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mixing HD on an SD simulcast channel?

Discussion in 'TVs' started by richard plumb, Sep 25, 2005.

  1. richard plumb

    richard plumb
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    Watching F1 today, I was imagining what it'd be like if it went HD. But that would need ITV to broadcast HD to get any benefit. Which got me thinking a bit more.

    For something like SkyHD, all existing SD channels will need to be rebroadcast as well. Will these be in MPEG4 for compatibility with the STB?

    Also, how trivial would it be for a channel to slowly introduce a limited HD service? Kind of like how ITV did with Dolby Surround in the late 90's? Broadcast a brief thing at the beginning 'broadcast in High Definition where available'. Then if you have HD you see the program in HD. If you have SD, you start to see these notices and it might encourage take-up of HD services.


    I think they do something similar in Japan. There are BS Hivision programs but not all the programs on a channel are HD, some are simulcast SD.
     
  2. Starburst

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    The existing SD channels will remain exactly as they are, the SKY+ HD can decode mpeg2 broadcasts with ease.

    I suspect any broadcaster offering piece meal HD will just use a dedicated HD channel which like Prem+ shows either a testcard or demo and is only active when needed but keeps a place on the EPG.
     
  3. Quickbeam

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    Sky One HD and Sky Sports HD are simulcast channels so will have to be downconverted to MPEG-2 SD for regular Sky viewers. High-def sporting content should look a bit better in SD than it does now: less noise, easier to encode. As for Sky One, most of the recent US filmed shows are high-def downconverts; the only difference when Sky One HD begins broadcasting is the point at which the downconversion happens. Anything originating in SD will be upconverted to HD on the simulcast channels, and downconverted again for SD viewers.
     
  4. Stephen Neal

    Stephen Neal
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    I think it is more likely that the HD channel will be full-time, and a simulcast of the SD service. SD shows will be upconverted to HD, and HD shows shown as HD.

    Whether HD subscribers have a different EPG mapping - so Sky One HD appears on 106 for HD viewers, and SD viewers get the SD version on the same channel, I'm not so sure. Would seem to make sense.

    I think it unlikely that the HD channel will go off-air and carry a test card when the SD service is showing SD material. I suspect the US model of SD upconverts is more likely - can you imagine how annoying it would be to have to re-tune when HD viewers are watching an HD show followed by an SD one???
     
  5. Stephen Neal

    Stephen Neal
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    Don't get that. The Sky+ HD receiver will have to be MPEG2 compatible, and thus will receive the existing SD MPEG2 broadcasts. No need for rebroadcast unless you are running an HD service. Effectively the HD box gets the additional HD channels on top of the existing SD channels.

    It is a different situation. The Dolby Surround service was compatible with NICAM stereo broadcasts - which themselves were compatible with mono FM audio. Other than NICAM stereo, Dolby Surround didn't require any new reception hardware - just an additional Surround or ProLogic decoder to derive the matrixed surround info.

    The on-screen logo was purely a promotion exercise. Sure if ITV1 launched in HD, they'd probably put an "HD where available" logo, just as broadcasters put "Subtitles/888" and "Stereo" on the idents before programmes in the 90s.

    I'd imagine that most channels will be HD/SD simulcasts. HD material will be downconverted for the SD services, and SD material upconverted for the HD services.
     
  6. Starburst

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    You could be right but I was looking at the situation of a part time service not a 24/7 full simulcast which was how I understood the early US networks handled HD. It's been covered in other threads but would a upconverted SKY1 or future BBC/ITV HD offering be acceptable to the public and the media?

    I actually think that HD channels will have their own EPG listing totally seperate to the current SD versions. I suppose this is rooted in my belief that a part time HD channel makes more sense than a 24/7 partially upconverted one. I know SKY have indicated simulcast but that doesn't mean 24/7 nor has been mentioned the SKY1 that exists next year will be the same as the one we have now. The announcment of SKY2 and SKY3 certainly points to some strategic alterations which may impact SKY1's programming and structure.

    Again you may be right, what was sensible for the US networks in the early days makes less sense for SKY when HD content is more abundant and upscaling hardware is cheaper and more powerful.
    Personally I would not problems with switching to SKY1 HD at 9pm for my Battlestar Galactica fix and then back to SKY1 for a SD Simpsons (used Simpsons as an example of a program will never be HD native, well apart from the movie:) ), hardly any difference with channel surfing now.


