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Thread: Xv video output has purple tint instead of beeing black

  1. #1
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    Default Xv video output has purple tint instead of beeing black

    Hi I've been searching for some solution for my particular problem but only found bug reports/solutions and talk about Nvidia and no mention off ATi in this regard off Xv video output having wrong/distorted colours. Or rather simple, black is dark purple and all colours are off a bit to the purple end whit that.

    X11 gives correct colors and black is real true black but I want to use Xv becouse it works better and gives less tearing and generally has better performance than the other ones.

    I'm using Ubuntu 8.04 64bit, Kernel 2.6.24-19 generic whit Gnome 2.22.3 and I use the ATi 8.7 fglrx drivers which work quite well except for some smaller problems.(video tearing and blinking video whit specific stuff) But those are not the concern in this matter. I'm looking for a solution to fix the Xv to show correct colours!

    My hardware is as follows:
    AMD Phenom 9750 2.4Ghz
    Gigabyte GA-MA78GM-S2H (780G+SB700, F4 bios)
    Corsair TWIN2X 6400C4DHX DDR2 4096MB 2x2Gb (can only use 3.4Gb thx to some bug in the bios whit linux over 4G memory mapping, everything gets graphics corrupted and eventually hangs...)

    Iv'e run xvattr and everything seems to be correct at default 0 values...

    I hope there is some help to be had into this matter.

    Edit: As no one had posted I started to do some more searching for myself and found this thread here at Phoronix
    http://www.phoronix.com/forums/showthread.php?t=10870
    It's exactly the same thing... As the thread died without a solution or proper investigation... well... I really would like to see if a bug report was made as it seems to be a bug... Some say the like the "washed out colors more" but I would rather have correct colours than incorrect! I don't like my black being dark purple >_>; or have the washed out colours "aka like my crt TV that can't show black but a gray instead" which is a piece of crap cheap TV....
    Bug is limited to the use of TexturedVideo it seems. The older VideoOverlay gives the correct colours in conjunction to Xv video playback according to them...
    I'm not entirely new to linux but I haven't really done all my homework so where do I go to check if this bug has been reported?
    Last edited by Nighthog; 08-12-2008 at 04:17 PM.

  2. #2
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    Quote Originally Posted by Nighthog View Post
    Edit: As no one had posted I started to do some more searching for myself and found this thread here at Phoronix
    http://www.phoronix.com/forums/showthread.php?t=10870
    It's exactly the same thing...
    So do you see purple in the brighter/+gamma screen shots in that thread - I don't.

    As the thread died without a solution or proper investigation... well... I really would like to see if a bug report was made as it seems to be a bug... Some say the like the "washed out colors more" but I would rather have correct colours than incorrect! I don't like my black being dark purple >_>; or have the washed out colours "aka like my crt TV that can't show black but a gray instead" which is a piece of crap cheap TV....
    Bug is limited to the use of TexturedVideo it seems. The older VideoOverlay gives the correct colours in conjunction to Xv video playback according to them...
    I'm not entirely new to linux but I haven't really done all my homework so where do I go to check if this bug has been reported?
    There is certainly a difference with xv - although for me using a CRT monitor it doesn't matter as I often have to run with gamma up to see detail in dark scenes anyway. Perhaps LCDs already compensate so it looks much worse to you.

    If you want to turn gamma down you could try something like -

    xgamma -gamma 0.8

    or with mplayer in software with

    -vf eq2=0.8

    Of course your problem may be specific to your chipset/monitor WRT the purple tint, which I can't see even though I can clearly see the gamma is up for xv.

  3. #3
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    My screen shows kinda purple when gamma goes up or colour profiles aren't fully correct in black but all what they reported and the pictures I could look at I have the same kind of colour distortion that their screen caps showed as well in all other colours. So the specific purple tint may be my actual LCD as I see that purple tint quite allot during boot up in the black but it goes correct once in windows or Ubuntu. (correct colour profiles loaded by then?)

    But Xv gives then the wrong colours. All the others give fully correct in line whit all other colours only Xv that gives the washed-out whit upped gamma/hue? black isn't 0 more like it starts at 16,16,16 or so in the 0-255 scale. (and then my LCD showing it as darkly purple?)
    I notice it and get irritated because black isn't black and clearly all colours are slightly different from normal. I have a 1920x1200 resolution 24" screen and any video always gives you those black border areas which are true black (in the sense as true as my LCD can manage to show black) but then the video has purple/gray instead and you see a clear line difference between the video black and the border blacks. As X11 manages to show video black and border black the same... but same video whit Xv has it black on my screen whit purple tint in contrast to the true black of the borders. It catches your eyes quite easily and you see easily that the black is to the purple colours.

    I have a LG L245WP-BN 24" widescreen LCD whit P-MVA panel.

    Those settings what will they set? System wide gamma or just Xv video playbacks settings?

    If I'm gonna change any settings its Xv specific settings as it's only when Xv is in use when colours aren't fully correct. Don't want to change anything else as they aren't wrong
    Last edited by Nighthog; 08-16-2008 at 09:19 AM.

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    Quote Originally Posted by Nighthog View Post
    My screen shows kinda purple when gamma goes up or colour profiles aren't fully correct in black but all what they reported and the pictures I could look at I have the same kind of colour distortion that their screen caps showed as well in all other colours. So the specific purple tint may be my actual LCD as I see that purple tint quite allot during boot up in the black but it goes correct once in windows or Ubuntu. (correct colour profiles loaded by then?)
    It may say in /var/log/Xorg.0.log what is happening.

