Some thoughts on possible future Freeview capacity usage at MPEG4 switchover
 

The following is basically me thinking about how MPEG4 switchover on Freeview might look. The end state, not the process. It is very appropriate, based on some rough mental arithmetic and some assumptions.

- Based on the current PSB3 HD multiplex on Freeview you can get 6x 24hr HD channels + 1 SD channel. However on Cable, Virgin Media have between 7 and 8 HD channels per multiplex, usually 7. So there's potential for more. For this we will average it out and say a HD-only Freeview multiplex has a potential 7 HD channels.

- An SD-only multiplex, based on the current D3&4 multiplex with full SD resolution has room for 12 full resolution (i.e 720x576) SD channels on one multiplex at the current MPEG2.

- An SD-only multiplex, based on Cable example on Virgin Media, has 24-25 channels on one multiplex with MPEG4.

- 4 SD channels tend to fit into the space of 1 HD channel, so that would be 28 SD channels based on the HD, but let's assume that Cable, with less capacity constraints, has found 24 works best and go with that for a SD-only multiplex.

-Based on articles I've read the plan is apparently to reduce the current 6 national multiplexes (I'm excluding the 2 temporary HD muxes and the Local ones) down to 5, to clear the way for mobile phone data, so all my ideas are based on there being a reduced number of multiplexes.

- Given 3 of the current main multiplexes have only 80(?) sites (covering 90% population) and the other 3 have 1000+ (covering 98% population) I'm assuming the expense of upgrading 1000s will be mean that the multiplex that won't be upgraded to MPEG4 will be one of the PSB multiplexes that have thousands of sites. One of the 3 PSB muxes is MPEG4 already, so one one more multiplex needs upgraded.

- Apparently it is cheaper and better to have all the regional services on as few multiplexes as possible. It should be possible to have them all on one, the suggested multiplexes I will outline will be based on this.

- I'm assuming that money will form a large part of the reasoning behind the planning for MPEG4 switchover so a large part of my suggestions will be based on this.

First of all I think the current MPEG4 (PSB3) multiplex will remain virtually unchanged.

BBC1 HD
BBC2 HD
ITV/STV/UTV HD
Channel 4 HD
Channel 5 HD
CBBC HD (until 9pm everywhere but Scotland where BBC Scotland HD takes over at 7pm)

The change based on More4+1 removal and potential extra space based on Cable example:
BBC Parliament (SD)
BBC Red Button 1 (SD)
ITV/STV/UTV+1 (SD)
Channel4+1 (SD)
BBC Radio (Various)

These last 3 are based on there being a regional element (C4 is advertising, not programming). Parliament, RB1 and national radio are the most likely of these not to be on this mux, space/tech limiting.

One of the two other 2 PSB muxes will be upgraded to MPEG4. I think it would contain.
BBC News HD
Cbeebies HD/BBC4 HD
And then 16 SD channels from current D3&4 PSB Mux + related ones.
ITV2 & +1
ITV3 & +1
ITV4 & +1
ITVBe
CITV

E4 & +1
More4 +1
Film4 +1
4Music
4Seven

Because one PSB multiplex won't be upgraded to MPEG4, the assumption is that the existing remaining MPEG2 multiplex would be switched off.

My idea is that it would only be switched off at the main 80 locations that cover 90% of the population. The 1000s of sites that cover the remaining 8% could have it remain on, as MPEG2 and transmit at least 12 TV channels that are found on the upgraded non-PSB multiplexes to the other 90%. It would be like an SDN-lite, to give those in relay transmitter areas a little more selection and save money decommissioning that multiplex at all those sites.

Anyway, this is all just a rough idea. Feel free to have fun poking holes in it... it'll probably be easy. ;)

Re: Some thoughts on possible future Freeview capacity usage at MPEG4 switchover
 

Firstly, you can’t radiate a mux from the 1000 or so small relays & not from the main stations. These Relays are just transposer sites, usually in remote places with just a power supply. They pick up the main stations transmissions, transpose them to new frequencies & then re-transmit them. The main stations are the only ones directly wired to the network. The only exceptions are the ones that operate as Single Frequency Networks with a main transmitter or another adjacent relay.

Also VM can shoehorn more channels into their muxes as they have complete control over the network they are operating on. DTT operates under a lot of external factors that do not affect cable transmission.

Re: Some thoughts on possible future Freeview capacity usage at MPEG4 switchover
 

A DVB-C multiplex in the UK carries about 51Mb/sec. A DVB-T2 one carries 40 and 36 in the present configurations. I don’t think the signal strength/quality in the UK would allow for the higher bitrates without reducing coverage significantly as a result.

Re: Some thoughts on possible future Freeview capacity usage at MPEG4 switchover
 

Exactly my thoughts and the situation is getting worse. As the number of available UHF channels decreases the risk of getting CCI (co-channel interference) from overlapping transmitters increases. This adds significant noise to the received signal & reduces the usable coverage area, especially during certain weather conditions.

Re: Some thoughts on possible future Freeview capacity usage at MPEG4 switchover
 

I knew there would be good technical reasons I didn't know of. Thank you nodrogd and jfman. :-)

You don't happen to know how much of a DVB-T2 switchover is done at main transmitters, the relays and how much before it even gets to the main transmitters? I'm trying to envisage what needs done where.

Re: Some thoughts on possible future Freeview capacity usage at MPEG4 switchover
 

I’d not waste too much energy on it. By the time it’s considered (and applied) it’ll be near redundant.

Re: Some thoughts on possible future Freeview capacity usage at MPEG4 switchover
 

The vast majority of transposer kit has been DVB-T2 compatible for some time & its more than likely most of this kit will already be in place. Arqiva has provided all the transmission services for the BBC since 2006 & with the commercial services in their control for considerably longer there is likely to be commonality across all equipment at these relay sites. The biggest issue that is still going on is swapout of the older type 700Mhz retransmission panels that are not efficient below these frequencies.

Re: Some thoughts on possible future Freeview capacity usage at MPEG4 switchover
 

It was just a thought exercise. I find it oddly enjoyable organising/planning things like that in my head. :D

---------- Post added at 15:27 ---------- Previous post was at 15:03 ----------

So I guess the individual cost of these panels, and how many need changing will be a major deciding factor as to whether the multiplex that gets removed is a PSB one or a commercial one?

Given the amount of space, I can see it now, "you won't see much benefit, you'll get pretty much the same channels, at the same quality, but you need to upgrade". I know they won't start it until DVB-T2 equipment is estimated to be in something like 70% of households, but it'll be a harder sell. Especially to Relay dependant households.

Fortunately I get a decent main transmitter signal (I even get COM 7 & 8) despite being in a Relay Area, so if 700Mhz clearance retunes don't change reception quality I won't be getting a reduced service compare to those officially served by the main transmitter. I will have to get some new tuners though as 3 of the 4 Freeview tuners aren't compatible, though only 2 boxes would need replaced as only 2 TVs have Freeview as their sole signal.

But there's no rush, it's just a bit of fun speculating. :)

Re: Some thoughts on possible future Freeview capacity usage at MPEG4 switchover
 

All the areas where 700Mhz retunes have already taken place have had these panels changed, which is now well over 75% of the country. When you consider that only the relays using UHF channels above 48 were affected then a lot of relays required no work at all.

Re: Some thoughts on possible future Freeview capacity usage at MPEG4 switchover
 

Looking at the DigitalUK checker it seems that the upcoming retune on our Relay transmitter is due to our nearest Main transmitter being above 48 and being moved to frequencies our Relay currently occupies, our Relay is already below 48.

Much appreciated nodrogd. :)