    Time will tell though and either way where do I pay the money:)
     
  7. Stephen Neal

    Stephen Neal
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    AIUI the US stations have to simulcast their SD service on digital (though it doesn't have to be HD many are) AIUI NBC had to get special dispensation to show different HD and SD Olympics coverage in 2004?

    I think that HD shows in HD and SD upconverts would be fine. This is how NBC, CBS, ABC, Fox and PBS operate in the US, as do HBO etc.

    For HD viewers you get the best quality upconvert of SD services (probably a lot better quality than SD broadcasts upconverted by a receiver), and don't have the annoyance of switching channels.

    Personally - if BBC One were to go HD I'd get VERY annoyed if I had to flip between two channels to watch an evening's entertainment as the programmes alternated between HD and SD.

    I don't think that HD availability is a compelling reason to alter the scheduling of a network.

    The Simpsons and 24 are both "Sky One" channels... Don't see either being sidelined to an HD or SD only service?

    My gut feeling is that simulcasting is the most likely eventuality for Sky One, BBC One HD etc.

    However Discovery HD may well be a stand-alone service.
     
  8. Starburst

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    I have no direct experience of US telly but the listings for the major networks indicate which shows are HD simulcast, it has certainly never been apparent to me that there are dedicated network simulcast 24/7 channels showing upconverted material when native HD is not an option.
    Happy to be proved wrong but a quick look on the NBC and ABC websites shows many shows that are not in HD, so they are either SD or unadvertised HD upconverts.
    To me it looks like a broadcaster can trigger the STB to flick between a SD and HD broadcast at will or heaven forbid tells the viewer that HD content is on Channel X while the current channel remains SD leaving them with the extreme effort required to press a button:)

    This is one of those times when a US viewers direct experience would be most welcome:)

    However it is done I would consider a PAY service which has a high percentage of upconverts to be fraudulent, for something like the BBC well that's less of an issue although at the end of the day it's all down to what you personally accept as reasonable.
    For many HD itself is unreasonable:)

    I can't see any difference between flipping from BBC1 to SKY1 to CH4 then back to BBC1 when compared to BBC1 HD to BBC1 SD to SKY1 SD to SKY1 HD then CH4 SD for example. It's exactly what we do today be it on DTT, Dsat or cable.





    I wasn't implying that it was, however there are changes afoot with MIX becoming SKY2 and SKY3 appearing on Freeivew and Dsat (PAY obviously).
    It isn't that far fetched to assume that SKY1 itself will be impacted by these changes and the upcoming HD variant must play some part in the programming chosen if indeed it is a simulcast service.
    Or so I would have thought:)

    I don't expect any current or future program purchased for SKY1 to be HD only, however it would not surprise me to see programming only shown in SD, maybe moved to SKY2 and SKY3 as influenced by age/broadcast rights etc.
     
  9. Nick_UK

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    Dolby Surround was child's play to introduce, since any system which can reproduce stereo sound with low phase distortion (i.e. NICAM) can reproduce Dolby Surround.

    As for ITV introducing HD - I wouldn't hold your breath ! ITV still haven't properly phased in 16:9 properly, and F1 racing is still in 4:3. ITV have never really been in the forefront of technical innovation. You also have the added problem that F1 takes feeds from the host country, so whatever you get will be completely in the lap of the gods.
     
  10. sprattgraham

    sprattgraham
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    The Belguim GP was recorded in HD and acording to Euro1080 there was a HD uplink to Japan.

    They also said there is a chance that the race will be shown on HD-1 but was not able to tell me when.
     
  11. StooMonster

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    I hope when they simulcast their SD service they don't mess with aspect ratios, and keep 4:3 in proper pillarbox presentation; it would be tres annoying if they zoomed it to 14:9 (like BBC are so fond of doing) or messed with it in any other way (like 'just' or 'smart' approaches).

    When I've watched simulcast HD services in USA the 4:3 material (mostly adverts) are kept in 4:3 aspect ratio with pillarboxes.

    Is this a setting in set-top box or broadcast that way?

    StooMonster
     
  12. Stephen Neal

    Stephen Neal
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    Depends.

    4:3 SD material included on 1080i or 720p HD channels is upconverted in 12P16 pillarbox by the broadcasters. In this case the ratio is set by the broadcaster (though a few set-top boxes allow you to crop the pillarbox bars and stretch or zoom AIUI)

    4:3 SD broadcasts in 480/60i are upconverted by the set-top box and how they are presented depends on the box in question.
     
