have changed - but for BBC programmes, the tape was kept on hand so that the MMO could whack it in a tape deck if the server copy fell over.

Most channels still accept programmes delivered on tape only; though I think commercials are generally delivered by file these days.

Thanks - very interesting! I'm particularly impressed with that Flexicart thing.

Don't be, anything mechanical like that is always a nightmare! Flexicarts weren't (they don't make them any more) the worst of that type of machine but they all go a bit haywire every now and then.

Pre-server (the NTA days) programmes were played from stand-alone VTs and trails from 2 machines called MARCs which was like a Flexicart but about 4 times as big. When the BBC first got servers, trails were cached onto them from Flexi but programmes were either cached manually or not at all. Even when they were put on server they'd usually be deleted the day after even if there was a repeat so it was a bit of a waste of time IMO, although there were some advantages with having a server copy though.


Yes, datatape is all very well but it's not as useful as having a videotape at hand. The tape data vaults are the modern day equivalent of the Flexicart except that if it all goes wrong you can't just fish the tape out and load it up in a stand alone machine

...so it helps to have your tape archive a couple of miles up the A40 and a courier on a motorbike, just in case!

Or in Wales?

As you said it's the BBC have the day's VTs on hand in the building anyway, IIRC they don't use a data archive?

Alright, a lot of miles down the M4!

How do the Sky News graphics work, they have different styles on HD and SD... do they use different Vision Mixers?