back to article Freeview HD goes live

With the launch today of the Freeview HD service, the UK can claim to be at the forefront of digital television - though most punters won't be able to receive the service until spring 2010. Today’s launch saw services switched on at the Crystal Palace and Winter Hill transmitters, between them providing coverage for around 22- …

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  1. Grail

    Reason for drop in Freesat BBC HD Bit Rate?

    "Video for each channel can range between 3Mb/s and 17Mb/s."

    So now we can see why they dropped the BBC HD bit rate - average channel will be 10 Mb/s ((3+17/2)) so that the HD picture quality on Freeview HD will be the same as on satellite.

    1. Nigel Whitfield.

      Not exactly...

      I don't think there's necessarily any cause or effect here, actually.

      It's quite possible that at many times, the bitrate for BBC HD on Freeview may be exceeding that for Freesat, due to the stat muxing.

      The coding for Freeview will be set to maintain a specific quality, not a specific rate, and if a higher rate is needed, then that's what it'll get.

      On Freesat, it's a fixed rate. The streams for each platform are distributed separately - it's not as if they take the pre-compressed satellite feed and stick that out on Freeview.

  2. BristolBachelor Gold badge
    Flame

    Actual picture quality

    I can't receive it, but am interested: Will the quality be able to match analogue TV?

    Normal freeview is compressed so much that all I can see is a mosaic of pixels 1/2" square when there is fast action or scene change on the screen on any channel that isn't BBC1.

    *1 Sorry, don't know what 1/2" is in std. reg. units.

    *2 Yes, this is with full signal stength and no errors.

    1. Anonymous Coward
      Anonymous Coward

      Eh?

      Sorry, but either you've got a crap aerial or a crap STB. We've got three Freview STBs ranging from a flashy DVR to a £15 jobby and none of them display any compression artefacts. And that's all with the aerials indoors.

  3. Registard

    Decisions decisions...

    My TV aerial needs new cabling, a new bracket/chimney brace and lashing and all the other gubbins you need to ensure it stays in place (~ £100 if I climb up there myself). Due to the expense, danger and difficulty in sorting this out I'm wondering if I wouldn't be better off going for a freesat installation instead?

    Seeing as how a satellite dish could be mounted 10 feet from the ground whilst the aerial needs to be on a roof, three stories up, is it likely to be the case Freeview HD and Freesat HD offer broadly the same services for the foreseeable future or does Freeview HD significantly leapfrog it? I live within the broadcasting area of the Crystal Palace transmitter...

    1. Nigel Whitfield.

      Pretty similar services

      I would imagine that, for the next few years at least, you will have a broadly comparable service whether you go for Freeview or Freesat. The PSBs, once they have an HD channel up and running, will most likely take them to Freesat as well, when they can find suitable transponder space.

      In theory Freesat has more capacity, and there are certainly more minority channels (Weddings, Asian music, and so on), but in terms of the main channels that get the bulk of viewing, there won't be much between them.

      I honestly don't think you'll see much in the way of Freesat-exclusive HD channels; launching an ad-funded TV station is pretty tricky at best of times, let alone in an economic downturn.

      So, for the time being, yes, I think you'll ultimately have pretty similar services from the two main platforms, with a few exceptions (eg Dave and Virgin 1 not on Freesat, lots of minority stuff not on Freeview).

  4. Richard Tobin

    Ads on the guide?

    I considered buying a high-end Panasonic TV a few months ago, but was put off by the presence of advertisements taking up a third of the Freeview EPG screen. There seemed to be no way to turn them off. Will this be allowed on Freeview HD? Are we going to have to put up with advertisements even to watch the BBC?

    1. Nigel Whitfield.

      Guide+

      Some sets include Guide+, which does indeed have advertising. But that's dependent upon the particular manufacturer, and nothing to do with the BBC.

      Whether or not the licensing agreement for the FreeviewHD badge will preclude any advertising appearing on the EPG screen where the Freeview logo is show, I don't know. But I will try to find out.

  5. Anonymous Coward
    Paris Hilton

    Lovely, an' all, but...

    will there be anything worth watching on? Or just the same-old-same-old vacuous bollocks?

  6. Anonymous Coward
    Thumb Down

    'will be expanded to five channels when encoder improve'

    Given that H264 encoders are now mature - improvements are marginal, so i call usual freeview/ofcom BS. What it will mean is we'll have a HD service with picture quality close to what the SD service would be giving if they didn't insist on 50 shitty channels eating all the bandwidth ... or insist on selling off all the bandwidth they could be using to give 20 or 30 multiplexes instead of the 6 we've had for years and will be stuck with post analogue switch off.

