USA user sues provider over compression.

Discussion in 'Satellite TV, Sky TV & FreeSat' started by Chris Muriel, Dec 19, 2006.

  1. Chris Muriel

    Chris Muriel
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  2. Starburst

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    That's a good read and certainly matches what I've heard about DirecTV's HD output and how the multipule branched distribution of HD from content providor on down causes so many issues with the final picture.

    I'm not quite sure if I can accept at face value that Canal Digital in Norway provides a channel at 45 Mbps at the domestic end regardless of the codec:)
     
  3. Tony Hoyle

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    From the wording I suspect 45mbps is the downlink, and it's compressed prior to delivery.

    At least sky haven't gone as low as 6.6mbps yet though.. Hope they don't get any ideas...
     
  4. `BK

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    Artsworld was between 4.5 and 6Mbit/s earlier today... >_>;
     
  5. arfster

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    Sadly, the capability of modern h264 codecs makes the term "HD" almost meaningless. You can compress 1080i down to 1mbit (seriously!) before any noticeable artifacting that might cause complaints - it just loses detail rather than artifacting. Admittedly the detail dropoff below about 6bmbit is particularly severe, although even 3/4mbit kicks the crap out of freeview.
     
  6. quinnmar

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    Would you mind telling me how to measure/monitor the bitrate of a given transmission?

    TIA
    quinnmar
     
  7. Whitey1977

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    19.4MB still doesn't sound much for a 1080i mpeg2 channel, not when Sky Movies 9 HD maxes at around 21Mb using H.264 which accorrding to the article is nearly twise as effecient as mpeg2.

    Whitey
     
  8. Starburst

    Starburst
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    Yet most of the US content at around 15mbps+ looks very nice indeed given the limitations of broadcasting compared to say pre-recorded media.
    The problem is that mpeg4 isn't doing the job it was designed to do in broadcast terms, mpeg2 isn't poor it's mpeg4 that is being driven harder to make up for possible problems in the encoders.

    The expected bitrates required for good PQ using H.264 are probably exactly what was allocated to the SKY branded HD channels and still used on SKY1HD and SM10HD.
     
  9. `BK

    `BK
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    Buy a DVB-S2 card and sit around watching the bitrates :)grin: ) or hop over to http://www.linowsat.com/0282/all/0282.shtml which has some nice figures and lovely graphs to look at.

    19.4Mbit/s is unfortunatly but a myth in today's US broadcasting environment... the best peak at 17.5Mbit/s (and that's some OTA/PPV), averages are much much lower depending on the channel.

    SM9 has also taken a hit recently... the average is now a steady 16-17Mbit/s (I'm almost certain some bitrate has been shifted into null packets) whereas before it wouldn't break a sweat pushing 18-20Mbit/s. Darkman 2 last night was around 15.4Mbit/s ~_~

    I'm also curious as to why Sky Sports 1 HD is broadcasting on two transponders and getting a higher bitrate average than SM9 when most of it's content is upconverted. Hopefully they'll be yet another channel reshuffle since NatGeo was there recently IIRC.

    I'm also disappointed to see that King Kong will air on SM10 on New Year's Day and not SM9... what a waste.
     
  10. Tony Hoyle

    Tony Hoyle
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    That's a marketing myth - the capacity of mpeg4 is roughly the same as mpeg2 at the moment. Maybe they'll make it more efficient in the future... it's probably capable of it, in theory.

    You'll never get 1080i down to 1mbit. You get horrible artefacting on Sky One HD (and SM10) at the moment.. and that's at 10 times that. Only BBC HD is consistently avoiding it - and that's at 19-24mbps.
     
  11. arfster

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    Nah, I'm talking from personal encoding experience. H.264 MPEG4 is astronomically better than MPEG2, although certainly other MPEG4 isn't that good (xvid). It's just Sky's live encoding equipment that isn't up to scratch - no doubt it'll improve, things have moved on enormously over the last 8 months alone.

    BBC HD is fixed rate 19.5mbit, and indeed it does impress. However, that's mostly expertly pre-encoded , whereas Sky is stat multiplexed (ie crappy live re-encoding). It's also a higher bitrate than really needed, simply because they have a whole transponder to themself to do their tests on.

    There's also the issue of peak bitrate - when Sky get their multiplexing working properly this will cope much better. HD-DVD can be used as a rough guide, with 12-15mbit ABR and 20mbit peaks, and a profile that should be possible to encode live in the not too distant future. Multiplexing won't allow for 20mbit peaks, but 12 peaking up to 15/16 at times should be manageable.


    For fun, here's a little 1.5mbit 1080i h264 sample:

    http://jfl1974.free.fr/upload/XMenIII.mp4

    Could be better with a bit more encoding care, that's just a quick encode someone did. It's a bit xviddish in the detail department admittedly, but considering it's 1/3 the bitrate of BBC1 yet has 5 times the pixels, it's extremely impressive.
     

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