News - 18m Freeview homes must retune today

[HEXUS]

Millions of Freeview viewers will need to retune their set-top boxes or TVs later today in order to retain access to key television channels.

Read more.

[Guy]

Finally an end to those pop up's that come on the screen everytime you change channel!

I have got sick of pressing the yellow button to clear the message about a million times in the last few weeks!

[Salazaar]

I hate retuning my box, I discovered that I had to manually search an offset frequency for two of the six multiplexes and the sixth doesn't like tuning at all.

Bloody TV cards.
Bloody mediaportal.
Bloody crap aerial wiring.

[Arthran]

this is why i will never have freeview or terrestrial telly anymore, new channel or a change and you have to re-do the lot.

I mean, isn't freeview digital? is it that hard to get channel 5? we had this when 5 first came out with terestrial telly, its been around longer than freeview, so why do they need to change freeview for it?

[Guy]

this is why i will never have freeview or terrestrial telly anymore, new channel or a change and you have to re-do the lot.

Err in 95% of the cases you just select update, or rescan for new channels, leave it a few mins and its done?

[OilSheikh]

Does anyone even watch TV anymore?

Terrestrial TV is utter junk.

I have set up my own TV-like schedule and download an episode a day of a set of TV shows and watch them every week.

[Salazaar]

I mean, isn't freeview digital? is it that hard to get channel 5? we had this when 5 first came out with terestrial telly, its been around longer than freeview, so why do they need to change freeview for it?

Yes it is digital but it doesn't mean that you don't need to tune it in. The digital signal is broadcast alongside the analogue one, your receiver just decodes them differently.

[directhex]

I mean, isn't freeview digital? is it that hard to get channel 5? we had this when 5 first came out with terestrial telly, its been around longer than freeview, so why do they need to change freeview for it?

Do you want the technical answer, or would you prefer to rant?

[Arthran]

Do you want the technical answer, or would you prefer to rant?

BOTH!

(a because i'd love to understand the technicalities of it and b good rants are fun to read)

[directhex]

BOTH!

(a because i'd love to understand the technicalities of it and b good rants are fun to read)

Okay.

Freeview is transmitted on six frequencies, named "multiplexes". Each multiplex is basically a data stream bundle of 18-25 megabits per second, containing a number of audio, video, and data streams. A "channel" is some defined combination of an audio stream, plus optionally a video stream, on a given multiplex.

With me so far?

Okay. Each mux has a given set of channels, typically defined by who actually owns the transmitting equipment in the broadcast towers - multiplexes 1 and B are owned by the BBC and contain only BBC channels, for example. Like with analog TV, there's an issue with available "spectrum space" (i.e. enough room for frequencies to be broadcast at high enough power to be received over a great distance without overlapping other frequences), and when prioritization is made, It's usually Mux A (S4C Digital) which is downgraded in terms of transmitter power. Mux A contains (or did before noon today) Five's 3 channels, Virgin 1, CITV, and useless crap like QVC.

Now, what happened today is that a number of channels were shunted around, from one multiplex to another, to basically move Five out of the low-reception Mux A ghetto (I believe it's now on Mux 2, with ITV and Channel 4), at the expense of ITV3 and ITV4 going onto Mux A (hence statements about 400k homes losing those channels). Other channels may have seen a bit of shunting too.

In the short term, that's what the change means - Five gets a new higher powered transmitter to call home.

A rescan is needed not because the frequencies you receive your TV from have changed (that will happen after switchover, see below) but because the stream ID mappings which define the channels have changed for a number of channels - and your kit needs to make sure it has accurate mappings in order to show you thw correct streams when you hit the "5" button on the remote

Now, it's worth talking long-term here too. Firstly, the digital switchover needs to be talked about. Once that happens (2011 where I am), then the current six muxes can now be "spread out" more, over frequencies previously used for analog TV, meaning broadcast power can be increased on all six muxes without overlap danger. This is a good thing.

Less good is Freeview HD. You know those six multiplexes? Well, the plan is to take all the channels on those, and squeeze them down into five. The only way to achieve that is to lower the bitrates used by the channels by about 20% (currently BBC1 is better-than-DVD bitrate on some shows, this may well end). The reason is that the sixth mux will be repurposed into a Freeview HD mux, with two or three HD channels on there (at the expense of image quality on the SD channels). And, here's the kicker, it needs a new Freeview HD set-top box.

I think that covers everything!

[Funkstar]

Less good is Freeview HD. You know those six multiplexes? Well, the plan is to take all the channels on those, and squeeze them down into five. The only way to achieve that is to lower the bitrates used by the channels by about 20% (currently BBC1 is better-than-DVD bitrate on some shows, this may well end). The reason is that the sixth mux will be repurposed into a Freeview HD mux, with two or three HD channels on there (at the expense of image quality on the SD channels). And, here's the kicker, it needs a new Freeview HD set-top box.

Aren't they going to move to a different encoding pattern to allow for more data in some of the MUX's? QAM 64 vs QAM 16 sounds about right. Combine this with the increase in power and I think they will be able to fit just about all the data from the current 6 MUXs into 5. If the bitrate does need to be dropped, it shouldn't be by much.

On bit rates, when Freeview was new, BBC3 and BBC4 regularly used to peak to bit rates higher than DVD. I know this because there were a few shows I had recorded with a DVB-T card that I couldn't put on DVD without transcoding them down to a lower bit rate MPEG-2.

[Dareos]

Does anyone even watch TV anymore?

Terrestrial TV is utter junk.

I have set up my own TV-like schedule and download an episode a day of a set of TV shows and watch them every week.

Pretty sure this is illegal, may want to not shout about it

[Arthran]

Pretty sure this is illegal, may want to not shout about it

Unless he's using skyplayer and bbc iplayer to download the shows to watch later! ;-)

[shaithis]

The Media Centre in Winodws 7 has quite a few series for download online as well.

Caught a few of the mitchell and webb episodes that I had missed

[directhex]

Aren't they going to move to a different encoding pattern to allow for more data in some of the MUX's? QAM 64 vs QAM 16 sounds about right. Combine this with the increase in power and I think they will be able to fit just about all the data from the current 6 MUXs into 5. If the bitrate does need to be dropped, it shouldn't be by much.

Okay, yes, I was trying not to overload on info. the reason for the 18-25 number I gave is 64-QAM muxes (VARIES BY REGION, but typically 2 and A) are 24 mbit, and the 16-QAM (1, B, C, D) are 18 mbit. In theory a move to 64-QAM throughout means no need to drop bitrates, even though it's one of the 64-QAM ones being axed - but 64-QAM is much more sensitive to reception problems, which is one reason the beeb have always avoided it where they can

On bit rates, when Freeview was new, BBC3 and BBC4 regularly used to peak to bit rates higher than DVD. I know this because there were a few shows I had recorded with a DVB-T card that I couldn't put on DVD without transcoding them down to a lower bit rate MPEG-2.

Yep. Well, again, it's a question of bitrates - that 18/24mbit number is shared by all the channels on a mux, so some channels can be quality-reduced to bump up one channel. In the early days, there was enough data for all. DVD is capped at 10mbit for all streams (where, say, every subtitle stream uses up some of that)

[Steve]

64-QAM is much more sensitive to reception problems, which is one reason the beeb have always avoided it where they can

Indeed, but don't forget that when the analogue switchoff takes place, digital will get a 10dB boost to transmit power AND there won't be an analogue signal to compete against any more. It should mitigate the instabilities of 64-QAM.

In fact I look forward to everybody's tuners clipping the signal when they can't handle the crazy waves coming through the amplifier they bought to deal with current signal weakness.