    But Xv gives then the wrong colours. All the others give fully correct in line whit all other colours only Xv that gives the washed-out whit upped gamma/hue? black isn't 0 more like it starts at 16,16,16 or so in the 0-255 scale. (and then my LCD showing it as darkly purple?)
    I notice it and get irritated because black isn't black and clearly all colours are slightly different from normal. I have a 1920x1200 resolution 24" screen and any video always gives you those black border areas which are true black (in the sense as true as my LCD can manage to show black) but then the video has purple/gray instead and you see a clear line difference between the video black and the border blacks. As X11 manages to show video black and border black the same... but same video whit Xv has it black on my screen whit purple tint in contrast to the true black of the borders. It catches your eyes quite easily and you see easily that the black is to the purple colours.

    I have a LG L245WP-BN 24" widescreen LCD whit P-MVA panel.

    Those settings what will they set? System wide gamma or just Xv video playbacks settings?

    If I'm gonna change any settings its Xv specific settings as it's only when Xv is in use when colours aren't fully correct. Don't want to change anything else as they aren't wrong
    I don't know what's going on really - maybe whatever correction your monitor needs to stop black being purple doesn't get applied to xv and the extra gamma just makes things even worse on top of that.

    The xgamma settings are system wide, but if watching full screen you could just set them back to 1.0 after watching. The mplayer correction is just for the video and is done in software.

    In both cases there are variants of the examples I gave that let you tweak red, green and blue separately. So you may be able to find a combination that corrects things so they look OK for you.

    xgamma --help and

    man mplayer | grep "eq2\[" -A 26

    will give details.

  5. #5
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    Yeah, I've had the same problem since some time ago (not the purple tint, I think that's because of your monitor). I deleted the image that showed the difference in that post, but it's basically the same as yours. Here are a couple of new ones:



    Notice the difference between the black-black in the first image (x11) vs the black-grey in the second (xv). If you take a color picker in the first image the black pixels are in the range #000000 and #030303-ish. In the second, however, the "black" pixels are always above #101010.

    In this one we can see the washed colors:



    Also, the subtitles are semi transparent (instead of white-solid) and with blurry borders with xv, which is quite annoying.

    I haven't found a solution yet.

  6. #6
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    I've tried with -vf eq2=0.8 and it makes things more... tolerable:



    but blacks are not blacks yet (see the hair in the second image) and light colors are too dark:



    so maybe brighness/contrast/saturation are also wrong. That's great :-/

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    I think I've found this same kind of problem on the Windows driver side as well... it's a bit old but it seems to describe the same problem in a sense somewhat.

    Here a link to avsforums: http://www.avsforum.com/avs-vb/showp...postcount=2121

    What it describes is that SD-video (standard definition video) uses the "non-expanded" colour levels or in other words "Video levels" which are colours between 16-235 instead off the full range of colours, which are the 0-255, or "expanded" "PC levels". which HD video uses.

    Our problem seems to be that whit Xv and TexturedVideo it uses the "Video levels" of colours for all videos. Instead off the "PC levels" that X11 and etc. seems to use.

    On the windows side this should be fixed in newer drivers, if not you could do some registry tweaks to fix it there. Or enable some thing that forces the "PC levels" onto SD video.

    So what we here seem need to do is force these "PC levels" if there now is a option for such a thing over here for all video.

    Anyone know where one might find such options?

    Edit: and Fran. The moon picture whit Xv. it shows that purple tint for me here. So seems the specific purple is just my monitor but I have the same effects otherwise.
    Last edited by Nighthog; 08-18-2008 at 10:29 AM.

  8. #8
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    It does seem like a color space issue - maybe with a bit of gamma in as well, but I tried a test pattern and you can see clearly that xv treats "video" black/white as grey and less than pure white. X11 and gl:yuv=x where x != 5 both convert video black and white to rgb black/white properly.

    It is possible to lower the black level (brightness) with keys 3 & 4 on mplayer and
    raise the white level (contrast) = keys 1 & 2 to get the test ramp I tried to look OK.

    When you change these settings they are remembered until you restart X - you can see them with xvinfo.

    The 1080*1920 stream I used is here -

    http://www.w6rz.net/ramp.zip

    the dotted lines mark IRE black and white.

    http://www.w6rz.net has other interesting patterns - there's a thread about them here -

    http://www.avsforum.com/avs-vb/showthread.php?t=570937

  9. #9
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    I tried a test pattern and you can see clearly that xv treats "video" black/white as grey and less than pure white
    Good idea. I tried with a very simple pattern (the classic TV pure RGB color pattern, get it here, the first file) and this makes it clearer.



    In the first image (rendered with x11) the colors are, in order

    ffffff-fdfd00-00fefc-00fe00-fb00fd-fd0100-0000fe-000000

    quite good, almost pure colors. In the second, however:

    eceaed-ebeb11-10eaeb-10ea0f-ea10eb-eb0f0f-1010ec-110f12

    the lowest value is 0x0f and the highest is only 0xed.

    I'm going to ask in other forums and see if other people have this problem (if they have, I can't understand why nobody else has reported it or is trying to solve it, because it's been there for months. at least since I reported it in the gentoo forums 5 months ago).

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    Would be great if the AMD Linux guy that hangs around these forums could answer but I read some post that he was on vacation right now I think.

    Kinda perfect timing >_>;

    Good idea Fran. Ask at other forums as well, so we can see how spread this problem is actually. Seems most seem to just ignore it or something and why it has gone by not addressed.

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