Sky Movies HD MPEG Artefacts.....

Discussion in 'Sky Digital TV Forum' started by ROBERTT, Aug 9, 2006.

  1. ROBERTT

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    Hi all,

    I have had Sky HD installed since the 22 June and so far have been quite impressed with the quality of the picture. The world Cup football on the BBC was outstanding as is the cricket on SS1. IMO Championship football is quite acceptable, if not as good as the BBC coverage.....HOWEVER.........

    I have watched the HD movie channels for a while now and generally the PQ has been good (depending on the film master given to Sky),but recently i have noticed MPEG artefacts that can only be down to lack of bitrate. For instance yesterday evening watching Million Dollar Baby althought the PQ was generally good, I could see block noise in scene fades and in darker scenes. I turned over to watch some of the Aviator and again noticed these artefacts (although I was looking out for them!)

    Is it me or has anyone else noticed this. Sky need to be reminded that for HD, PQ is everything and I would rather have 5 channels of excellent quality HD than 15 channels of HD lite......

    Interesting on hearing other people's views on this........
     
  2. gangst

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    What are you watching Sky HD on?
     
  3. danvitale

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    You need to remember that 1: It's broadcast HD, and 2: the movies depend on what quality source Sky has themselves.
     
  4. TimmyH

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    Regarding the bitrate comment, some of the HD stuff that I record now does not seem to take up as much disk space as earleir HD stuff I recorded in June.
     
  5. danvitale

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    Again, depends on the source (bitrate etc)
     
  6. Gordon @ Convergent AV

    Gordon @ Convergent AV
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  7. ROBERTT

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    Hi Gordon,

    Yes I fear this is the case :eek:

    If so, we all need to complain to Sky otherwise they will slowly squeeze the bit rate to fit more HD (Lite) channels in at the expense of quality, the same as eventually happened to the standard channels over the years.

    For me to notice mpeg compression artefacts after a couple of months is very worrying. I will be watching the next few HD movies very carefully:devil:

    ps I have an old (but still very capable) Pioneer 434HDE. Looking to maybe upgrade to a Fujitsu 58 series (50") in the near future;)
     
  8. Starburst

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    The bitrate has to drop otherwise using mpeg4 and a whole new generation of STB's was a waste of time and effort.

    Of course a drop in bitrate thanks to more efficent and better encoding is one thing, bitrates dropping do to poor stat-muxing or squeezing another channel onto a transponder even with DVBS-2 is another.
     
  9. zAndy1

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    Yeah I've noticed it too, to be honest I'm cancelling at the first opportunity I get if it carries on like this. I'll be getting a HD-DVD player for movies, enjoying BBC HD for free and getting freeview and saving myself £50pm. After the initial novelty wore off I haven't watched Discovery HD or Nat Geo HD for ages, never watch Artsworld HD, not bothered about Sport so frankly if the movie channels continue to be as poor and repeat ridden as they are I don't see any point continuing to subscribe. Just my 2 cents worth....
     
  10. IanMerseyside

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    I agree that the films are generally of poor quality with the odd exception, e.g Lord of the Rings and Narnia. I flicked over last night just to compare between SD and HD on a film (can't remember the title but Tom Hanks was in it) and there was hardly any difference between the 2. The football and the cricket are generally very good on Sky HD but all the BBC stuff is far better. I suspect Sky are trying to get away with as poor a PQ as they can without losing significant subs. At this rate we will eventually reach a situation whereby a good SD braodcast will be as good as a poor HD one. If it wasn't for the football I would be cancelling my HD sub at the first opportunity.
     
  11. andijames

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    I'm due to get sky HD installed on the 30th August but have been a keen reader of these forums for a long time! I think it's very worrying that they are dropping the bitrates to a level where people can notice the drop in quality. The problem is there is no real competition for sky in the HD arena at the moment so they can pretty much get away with what they want. I personally think things will only start improving once the competition increases and then the consumer will go with the best quality vs price package

    My 2 cents :)
     
  12. ROBERTT

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    Hi Guys,

    Quick update......

    Am in the process of watching Resident Evil Apocolypse (SM10) and in certain scenes, large walls etc there is clear posturization going on due to lack of sufficient bandwidth.:mad: :mad:

    I watched this film when it first appeared on Movies HD and definitely did not see these artefacts then. They really are THAT NOTICEABLE......

