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Bit-rates for channels

Discussion in 'Satellite TV, Sky TV & FreeSat' started by StooMonster, Jun 17, 2003.

  1. StooMonster

    StooMonster
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    There is plenty of discussion about high bit-rate and low bit-rate channels on the Sky digital (and digital cable) platform. With Channel Five being praised for highest bit-rate, and the "UK" and some of the music channels being the lowest.

    On a big screen it’s obvious which are higher, and which are lower; but does anyone actually know what the average bit-rates per channel actually are? I’d like a nice table please.

    StooMonster
     
  2. Starburst

    Starburst
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    I doubt there are many digiboxes that have been hacked to output bitrate data at least in the domestic arena.
    SKY+ can give you a rough estimate of bitrates based on the amount of HD capacity it uses to record a program but it does roundup/down the numbers.
     
  3. StooMonster

    StooMonster
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    Dang namit, I thought of that in the shower this morning -- then duly forgot by time of first cup of coffee. Thanks for the reminder Starburst!

    Hrm... may play around with Sky+ later.

    I've heard people quote that their mate can measure bit-rates and all channels have dropped 20-30% since Sky digital launch so many times I wondered if there is actually any publically available data.

    Could measuring channels' bit-rates be possible with a Hauppage card and FTA channels?

    StooMonster
     
  4. Starburst

    Starburst
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    Every man and his dog has a mate who can say such and such but unless bitrate data comes direct from official SKY sources or other broadcasters on the platform it's rather meaningless.
    When I first got SKY+ I posted some numbers in one of the SKY newsgroups, intersting but hardly scientific:)
    By chance a quick search of my "Sent Items" in OE turned up the post dated 9/12/2001....

    Paramount.........Spin City...........6 meg/second

    UK Horizons.....Clarkson............5.29 meg/second

    Channel 4...........Leon..................3.64 meg/second

    UK Living..........Charmed............5.74 meg/second

    Channel 4...........Southpark.........4.3 meg/second

    SKY 1..................Xena..................5.29 meg/second

    ITV 1....................Fun Animals.....7.14 meg/second

    It will be interesting to compare some of the numbers :)


    Personal opinion only but most of the alligations about wide spread bitrate reduction on SKY D have come from shall we say posters who seem to have a pro DTT stance. Nothing wrong with a pro or anti postition on any subject afterall we can't have much of a discussion if everyone agrees but some seem incapable of accepting a viewpoint other than their own:)
    I certainly have had some "interesting" discussions about the subject on another forum !

    Either way I think we can all agree that digital TV in the UK on every platfrom would benefit from enforced standards and a widespread increase in bitrates.

    Yes I believe some of the PC DTT and Satellite cards have the software to display bitrates so you could certainly get accurate figures on FTA channels on DSat, BBC will be interesting as they have rented 2 more transponders from SES. So far the BBC have been running their service with reduced bitrates and I hope some of the new capacity will remedy this and not just be used for the regional services.
     
  5. KeithO

    KeithO
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    The bitrates on all Sky channels are dynamic, not fixed. if one channel needs more, it is stolen from the 'pool' available via the satellite and so some other channel gets less. This is automatic. Thus, the more crappy channels Sky keep pushing onto the satellite, the worse the bitrates will get for all the channels.

    A bitrate display is useless anyway, as it's a snapshot of a particular moment in time (try checking it out on a DVD...most players have bitrate display). Largely static scenes require very little bitrate to look good, rapidly changing ones need high bitrate to look good. So a display of bitrates would only show you what was being broadcast at that particular moment.

    Sky's general opinion is that the benefit of satellite TV is NOT to be gained in improved picture/audio quality, but (as far as Joe Public is concerned) comes in the form of increased choice of channels. So they aren't generally concerned with the quality of what they broadcast, only the quantity.
     
  6. Starburst

    Starburst
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    Accurate but only upto a point.
    First SKY has direct control of only so many transponders. Most broadcasters rent capacity/transponders direct from SES or Eutelsat so they decide what maximum bitrates to use on their programming. Statistical multiplexing is used by many broadcasters but that only works on a per transponder basis and then a broadcaster can only manipulate the capacity they have rented on that transponder, they can not take capacity away from another channel without their permission :)
    Both the BBC and ITV use this method to maximise the useage of their bandwidth, alas more often than not all it achieves is every channel within the system getting less then it requires to produce a good picture.

    Look closely to the channels you can pick up using a minidish focused on 28.2 degrees, you will find that the majority are not owned or controlled by SKY. SKY can not stop third party channels
    from appearing nor can they stop legal channels from using their EPG system. A shopping channel wants to launch, they go to SES and rent some capacity (Which is currently not being used) and then they buy an EPG slot and start broadcasting. This channel has not taken anybody elses bandwidth not has there existence reduced the quality of other channels. It's very easy for the uninformed to believe if it's on satellite and being broadcast to the UK then it must be SKY :(

    Yes a bitrate meter will only give you a figure for a specific point in time but it does allow you access to max/min bitrates used and you can work out an average which is what you want when comparing channels across the platfroms.
    Bottom line is if the picture looks ok on your display then it's being broadcast at a suitable bitrate, however TV technology is rapidly improving and one thing Plasmas/LCD and larger widescreen CRT's need is a broadcast digital source comparable to a professionally mastered DVD.

    No argument that SKY's view is quantity rather than quality however they are finally taking the w/s avenue and supporting DD5.1 audio. They are not doing this out of the goodness of their hearts but because right now it makes good marketing sense. FOX in the US took the same view, while other US networks embrace High Definition TV only FOX refused to use extra digital capacity to increase PQ, they wanted more channels. The US government in a beautiful move told FOX they would be barred from buying any new digital capacity after analogue shutdown unless they supported HD, faced with that crippling option they have partially supported HD.

    We lack a government/regulator with such an aggressive far sighted approach to the future of UK digital broadcasting on all platfroms:(
     
  7. StooMonster

    StooMonster
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    I know how MPEG works; but average bit-rate is the best measure of quality we have available. For example, if over several hours of regular television (not static graphics) one channel has a bit-rate that was twice another's could we not assume that the picture quality on the channel would be higher?

    Over at digitalspy.co.uk Terranus said "BBC is using an average of 3.5-4.3 Mbit/s, many Sky channels are bit lower. Also many Sky channels are using a reduced resolution of 528x576 pixel instead of 720x576. This can be easily checked with Nokia or Lemon digital boxes."

    If what he says is true, we're losing resolution as well as bandwidth on PQ. Considering that screens are getting larger, I'm puzzled that PQ isn't more of an issue. Although I guess it's easier to make a business case for more channels rather than better quality.

    The drive for more channels and thus choice, but with smaller audiences for each must have some kind of business model to work. Although the BBC will be decreasing PQ for everyone when complete regional service starts, thinking about it, only at regional programme times though. But could explain why they have recently rented another two transponders post their move.

    I don’t think quality is going to stand up to quantity in the digital world, another example is digital radio and the infamous quote of a broadcasting executive “Sod the audiophiles, they can listen to CDs. It’s about more stations, more choice.” Ever wondered why there are so many audiophile DAB radios for sale on eBay?

    StooMonster
     
  8. KeithO

    KeithO
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    Starburst, thanks for tidying up some of the looser points in my post!;)
     

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