  7. Chris 3
    Unhappy

    What I would actually like...

    HD would be lovely and all, but I was thinking about this last night and realised that the only reason I would really want HD would be to get rid of some of the compression artefacts that muck up standard Freeview.

    I find it particularly jolting when (frequently) a close up of a character speaking is rendered as an unmoving mask with only the regions around the eyes and mouth moving.

    Am I the only one? Wouldn't it make sense to improve the standard picture for the viewing public before moving on to HD?

  8. Peter Kay

    Bleeding edge..

    Not only aren't there any receivers, there also aren't any tv cards at consumer or even pro level. The available cards appear to be at 'engineer level' and hideously expensive.

    Then again, I don't watch TV, so it's a moot point. Slightly ironic that I'm in line of sight to the Winter Hill transmitter (or would be, if the cloud cover wasn't surrounding Winter Hill).

  9. Ken Hagan Gold badge

    Re: Lovely, an' all but...

    "will there be anything worth watching on?"

    Er, no. You must have missed the bit in the article where it said...

    "Launch channels are BBC HD on EPG channel 50, and ITV 1 HD on position 51. "

    ...so in fact the BBC appear to have no plans to make even BBC1 and BBC2 available. How crap is that?

    Top tip: the actual kit will be a tenth of the price if you wait until there's something worth watching. (Probably best not to mention this in the presence of hardware vendors.)

    1. Nigel Whitfield.

      Multiple channels in future

      There is a degree of logic in the way the BBC does things. Firstly, there's not the capacity right now for them to have two HD channels; I can imagine the fuss from some quarters if half the channels available in HD were from the BBC, and the accusations of them squeezing out other players.

      Secondly, they'd of necessity be broadcasting a lot of upscaled material, as does ITV. And that raises other issues - why should people who watch BBC3 or BBC4, for example, miss out on seeing some of the shows on those channels in HD, just so that a quiz show or (pick any show you don't personally like) can be upscaled on BBC1HD or BBC2HD?

      Given the bandwidth constraints, and the number of channels they have, I can understand entirely why the BBC decided to go with a 'best of' channel that just shows HD, from all the channels in their portfolio.

      I think sometimes, when you try to work out what the BBC is doing and why, you need to imagine "What would the Daily Express say?" And in the case of a simulcast of the two main channels, perhaps it would be something along the lines of "Auntie wastes millions of YOUR money broadcasting HD channels to a handful of viewers - and most of the programmes aren't in HD"

      The situation may change in time, but right now, I think there would be plenty of people howling in outrage if the BBC were gifted two channel slots for HD.

  10. John H Woods Silver badge

    PS3 + Play TV?

    "As of today ... there aren’t any receivers available to buy."

    I may have misunderstood, but I thought Sony had updated its PlayTV add-on for the PS3 so it is already HD capable? I can't test it till 2010 as I am in the Midlands ... anyone know for sure?

    OFB: PlayTV on the PS3 is one of the best Freeview receivers you can get. Well it will be when they have series linking properly working :-)

    1. Rob Beard
      Boffin

      re: PS3 + Play TV

      If I understand correctly, the Play TV won't support Freeview HD as it doesn't support the DVB-T2 standard which Freeview HD uses, only DVB-T which standard definition Freeview uses.

      The Play TV does support HD TV but only in countries that are broadcasting HD TV using the DVB-T standard (France for instance if I'm right).

      Still that's not to say Sony won't release an updated version of the Play TV adaptor (I'd be interested to know if the PS3 supports running two Play TV devices at once for dual channel recording?).

      Rob

    2. Nigel Whitfield.

      Play TV

      No; Play TV is not compatible with the UK service, because it uses a DVB-T tuner, rather than a DVB-T2 one. A software update is not possible for that.

      The 'HD' software tweaks for PlayTV are to allow reception of HD services in other countries where they use DVB-T for HD. You can find out more about that at

      http://www.reghardware.co.uk/2009/11/23/freeview_hd_questions_answered/

  11. Peter Kay

    Demodulation vs decoding

    There's already been some HD transmissions, but they've been on the existing DVB-T modulation. The current TV cards and set top boxes simply aren't capable of demodulating the signal.

    Once the signal has been demodulated it then needs to be decoded. This can be done on a suitably powerful PC, or by the time the technology evolves, by a DSP on a set top box or a second/third generation TV card.

    PCs are capable of decoding the new HD signals, but there's no hardware to demodulate the signal, other than some very expensive analogue to digital converters.

    1. MiaScreams
      Alert

      This has been keeping me on the fence...

      I have been looking for a cell phone.. forever it seems...and the top two have problems. And 1 is if a new way of thru HDTV is going to be easier I would rather wait a couple of months to get it more DEFINED then what it is now?