    Has anyone got a Sky email address I can complain to (that will be read by someone in a position to do something about this) as this is definitely unacceptable IMO:mad:

    Not a happy bunny:mad:
     
  13. zAndy1

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    Noticed blocking in the background on the Artsworld Aquarium programme I recorded at 2am last night as well. Very worrying trend here...
     
  14. ROBERTT

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    Guys,

    Complaint duly sent..................

    Hello,

    I am a subscriber to Sky HD and have the full package of Movies and Sports. I have had the system installed since the 22nd June and was an early adopter to your Premium product. In general, I have been extremely pleased with the Picture Quality offered, but have noticed that in the past week, I am seeing MPEG blocking artefacts in the picture. This can only be because of a reduced bit rate and I find this unacceptable.

    Sky HD is pitched as a premium product with one aim in mind and that is a quality 1080i image. What is the point in a higher resolution if the image is spoiled by MPEG artefacts. A case in point tonight was Resident Evil Apocalypse. I could clearly see moving blocks in solid areas (background walls), that were not there when I viewed earlier screenings of this film.

    I am a member of the www.avforums.com website and have posted my thoughts on this for other members to comment on. I really hope that Sky is going to deliver a QUALITY HD service and not try and skimp on the bit rate to fit in more channels (as happened with the SD service over time). If this is the case there would be no point subscribing.

    I really hope I get an informed response to this email and not just a standard generated response like most enquiries.

    Lets see if I get a reply ;)
     
  15. SwinBob72

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    Only had SkyHD for a week so can't comment on what it was like at launch, but I am very disappointed with the quality of the couple of movies I've watched so far. Resident Evil tonight had some terrible artifacting in the darker scenes.

    I've had a HDCI-2000 box since before the world cup, and have got to say that the HD movies on Germany's Premiere are almost completely free of artifacts compared to what I have seen so far on SkyHD. Having said that DiscoveryHD on sky seems to be of a consistently high quality, as do the sports channels.

    I just hope that as they add more HD channels, they get the bandwidth from dropping crappy SD channels that no-one watches rather than reducing the bandwidth on the HD channels. Unfortunately I don't think they will. As commercial pressures increase all they will do is cram more and more, lower quality channels on the platform to try and increase advertising revenue. It happened to OnDigital, then Sky Digital, and next SkyHD.
     
  16. Pebb

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    It all depends on the movies used, because movies filmed in real life and recorded in HD is bound to not look as nice as HD movies in CGI. But over time, they will use better HD cameras, for movies filmed in real life.

    But remember Video proccessers in HDTV's will become even better in the future.
     
  17. Mike_CA

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    I'm not quite sure that Sky has 100% control over the maximum bit rate for movies. The reason that I have my doubts is because of my experience with movie channels in the US. Although, distribution in the US and UK are completely different, some of the same restrictions may apply.

    In the US, all distribution of HD content to cable/SAT/OTA providers is performed via SAT feeds. This includes multiple feeds from the movie channels HBO, SHO, STARZ, and CINAMAX.

    In the US most cable companies put a maximum of 2 untouched movie channels on one 256QAM band (maximum 38.6 mb/s). When checking the bit rate of the movie channels, the average movie appears to have bit rates between 9.5 mb/s and 12.5 mb/s and occasionally (1 out of 20 movies) will have a bit rate of about 14.5 mb/s. This would indicate that the cable company would not have any reason to limit bit rate since there is plenty of bandwidth on the band.

    Now comparing the movie channels to other channels, the bit rate seems to vary upto 50% on movie channels as compared to less than 10% on other channels. That great deviation of 50% could be explained if the movie channels were STAT muxing the channels but that does not appear to be the case since a high action movie such as Batman Begins indicates an average bit rate of 10.503 mb/s as well as Star Wars Episode III only indicates an average bit rate of 9.906 mb/s. Yet a slow moving movie such as The Accused indicates an average bit rate of 14.010 mb/s.

