BBC News Channel General Discussion

Sync Pulse Generator: A There'll probably be two, A and B, and an auto change over unit should A fail, though both will be genlocked to the BBC's master SPG system

With it being less than a year after 9/11, the story goes that one of the big wigs at the BBC felt it was unnecessary to go through all the usual measures for a royal death. They supposedly couldn't justify going into full obit mode for one death when several thousands died six months earlier, so they started to take things slightly more casually, hence the lack of black ties.

It's worth noting the the VD but still appeared on screen.


I searched Wikipedia for it (always a reliable source) which listed that for HD sources it uses a tri-level sync. When I clicked on tri-level sync the first sentence said it was used for locking of HD video and in parenthesis (genlock). So how different is SPG versus Genlock? Sounds like they are similar.



To be honest if the BBC were to that they should just invest in suit jackets and ties for these purposes. Now a days I would imagine death coverage would be handled primarily at the desk as has been the case in recent major events that appeared on BBC World.

But the very fact that there was dead air means that they couldn't put out anything proper for whatever reason. Getting a breakdown slide on air might be just as easy as getting the correct content back

Genlock is the state of having all of your equipment synchronised together so they all operate with the same timing information (primarily so the start of a frame is the same on all equipment). A Signal Pulse Generator generates a signal that is used to get that timing information. A tri-level-sync is one of those types of signal.

To summarise: A SPG generates a sync signal that you use to genlock your equipment.

Could the problems not be linked to the work happening overnight at NBH at the weekend, gremlins in the system? (For those who don't know, Millbank was in use rather than studio C).

Nope, completely separate issues.

Given how long it can take BBC1 and BBC2 with their proper continuity suites to react to a programme falling off air sometimes (see Something for the Weekend BT line switch and the One Show fire alarm examples) you can forgive a news studio that goes directly to air rather than through a presentation area for not being too slick in how they deal with breakdowns.

Outside Source has returned to it's normal length at 2100, so no longer an extra edition of Sportsday to fill the gap.

An SPG is a Sync Pulse Generator. It will generate timing reference signals (HD Tri-level syncs, SD Black and Burst etc.) and usually will also generate colour bars for the studio, as well as other test signals. It will sometimes generate more than one feed of syncs, to allow some equipment that adds more delay to be referenced to an 'earlier' sync feed so that its output is co-timed with other gear that adds less delay that is referenced to 'later' syncs.

You will usually have two SPGs at least in a studio, running as a main and a backup (as it is one of the most vital pieces of kit), with a changeover switch selecting which is in circuit.

The SPG timing reference signals are distributed to camera CCUs, vision mixers, CGs, Frame synchronisers, VTRs, Disc servers etc. to ensure that all sources in the studio are correctly co-timed, so that as you cut between cameras, the images are 'in sync' without needing to constantly use frame synchronisers (which can add a frame of delay).

The action of locking a piece of equipment's internal sync generator to an external reference signal is often called 'Genlocking' and the input is sometimes (particularly on camcorders etc.) called 'Genlock'. It is so called because you are locking your internal sync generator to an external source.

In multi-studio operations SPGs themselves are usually genlocked to a master 'station syncs' feed.

What you almost certainly saw was the Studio B colour bars output, which was labelled as SPG (because it was generated by the SPG). This is often present on the studio output change-over switch to allow a studio to uniquely identify its output. (So if you are lining up with a Master Control you would put bars on your output to identify they had the correct feed. You wouldn't conventionally do this on the vision mixer as that could be present on multiple feeds from the studio. It will usually also route tone to line at the same time. As most studios have a Main and a Reserve feed output - you often put bars and tone on both, and then remove them from one (but not both) of the feeds to uniquely identify which is Main and which is Reserve (which is vital to know in cases of breakdown)

Most studios will have a lock-out facility that disables the "Bars to Line" switch from putting bars to line when the studio is put into 'Transmission' mode (i.e. the red lights are put on). This will sometimes also disable other functions, like loudspeaker talkback feeds from the gallery to the studio floor etc. which may only be needed in rehearsal and could be positively dangerous during transmission.

At the BBC, until the closure of the analogue network transmission area, the 'transmission' mode in TVC studios was actually remotely controlled from Master Control (aka Pres) so that when they put you on-air, your studio at TV Centre actually got a Tally feed from the MCR playout area that switched on your red lights and disabled bars to line. The feed wasn't a straight tally from the MCR mixer as it was usually flashed at 2'00" to TX etc. It was also possible to locally enable 'transmission' or 'on-air' mode for local recordings, or for when the studio was working into a different broadcaster.

Sometimes that remote bars to line cancelling worked too well in Bristol Studio B!

https://groups.google.com/forum/#!original/uk.tech.broadcast/Ux_CQ0B_NYQ/PXqYQAq-79AJ

(Don't ask how the hell I remembered reading that post years ago and managed to find it!)

Edit: not sure that the link works. So, in a nutshell - Bristol gallery B would put up bars and tone before feeding a contribution to the news area at TVC and go for coffee while the London guys got lined up. Occasionally they would come back to find the bars had been cancelled and the remote studio weren't happy.

It eventually transpired that their knackered old phone system had a fault ( which happened more often when it rained and when more circuits were required than normal) where a different line ringing could monetarily activate the studio red lights as if a Pres area was cueing the studio, which killed the bars and tone.

Turned out to be due to water getting into some long forgotten cables underneath the car park, which dated back to their old, long ripped out TV continuity suite.

Does the second half hour of Outside Source start at :29 past the hour. For my TiVo on BBC WN the beginning of the second half hour is cut off because of this.