Saturday Night Takeaway 2021

Digital delay is what you call 'progress'!

There are a couple of ways to help reduce it. The most common is to use a mobile phone for the return cue* / IFB to the presenter / guest. Comes with it's own risks of course, but it's pretty much standard practice, especially for links using Cellular bonding etc. (That kit does now tend to offer return audio, but it has often been tricker than you'd think to get working reliably. Everyone is now so used to using mobile phones for return audio they tend to stick to that.)

The other alternative - used for bigger set piece set ups - is to use an IP audio codec to send a low delay return cue. Thats worked as far away as New Zealand - with an outgoing path on satellite and IP audio for the return cue over 4G. Really just a development from using POTS lines and 4 wires.

It also kicked off some remote working - originally a low delay feed of the audio of a reporter / presenter on location (at at home), allowing the autocue operator in the studio to scroll the text that they then see on a low delay (and lower quality) return vision feed over IP.

These things have all become much more widely used over the past 12 months!

(*Cue being an often used term in TV for clean-fead / mix-minus. Confusingly, in radio, cue meant sending everything back down the line including their own feed. Only used in very particular circumstances.)

The microwave link though was harder to set up right? It required line of site for the OB unit is that correct. I read that on Transdiffusion website, where OB units using microwave links had to ensure line of site from their OB unit to the nearest microwave station.

There was often a mid point or two. Commseng of this parish can give chapter and verse, but yes very labour intensive, but no other option before satellite became feasable and affordable

Also I read the post office managed cable links throughout the country, with access to the cable network as another way of bringing the OB to London headquarters.

Until the 1980s the broadcasters were only allowed to operate their own permanent microwave links only if the GPO for whatever reason wouldn't or couldn't do so themselves. There were even cases of some transmitters being fed for vision using a broadcaster microwave link, but the sound going by GPO landline.

Also similar rules sometimes applied to OBs. One summer (1980?) the BBC's cricket coverage was pictures only, because a GPO strike meant no audio circuits could be provided.

Up until the early 90s national distribution circuits for all four channels was provided by BT.

Generally the idea for an OB was to get the signal into the receive points which were installed on transmitter masts (taking advantage of the height) which had BT circuits back to the relevant studio centre where it could be fed into the contribution circuits the BBC permanently rented from BT.

I gather there were occasions where they would set up a temporary receive point at a BT exchange or similar. I think this tended to be done if the permanent circuits were already booked for something else or if the OB location made that easier than having lots of midpoint hops to get to BBC premises.

Sometimes. Though in my part of the world, Hannington an obvious choice for having an OB receive position, had nothing.

When the Beeb covered racing from Newbury, they'd set up a mid point on Walbury Hill (near Hungerford), and send the signals back to (I think ?) Crystal Palace from there. (Quite a distance !)

There's a photo I can't find at present of the hill the day after the Hungerford Shootings, showing BBC, TV-am, ITN, and I think also TVS vans up there.

https://en.wikipedia.org/wiki/Walbury_Hill

I can indeed give you chapter and verse on microwave links for programme contribution, myself and my colleagues spent many years doing it.
The practice was simple enough, getting circuits back to the nearest studio centre which had circuits out of them to where they needed to get to - so for example an OB in Birmingham might link directly into dishes on the roof of Pebble Mill, further out, there were mast head receivers on some of the major tranmsitter sites such as Sutton Coldfield, and BT circuits back from there to PM. However if neither of those could be seen (it had to be line of sight) then you would have to receive it and re-transmit it on different frequencies. This was the midpoint.

Midpoints could be in trucks on hilltops with a small diesel genny towed behind the Bedford truck. They could be on building rooftops with local power. You could daisy chain them together, so a OB site far away from any permenant facilities could be used. One example I often use is Portman Road, the Ipswich Town FC. That required 4 hops of links. OB -> building roof -> hill top -> water tower -> Swains Lane mast north of London and then cables into Broadcasting House and then TVC.
Each of the points required staff, who travelled, stayed in hotels and needed T&DE paying. It could be 15 people for 4 days for the example mentioned.

