[Technologist]

I think only having one multiplex that supports DVB-T2 limits the HD channels on Freeview. In the short-medium term it would be preferable if all (or at least one) multiplexes except PSB1 & PSB2 migrated. Then eventually just one of these two remaining as DVB-T to provide a basic/legacy service, with the other having national capabilities.

But the Vaizey plan was to,make PSB emit HD only in all platforms
Which moves the technology of tv forward by (sensible) intervention.
As I mention elsewhere a sensible solution was a PSB regional mux ..
(roughly what PSB B is about to be plus some BBC local,radio )
And a PSB national mux being other BBC s4c Alba and BBC uk radio maybe uktv
And PSB UK. Wide mux with the daughter channels on.
That is just over 200 coders compared to the about 450 we have .

But there are many commercial issues etc etc so there was a lot to be solved !

Maintaining  a legacy service for anything longer than a few weeks
Like we did at DSO is not a good way forward ….

[bkman1990]

Was the Vaizey Plan put out by the DCMS before DSO or after it?

I think I recall having a discussion about it when a lot of us were members of TV Forum. I'm quite stunned about the amount of decoders that are in use out there to transmit all of those TV stations at the moment. Going from what I have read in your post; are those 450 decoders are just for Freeview only or are they for other platforms as well?

[Technologist]

The Vaizey plan was first mentioned at the DTG summit in 2011
And again the next year … the aim was for DTT To do it at 700 MHz clearance.

150 coders per mux is a rough figure
but say around 18 regions and 7 coders per region plus say 4 spare sets of kit
(Two per centre ….. assuming some sharing if you loose one centre)

The 200 is Regional 150 or more
plus national 4+1 *7 = 35 plus uk wide two sets =14 .
But it could be say 30 more !

The BBC is repurposing some of the old PSB 3 BBC B coders to do DSAT
Say about a dozen at each centre.

[SunburntRock89]

twitter.com 

[Stooky Bill]

Excellent decision. Hopefully we can also bin the DVB-S transponders too, switch to S2 so there is plenty more room for HD channels.

My understanding is that they'll have one DVB-S transponder (for the legacy SD services) and the rest will be switched to DVB-S2 (for the HD ones)

[SunburntRock89]

Excellent decision. Hopefully we can also bin the DVB-S transponders too, switch to S2 so there is plenty more room for HD channels.

My understanding is that they'll have one DVB-S transponder (for the legacy SD services) and the rest will be switched to DVB-S2 (for the HD ones)

This was what I thought would happen but the tweet above claims otherwise.
See the first image

And later in the year, SD versions of BBC channels on satellite will close entirely.

[Stooky Bill]

Was the Vaizey Plan put out by the DCMS before DSO or after it?

I think I recall having a discussion about it when a lot of us were members of TV Forum. I'm quite stunned about the amount of decoders that are in use out there to transmit all of those TV stations at the moment. Going from what I have read in your post; are those 450 decoders are just for Freeview only or are they for other platforms as well?

Encoders not decoders. 

Yes it's surprising and something I hadn't appreciated until fairly recently...

Because the DTT muxes are statistically multiplexed (each service changes it bitrate according to need) each service needs to be encoded seperately for each version of the MUX. So for example even though Channel 5 HD for example is identical in every region, it still needs encoding seperately for every region. Otherwise if suddenly Look North was requiring more bits but elsewhere in the country something else needed more then it can cope with that. 

So for example if there's 17 versions of a MUX and there's 9 services on each that's 153 seperate encoding processes. Then double that so there's some resilience!

---

My understanding is that they'll have one DVB-S transponder (for the legacy SD services) and the rest will be switched to DVB-S2 (for the HD ones)

This was what I thought would happen but the tweet above claims otherwise.
See the first image

And later in the year, SD versions of BBC channels on satellite will close entirely.

That's not contrary to what I said. 

The closure 'later in the year' will be the remaining DVB-S transponder I mentioned

[SunburntRock89]

Was the Vaizey Plan put out by the DCMS before DSO or after it?

I think I recall having a discussion about it when a lot of us were members of TV Forum. I'm quite stunned about the amount of decoders that are in use out there to transmit all of those TV stations at the moment. Going from what I have read in your post; are those 450 decoders are just for Freeview only or are they for other platforms as well?

Encoders not decoders. 

Yes it's surprising and something I hadn't appreciated until fairly recently...

Because the DTT muxes are statistically multiplexed (each service changes it bitrate according to need) each service needs to be encoded seperately for each version of the MUX. So for example even though Channel 5 HD for example is identical in every region, it still needs encoding seperately for every region. Otherwise if suddenly Look North was requiring more bits but elsewhere in the country something else needed more then it can cope with that. 

So for example if there's 17 versions of a MUX and there's 9 services on each that's 153 seperate encoding processes. Then double that so there's some resilience!

---

This was what I thought would happen but the tweet above claims otherwise.
See the first image

That's not contrary to what I said. 

The closure 'later in the year' will be the remaining DVB-S transponder I mentioned

Ahh my bad sorry

[Keith]

I think only having one multiplex that supports DVB-T2 limits the HD channels on Freeview. In the short-medium term it would be preferable if all (or at least one) multiplexes except PSB1 & PSB2 migrated. Then eventually just one of these two remaining as DVB-T to provide a basic/legacy service, with the other having national capabilities.

But the Vaizey plan was to,make PSB emit HD only in all platforms
Which moves the technology of tv forward by (sensible) intervention.
As I mention elsewhere a sensible solution was a PSB regional mux ..
(roughly what PSB B is about to be plus some BBC local,radio )
And a PSB national mux being other BBC s4c Alba and BBC uk radio maybe uktv
And PSB UK. Wide mux with the daughter channels on.
That is just over 200 coders compared to the about 450 we have .

But there are many commercial issues etc etc so there was a lot to be solved !

Maintaining  a legacy service for anything longer than a few weeks
Like we did at DSO is not a good way forward ….

I wonder whether these Freesat changes happening, combined with the need to save money might result in some changes/upgrades to the freeview multiplexes.

Presumably at present PSB1 and PSB2 both have to support regional TV, whilst broadcasting BBC One ITV1 respectively in SD via DVB-T. In theory if one of these was to initially convert to DVB-T2 and have only support for nations that would reduce the number of decoders required. Then longer term the other could be upgraded with just UK wide support, or nations if still required for advertising or other reasons.

The argument for keeping some form of legacy (DVB-T) service in the short-medium term is that not everyone can afford to replace their TVs to receive HD channels, as until a few years ago incompatible TVs were still being widely sold. I dare say by OFCOM (or whoever) dragging their feet on implementing the Vaizey plan this is less of an issue than it was a couple years ago, and in a few years' time if/when it happens even less as more people naturally replace their devices.

[Technologist]

As at next year all PSB muxes will be regional,
Numbers See my post #23
Say 150 to,170 coders on a regional mux this carries BBC local radio
Say 35 to 50 coders for national BBC mux thus carries BBC UK and national radio
Say 24 coders fir uk wide mux commercial PSB daughters
But there are many issues about this allocation but less than others !

But if the government gave back the £400 million from the help scheme surplus ..
That quite a few stb for those with DVB T only receivers