      And I would like to find out that if I got one of these mini portable TV's that it would be worth it.

      Someone please let my inexperienced self know.

      Mia

  12. M7S

    IPTV capable - Blast

    I do want my TV to deal with everything reasonable, but if any content or extras require broadband, as we dont get more than 400kbps anyway, it rather defeats the point.

    That's why we like the material broadcast over the air. If we had decent bandwidth, we'd just download it all.

    If they'd spent the money on installing FTTC or better nationwide, it would cost the country less than the digital upgrade and we'd all be enjoying more flexibility and choice.

    Still, I hope it works now its starting to arrive.

  13. Anonymous Coward
    Anonymous Coward

    @PS3 + Play TV? # Posted Thursday

    I understand PS3 is DVB-T (but stand to be corrected!)

    The new HD is DVB-T2 and needs new hardware to demodulate it, not software to decode it, so as I understand the situation the PS3 cannot receive freeview HD on DVB-T2.

    DVB-T hardware cannot demodulate DVB-T2 modulated signals.

  14. GettinSadda
    WTF?

    subtitles 200Kb/s

    Surely you mean 2Kb/s not 200Kb/s?

    CEA-608 captions are only 960 bits per second, and they support everything I have yet seen done on Sky or Freeview, so I doubt there will be any need for a vastly higher bitrate. Even CEA-708 is only 8.6Kb/s and that provides a huge amount of extra functionality (most of which is used to make subtitles look like a 1990s website rather than anything useful for the deaf or hard-of-hearing).

    I expect that you would have no great difficulty encoding on-screen signing in 200Kb/s

    1. Nigel Whitfield.

      Bit rates

      CEA-608 is an analogue standard, isn't it? As far as I know, it's transmitted in one of the VBI lines.

      Freeview and other DVB services transmit the subs as a stream of bitmaps, rather than just the text, and so you do tend to need a higher rate. The broadcaster gets to choose the font (Tiresias in the UK), rather than the equipment manufacturer.

      A BBC R&D paper from 1999 looked at subtitling for DVB, and the tables in that give example bitrates for two programmes - an episode of Neighbours with pre-prepared subs, and the news, with live captioning.

      In those, the peak rate is around 65kbits/sec for pre-prepared and abut 70kbits/sec for live. The paper suggests up to 192kbits could be necessary.

      Presumably, for an HD service, the bitmaps will be of better quality than for SD, so given those peak figures, 200kbits/sec for the titling does seem about right, I'd have thought.

      You can see some of the numbers at http://downloads.bbc.co.uk/rd/pubs/papers/pdffiles/ibc99net.pdf

      1. GettinSadda

        Bit rates

        CEA-608 has always been digital, but is carried in line 21 of analogue transmissions. CEA-608 is widely used in the USA, as is CEA-708 which is designed for HD and includes a CEA-608 sub-stream for compatibility.

        I was aware that DVDs use bitmaps for subtitles, but am disappointed to find out that this is also done for DVB. It is ridiculously inefficient!

  15. Anonymous Coward
    FAIL

    The lights are on but nobody's home

    They may be broadcasting, but nobody can receive it yet, so it's a bit pointless.

  16. Paul Westerman
    Thumb Down

    Pah!

    I've been holding off getting a new TV 'cos I thought I'd go straight to integrated Freeview HD rather than buying another STB. But not only am I unable to buy a Freeview HD telly of any kind, I don't get the HD signal for another three years because I live in a remote, under-populated enclave called 'Sussex'. Ridiculous. I'm off to either Freesat or Virgin V+HD. Perhaps the SD picture will be better than the mosaic-y, blocky Freeview nonsense (as previously mentioned) as well?

    1. Nigel Whitfield.

      Blocky freeview, Sussex

      Admittedly I live in London, and have a robust aerial, and don't watch some of the crappier channels, but I don't think it's fair to criticise Freeview as blocky. The main channels provide pretty robust signals these days - a far cry from the days of OnDigital when I could never get a decent signal on the ITV mux for around half the year, with plenty of break-up.

      As for regions like Sussex, I'm afraid the delay for those is a necessary part of the international co-ordination involved in DSO. Transmitters in the bottom right corner of the UK can potentially cause interference with the French, Belgian and Dutch services, so there's a fair bit of planning necessary to make it all work smoothly.

  17. Spiracle

    Something to look forward to when the World Cup's on.

    "... the services will be statistically multiplexed – which means bandwidth is dynamically allocated between channels, depending on the complexity of the images."

    i.e. 'you'll have to put up with a low a low bitrate when the football's on the other channel"

  18. nichomach
    Coat

    Disregarding the merits of the service...

