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Rebuilding Freeview High Definition from 2019 onwards

There is a bit of a dip in the space available on Freeview HD for high definition channels once 5G mobile services start next year, but the capability will return.

Understanding the capacity on Freeview HD is very lego  Photograph: Shutterstock
Understanding the capacity on Freeview HD is very lego Photograph: Shutterstock
published on UK Free TV

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.

Multiplex name

 

Expires

 

HD mode?

Coverage

Mode

Bitrate today

com7

 

21 June 2020

 

Yes

76%

6

40.2

com8

 

21 June 2020

 

Yes

76%

6

40.2

D3&4

 

15 November 2022

 

No

100%

3

24.1

ARQA

 

15 November 2026

 

No

90%

8

27.1

ARQB

 

15 November 2026

 

No

90%

8

27.1

SDN

 

15 November 2026

 

No

90%

8

27.1

BBCB

 

16 November 2026

 

Yes

100%

6

40.2

BBCA

 

31 December 2027

 

No

100%

3

24.1

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? 



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Comments
Sunday, 10 May 2020
C
Chris.SE
sentiment_very_satisfiedPlatinum

10:49 PM

Ah, StevensOnln1posted whilst (with interruptions) I was compiling my reply ;)

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Chris.SE's 2,581 posts GB
Sunday, 31 May 2020
D
David Warner
sentiment_satisfiedBronze

9:32 PM

I just found your excellent article "Rebuilding Freeview High Definition from 2019 onwards" - and it explains a lot.What it doesn't explain is the rationale behind COM7 and COM 8 not being public service provision that license fee payers have the right to receive.

I understand that OFCOM's process for auctioning off the 5g 700Mhz frequencies is delayed - not least no doubt because of the present public health considerations.
Your article postulates an overall improved service when BBCA and D3&4 mulitplexes can be upgraded to HD, and this in turn depends on when it is deemed that the vast majority of TV receivers are capable of provcessing the DVB-T2 signal.

Anybody have any idea when that is likely to happen? I discovered yesterday that as well as myself getting very ropy reception on COM8 and none on COM7 (Crystal Place - 3 miles away), my brother who lives in Swaffham and uses Tacolneston has similar problems on these COM7&8 transmissions.

With regard to the use of COM7 and COM8 on synchronised frequencies - is this a short-term experiment? I see there is theoretical literature about Single Frequency Networks - including guidance from the EBU.
I would like to know why the COM7 and COM8 transmissions are only 20% of the power of the main multiplexes - especially as even an increase to maybe 100kW would most likely cure by my problem and my brother's problem with poor reception. Please note also that the theoretical information from the EBU suggests that interference from neighbouring transmtters is POSITIVE but only when an omni-directional receiving aerial (such as on a portable TV) is in use.

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David Warner's 24 posts GB
S
StevensOnln1
sentiment_very_satisfiedPlatinum

10:36 PM

David Warner: COM7 & COM8 are temporary multiplexes that were created using spare frequencies and equipment to encourage the take up of Freeview HD receivers. There was never any intention of them having any sort of PSB status and the the TV licence does not give a right to receive any particular service.

There has never been an announcement of when any further multiplexes will be converted to DVB-T2, just speculation based on a plan that was proposed several years ago.

COM7 & COM8 have been turned into single frequency networks in order that they can continue to broadcast by occupying the same two frequencies (in the centre gap of the new 700MHz mobile band) at each transmitter and will stay like this until they close, no date has been announced at it will depend on when the mobile networks who win those frequencies in the 700MHz auction are ready to bring them into use. Increasing the transmitter power will cause destructive interference to viewers of more distant transmitters and is not something that will happen. If you are very close to the transmitter but not getting a good signal you are likely to either not have a wideband aerial or your receiver is being deafened by receiving too much signal for it to cope with.

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StevensOnln1's 3,154 posts GB
Monday, 1 June 2020
D
David Warner
sentiment_satisfiedBronze

10:28 PM

StevensOnln1: re your comment - I have a broadband - or to be specific a Band T - aerial.
I'm not familiar with how DTV receivers work, but possibly I will be if I have to keep researching and posting. You suggest that I am suffering from excessive signal strength.
I say to you - I have perfect reception (near enough) on the multiplexes operating on 482MHz (200kW), 490MHz (200kW), 506MHz (200kW), 514MHz (200kW), 530MHz (200kW), 546MHz (200kW) and 586MHz (20kW).
On the other hand I currently get ZERO reception on 746MHz (43.1kW) and intermittently good/poor/nonexistent reception on 754MHz (39.8kW).
I noticed this comment on the RxTxLog website:
"Preparations for 5G arriving have been made though: in order to maintain a guard between 5G and the temporary multiplexes in the centre gap, a 167kHz offset is applied to multiplex COM8, which carries channels including FreeSports and BBC Four HD. This has reduced the amount of bandwidth available. To ensure reception of the multiplex remains robust, the forward error correction was changed to 1/2 earlier this year, which in our observations has made the signal slightly more reliable than before the change."

