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dosxuk4,276 posts since 22 Oct 2005
Yorkshire Look North (Yorkshire)
I do wonder why they think the benefit of having the correct HD feed to the correct transmitters is so limited.


Because their primary concern is whether or not they can get additional advertising revenue by equiping and transmitting and additional region - not whether people will be able to see the correct regional news programme.
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TedJrr201 posts since 11 Sep 2005
Anglia (East) Look East

Strange. I could have sworn that I had previously read here that the regional feeds were being delivered to the transmitters by satellite. But if that's not the case, then yeah, it would have some additional cost to it, though I do wonder why they think the benefit of having the correct HD feed to the correct transmitters is so limited.


The BBC use satellite as a standby feed, but only the nations and not the regions are included, a couple of very remote relays in Scotland are fed this way for the primary feed


CityProd may have to referring to those analog interim measures (eg Sandy Heath) where D-SAT was used to feed the correct region leading up to DSO.
Technologist83 posts since 10 Oct 2018
London London
Having done both the Channel Island ( as radio link frequencies were grabbed by the French ) and the Sandy Heath ( to save the BBC a lot if £££ in microwave links in Cambridge and to make the move of BBC Cambridge a doddle for tv )
analogue from DSAT installations...
both had better picture quality than the legacy analogue system, (using sky stb)

I also demonstrated to the BBC a very complex MPEG processing box which allowed you to drop a service (may be even two) from a CBR or VBR / stat muxed signal .. and add a Service from another mux again could be VBR or just a bit more CBR .. all in MPEG 2 without decoding

Think if this as the woolacombe relay on the N Devon coast ..
it can see Wenvoe very well ..
So pick BBC west from DSAT to replace BBC one Wales on DTT ...
But it was very pricey ! In itself and we needed to. add a DVB txt to DVB ST encoder
I remember the date well 6/7/2005 the day London got the Olympics !
Last edited by Technologist on 8 July 2019 7:40pm - 4 times in total
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Markymark7,333 posts since 13 Dec 2004
Meridian (North) South Today

Think if this as the woolacombe relay on the N Devon coast ..
it can see Wenvoe very well ..
So pick BBC west from DSAT to replace BBC one Wales on DTT ...
But it was very pricey ! In itself and we needed to. add a DVB txt to DVB ST encoder
I remember the date well 6/7/2005 the day London got the Olympics !


It was the Countisbury relay I think, (serves Lynton and Lynmouth), it's had a long
history of not being able to properly receive a feed from Mendip

http://downloads.bbc.co.uk/rd/pubs/reports/1987-14.pdf
Last edited by Markymark on 9 July 2019 9:04am
Inspector Sands13,974 posts since 25 Aug 2004

And even Cornish viewers getting commercials for the likes of Wookey Hole wouldn't be quite as extreme as getting commercials for shows at the Birmingham Hippodrome!

I've seen adverts for TfL and other London specific things on Channel 4 HD... and that's seen everywhere in the UK
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Inspector Sands13,974 posts since 25 Aug 2004

Yep - I think people assume that making a new ITV region HD on terrestrial just needs a new 'feed' of that region, ignoring that if that is a new unique combination of channels EVERY channel in the PSB3 mux (BBC One HD, BBC Two HD, ITV HD, C4 HD, C5 HD etc.) will require a new encoder (even if its carrying the same content already being encoded elsewhere) and for redundancy, that will mean two new sets of encoders, plus a new unique combination of services will also need dual redundant fibre distribution to the transmitters taking it

Is that right? Why do they have to seperately encode each service seperately for each mux?


BBC News Channel for example is the same everywhere, so surely they can just encode it for DTT using several redundant encoders) and then use that to provide that for each Mux? Is it just a redundancy thing?
Markymark7,333 posts since 13 Dec 2004
Meridian (North) South Today
It was the Countisbury relay I think, (serves Lynton and Lynmouth), it's had a long
history of not being able to properly receive a feed from Mendip

http://downloads.bbc.co.uk/rd/pubs/reports/1987-14.pdf

Thanks - an interesting read.
It shows that height is not always the answer and it's as important to reduce unwanted signals as much as maximise the signal level on wanted ones.


Indeed ! I’m slightly surprised they couldn’t receive a feed from Stockland Hill or Huntshaw Cross, the South West region would arguably have been more appropriate. I’m sure if there had been a decent signal it would have been used. Since Sept 2014 PSB 1 and 3 have been fibre fed there.
Technologist83 posts since 10 Oct 2018
London London
I agree a very interesting read and a reflection of innovative ways of recording tv by a camera ...
Actually in 2005 the local MP for Woolacombe was bending a lot of BBC ears !!!
Hence the example ..
One issue with most N Devon /Cornwall relays is that they were shielded by terrain from the main transmitters .... valleys never pointed in the right direction!!

But reflections and co channel were a great issue ...
i needed a 23 element yagi mounted about a metre off the wall
and 2m above the parapet
of the Greenwood Theatre to get sufficient nulls for the reflections from surrounding buildings .... and using the first side lobe for reception of CP...
the problems of analogue tv !!!
I can imagine digital would give great reception from a coat hanger !!!!
commseng297 posts since 8 Dec 2016
London London
The Greenwood Theatre is one of those odd BBC sites long since gone from TV usage.
Wasn't it there due to a will donating money for a theatre to be built, so it was assumed that it was a theatre for entertainment.
However there was some doubt that it may have meant an operating theatre, as it is in King's College grounds, which has medical facilities? Or is that an old wive's tale?
Technologist83 posts since 10 Oct 2018
London London

Yep - I think people assume that making a new ITV region HD on terrestrial just needs a new 'feed' of that region, ignoring that if that is a new unique combination of channels EVERY channel in the PSB3 mux (BBC One HD, BBC Two HD, ITV HD, C4 HD, C5 HD etc.) will require a new encoder (even if its carrying the same content already being encoded elsewhere) and for redundancy, that will mean two new sets of encoders, plus a new unique combination of services will also need dual redundant fibre distribution to the transmitters taking it

Is that right? Why do they have to seperately encode each service seperately for each mux?


BBC News Channel for example is the same everywhere, so surely they can just encode it for DTT using several redundant encoders) and then use that to provide that for each Mux? Is it just a redundancy thing?


Because DTT Uses stat muxing it needs each if the services in a mux to have its own coder ... it's what enables (to use the PSB 3 HD mux as an example) a service to have 15++ Mbit/sec when it needs it to hold quality
... while most of the time taking say 3 to 4 Mbit/s
See http://en.digitalbitrate.com/dtv.php?liste=1&live=9&lang=en&mux=BBCB-PSB3

So if you split off a channel to be fed to all regional muxes what constant bit rate do you give it and thus subtract from the statmuxed pool ...
if you said say 8 Mbit/sec that would mean that the statmuxed pool would have
to have one fewer channel ...
and also some if the statmuxed gain would be lost ...
so probably not a good thing !

And if you turn it around if you stat mux the uk wide channels and the drive a encoder per region to complete the mux ... but the regional coder only gets the bit rate that's left which is not the quality that would be sought for a premier channel like a PSB .. but there are some things that you can do to improve the quality but it gets so complex ..and not predictable.
You then get into the realm Of the Transmux that I described fr Woolacombe ... but I have not seen one in AVC .... it was mind bendingly complex in MPEG 2.

Hence a set of coders statmuxing for each region is more or less the only way
but at a cost. ( times number of regions )

Just to make it more complex the DTT Hd mux uses two pass encoding so it is coding once and then seeing if it can make it better by using a different encoding toolset / bit rate ....
Last edited by Technologist on 9 July 2019 11:35am
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