1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

hidef

Discussion in 'TVs' started by thekingbeyond, Aug 8, 2005.

  1. thekingbeyond

    thekingbeyond
    Well-known Member

    Joined:
    May 24, 2004
    Messages:
    5,180
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    106
    Location:
    oxfordshire
    Ratings:
    +292
    I downloaded some hidef wmv files and could see compression artifacts like bands of colour rather than smooth graduation in underwater scenes etc.
    Whats the point of going hidef if we can still see mpeg artifacts? I would love to see hidef uncompressed movies, are we going to see these with blu-ray and hidef dvd

    paul
     
  2. phillfyspoon

    phillfyspoon
    Banned

    Joined:
    Oct 21, 2003
    Messages:
    2,128
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    51
    Location:
    Hampshire
    Ratings:
    +76
    WMV are compressed at about dvd rate were ts streams are upto 35mb a sec. what are u viewing these clips on? some monitors displays show these artifacts more then other types.
     
  3. thekingbeyond

    thekingbeyond
    Well-known Member

    Joined:
    May 24, 2004
    Messages:
    5,180
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    106
    Location:
    oxfordshire
    Ratings:
    +292
    I see it on dvd as well m8, its a common artifact caused by compression.I have seen it on our new dlp tv(going back soon), our new sony wega lcd rear pro and our sanyo z3 pj.
    I would rather have no compression than hidef any day of the week
     
  4. Caimbeul

    Caimbeul
    Active Member

    Joined:
    Jun 7, 2005
    Messages:
    734
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    31
    Location:
    Kent
    Ratings:
    +26
    :hiya: Kingbeyond - How come you are sending your SP46 back :confused:
     
  5. thekingbeyond

    thekingbeyond
    Well-known Member

    Joined:
    May 24, 2004
    Messages:
    5,180
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    106
    Location:
    oxfordshire
    Ratings:
    +292
    I get the Rainbow effect badly on it :( , so severe it gives me headaches :mad: dlp looked really good on paper, hidef, hdmi, good blacks etc. but its not for me. Aside from the rainbows it has one of the sharpest clearest pictures i have seen with loads of contrast.
    If you don't suffer the side effect then its a cracking buy. I would consider dlp again when the 3 chip versions come out, with out the colour wheel
     
  6. dsb

    dsb
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    if you calculate the data that even a SD signal takes up uncompressed, you know it will be a format beyond the next generation that uses uncompressed video data.
     
  7. quig

    quig
    Standard Member

    Joined:
    Jan 17, 2004
    Messages:
    20
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Ratings:
    +1
    While DVD is restricted to MPEG2, HD-DVD and Blu-ray give the opportunity of using more advanced codecs, such as used in the WMV files you have experienced. Artefacts are designed to be less noticeable in these codecs than MPEG2, allowing lower bitrates to be used.

    Unfortunately, there is always a point at which the picture quality becomes unwatchable. Whatever codec and resolution are used, if the bitrate is low enough you will see compression artefacts, and HDTV is no different. A low bitrate HDTV picture can look worse than a high bitrate SDTV picture. I feel that if SDTV broadcasts were higher bitrate, there wouldn't be as much difference between them and HDTV.

    Many standard definition digital TV channels seem to be broadcasting at the lowest bitrate they can get away with. I fear that this will also happen with regards to future HDTV broadcasts. However, there is hope that as Sky's service will be sold as premium, higher picture quality channels, broadcasters will not risk viewers unsubscribing.

    Similarly, disc based video such as DVD tends to be better compressed than television broadcasts. Firstly, there is often variable bitrate, multiple pass encoding. Secondly, both hardware and software will be priced at premium levels. Considering that many consumers will have to buy new HDCP compatible equipment, the new formats will not be financially successful unless the quality is very high.

    Bandwidth is at a premium on the internet, so a lot of video, even in HDTV, is highly compressed. However, there is some uncompressed video files available for download from ftp://ftp.ldv.e-technik.tu-muenchen.de/dist/test_sequences/, in 720p, 1080i and 1080p. You will need a YUV compatible player, such as YUVplayer to play them.
     
  8. Stephen Neal

    Stephen Neal
    Well-known Member

    Joined:
    Mar 29, 2003
    Messages:
    6,080
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    133
    Ratings:
    +681
    Hmm - though 50Mbs I-frame only MPEG2 at standard def is widely deemed to be Digital Betacam quality - and very close to the quality of uncompressed video. (So close that very few people can tell the difference on most material)

    50Mbs is only twice DV-25's data rate, and entirely feasible on a BluRay disc (in fact Sony's XDCam system is based on a BluRay-type disc carrying either DV or MPEG data)

    I think the difference between 270Mbs (nearer 180Mbs active) uncompressed and 50Mbs MPEG2 (or DV-50) is so tiny that 50Mbs is a useful "as good as uncompressed" SD benchmark for many formats.

    If you go for a medium-to-long GOP format of MPEG2 (rather than I frame only) then 34Mbs is a good benchmark. (It is the EBU standard for non-news programme distribution for example)

    The colour banding that is seen by many is usually a quantising issue. MPEG2 4:2:0 as used for broadcast in the UK only uses 8 bit sampling (and only really uses the levels 16-235 for luminance and 16-240 for chrominance) - and this can exhibit real stepping and banding issues - especially on the low-luminance blue components. Some broadcast production gear now uses 10 bit interconnection and/or some clever dithering algorithms to remove/mask this.

    Plasmas and DLPs often use all sorts of processing to generate their greyscales - and combining this with a "steppy" source doesn't do much for image quality - often making the banding really obvious.

    This isn't so much a "compression" issue as a "sampling" issue in many cases.
     
  9. thekingbeyond

    thekingbeyond
    Well-known Member

    Joined:
    May 24, 2004
    Messages:
    5,180
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    106
    Location:
    oxfordshire
    Ratings:
    +292
    And to think I used to put up with vhs, now I am complaining about dvd quality, it would be great to see some hidef movies on the new formats with out as much compression.
    I watched the extended cut of the return of the king on my sanyo z3 and samsung dlp and was blown away by the quality, so dvd can look great upscaled .
     

Share This Page

Loading...