Each hop was made up of two identical links in a main and spare configuration, and they were lined up and tested all the way through to meet very high standards. Only the main was generally offered through, and was switched to the spare only if required (although the spare could be offered on a "Match of the Day" basis - you can put camera 1 on it, but if the main fails, we will switch it at both ends and you'll only have the main output. The reliabilty suffered at each midpoint, as there would be a point of failure - usually the diesel genny, and I have spent many hours listening to the purr and occasional hiccup followed by swearing as we try to restart the damn things. There was battery backup which may cover you while the genny is being tended to, but sometimes the batteries wouldn't hold their charge as well as they might. There may also be missed alarm calls for staff at some points in the chain for early starts, and many many other problems too.

We could fire into some BT Towers, but that was rarely done for OBs, it was more common for News jobs, they would also bounce signals off buildings - fine until something changes, like a window being opened - but no good for an OB with a whole programme to get to air.

When satellite came in it was significantly more expensive, and so it was only done where there were no other means - such as the Channel Islands or abroad, or where the sheer number of hops was impractical. When capacity increased, costs came down, and then the move to digital satellite encoding reduced the space required further, the finances changed.
It would still be worth providing a microwave link of one hop (also now digital) straight into a mast head rx, once it is on it doesn't matter if it is on 24 hours a day for weeks on end - so useful still financially for long shows. It is also a very robust link - unlikley to be affected by heavy rain.
You can see that the staffing for the Ipswich FC OB is now one man who drives the uplink truck to site, does the show, and drives it back the following day - so much cheaper.

There is still a place for microwave links, but with fibre at a lot of major venues, satellite space fairly cheap, bonded cellphones for inserts into news and other shows, it is not so common for main line links. Radio Cameras obviously still use microwaves, and there are some reasons why you may use it.

The last major show I did extensively with links was the BBC 1 New Year's Eve display - that was mainly links with some satellite capacity used from Wembley and the O2 Arena. Timing was important, reliability too, and we even used a building roof midpoint. The whole programme was microwave link back into BT Tower and then to TVC. Backed up via satellite, just in case.

There is probably a whole thread about what went on in the Comms Dept in the BBC, and the various links sections of the ITV companies and of BT too. They were fun days, and I miss sitting on hilltops in the sunshine. I forget the days of ice and snow when the truck wouldn't get up the hill, the genny failed to start, and a host of other stories........

The other 'digital delay' is Long GOP codecs being used - like MPEG2 and h.264 (aka MPEG4 in Comms Land) - which often have to buffer a number of frames for motion analysis before they can send the data fully and before the receiving decoder can output a video signal. These delays are added to the path delay - so even with a very low delayed path, if you only have <100Mbs of bandwidth, you may well end up with codec delay in the mix too.

If you can get enough bandwidth - and bandwidth = £££ - then you can use Intra-frame codecs like J2K (aka JPEG2000), AVCi100, Dirac Pro, or even uncompressed codecs - which may only introduce a frame or two of delay over-and-above your path delay (i.e. how long it takes for the actual data to travel from A to B) It's not always possible to get that kind of bandwidth (it's almost always delivered over dedicated fibre) - but if you can, you can significantly reduce latency.

This kind of technology is the backbone of remote production. Relatively recent World Cup Skiiing events in Sweden have used 75 camera feeds with J2K compression for remote production - all using intra-frame low-latency compression rather than Long GOP. But they had a large, fat, dedicated fibre pipe between the location and the remote production centre in Stockholm (albeit without much of a backup AIUI)...

I've spent a lot of time on Walbury Hill, as you say a long hop into Crystal Palace, but one of the better sites, with a decent pub down the road for lunch.
I suspect Hannington not getting a receiver was down to getting circuits out of there to London or Southampton - if Newbury Racing required more than one circuit then doing that via a midpoint wasn't a problem - Party Conferences had load of circuits for example. If Hannington had a line, which was very expensive, then you may find one is not enough. It doesn't have to be a circuit, it could be no more than a link out to Rowridge or Crystal Palace, but then that needs staffing too - so the finances don't work out again. A midpoint truck was bought, paid for, and the staff T&DE was the only extra cost.

The fun factor you've not mentioned, are over water or tidal paths. Didn't some of the Bournemouth party conference links go the non intuitive route 'inland' back to Mendip, and Bristol, despite Rowridge being the obvious choice ?

Hannington was also an off-air rebroadcast transmitter for BBC analogue TV services wasn't it (or am I totally wrong) - so there weren't 'BBC circuits' going to it? I have a dim recollection of ITV having circuits to the transmitter but the BBC not.