[noggin]

Not sure what you mean? All the UHD tests I've seen so far have been using AAC rather than AC-3. I think there's an aim to avoid Dolby proprietary stuff where possible for basic services. AAC also seems to run at lower bitrates?

The UK OTA standard is MP2 for SD and AAC for HD (partially because Dolby didn't have an Audio Description solution for TV) The BBC HD channels dynamically switch between AAC 2.0 and AAC 5.1 for surround content (and change audio bitrate too - bumping up the bitrate for 5.1 stuff)

The BBC UHD tests on DVB-T2 in 2014 (World Cup and Commonwealth Games) were AAC 2.0 too.

I don't know. I thought I read somewhere that UHD-1 DVB standards specified AC-3 for audio. I think the U.S. broadcasts are looking for AC-4. Looks like ATSC committee has recommended AC-4 over MPEG-H Audio Alliance System for ATSC 3.0

DVB isn't really like that. You can pick and chose from the buffet of standards in the DVB specs.

There are then platform standards - like the UK Digital TV Group's D-Book for OTA SD and HD receivers, or the NorDig standard (which is for Sweden, Norway, Denmark, Finland, Iceland and Ireland - even though Ireland isn't a Nordic country...) which is similar (but has some regional variations) plus then the Pay-TV platforms can do some of their own thing.

The ATSC kind of encompasses both the DVB and UK DTG group in one - to create a US receiver standard. DVB is a bit wider than that as it recognises different broadcasters and territories have differing needs. There can't be a one-size-fits-all standard (whether it's audio codec or interactivity system)

We don't have a totally nailed down 'every DVB broadcast should use this' - but there is a basic set of standards that you can reasonably expect to be supported (and in some cases they may be mandated)

One major issue with AC3 - which is why the UK OTA standard doesn't use it - is that there was no Dolby 'receiver mix' functionality for low bitrate audio description to be mixed (with panning vectors and audio dip functionality) with the main programme audio in 2.0 and 5.1 content.

DVB has too many flavours - and too many platforms to force specific codec choices on all users of it. We have multiple subtitling standards (WST teletext legacy and DVB bitmap), multiple interactive text services (MHP, MHEG-5, HbbTV plus things like OpenTV), multiple audio flavours (MP2, AC3 and AAC), and multiple video codecs (MPEG2, H264, HEVC), with multiple modulation options (DVB-T, DVB-T2, DVB-C, DVB-S, DVB-S2 etc.) as well as IP options. However there is a reasonable standardisation process in most countries, so it works well for us it seems.