    ...for a moment, "Ilse Howling, Managing Director of Freeview"? Presumably held a similar post in Überwald before taking over the clacks service...?

    *Mine's the one with a large firework in the pocket - "Fetch! BATH-time!"

  19. Chris 3

    Re: Blocky Freeview

    I live in East London with a roof-top ariel that is only 2 years old, when my wife, who's not very interested in TV technology is watching a film on Freeview and suddenly says: "Hey, why has Sean Connery's face gone weird" you know the compression system is not up to snuff.

  20. Derek Hellam
    Thumb Down

    Honestly?

    Whats the point? It is the content that is crap, not the picture quality. I'd buy an old 405 lines Black and white TV if it had anything worth watching on it. More useless game shows, reality? TV (in which reality/parallel universe I'd like to know), more American imports? pah, just an excuse to sell more hardware that no doubt will be at the recycling centre within 5 years, just like the VHS, Betamax, and current freeview boxes.

  21. Anonymous Coward
    Anonymous Coward

    @Chris 3

    Chris,

    You should not be seeing any compression artefacts at all on Freeview.

    I've been using Freeview for a long time, and I run off the Crystal Palace transmitter, I'm 30 miles away and require a high gain antenna which also needs additional amplification.

    I don't see any compression artefacts at all.

    What you are seeing are not compression artefacts, what you are seeing are errors in the datastream, caused by either a)interference on the signal, or a weak signal. I would suggest you take a look at your antenna, cabling and determine what the signal strength is and what you need to sort the issue out.

    Everyone seems to be so obsessed with the idea of compression artefacts, but in reality there aren't any, what people are observing are errors in the datastream which can't be corrected the forward error correction codes.

    1. Quirkafleeg
      Boffin

      Compression artefacts

      There's a large difference between a compression artefact and a reception error.

      Compression artefacts show up as low detail, stepwise colour changes where the change should be smooth, or fuzz around sharp changes in colour (as seen in all too many JPEG images where some non-lossy format should have been used instead),

      Reception errors cause disruption of part of the picture with the appearance of lines of randomly-coloured or otherwise mangled blocks, part of the picture to "jump", and pops, noise and silences in the audio. The visible effects always vanish when the next key frame is shown. (Key frames occur at intervals of ½s to 2s, depending on available bandwidth.)

    2. Anonymous Coward
      Anonymous Coward

      No compression artefacts?

      I'm sorry, but what you are saying is completely wrong. You can't just shout someone down and say there are no compression artifacts in Freeview and that it must be a signal problem.

      Standard definition Freeview is compressed to within an inch of its life. Stand anywhere near a large flat panel screen and you can see all sorts of issues.

      And before you tell me to go read a book on data compression, I've read plenty of them. I've spent the last 10 years developing Freeview (and other digital) receivers - hence the anonymous post. You can't get a silk purse out of a sow's ear and Freeview is the classic example of that.

  22. Anonymous Coward
    Anonymous Coward

    @Chris 3

    Chris 3, firstly the age of your aerial is not likely to be a factor in your receiving a blocky signal on Freeview. Aerials don't deteriorate with age, there aren't any moving parts and it is entirely passive, there are no active components to degrade.

    Secondly, the blocky artefacts are not an issue with the compression, that's your lack of knowledge which is showing up. The artefacts are errors in the data stream which can be caused by a number of things, but most likely a weak signal.

    Would suggest you read a book on data transmission. Please stop repeating that the compression is at fault : it isn't. It's your knowledge and understanding of data communications which is at fault.

  23. Anonymous Coward
    Anonymous Coward

    @Chris 3 - Crystal Palace Transmitter

    And Chris if you live in East London and you're getting a blocky signal, then you really do have a problem.

    Depending on whether there are any obstructions, you should be able to pick up a signal from the Crystal Palace transmitter. I pick up my Freeview from Crystal Palace and I'm much, much further away from it than you are. I'm precisely 30 miles away. And I get a perfect Freeview signal 99.99% of the time. So you should easily get a good signal.

    Get your equipment looked at by someone who knows what they are doing.

  24. Anonymous Coward
    Anonymous Coward

    Less Channels, Higher Quality.

    I'd rather have two high def channels at the highest possible quality than 4 channels at lower quality.

    Then gradually over time, as more spectrum is freed-up more channels can be created.

    You know what's going to happen, the more channels they transmit, the lower the quality of the programming material.

    Look at the 60 or more channels on Freeview we currently have..how much of it does anyone actually watch? Ok, your lowly educated East Enders watchers and Coronation Street watchers will probably watch all the crappy shopping channels, but aside from the uneducated who would probably complain, let's be honest, there really is a lot of cr*p on Freeview.