    Since the movie channels distribution feed does not appear to be STAT muxed and the maximum bit rate of the distribution feed appears to be about 15 mb/s, why is there such as variation of average bit rates between the different movies? You would think that the movie channels would set their encoder on the distribution feed to to output a maximum of 15 mb/s creating an average bit rate in the 14 mb/s range for all movies much like many other channels.

    So my speculation is that movie channels may not be getting high bit rate source from the studios for HD like they do for SD source. Since the studios seem to be paranoid about security, maybe they are worried that there may be a possibility of the high bit rate HD source being stolen and high quality pirated HD DVDs or BDs will be produced.

    This is pure speculation but I can't think of any other reason for the high variation in bit rates. It may be that studios are distributing the source to movie channels at exactly the bit rate that they want distributed to the end customer. If the movie is very prized, it may have a very low bit rate and if it is not that prized, it may have a higher bit rate.
     
  18. ROBERTT

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    Hi Mike,

    Interesting theory and nothing would surprise me :)

    What is worrying though is I definitely did not see these artefacts on earlier screenings of the movie.

    I watched a little of the 4400 in HD last night and call me paranoid but there was also mpeg blocking noise in that programme as well:eek:

    Something has to be going on Sky's end as since the service started I was specifically looking for these type of artefacts and there were none......NOW THERE IS:mad:

    Im surprised that no other members have noticed this over the last week
    Maybe its my plasma:devil: :eek:
     
  19. AndyH

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    The world is indeed a crazy place if that it true. It isn't going to help viewers reach the same conclusion about their highly valued content if they can't see it in all its glory.


    Anyway, shame about last nights RE:Apocalypse, I missed earlier broadcasts of that so was looking forward to it.

    I too have noticed a lot of the stuff described in this thread and several times I've had people around for the A/B Sky Movies demo. Everytime, with one exception, people went away definately NOT interested in SkyHD as the difference between 9/10 and 9HD/10HD is minimal (and my setup ain't bad). OK, they like the dribbling water, bouncing animals and leaves floating in the breeze - but as pointed out earlier, that isn't what you tend to watch :)


    I'll join in with any comms to Sky, as well as expressing my displeasure on the internet :). Premium service indeed.. *mutter mutter*
     
  20. Mike_CA

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    Robert,

    As I said, it is pure speculation and there is no way to prove it unless an insider can verify the process.

    However, there are many other things that is done with HD in the US that shouldn't be done that is well known.

    For instance, the distribution SAT feed for ESPN HD, ESPN2 HD, and Discovery HD is MPEG2 at a maximum rate of about 19 mb/s. This is not a problem with cable providers since they just put the feed directly on the cable system. However, for SAT providers, they sometimes do not have the bandwidth available to directly use the feed and have to decode/encode the stream to get the correct bit rate. Usually the rule of thumb is that the input stream should have a bit rate of at least 2 times the output stream when decoding/encoding but that would not be possible with such a low bit rate on the feed. So they do it and it doesn't appear to have a significant impact on the PQ.

    In another example, NBC, CBS, and ABC does their distribution feed correctly feeding MPEG2 at 35 mb/s. When the OTA affiliates across the contry receive the feed they decode, insert branding and comercials, and then encode the stream to the correct bit rate. Now this would seem to be the way things are suppose to work. However, some of the OTA affiliates multicast upto 2 SD channels on their 19.3 mb/s band causing the HD stream to get greatly reduced. This stream is then broadcast and sent to SAT and cable providers.
    Fortunately in my area, NBC and CBS do not currently multicast so I get a feed of about 19 mb/s on those channels. However, on ABC, they multicast 2 SD channels so the feed that I get averages about 14 mb/s.

    In the case of FOX, they distribute their feed at 16 mb/s and all the FOX affiliates are required to have a Splicer HD system which will allow for branding and comercial insertion without decoding/encoding. Therefore the 16 mb/s feed is sent to cable and SAT providers. 16 mb/s was chosen to allow 1 SD channel to be multicast by the affiliate.

