Chroma Bug

Discussion in 'Blu-ray & DVD Players & Recorders' started by chicken balti, Nov 12, 2001.

  1. chicken balti

    chicken balti
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Can someone enlighten me as to this particular ailment. What exactly is it? How do I know if I've got it? How can I get rid of it? Is it the kiss of death that most people reckon it is or is it so microscopically small that only flat-earthers can see it?

    Answers with particular relevance to a Sony VW11HT PJ, Grayhawk screen and conponent/progressive PAL and NTSC would be very much appreciated.
     
  2. RichardA

    RichardA
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    OK, I guess as one of the first people to witness the Chroma Bug (I was the S&W person who showed it to Stacey Spears at CES a few years ago) I could give a basic guide!

    First off it's not a killer - my standard set up here in the office uses a Proceed PMDT and this machine certainly suffers from it - The bug is easy to see through most of the time, but in certain occasions it does scream a little. Very much in the way that de-interlacing errors can occaissonally get in the way of getting onvolved in the movie, the chroma bug does the same.

    Now, to what it is and how and when you would see it;

    The Chroma Bug occurs because on a DVD the colour information is only sampled on alternate scan lines (called 4:2:0). In the DVD player (or digital TV receiver) the colour information (colour info is called Chrominance or Chroma) should be filtered back onto all scan lines to smooth out transitions (changes in info, or edges for example). On machines that have the Chroma Bug this filtering is done badly if at all, which results in very coarse edge transitions in the colour information.
    Because the DVD information is stored in Component form, the error can be best seen on strong, highly saturated areas of Red and Blue. What you would see is a stair-step edge to a diagonal or curved transition - i.e if we had a Red to Black egde it should look like;

    RRRRRBBBBBB
    RRRRRRBBBBB
    RRRRRRRBBBB
    RRRRRRRRBBB
    RRRRRRRRRBB
    RRRRRRRRRRB

    Rather than with the chroma bug

    RRRRRBBBBB
    RRRRRBBBBB
    RRRRRRRBBB
    RRRRRRRBBB
    RRRRRRRRRB
    RRRRRRRRRB

    (Hope that's clear!)

    Importantly it is almost impossible to see the Chroma Bug on an interlaced display (i.e. a TV set) It only becomes apparent when in Progressive scan.

    Classic scenes to see the effect are;

    StarTrek Insurrection - opening titles - Red letters on black

    5th Element - reconstruction sequence - red 'destruct' button

    Bugs - opening sequence - the blackberry as it lands on the ant's head

    Toy Story 2 - opening title logo

    There are numerous others - as it affects strong colours more visibly animated features tend to be worst.

    I would re-iterate though that this is not a huge deal in the majority of applications and the majority of movies, it is just that once in a while it gets in the way of enjoying the movie.

    I hope this helps!
     
  3. chicken balti

    chicken balti
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Richard,

    Many thanks for the info, now I know exactly what you mean. Given that the 'problem' resides with the ability, or otherwise, of specific dvd players to filter this out properly there would presumably be a selection of 'good' and 'bad' players affected by the chroma bug. Is there a list of machines available that cope better than others, I am specifically interested in the performance of the Denon 2800 and Toshiba SD900E.

    Any information regarding these or any other players would be greatly appreciated. Thanks once again for your most lucid explanation.
     
  4. RichardA

    RichardA
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I was hoping to post a direct link to the original article written by Stacey and the relevant threads over at AVS Forum (www.avsforum.com) but the connection is down.

    You are correct that certain models have the problem and others don't - it's generally down to the chip-set used in the M-PEG decoder (so SDI modified players also have the problem)

    Also no scaler - contrary to popular belief - actively removes the Chroma Bug, no matter what you might read elsewhere. However some scalers do seem to reduce it's impact due to other 'accidental' factors.

    I don't have a full list of players that suffer from this problem but the ones I know for certain do have it are;

    Samsung 709
    Meridian 800
    Proceed PMDT
    Denon 2800

    There are many, many others - these are simply the ones I can remember!

    Those that don't include;

    Earlier Toshiba (last I tried was SD200)
    Denon Interlaced models (i.e. all except the 2800)
    Meridian 586.2

    I hope this helps!
     
  5. johnson

    johnson
    Active Member

    Joined:
    May 12, 2001
    Messages:
    550
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Essex
    Ratings:
    +6
  6. RichardA

    RichardA
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    That's the one I was looking for !

    Thanks Simon
     
  7. chicken balti

    chicken balti
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Richard,

    Looks like both of the players I mentioned are stricken with the bug! Given that the 'spoiled' signal is output from the dvd player itself is there any gizmo that can intercept and correct the signal before it gets to the projector? I realise that newer players will (should?) have the problem resolved by implementing mpeg decoders that have this issue fully resolved, in the meantime is there anything that can be done to eradicate or minimise its effects?

    Cheers
     
  8. CarlB

    CarlB
    Active Member

    Joined:
    Jan 8, 2001
    Messages:
    1,101
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    51
    Location:
    Godmanchester, Cambs
    Ratings:
    +86
    Richard,

    You mention that it is not usually possible to see the effect on an interlaced display, but I have the exact same problem on my Toshiba 40WHO8B.

    I am using a Toshiba SD9000 DVD player connected via component to the TV and have noticed the heavy 'stair-stepping' effect on the DVDs you mentioned.

    Do you have any idea why these artifacts are displayed? It may have something to do with the 'natural' processing mode on the TV, I will try switching to standard 100Hz mode (no frame store) later today and report my findings.
     
  9. RichardA

    RichardA
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Guys,

    There is no way to fix the bug once it's there - it's a fundamental problem in the chipset, with this problem you can't reverse it succesfully.

    It may be visible on a 100Hz set due to the reduction in flicker in the display - that's what hides it from view on interlace sets.

    Hope this helps
     
  10. uncle eric

    uncle eric
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    A screaming example of the Chroma bug can be seen on the movie '3000 Miles To Graceland'.
    In the opening scenes where Kurt Russell parks his Red American classic and the kid is messing around with it, the whole car is in smears (as viewed through a freinds Denon 2800) particularly the edges are virtually screaming chroma bug HERE.

    Eric
     

Share This Page

Loading...