    We have the opportunity here to create a fantastic television system, it's like having a Porsche that can do 150mph, but it's limited to 70mph.

    We suffered for a number of years because OFCOM wanted to go down the route of having more SD channels because they decided for us that we wanted more channels of cr*p (more variety as they called it) - more shopping channels, more po*n instead of HD channels.

    OFCOM eeem to be catering for the masses, the muppet class, which are the Eastender and Coronation Street watchers. Let them read the Sun, the Mirror, the News of the World.

    And who really gives a s**t if Eastenders is in HD! It's the science programmes that will really benefit from it. It's the uneducated that wouldn't give a damn about HD, and probably wouldn't notice it! Let them listen to mp3's and think they're wonderul.

    1. Nigel Whitfield.

      Fry and Laurie ...

      Did a great sketch, back in the 90s, where Fry was maitre'd in a restaurant, and apologised profusely to a broadcasting minister, taking away his silver cutlery.

      He return, upending a bag of plastic cutlery all over the table, and when the minister asked what the junk was for, told him that was surely what he wanted - lots and lots of choice.

      Sadly, I've never been able to track that clip down, but it was fairly prescient.

      Unfortunately, it's no longer fashionable to be patrician.

  25. pootle
    Go

    bleeding edge bandages

    H264 doesn't need expensive hardware - It's working very nicely on my laptop right now from freesat using GPU based decoding on the nvidia 9300m GS chipset under linux. Works even better on my linux desktop with an nvidia GT220 video card.

    I believe this decoding in the GPU also runs under windoze for those who still feel it necessary to support the Gates foundation with every PC purchase.

    Now all I need is a twin tuner DVB T2 card that I can run under linux to get away from the single tuner per card that come with current DVB S2 cards.

    Still not quite as high a WAF rating as a humax freesat PVR box, but getting close......

  26. Nigel Whitfield.

    Network architecture

    The BBC's Flickr photostream contains this shot, showing the network architecture for Freeview HD, which was one of the more interesting slides, I thought.

    Thankfully, this saves you all from having to suffer the version I jotted down in my notebook!

    http://www.flickr.com/photos/bbccouk/4153216652/

  27. Chris 3
    Grenade

    @rotacyclic

    Thanks for your comments, but I'm not an actual knuckle-dragging imbecile. Consequently I can tell the difference between compression artefacts and interference-related break-up.

    The reason I mentioned my arial? Because, yes they do deteriorate over time: corrosion and water ingress into the coax can significantly degrade signal strength.

    I mentioned the fact that I bought a new arial, simply as a shorthand to signify that the ariel was specced and installed to be sufficient for good digital reception. The guy was a specialist and the admittedly simplistic signal strength meter on my set shows a good 90%, most of the time.

    You say: "Everyone seems to be so obsessed with the idea of compression artefacts, but in reality there aren't any", It's curious that "everyone is obsessed" with this, but you, no? To adapt your final comment somewhat. "Get your eyes looked at by someone who knows what they are doing."

  28. Dick Emery
    Stop

    Blocky picture

    Err...guys. With digital it's either on or off. Unlike analog you won't get inteference or degredation in the picture. You might get breakup of the signal if your signal is weak but that would mean the screen would freeze up along with blocking. But that's because the signal has been lost. If he gets a continuous picture and see's blocks that is due to compression artefacts. Usually from too low a bitrate or a bad hardware encoder being used for certain scenes like movement, water (water is a bitch) etc.

    It will be more noticeable on large LCD screens (LCD being so sharp tends to show it up more than CRT or plasma).

  29. John H Woods Silver badge
    Happy

    PS3 + Play TV?

    Thanks to all for clearing that up for me.

  30. Tom 38

    You do get compression artifacts on Freeview

    Just watch some football on ITV4. I can get higher bitrate than that off interweb.

  31. Jdyson

    Forefront of HD? Maybe I misunderstand?

    Here in very average Indianapolis, in the USA, we have no troubles receiving (INDOOR ANTENNA) at least 5-6 terrestrial HDTV CHANNELS -- some with some low BW SDTV for aux info, many are 1080i (mostly deinterlaced when displayed, or generated from 1080p24 and reintegrated into to 1080 progressive at the receiver), some 720p, most barely compressed at all most of the time. Most of the USA has HDTV -- free -- fairly easy to receive with indoor antennas up to 10miles -- I can do approx 20miles inside -- careful set-up, and super easy at xx miles with any kind of outdoor rig. This has been true for at least several years, but even 7-8yrs ago we were getting many of the network shows (CSI, NYPD BLUE, movies, other stuff) in true HD. It is only recently (2-4yrs ago) that the local TV stations really had full HDTV switching, and within the last year or two that local origination was HDTV. In the US, we have both HDTV enabled networks (a few would be roughly equiv to BBC), and 100's of HDTV enabled local stations.