    SAT and cable companies cannot receive feeds directly from the distribution SAT for OTA networks (FOX, NBC, CBS, ABC, UPN, WB, and PBS) and must get the feeds from an affiliate station. So it is bad enough that the affiliate may drastically reduce the bit rate but SAT companies have another problem. Prior to 6 months ago, you would have to get those channels over the air (OTA) if you were a SAT subscriber. But in the last 6 months SAT companies started to provide regional service (NY, LA, Dallas, Miami, etc.) for those channels. The problem is that the SAT companies wanted to implement MPEG4 for those channels and all distribution feeds are MPEG2 in the US. So they just decoded the feed from the OTA affiliate and then encoded it into MPEG4 at the correect bit rate. Converting from MPEG2 to MPEG4 should be done at about a 400 mb/s bit rate but again the loss in PQ does not appear to be significant when converting at a low bit rate. The SAT companies currently have plans to convert all HD channels to MPEG4 over the next 2 years.

    Finally, the DirecTV (owned by Murdoch) SAT provider also converts all 1080i streams to HD Lite (1280x1080) to save bandwidth.

    Most of the issues with SAT companies in the US could be resolved by doubling the number of distribution feeds (both MPEG2 and MPEG4) but that will never happen since the current feeds now cost about $50m per year and the SAT companies only save a couple million dollars and SAT only provides about 15% of the households.

    So as you can see, things are a mess and I'm sure that each of those processes introduce some degree of artifacts.

    I imagine that a little bit of what is going on in the US is also going on in the UK. For example, during the World Cup, I expect that the BBC transmitted a MPEG4 stream from Germany to the UK (it would be highly unlikely that the would have paid for both MPEG4 and MPEG2). So I expect that Telewest customers got a low bit rate conversion to MPEG2. Even local BBC programs are maybe converted at Telewest from MPEG4 to MPEG2.
     
  21. contraste

    contraste
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    Had Sky HD since day two and there is no doubt in my mind that Sky are reducing the bit rate at times. Noise blocking is particularly noticable during fade outs/ins and in scenes with deep shadows.

    Very disappointing!
     
  22. linowsat

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    I've started bitrate measurements for my homepage of DVB-2/HDTV muxes. The Sky-HD channels have a bitrate between 15 - 20 Mbit/s. That's not bad. It's at the same level than the HD bitrates of the german pay-tv provider 'Premiere'. Pro7/Sat1 need for the most HD upscaled content less than 10 Mbit/s.

    I've just started the HD/DVB-S2 measurements 3 day ago. For SDTV/DVB-S I do this since the last 6 month.

    If someone is interested I can post an image of a bitrate-chart from my homepage. Maybe this could be an good argument for your provider to offer more bitrate/quality. ;)

    Regards from germany
    Oliver
     
  23. plaver

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    I for one would be very interested
     
  24. rbentley

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    Please feel free
     
  25. linowsat

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    This is the situation in the Sky-HD mux at 11.798 GHz, Hor

    [​IMG]

    and this is at 11.344 GHz, Hor

    [​IMG]

    I also have charts of each channel over the last 10 days, but because I've just started with my measurements it doesn't make sense to post these today.

    On my page you find the charts of all other SDTV and HDTV channels from 13°E to 28.5°E.

    Oliver
     
  26. Tony Hoyle

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    Wow, what happend on the 12th?

    It'd be interesting to see what SS2 has done to the bitrates too.. I presume everything on that mux has its bandwidth lowered to fit it in.
     
  27. Starburst

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    According to Lyngsat SS2HD is currently the only channel on 11720 H so it's launch would have had no impact on the existing lineup. Nice to see SKY spending money on a fourth transponder.
     
  28. linowsat

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    Yes, you are right that there is no impact.

    But interesting, SKY is testing on the 11.720 tranponder. There are two aditional active avc streams:

    [​IMG]

    Nice to see how SKY in the UK is supporting the hdtv transmissions. Well, premiere in germany just have a single transponder for hdtv.

    Oliver
     
  29. Mike_CA

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    At what time of the day were the bit rates taken? If they were taken between 17:00 and 0:300 it appears that the Sky Movie 9 & 10 HD somehow are being restricted to 10-11 mb/s (expect 12.8 on 12.344) similar to what is happening in the US.

    Since SBO HD1 is transmitting at a high rate, I wonder if Sky is restricted on the maximum bit rate by the studios if they are not transmitting on a PPV channel.

    Transponder allocation:

    http://www.lyngsat.com/hd/28east.html
     
  30. contraste

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    Great work Oliver and thank you!:clap: :clap: :clap:
     

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