[Technologist]

D3&4 have moved supplier of code and mux and the connectivity either side
To a software coder (like PSB3 it’s ATEME) and virtualised on the Vena platform
So in theory changes at the click if a mouse looks easier !

For PSB3 the investment by itv has more than enabled the BBC to change its stated intent and emit regional HD services rather than use IPlayer/Bidi.
So one can see itv wanting to get its value for its money …

But now All three PSB muxes are regionalised for 2 tv channels (and a national slot) plus local radio
The only benefit seem to be to the coder manufacturers who have sold about 2 1/2 the number if coders needed for a regional/national/uk wide split of the muxes…. If the Vaizey plan had been implemented …

[CCFG]

The fact that in the last year we have actually lost HD channels on Freeview when all the other platforms are at-least somewhat trying to move to HD by default. We've lost BBC News HD, Quest HD, QVC HD and QVC Beauty HD all on Freeview, even then CBeebies HD and BBC Four HD took over 2 months to be reinstated. (though I do understand that the reason this happened was because of technical issues)

On the other side, ITV2, ITV3, ITV4 have all gone HD on Freesat, Channel 4 HD has been regionalised making it able to be put in the first 5 LCN's of the EPG (except in Wales) on Freesat, Sky & Virgin. In January, a whole sweep of SD channels were removed from Virgin, and of course the BBC have regionalised HD and are switching off their SD channels on satellite (having already done so on Virgin).

[Technologist]

If there was money in going HD on the UK DTT platform it would happen!

But it has very chequered past with few other than the PSB and LCN 16 supporting it - and yet is very successful 20 years on!
it also has more government interference in what it does than other platforms...
Although some of this can be good - like the Vaizey plan (2011/2)
which was also good because it mandated the PSB to go HD on ALL platforms and stop SD emission - but being political did not happen -it was meant to be co timed with the 700MHZ clearance

or bad - like to pay to move temporary Muxes carrying HD services to the middle of the Mobile band until someone wanted to use it!
Rather than encourage (with the money wasted) more Muxes to become more efficient by converting to DVB T2 AVC AAC.
as a UK wide one would have been very nice and cheap! (some almost new coders and Modulators being unused!)
With PSB3 changes PSB2 could more easily justify going UK wide ....
But D3&4 have just got a new Regionalised mux !!!! Or itv could take COM1 ....

But as was one of the features of the Vaizey plan using DVBT2 AVC AAC - taking All PSB HD tends to end up with an empty mux.... and is there the income to fund at PSB mux prices - noting that the temporary muxes which were dirt cheap did not have Sufficient takers .... all be it they had limited coverage.
Or if a COM mux converts are there enough broadcasters in the queue to pay for space to cover the costs of conversion.???

If the Vaizey plan had gone ahead that was a time when the platform (emission) was booming... but did require more DVB T2 AVC AAC STB in the population - but as Digital Help Scheme underspent by £400Million that could have been prised out of the consolidated fund which gobbled (LF money) up.

These days being about halfway from Digital Switch On/Over to Digital Switch Off
- people are not looking at the expansion of emission.

[TheMike]

The press release relating to the D3&4 changes, referred to upthread.

newsroom.bt.com 

TV upgrade for the UK: Freeview channels move into the cloud in landmark move fr…
ITV and Channel 4’s terrestrial Freeview channels move to cloud processing, and …
  Source: newsroom.bt.com

[CCFG]

Quick question. For this, I have an example point. (BBC2 HD) A nip around DigitalBitrate reveals that all of the BBC2 HD variants are broadcast in some form of AC-3 on satellite and cable. (BBC2 Wales HD and BBC2 NI HD are broadcast in 2.0 Stereo on satellite with BBC2 England/Scotland HD being in 5.1 Surround. I don't know about cable because all of the BBC2 HD variants are encrypted and DigitalBitrate doesn't specify a type of AC-3 for encrypted channels) A look for BBC2 HD on Freeview shows AAC Stereo.  Is there a technical issue preventing HD channels broadcasting AC-3 audio on Freeview?

[Technologist]

Here is the answer ….. it’s all to do with AD compatibility
www.bbc.co.uk 

BBC - BBC Internet Blog: Questions around surround sound on Freeview HD
Some people have asked why we don't currently use Dolby as the sound solution fo…
  Source: www.bbc.co.uk

…… And May be pressure for commercial reasons from the CE industry in the D book …..

Just a comment on some of the comments
AD is on between a over a fifth and over a third of BBC programmes
2022 figures from OFCOM www.ofcom.org.uk 

Television and on-demand programme services: Access services report for the firs…
The extent to which broadcast television channels and on-demand programme servic…
  Source: www.ofcom.org.uk

[ASnep]

Quick question. For this, I have an example point. (BBC2 HD) A nip around DigitalBitrate reveals that all of the BBC2 HD variants are broadcast in some form of AC-3 on satellite and cable. (BBC2 Wales HD and BBC2 NI HD are broadcast in 2.0 Stereo on satellite with BBC2 England/Scotland HD being in 5.1 Surround. I don't know about cable because all of the BBC2 HD variants are encrypted and DigitalBitrate doesn't specify a type of AC-3 for encrypted channels) A look for BBC2 HD on Freeview shows AAC Stereo.  Is there a technical issue preventing HD channels broadcasting AC-3 audio on Freeview?

I would be cautious about what DigitalBitrate shows in regard to surround sound. Broadcasters can change from Stereo to 5.1 and back on both AC3 and AAC (yes, AAC also can do 5.1). So for DB to show 5.1 the last snippet they recorded had to have been during a 5.1 broadcast. They used to have a chart showing Stereo or 5.1 for all recent samples they recorded (like they do for the bitrate), but they have removed that for some reason.

The last snippet they have from BBC 2 HD on satellite looks like it just so happened to be taken during a 5.1 broadcast. Movies do often carry 5.1 sound.

As for Freeview DVB-T2 can do AC3 (and E-AC3) just fine. And according to Ofcom's Reference Parameters (www.ofcom.org.uk ) both AAC and AC3 are permitted as "Alternative Audio Encoding" to MP2 audio (see section 2.19). So it basically just comes down to the preference of the broadcasters (or just preference of the BBC since they are responsible for the multiplex).

EDIT: Or the solution they choose for AD like Technologist mentioned.

[Keith]

I guess this is where Next Generation Audio may eventually come in.
www.bbc.co.uk 

Next Generation Audio - BBC R&D
Enabling the BBC to deliver personalised, accessible and immersive listening exp…
  Source: www.bbc.co.uk

[Technologist]

NGA encompass AD as part of the overall specification
But just as part of how object audio works Which is very good ……

But the AD we have on DTT ..”receiver mix” is object audio
As the narration is a mono audio plus a byte to pan the audio across the stereo scene,
And a byte to dim the programme audio …

Just reflecting back on the proportion of AD etc
The BBC play out facilities from the start (on air 1998) were designed in the basis that the system
Would always carry video , stereo audio, subtitles and AD, (embedded in the video )
And monitoring was in to ensure that video audio and subtitles were there 100%
Itv etc had a separate AES 3 audio circuit which they added to do,AD.at it’s launch in 2000.