    1. Nigel Whitfield.

      Technical terms

      We're at the forefront not in terms of the number of channels (lots of people have more, of course), but in terms of the technology deployed.

      We are the first country to deploy DVB-T2, which is much more efficient in terms of spectrum, and the general spec means that every box that people buy for the service will be IPTV capable; it's pretty much a dead cert that iPlayer will be available, and likely ITV player too, as that's going on Freesat and will probably follow on FreeviewHD.

      So, in terms of the technology that you'll be able to wander into a supermarket and buy, without any need for subscriptions, I'd say that will be a pretty advanced proposition.

      Of course, it's somewhat marred by the lack of spectrum available; the Ofcom guys at the launch presentation suggested that if someone were to bid for spectrum, then there'd be the capacity to do another two muxes nationwide, and the existing ones, longer term may convert to DVB-T2 too. Of course, that's all a long way off, and I doubt we'll ever have quite as many FTA HD channels as elsewhere.

      But technically (at least until the Finns build out their network, starting end of this year), it is at the forefront (or cutting edge, if you prefer to put it that way).

  32. Anonymous Coward
    Anonymous Coward

    @Chris 3

    Chris, you were repeatedly complaining that your problem with your Freeview signal is caused by compression artefacts, yet the symptoms you were describing were not of that, they were of errors in the datastream.

    Enough said.

  33. Anonymous Coward
    Anonymous Coward

    @Chris 3

    Chris, although I said aerials don't degrade over time, I deliberately ruled out environmental factors.

    There's a difference between electronic components and devices that will fail in normal use, and those that are subject to environmental conditions which lead to failure.

    To try to compare aerials with electronic components such as chips, transistors, capacitors would be crazy.

    If you take an aerial and quite happily use it for years, 5 years, even much longer without degredation.

    Take any kind of electronic component, and subject it to extremes of temperature, moisture, then yes, they will fail, in time.

    I've been working with this kind of stuff for nearly 20 years mate.

  34. David Austin

    title

    It always amazes me the depth and breath of knowledge that shows up in the comments section of stories like this. some very interesting posts to digest.

    The IPTV Support is the most interesting part to me: Can't remember the last time I turned on the Freeview box, and don't have satellite. All the television I've been getting this year is via iPlayer/ITV Player/4oD. The last few weeks since the new iPlayer Wii channel launched have sold me on the idea of a (good) set top box on demand solution - yeah, Wii had iPlayer support for a long time, but the channel is a much more pleasant experience, to the point where I had my technophobic mum using it last week, and I had to give her a two hour training session with her Humax DVR last Christmas...

    Any movies I really care about the quality for, I grab on Blu-ray: Acceptable rights restrictions, permanent, and tangible.

  35. Anonymous Coward
    Anonymous Coward

    Compression artefacts

    I did say that that there weren't any compression artefacts with Freeview. Technically, that statement is not 100% accurate. What I was doing was trying to impress upon Chris 3 that the effects he was observing are not caused by compression. I've been using Freeview for years on a large screen, and I don't see any compression effects., not from my viewing distance.

    As we all know, Freeview uses a lossless compression technique. When the signal is reconstructed, because information is lost in the compression process, obviously, the reconstructed signal is not identical to the original signal prior to compression.

    One of the sources of loss of the information is caused by the conversion of the time based signal in to the frequency domain using the discrete cosine transformation, where the coefficient of the terms (harmonics) are finite in number and appoximate the waveform prior to the DCT.

    So yes, there are issues, but to most people in normal day to day viewing of Freeview, do not notice these effects.

    A developer in a Freeview system may have to concern themselves with them, but Joe Public mostly does not.

    1. Anonymous Coward
      Anonymous Coward

      Lossless?

      "As we all know, Freeview uses a lossless compression technique."

      No it doesn't. It's lossy, as you describe in your next paragraph. Just like JPEG and the MP3s you were slagging off earlier (along with half the UK population). And why would we "all know" that anyway? The Reg readership is pretty diverse.

      I don't doubt that you are a clever bloke, but you've taken "patronising" to a whole new level, even for a Reg comment - and that's saying something.

  36. Anonymous Coward
    Anonymous Coward

    MP3's, JPEGs

    I didn't slag of JPEG, but I did slag off MP3's.

    Have you actually done a comparison of MP3's and CDs? I have. CDs are superior.