  13. Stephen Neal

    Stephen Neal
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    In the US it is common for the HD and SD analogue outputs of a station to be simulcast. The network provides HD feeds of the HD shows, and SD upconverts of the SD shows, alongside a network SD feed. Local stations also upconvert their local SD programming - and most importantly their adverts.

    Most nets send a high data rate MPEG2 HD feed, which is decoded by the local station, processed, and then re-encoded for broadcast.

    Fox is the odd one out, as it moved to HD more recently. It distributes a transmission data rate network feed directly to affiliates, and they don't recode for transmission - they just pass it on through a "splicer" that allows for local logos to be burned in in the MPEG2 domain, as well as allowing stations to cut to local SD->HD upconverts for commercials, local shows etc.

    It is quite common for US local stations to get the switching between SD and HD wrong, and for them to upconvert an SD version of an HD show rather than showing the HD feed - with a switch being thrown mid-show in some cases.

    The HD in the listings is to flag up which shows are actually produced and broadcast in HD (local stations permitting) - the actual HD streams are usually running 24/7. (PBS is different)

    There is still a lot of 4:3 SD (and a small amount of 16:9 SD) production. These shows will be upconverted to HD on the HD feeds from stations.

    A lot of NY studios are being upgraded to HD this summer - so the new series of Saturday Night Live will be in HD, as I believe will Good Morning America at some point in the near future (they are currently producing from an outside broadcast truck AIUI)

    Whilst this is technically possible (though switching streams is not easy to implement in a practical operational manner - and would cause nasty switching issues) it isn't what is done.

    In the US - when you tune to "ABC Channel 7 HD" (which is likely to be on a different RF channel to 7, which is the analogue channel number!) you will likely get a single HD stream containing the same output in programme and commercial terms as analogue ABC Channel 7 - but with SD material upconverted to HD, and HD material presented in HD. You may also find a few multi-cast SD channels, like a local weather radar loop, a news channel or a repeat of the local news etc. By law the US broadcasters have to simulcast at least an SD digital version of their analogue SD service - though most simulcast in HD (PBS is different).

    When NBC showed the Athens Olympics in HD, their HD and SD services WERE different, and I believe they had to approac the FCC (or similar) for permission to show different things on analogue and digital (for the stations that couldn't run an HD service AND an SD simulcast)

    AVSForum is a good place to find out about this stuff. I've just got back from a trip to the US - and saw some of the studios in question.

    I think as long as the material is correctly flagged and SD material isn't passed on as HD then it shouldn't be an issue.

    It may well be different for channels like Sky Sports - where they may be able to create a standalone HD channel. For a general channel like BBC One or Sky One then it would be more of an issue - I suspect it would only work if they re-named the channels to differentiate - say "BBC HD" rather than "BBC One HD"

    I thought you were suggesting that BBC One HD would be part-time and only carry output when BBC One was showing HD shows. Can you imagine how annoying it would be to have to flip back to BBC One SD from BBC One HD if the channels weren't simulcasts of each other?

    I suspect that the relevance of the programming to the target audience of the channel would be the bigger issue. For example I can't see Sky shunting the Simpsons off Sky One because it isn't produced in HD...
     
  14. Howard Pitfield

    Howard Pitfield
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    German sat stations Sat1 and Pro7 start HD services on 26 October (next month!).

    They will show HD material as is, in HD, and upconvert SD material for the rest of the time. That could prove a way for broadcasters to start HD services.....Can't wait - schnell schnell!

    Howard
     
  15. Stephen Neal

    Stephen Neal
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    Yep - that makes a lot of sense - especially for channels which already exist in SD.

    At the end of the day it depends whether you think of HD as another delivery system - like DTT, DSat and DCable - for an existing service, or as a new, and separate, service.
     
  16. richard plumb

    richard plumb
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    steven,

    So your best guess, based on current examples, would be that a hypothetical BBC 1 HD would be a completely HD delivered channel, but some of that content would be upconverted SD, some proper HD. Effectively as a consumer I see only one channel.


    If so, and I think this is an important point - would Sky HD therefore offer potentially much better SD programming that what we currently get? i.e. less artifacting etc?
     
  17. DanDT

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    I'm still hoping they will, though i'm a chronic pessimistic, so i'm kinda not raising my expectations too high.
     
  18. Howard Pitfield

    Howard Pitfield
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    I would hope that Sky don't tinker with the bitrate of their new HD channels and leave upconverted SD material running at full resolution - otherwise what's the point of spending all that dosh on new broadcast playout equipment etc. We shall see soon enough....

    H
     

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