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Response from Arcam on Chroma problem

Discussion in 'Blu-ray & DVD Players & Recorders' started by nigel_williams, Jul 9, 2002.

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  1. nigel_williams

    nigel_williams
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    I mailed Arcam yesterday about my DV27 FMJ saying:

    Although the picture is generally very good, I find that bold red's tend to "bleed", a condition which I now know is called the "Chroma Bug".

    and got a reply today stating:

    I'm using Van Damme 10m component cables from Joe. I was just looking at Toy Story and I've found that the (Mr) mic in Chapter 4 is really bad - the mic and the lid of the tub Woody stands behind has some serious banding and flaring.

    I've tried reducing the colour of the VW down to the point where it no longer flares but at 39, the rest of the picture looks washed out even on High and Low colour temperatures.

    Has anyone got any advice/tips that might help?
     
  2. Jeff

    Jeff
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    Chroma bug does not effect red?, Mr Dawson we have a problem.
     
  3. RichardA

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    Sadly, Arcam customer service have got it wrong!

    The Chroma Bug affects ALL colours, but is more noticable on strongly saturated coloured areas.

    In many instances the bug is more noticable on Red than it is on any other colours (it is certainly the first colour we spotted it on !), with Blue second place, other colours are very hard to spot.

    This is because the bug is visible where there is a strong change in colour intensity (In Cr or Cb)at the same time as a strong change in brightness - the bug is visible due to the edge of the colour information not following the same edge as the brightness information - curved or diagonal brightness edges have stair-stepped colour edges. The largest value of Cr and Cb are towards Red and Blue respectively, producing the biggest value change.

    Generally, in movies and TV, there is more likelyhood of seeing strong, saturated red areas than there is saturated blue, so most often Red is the colour to look out for.

    The Home Theatre Hi-Fi article gives a very good explanation of what causes the problem, how it appears, and which players have it, so I won't bother to go through it all again here.

    However it's important to remember that Chroma Bug is extremely had to spot on an interlaced display, the flicker between the two fields masks the effect. On a progressive display the lack of vertical colour filtering is much more noticable.

    It isn't possible to fix the bug once it has passed through the M-PEG decoder, it's only possible to mask it - and that usually means using a vertical filter to average out the edge steps in colour - and that generally results in softening or blurring.

    Classic clips to check (as well as those shown in the article mentioned) are;

    Fifth Element - Reconstruction sequence - close up of the red 'abort' button on the console.

    Star Trek Insurrection - opening title, red on black background.

    Bugs Life - first sequence, virtually everywhere, but especially the blackberry landing on an ant.

    I hope this helps!
     
  4. Charlie Whitehouse

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    Richard,

    I saw over at the AVS Forums some time ago, a contribution from Charles Hansen about the Ayre DVD player where he said that there isn't a single Chroma Bug. The gist of his argument seemed to be that since the specifications for correct MPEG decoding seem to be a bit woolly, different MPEG chips do things wrong in different ways.

    He went on to say that Ayre had a method of correcting for the errors in the Fujitsu-based chip in their player. While there was some streaking apparent with their player, it wasn't due to classic chroma bug and could therefore be corrected. I'd be interested in your view. :)
     
  5. John Dawson

    John Dawson
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    Guru Richard is of course correct and my young helpdesk colleague was simply doing his best to explain a tricky technical issue for the first time, after a brief introduction to the topic from me, when he comes from a retail rather than an electronic engineering background. He'll most likely pass similarly tricky replies by me first in future :)

    I am still not sure that the red bleed as originally described by Mr. Williams is a chroma upsampling related problem and that is what we were trying to suggest in our reply. We have used a Sony 10HT here in the original development of the DV27 and I don't recall seeing what I would call bleed, but then words aren't very good at describing exactly what is actually seen by an individual - a screen shot would help.

    BTW I don't think Mr. Williams that your player software version has a switch in it for "below black" but if it does please turn it off after initial set up on Video Essentials. This is because some discs (and certain versions of Toy Story were implicated IIRC) have illegal digital information on them which can throw our MPEG decoder and cause flicker and other problems. Worth pointing out even if not the issue here.

    In any case upgrading the software to 1.79 wiill bring benefits to CD replay among other things but cannot fix the chroma behaviour which is hard coded in the MPEG IC.

    I would suggest a fulll ISF calibration of the projector would be a really good investment - my colleague Gordon Fraser comes to mind - as then you will know exactly what the projector can and cannot do.

    HTH and I welcome any other constructive views on this issue.

    John Dawson (Arcam)
     
  6. Jeff

    Jeff
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    John,

    Moulin Rouge chapter 4 and the opening title on Star Trek Insurrection are very good examples of bleeding reds caused by the Chroma bug.

    Thanks,

    Jeff
     
  7. nigel_williams

    nigel_williams
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    Thanks for taking the time to respond personally John. My description of the problem wasn't very technical, but it does suffer from the symptoms descibed above by Richard - reds in particular are most affected in animated films and I do see horizontal streaks. I will try the new firmware upgrades as you suggest and make some additional tweaks.

    I don't think I can remove the problem entirely, but I can try and minimise it's appearance.