    I worked in professional audio with high-end studio equipment. Am I critical of MP3's? Absolutely. Even Apple are aware of the flaws in MP3's, that's why they adopted the AAC coding standard.

  37. Anonymous Coward
    Anonymous Coward

    @Dick Emery

    Your description of the failure modes of analogue verses digital signals are partially correct but not complete.

    A digital signal can degrade partially, or fully.

    You are right in the context of a full loss of signal, there is no data stream, so what is the receiver to do? If the loss of signal is long enough then there can be only one result, loss of picture.

    In a partial degredation scenario, which could be caused by a number of factors:

    A weak signal, resulting in low signal to noise ratio

    an interference signal superimposed on the information signal.

    The datastream contains redundant data bits, which correct the errors that occur in these scenarios. If the errors can not be corrected, then the receiver has to decide what to do with the errant data. It knows it's errant data but what should the receiver do with it?

    This could be just a few pixels in an image frame that are errant.

    The receiver could try to interpolate ( and CD players often use this technique), or it could just display a blank pixel.

    Your assertion that the pixelation on the image MUST be caused by compression artefacts is wrong.

  38. markp 1
    Boffin

    jesus, guys...

    Let's get some sense and technical truth on the go here.

    Freeview is far from lossless. It uses MPEG2, same as on DVDs, but typically at a lower, constant bit rate (vs DVD's high, typically variable rates) and sometimes at lower pixel resolution too.

    When it's fed a decent amount of bits, has a good encoder at the broadcaster end, and the material shown is sympathetic to MPG, it looks fantastic, slightly sharper than broadcast and without the dot crawl and slight fuzz that my local analogue transmitter produces. When it has less bits available (channel overcrowding and bandwidth/resolution choices made by the same clueless cretins that think 96kbit stereo is just fine for MP2-based DAB), a poor encoder or more demanding material, it becomes a horrific blockfest that will have you offering your writing arm as sacrifice to get good old PAL-I UHF back. This year's Eurovision repeats and Glasto coverage were a stark case in point - some of the shows were nearly unwatchable thanks to blocking, as it appeared to be attempting full DVD resolution with VCD bandwidth, in order to transmit some very high motion performances with intricate and very colourful detail. A resolution drop might have helped, and a quiet fallback to 25fps progressive (slightly jerky and aliased 352x576 with moderate distortion beats a screenful of 8x8 blocks moving at 50fps interlace in a 720x576 frame), but you can't count on the guys at mission control to think of such stuff.

    Your results WILL depend on where you are, what channel you're watching, and when, as the different multiplexes in various parts of the country will have their own bandwidth limits and number of channels fighting for slots within that. As well as different content being shown, and actual number of airing channels differing throughout the day. You may never have suffered this disease, or it may be the bane of your life. I count myself fairly lucky that it only rears its head once in a blue moon, but then I do tend to stick to the main BBC stuff (...and Dave/Virgin1) which gets a bigger slice of the pie. Wierdly, the shopping channels also seem to be smooth as silk.

    It's definitely nothing to do with signal strength though. MPG failure results in a whole barrel of other image freakouts, instead of simple blocking. That's one of the weaknesses in the system, at least until the promised power boost that comes with analogue switch-off. An oldskool signal will remain sort-of watchable with crap reception, until the audio becomes drowned out by noise and the image circuits are no longer able to derive accurate sync pulses (by which point, colour has gone, and you're left picking out silhouettes from the snow anyway). It's very graceful and gradual in it's failure mode, and I was very glad of it when living in north Wales, where our student dinner time Buffy fix gave the impression that the hellmouth was, unlikely as it seems, wrapped in a perpetual blizzard. With freeview, we'd have got nothing. Depending on your receiver, the picture will either continually lock up, or it'll go to a blank "no signal" screen, or - like my nan's cheap telly - display the signal in the raw regardless, with all the nightmare fuel that is the unmoderated output of a f***ed up mpg stream. Download some mpg files into your PC, use whatever method you feel like to throw a very small amount of random noise into the data stream (to emulate the sort of noise you'd hardly notice on analogue being _mostly_ but not entirely filtered out by the transport stream's ECC), then drop it in media player and watch the hideousness unfold. "Paint walls", psychedelic colours and distorted faces abound. The effects are often block-based, true, but rarely give a "proper" blocking effect unless it's your decoder being VERY clever in it's error correction.

    So lets hope they can implement better signal strength AND higher bitrates somehow.

