Mac:
I set the driver to 256 via the display icon in the control panel.
Everything works fine now.
Thanks!
John
----- Original Message -----
From: "Mac Reiter" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, March 09, 2001 10:10 AM
Subject: Re: PLANAR vs CHUNKY
> >"vncDesktop: Current display is PLANAR, not CHUNKY! WinVNC cannot be used
> with
> >this graphics device driver."
>
> I received this error while trying to set up WinVNC on an embedded system.
> Fortunately for me, I knew what the terms planar and chunky meant from my
> own graphics programming experience.
>
> To the VNC team - since this appears to be a growing problem, this error
> message needs to be updated. I doubt that more than 5% of computer users
> even stand a chance of knowing what this message is talking about. A more
> directly useful error message would be "WinVNC requires a display with 256
> or more colors. Please adjust your video settings, update your drivers,
or
> change your video hardware." EVEN BETTER - WinVNC could attempt to
> automatically switch to a 256+ color mode with ChangeDisplaySettings or
> ChangeDisplaySettingsEx. Then, if that worked, the user wouldn't have to
> do anything else. If it failed, the error message could be even more
> explanatory.
>
> Please keep in mind that this is a problem on the SERVER end, not on the
> viewer end.
>
> History and technology lessons follow for those of you who are
interested...
>
> For those of you who are interested, this is a problem because WinVNC must
> pull the image of the screen from the system. It does this with GetDIBits
> (probably with some intermediate work, but this is the core routine), a
> function supplied as part of Windows. To process the pixels, VNC wants
> full 24bit color values. GetDIBits refuses to convert images from planar
> (definition below) screens into 24bit color values. It *would* be
possible
> to replace GetDIBits with a looping call to GetPixel, but the speed
penalty
> would be unimaginable. GetPixel is PAINFULLY slow.
>
> As for what Planar and Chunky mean -- the image on your screen is stored
in
> memory somewhere. In a Chunky system, all of the information necessary
for
> displaying one pixel is in a single contiguous "chunk". 256 color
displays
> use 8 contiguous bits, 24bit displays use 24 contiguous bits, and so on.
> You can represent any pixel by one single address and a knowledge of how
> many bits you are interested in. By contrast, Planar video modes store
> data in bit planes. This is usually only used for 16 color or lower
> displays. 16 colors requires 4 bits per pixel to store. It would be
> possible to store those 4 bits contiguously, in a chunky format. But when
> 16 color modes first came around, the hardware was not fast enough to
> handle that. The designers had to split the work out into parallel units.
> So they made 4 different regions of memory, called bit planes. Each bit
> plane stored one bit of each pixel for the display. The first bit plane
> stored the first bit of all the pixels. The second bit plane stored the
> second bit, etc. That allowed the hardware to use a separate piece of
> equipment on each bitplane to construct the necessary signals to send to
> the monitor. (Keep in mind that pixel clocks, the frequency at which
> values must change for the monitor to display a pixel, exceed 28MHz for a
> 640x480 60Hz monitor. In the days when an 12MHz 286 was a hot machine,
you
> couldn't expect a single pipeline to manage all of this work at 28MHz.)
> Anyway, planar mode became the standard for 16 color modes, and continued
> as such even after the hardware no longer needed it -- software written
for
> planar mode would not be able to work in a chunky format.
>
> The practical upshot of this is that the standard VGA driver that will
work
> on almost any video card runs in 16 color planar mode. Unless you can get
> the SVGA driver or some chip specific driver to support 256 or more colors
> on your hardware, you won't be able to run WinVNC. And there isn't really
> anything reasonable that the developers could do to change that -- as I
> mentioned, the only alternative (GetPixel) is too slow to even consider.
> Screen updates would take around a minute, even on fast CPUs, and worse on
> a 486 or Pentium 75.
>
> Mac
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