    As the bug seems to be a "feature" of the chipset, are we likely to see Arcam produce a new progressive board for the DV88/DV27 which has fixed the problem?
     
  8. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Thanks John,

    I had actually typed out a reply last night but was a bit drunk after having a bottle of wine so I thought I'd wait till this morning...of course Richard and others beat me to it....

    Gordon
     
  9. RichardA

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    Charlie,

    There does appear to be some differences in 'Chroma Bug' between different chipsets.

    The Chroma Bug is really variations in implementation in vertical re-construction filters, converting the 4:2:0 sampling back to 4:2:2 or 4:4:4.

    It seems that the 'original' version of the bug (as we came across, and I then showed to Stacy Spears) appeared to use chroma information from the wrong set of samples (i.e. the colour samples relating to lines 1 and 2 got applied to line 2 and 3 instead) this was a severe and objectionable problem!

    Other variations of chipsets and implementations seem to vary the kind of mis-alignment of the reconstructed colour samples relative to the luminance samples.

    Over time the term Chroma Bug has been applied to virtually any 4:2:0 to 4:2:2 converion that isn't done perfectly, when often it isn't the real thing.

    So Chroma Bug isn't a single cause, but all the causes result in a single symptom.

    The problem with this kind of thing isn't that the M-PEG specs are vague (they are actually pretty tight) but that the conversion technique from 4:2:0 to 4:2:2 is not specified and there are differences in methods used.

    I haven't spent enough time with the Ayre DVD player to be able to judge what they have been able to do but I still believe that it is impossible to remove any of the causes of Chroma Bug complelty without modifying the M-PEG decoder chipset internally but they may well have been able to reduce it's impact in some way (and they are unlikely to tell anyone what they've done exactly!).

    Also it's worth noting that Chroma Bug is not limited to DVD, it is apparent on anything using an M-PEG type decoder, so Digital Satellite and Digital Terrestrial receivers, Digital VTRs and so on can also suffer (I know that many early set top boxes suffered) and that there is a thread over at avsforum debating whether it's on the Digital VHS HD players!


    John,

    I have to admit that the Arcam response sounded a bit like someone non technical getting the wrong end of the stick with the description - but they should atleast be applauded for pointing out the Home Theatre Hi-Fi site for the fuller description of the bug!
     
  10. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    The fact it's on other mpeg devices is intersting and something I had thought for a while. I'm sure I have witnessed it on Sky boxes. Is this likely Richard?

    Gordon
     
  11. RichardA

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    Gordon,

    It's VERY likely!!! ;)

    Richard
     
  12. Jeff

    Jeff
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    I have seen the Chroma bug on Sky, the best place to see it is the Fox kids logo, or so my kids tell me.
     
  13. Charlie Whitehouse

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    Richard,

    Thanks for the input. Since posting this morning, I note that there has been another more recent exchange of views about the Ayre player involving Mr Hansen, Stacy Spears et al over at AVS Forums. I have a passing interest in the Ayre player since like my Theta David II, it shares the same Fujitsu MPEG chipset. I doubt that Theta would ever bother to fix the bug on their player but it is interesting to see what other manufacturers are prepared to do to get around it. :(
     
  14. patmyhead

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    Hi is it realy true arcam replyed to a question
    what is the screcret ?
    did you greese palms ?
    P@
    :confused:
     
  15. rob@rar.org.uk

    rob@rar.org.uk
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    John Dawson (Arcam's managing Director) is a frequent poster on these boards, responding to questions and comments about his products as well as contributing to general discussion on some issues. It would be nice if other manufacturers were prepared to commit to the same level of customer service, but it doesn't happen very often...

    Regards

    Rob
     
  16. John Dawson

    John Dawson
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    If Patmyhead would let me know his real name/ e-mail address then I would be happy to investigate at our end why his e-mails are apparently not answered or go astray. AFAIK we are broadly up to date in our resoponses though there have been problems in the past (especially a few months ago) with servers and staff shortages.

    John Dawson (Arcam)
     
  17. patmyhead

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    Hi
    Its a pity that John Dawson s employes dont follow his example
    dispite spending £1380 on arcam products arcam never responds to my emails
    They may make good products but their customer care stinks
    P@:mad:
     
  18. John Dawson

    John Dawson
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    I will say this again - for the last time - either please identify yourself (a private message to me is fine) whereupon I will investigate why you are not apparently receiving responses from us - or please desist from your suggestions that we don't answer e-mails and that our customer service team is not doing its job.

    John Dawson (Arcam)
     
  19. jont

    jont
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    John

    Nice to see you're up with the rest of us !!

    A little OT but any chance of an anticipated date for the sacd u/g board for the dv27 ? ;-)

    Patmyhead ... (not a flame) but if i had the MD of Pipex repeatedly asking me to contact him personally to see why my adsl has been running at half speed since March despite my many attempts at discussions with them and BT i'd be there like a flash ... you very rarely see a level of customer support like that ... use it :)
     
  20. John Dawson

    John Dawson
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    Hi Jont - up at 11.30 pm with a full day's work ahead tomorrow on AVForums - sad or what?

