Rebuilding Freeview High Definition from 2019 onwards

Understanding the capacity on Freeview HD is very lego Photograph: Shutterstock

Brian Butterworth published on UK Free TV 8th March 2019 at 12:27

As Freeview High Definition users in Cornwall already know, the number of TV channels being broadcast in the UK will be cut back in mid-2020  to make way for the fifth generation of mobile phone data services.

This is because the number of multiplexes being broadcast will be cut back to the original six.   The extra two were provided as a “interim service”.    A Freeview multiplex is a single broadcast of binary data that occupies a 8MHz frequency range.    In the UK each of these can carry 24.1, 27.1 or 40.2Mbps or of data.

Because older TV sets and set-top boxes can only work with 24.1 Mbps, it is only possible for the owners of the multiplexes to use the higher capacity modes when every home has switched to Freeview HD capable equipment.  This equipment is marked with “DVB-T2”.

As illustrated, the total bitrate (in a home that can receive all the multiplexes) will change over time.

Meet the multiplexes

Not all the multiplexes are the same:

• only three are broadcast to the whole of the UK;
• a different three are broadcast in the better DVB-T2 mode;
• legally, only BBC channels may appear on BBCA
• also, legally, only public service broadcast channels (ITV, C4, C5) can appear on D3&4
• The HD mode multiplexes have more bits and use a more video efficient encoding system (MPEG-4)
• The current license to broadcast have different end-dates

This can be summaries in this table.

Freeview requires about 2.2Mbps for a standard definition channels and three times that for a high definition one (6.7Mbps). 

The Freeview HD EPG problem

One problem for people with Freeview HD receivers will note is that HD channels are grouped together in the program guide, rather than appear as replacements for the standard definition channels as viewers expect.    This is because the six channels on the BBCB multiplex (BBC One, BBC Two, CBBC, ITV, Channel 4 and Channel 5) can only be seen on newer boxes, making channel number replacement impossible without breaking the oldest Freeview equipment.

Basically the UK-wide BBCA and D3&4 multiplexes can’t change mode until ALL homes can receive them.

The interim position

There is good news, however, for the SDN, ARQA and ARQB multiplexes.    They can switch modes to the high definition whenever they feel that it is commercially practical.   This might be at a lower level of Freeview HD box use, perhaps 80% or 90%.   

By switching to DVB-T2 mode, each of them can increase their capacity from 27.1 to 40.2Mbps and take advantage of MPEG4. 

So, of the 80Mbps lost when com7 and com8 close, half of that can be got back by SDN, ARQA and ARQB upgrading, which would be enough for an extra 6 full HD services.

The HD public service channels

This diagram explains what will happen to create space six more Freeview HD channels.

The gains for the BBC when everyone has a DVB-T2 receiver are larger.     It will:

• No longer need half of the capacity on the BBCB multiplex (20.1Mbps) as it can move these channels to BBCA
• Gain 16.1 Mbps on BBCA due to the mode change;
• Gain 6.6 Mbps from not simulcasting three services in SD and HD
• Use the “gained 22.1Mbps” Be able to supply all the BBC television channels in HD to all UK homes

For the D3&4 multiplex, the gains are similar:

• No longer need the 20.1Mbps on BBCB, making it available for other UK-wide services.
• Gain 16.1 Mbps on D3&4 due to the mode change;
• Gain 6.6 Mbps from not simulcasting three services in SD and HD
• Be able to broadcast ITV, C4 and C5 in HD to all UK homes

I hope that's as clear as possible!  Any qestions?