OT: cable capacity for on demand video ?

Discussion in 'Professional Video Production' started by marks542004, Nov 9, 2005.

  1. marks542004

    marks542004 Guest


    This may be off topic - please suggest other newsgroup if applicable.

    There was a report on my local TV news about several cable companies
    carrying several TV series on-demand.

    Does anyone know the carrying capacity of a cable network for this type
    of thing.

    When I was involved with computer networking 15 years ago video
    conferencing always wound up killing the networks.

    I know speeds have gone up considerably but there must be a point at
    which the on-demand capacity breaks down.

    marks542004, Nov 9, 2005
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  2. marks542004

    AnthonyR Guest

    Not sure on the answer but i thought the same thing.
    In fact Time Warner offers me so many OnDemand channels now it's impossible
    to watch a fraction every day.
    Besides Movies from HBO, Showtime, TMC etc... they offer A&E, CNN,
    FoodNetwork, Comedy Central you name it
    everything OnDemand now. I don't know their limits but so far everything
    runs pretty smoothly.
    I wonder after every single customer goes digital, uses broadband and movies
    over IP at the same time what will happen?

    AnthonyR, Nov 10, 2005
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  3. marks542004

    Bill Fright Guest

    To me it's all about the bandwidth. Sure they can cram more programs
    into the pipe as they continue to lower the quality. Any of you guys who
    are compressing your high quality shows to mpg2 (DVD) know what I'm
    talking about. The shorter the show the higher the quality.

    Maybe I have too much time on my hands or I'm a huge nerd but I love to
    go to retail home theater stores and talk bandwidth with people. My
    favorite is to have them show me HD via satellite.

    So nothing will happen (as far as a major system crash) they'll just
    keep lowering the bit rate and decrease the overall quality to fit more
    programming in the pipe.

    Next time I hear digital quality I'm gonna throw my cell phone at somebody.
    Bill Fright, Nov 10, 2005
  4. marks542004

    AnthonyR Guest

    Bill Good Point,
    But normally a cable company can squeeze say 800 channels into a cable and
    send that to 8 million people in nyc, right?
    But if all 8 million people ask to see an On Demand Movie or show, each one
    starts and pauses it separately, so now how does the cable company fit the
    800 channels plus the 8 million movies all playing into that bandwidth,
    squeeze it more?
    wow, that's a great trick if they can pull it off.

    I suspect, they have many distribution points, so each neighborhood handles
    it's own Ondemand bandwidth independently of the entire system, sort of how
    cell phone companies have many cells. But I don't really know, just guessing

    Your comment about "hearing about digital quality" is funny. That's how they
    sell us new stuff, promise better quality to get us to change then deliver
    less. Overhaul it still is better than I was getting with my rabbit ears
    years ago, even with occasional digital breakup. :) I don't miss the snow
    and double images and ghost of analog tv.
    I wonder how much better digital tv transmission will be once they convert

    AnthonyR, Nov 11, 2005
  5. marks542004

    Bill Fright Guest

    Okay now I have some home work!!! I'll look into this and figure it out.
    But I suspect I know the answer already. I'll bet the on demand programs
    reside in RAM type memory and since it can be accessed at different
    points simultaneously and the bandwidth is low it will accept several
    "demands" at one time. For example if you have a terabit of RAM on a
    server you could have people access it simultaneously all a across a

    I will look in to this.
    Exactly, less quality but they sell it like it's the best ever.

    You just touched my favorite point. Put a pair of studio monitors side
    by side with a waveform/vector scope for each one. If your antenna
    receives the analog signal correctly it will have a much higher
    resolution than a cable or satellite signal. The key here of course is
    the antenna. This goes double for HD. So the answer to your question is
    yes, digital over the air transmission is going to suck just like cable
    and satellite because it's going to be compressed the same way. So in
    2008 when they pull (supposedly) the plug on analog transmission you'll
    lose the highest quality you could ever receive at your home as a
    consumer. Like the plague mpeg2 is coming to get you!

    Perhaps I'm bordering on insanity but the pixilation and blurred
    (averaged) back grounds are artifacts I don't find acceptable in a video
    signal. Of course my production company delivers mpeg2 products just
    like everyone else but I never turn in mpeg2 products for broadcast.

    Hell I'm so determined I still shoot on Betacamsp over DVcam even though
    it's much less convenient.
    Bill Fright, Nov 12, 2005
  6. marks542004

    AnthonyR Guest

    Thanks for the detailed reply.
    If you do find out more on this OnDemand scheme, I'd be very interested.
    I understand what you are saying.

    AnthonyR, Nov 13, 2005
  7. marks542004

    Bill Fright Guest

    I can't guarantee the accuracy but this looks pretty plausible to me.

    Bill Fright, Nov 13, 2005
  8. marks542004

    AnthonyR Guest

    Thanks Bill, i will read it in more detail later on. :)

    I like this guys question however. :)

    Having read Tristans description of how VOD works it got me thinking. Would
    it be possible to supply the normal digital channels using the same method
    as VOD but without the pause, rewind, etc. that VOD has? That is just
    transmitting the live pictures from the selected channel to your TV. At the
    moment all 200 or so channels are sent to every STB taking up a hell of a
    lot of bandwidth. If only the selected channel was sent to your STB from the
    headend or hubsite there could be plenty of bandwidth available for other

    Yes, it's known as Broadcast On Demand (BOD). See here for a presentation.
    (Although that's not about cable, the same principle applies).

    That idea sounds interesting to free up bandwidth, no?

    AnthonyR, Nov 14, 2005
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