    The upcoming upgrade for our DVD players is to support DVD-Audio not SACD, as to do the latter would require junking pretty much the whole of the present design which is not on for obvious reasons.

    The hardware is largely done - it's certain fairly chunky bits of software that need to be completed and some of this is in the hands of Zoran, our chip supplier. When that's done it has to be thoroughly tested, as you would expect, then we can release it. I would think sometime close to the end of the year looks realistic.

    John Dawson (Arcam)
     
  21. patmyhead

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    Hi
    you have mail John
    P@
     
  22. gringottsdirect

    gringottsdirect
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    I'm not commenting with regard to p@t.
    John Dawson is highly prized, why haven't we a DenonJeff, a KefJeff or a LoeweLou.
    Look at the Denon 2800 thread, wouldn't it be terrific to have a Denon representative posting.
    Obviously it could be abused but we are all able to filter out.
     
  23. nigel_williams

    nigel_williams
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    I've been away for a couple of days so I'm just catching up with this thread.

    It seems that John has acknowledged that the DV27 does suffer with the Chroma bug although not as bad as some other players.

    The question still remains... what is Arcam going to do about it? Will there be a fix to the existing boards or an upgrade in the near future?

    Calibrating the projector might reduce the effect of the bug but it is still there.
     
  24. Nic Rhodes

    Nic Rhodes
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    I think too much is made of the Chroma bug. Many players (majority?) actually have it and most people don't know. Many consumers / suppliers live with this without knowing the problem for years. Fixing the Chroma bug would need a MPEG chipset replacement and I don't think any manufacturer does this. Fine it can be fixed in mark 2s but I think if you have it now you will have to live with it. It really isn't that imporatant. There many far more fundamental problems afflicting DVD player IMHO which deserve more serious attention.

    Don't worry about there is nothing you can do.
     
  25. patmyhead

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    Here is the reply i got from arcam
    dear pat sorry about the problems you have experenced from our customer service
    as a gesture of our deep regret when the new dvd audio module is ready in 2005 we will fit it for you at no expence to you
    again i must again say sorry & grovel to you

    well this account is not quite true the reply i got to the PM i sent to John Dawson last thursday was
    ----------------------------------------------------------------------------
    --------------------------------------------------------------------------
    or words to that effect
    P@
    :D :D
     
  26. nigel_williams

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    When you spend £1,600 on a DVD player, I'd expect better service. I can live with the problem provided Arcam commit to rectifying the problem in the near future. It's clearly a problem that Arcam are aware.

    The demonstration I had of the FMJ did not show up the problem as my local dealer was using on S-Video.
     
  27. ian_guinan

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    ...and then we wonder why manufacturers aren't keen to have open forums for debate of their products.

    I really appreciate the efforts John Dawson takes and the interest he shows in the thoughts and experience of end users. I don't think he deserves to be beaten around the head for any perceived lack of service when he has shown interest in answering queries.

    If you really want to be ignored by the manufacturers of your expensive gear you've bought then there is a long list I could give you. Often once you've parted with your hard earned cash you are little better than something they've trodden in.

    Usual response is...'you'll have to buy the new model' to correct the problem with the rush released old model, instead of trying to allow any sort of upgrade path. Arcam deserve praise and not brickbats.

    Let's not scare Mr. Dawson away with rudeness please. I'm sure he welcomes any constructive comments you have to make.

    Regards,
    Ian Guinan
     
  28. Nic Rhodes

    Nic Rhodes
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    Well said Ian.
     
  29. Jasonjo

    Jasonjo
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    I second ian's comments - at least Jonh is trying. Just look at the numerous thread on the infamous Denon 2800 and all the problems - has anyone from denon even posted? has anyone talking to denon support been given a plausable explanation? hmmm...no

    P@ - if you are really that unhappy go to your nearest Arcam dealer and discuss it - maybe with John's intervention they can sort out some form of refund or trade-in. I think you will be very, very lucky to find a DVD player with no chroma bug which is as good and video and cd replay as the DV27 though...

    Personally I was amazed to find any manufacturer that participated in these types of forum - whats more John is so, so helpful - I bought my DV88 based largely on the support on offer from the likes of John and my local Arcam dealer.

    All IMHO of course ;-)

    JJ
     
  30. nigel_williams

    nigel_williams
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    Personally, I'm happy that people like John have not only shown an interest in these forums but also taken time to offer support and advice where possible. I'm sure forums like this are also useful to (some) manufacturers who care what their customers think of their products and what problems they might be having. This is what generates brand loyalty to expensive specialist kit - it's not the kind of stuff you buy for £100 in Dixon's!

    As you see from my initial post, I was not entirely happy with Arcam's response. Getting a full explanation of the problem from the many professionals who post here (and advice we all gratefully receive) is useful in getting an un-biased opinion. Getting an answer "from the horse's mouth" is a bonus.

    Apart from the Chroma problem, I'm very happy with my FMJ. Of course I'd be even happier if there wasn't a bug hence my enquiries on how Arcam intend to resolve this problem.

    I hope John will continue to support these forums, his contribution is much appreciated by many.
     

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