Output signal for adverts?

[pedro d]

Not owning an oscilloscope, (if that is the equipment required) or even the knowledge to do so, can somebody please enlighten me, as to whether there is a specific output signal transmitted, to signify the strart and finish of the dreaded advertisemnt breaks on all our tv channels?

[BillyNoMates]

There has been quite a lot of research into this. In fact there was a box - I think one of these new digital recording boxes which eliminated the adverts.

It was deemed illegal eventually so was withdrawn.

Nothing wrong with using the fast-forward function is there ?

I am sure there is some sort of signal sent but only to those controlling the transmission centres. You would probably never pick that up, oscilliscope or not. 

[jake-the-peg]

I think Sky have recently been awarded a number of patents in this area. They are stating that they currently have no plans to implement but a number of chanels are getting twitchy.

[fly258]

I'm sure the volume goes up when the ads come on, anyone else noticed it?

[Dudley]

Good question Fly258.  About fifteen years ago I won a prize from TV Times for letter of the week pointing out that the volume is increased when the adverts come on. Nothing has changed though. Why should they be allowed to do this? It is most irritating having to adjust the volume constantly.

[Hippy]

On the technical side, the TV people cannot adjust the sound volume on your set, but what happens is that during films and programmes, quite correctly, the majority of the sound information is contained in the lower 40% of the maximum power level. when the action moves to a street or noisy environment, the background noise occupies the lower 25% and the dialogue is then increased to compensate so that (40 + 25 = 65%) of maximum power is now used for the majority of the information. There is naturally such a thing as dynamic range in music and speech, so some spikes of information may reach the 100% level, but only for very short times. Not even the effect of a nuclear explosion will be at 100% modulation as it would not sound effective.

When the adverts are created the sound is "compressed" in that the dynamic range is vastly reduced. The difference between the lowest and highest power is much less than natural speech and music. This allows the soundtrack to occupy 75 - 80% of the available power level without amplitude distortion. This make the damned adverts blast out at you. The advert makers assume that you have disappeared into the kitchen to put the kettle on so try to turn your humble TV into a Tannoy!

[rojash]

Thanks Hippy, for a really enlightening post.