    On which subject, I'm all for the variable bitrate idea, it's excellent for squeezing good quality into smaller filesizes in digital media... but I dunno if it's going to work in the broadcast arena. Or if it's even necessary. What happens if all, or even just a majority of the stations on a multiplex want to go to high-bitrate mode all at once? There's not going to be the bandwidth to allow it. There'll be massive compromise (and how in heaven's name do you balance it all anyhow, unless the encoding is only done all-at-once at the actual transmitter and everything to that point is either uncompressed or full-bore?) ---- and once you hit the point of that happening everyone once in a while, kiboshing the attempt to give a consistent apparent quality*, you may as well stay with CBR instead. Oddly, this is even what the iPlayer does, despite being online and serving up largely non-live material, where you could make good use of VBR efficiency. All the iP streams are fixed-rate. But, in doing so, they've also shown that there may not be need to vary the rate so much - the highest bandwidth offering at the moment is 3Mbit/s, for 720p (25fps, mind... unless it's my media player being wierd, cuz I could SWEAR it's said 50fps and gone smoother occasionally), and under almost all circumstances it looks just fine thanks to the MP4 (H264) compression that DVB-T2 also uses. Treble that to reach 1080p at 50fps (economies of scale occuring in both size and framerate) and you're still under the magic 10Mbit/s "average", which gives you a bit of overhead for those insanely OTT subtitles (MUST have a signing option, surely... I'm sure ceefax 888 got away with about 200 bits/sec for text), audio description, error correction, a slight quality boost, etc.

    (It also has "ED" rez stuff (832x468, 25p framerate) at 1.5mbit and SD-ish (640x360) at 0.8...... and it still looks alright, meaning with such encoding we could probably cram in 50% more channels on each existing multiplex and it'd STILL look better and have less blocking. However the effects of interference would propagate for longer, given the bigger intervals between keyframes - a lot more of MP4 is made of "delta" frames that merely encode changes from the previous one, so if your TV thinks one frame is different from how it should be, that mistake's going to stick around for 3 or 4 seconds rather than the half-second or so maximum for MPG2)

    Sooooooooo this'll be interesting to watch. It could be made of win.... or divebomb spectacularly. Let's hope it's the former, because like DAB it's unlikely we'll see a U-turn regardless of how horrid it gets.

    (Now, can we maybe ditch DAB before it gets too much more market penetration and replace it with something using a more widespread and modern standard, maybe like what they have in europe or the states? Perhaps something like the AAC used in MP4 files. That sounds perfectly spiffy at 128k... Or at least can we use better MP2 encoders? I've used good quality ones that actually turn out listenable files at 160-192k, 128k when downsampled to typical broadcast quality (15.5khz) and 112k if you further compromise the headroom, though 96-stereo is still unsalvageable. Problem is, they're slowwwwwwww (maybe 2x realtime on my modern laptop), but it should still be OK for piping thru a server and out to air. Then we can work on beefing up the signal strength)

  39. markp 1
    Megaphone

    and another thing

    BTW do they not even compress the subtitle bitmaps or use a "no change" flag? For plaintext with minor antialiasing, PNG crunching and an arbitary 1/2-sec update rate I'd expect to see the entire display covered with text at 200kbit/s. It might be more efficient with that kind of bandwidth to send an actual font file to the reciever every 10 seconds (well, on continuous repeat and spread across the whole 10s... 2000kbits=256kb=one _enormous_ font, whether bitmap or vector) with plaintext for the actual content. Even DVD bitmapped subs don't need anything like that amount of overhead.

    Can I also second the plastic cutlery, too much choice argument. There may be room in e.g. the USA for 30+ channels of actual content (the other 50% of Freeview at the moment is QVC-a-likes, dodgy quality music channels, poor-man's-sky-sports and encrypted grot that almost certainly isn't worth paying for), but here that represents 2 million viewers IF each channel was evenly split AND everyone in the whole country was watching (which they're not, and they don't). Those kind of viewing figures, with promise of even more meagre slices to come, means serious bad news for the revenues needed to make new programmes - little wonder that a lot of the rest of the material on the "worthwhile" channels is itself endless repeats of older classic stuff. There's probably 15-20 channels actually worth anyone's time on freeview (and the same was true when my area was getting analogue cable in the mid 90s... including the bizarro foreign channels like Sat Eins and it's 6pm porno), if we can somehow democratically cut it down to that level we'd get a much better viewing experience (clearer picture, more money for making good programmes) and yet nothing of value would be lost. If there were genuinely interesting, niche channels that this would mean the axe for, then I wouldn't propose it... but there aren't. None that you don't have to pay for, anyway, with the exception of Film4 and Teachers TV which could be preserved as "public service" stations.

  40. Anonymous Coward
    Anonymous Coward

    Sandy Heath...

    ...not till 2011? Oh well, I guess I'm not missing much, what with the dodgy codecs and bitrates and all.

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