Why some Freeview services are getting a stay of execution - RXTV Info | RXTV log


Does this explain which I can sometime get COM8 signals at present, but NEVER COM7?


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David Warner's 24 posts GB
Tuesday, 2 June 2020
C
Chris.SE
sentiment_very_satisfiedPlatinum

5:06 PM

David Warner:

If you'd read my post here on the the 10 May 2020, 4:42 PM, (p12) you'd have noted that I stated about when such changes may/may not occur. In addition to that, PSBs 1&2 are very likely to be the last to be converted.
As regards you and your brother's reception, if you used the links I gave in reply to your other post which were highlighted by another poster here My Freeview box has no EPG, is blank on FIVE, ITV3, ITV4, ITV2+1, has no sound o | free and easy then you would have seen your brother's predicted reception which will be entirely dependent on his location and have no bearing on yours. I'll be making further comment over there after that post especially about your front end possibly being deafened (two of us now suggesting that possibility - "perfect" reception of the other multiplexes is no "guarantee" this isn't happening, nor to be fair that it is! - it's a possibility).

SFNs are NOT some sort of "short-term" experiment. Virtually all the transmitters in the National DAB networks are SFNs, and some Local muxes where there's more than one transmitter for the mux. Only Trial muxes and Local ones with one transmitter won't be an SFN.
COM8 was not using the full available bandwidth which enabled a FEC change on the 10th Feb. as I mentioned to you in reply to your other post BUT it is not currently transmitting with a 167kHz offset. IIRC it did at the time of the FEC change, but this no longer seems to be the case based on all available tech & reception data that I've seen. (Having said all that, I personally think that there may be a touch of SFN experimentation going on with COM8).
As regards the COMs 7&8 transmission powers at Crystal Palace, as I also mentioned, there's DUK/Freeview documentation that states they are 80+kW. However I also mentioned that there are many inconsistencies as even OFCOM documents have not been updated in some instances. Additionally there are many websites that are out of date and have incorrect information about COMs 7&8. Oh, btw, those replying to you here are professional engineers, there's no need to quote data from other websites which in this case is not 100% correct.


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Chris.SE's 2,581 posts GB
J
js
sentiment_satisfiedGold

8:06 PM

Chris.SE: Would you care to elaborate? "COM8 ... it is not currently transmitting with a 167kHz offset"

It most certainly is from Winter Hill: C56-, 753.833MHz,

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js's 790 posts GB
Wednesday, 3 June 2020
C
Chris.SE
sentiment_very_satisfiedPlatinum

2:17 AM

js:

Hi js. I did say "based on all available tech & reception data that I've seen", and I have to admit I didn't do an exhaustive check, so now apologies, and I misread my own data which was after I looked at DigitalBitRate for London COM8 http://www.digitalbitrate…g=en which is obviously erroneously quoting the frequency for C56 rather than measuring it. But what's worse is that the DUK/Freeview documentation is not showing C56- so consequently I was sloppy in checking other data. So apols as well to David Warner for that incorrect comment, not that it makes the slightest bit of difference to his reception problem, that issue is the same!

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Chris.SE's 2,581 posts GB
Wednesday, 10 June 2020
D
David Warner
sentiment_satisfiedBronze

11:25 PM

Regarding COM7 and COM8 I just spotted this on the RxTVLog site:
11th February 2020
A technical change has occurred affecting the COM8 Freeview multiplex. No action is required from viewers. The FEC has changed from 2/3 to 1/2, resulting in more robust reception.

Can either of you omment on this? It does possibly explain why I've been able to receive BB Four HD and PBS America+1 for the last several weeks, but not BBC News HD or Chanel 4HD+1.
------------------------------------------------
Further to that of course Freeview are now flagging a further change on COM8 (and presumably COM7) - their Freeview TV warning and website tells people helpfully they can get Channel4+ 1 on Freeview 15 (non HD of course) and various other stuff. Any idea what;'s going on here?

I must say OFCOM/Freeview/Arqiva have no idea of public consultation. We in Brixton just had a sustained three months NHS consultation campaign asking ask residents to approve the demolition of the local 25 year old mental hospital "to improve services to patients".
Can't see OFCOM or Freeview asking anyone what level or indeed what services they want!

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David Warner's 24 posts GB
C
Chris.SE
sentiment_very_satisfiedPlatinum

11:46 PM

David Warner:

If your read my replies to your other posts you have seen what I said about COMs 7&8. As far as the latest announcement from Freeview 22 Jun 2020 - Important channel broadcast changes | Freeview COM8 is closing.
See also https://twitter.com/Chris…s=20

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Chris.SE's 2,581 posts GB
Tuesday, 23 June 2020
D
David Warner
sentiment_satisfiedBronze

10:39 AM

Can anyone say what exactly I ought to be able to receive now?
CBeebies HD is the only COM78 service I have on - and it has moved from 205 to 209

Otherwise everything else has GONE.

No PBS America +1, No BBC Four HD No BBC News HD etc etc,.

Personally I'd happily settle for:
1. PBS America (not +1) to be on 24 hrs a day
2. No HD and a refund for my two HD TVs

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David Warner's 24 posts GB
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