Re: [Dri-users] questions about 24-bit colour with 16 Mb ATI Rage

[Chris P. <chr...@ma...>]

Hi Alex,

Alex Deucher wrote:
> --- Chris Pickett <chr...@ma...> wrote:

>>3)  Mostly I'm concerned about watching DVD's on my laptop (and
>>playing 
>>some games occasionally, but usually not at this resolution). 
>>Assuming 
>>I have a nicely mastered DVD, will colour depth noticeably affect the
>>
>>image?  Or is it irrelevant because the image has been compressed?
>>
>>FWIW, I had W2K 32-bit colour working with this card and I was able
>>to 
>>watch DVD's with it at 1400x1050 with the video player telling me 
>>hardware acceleration was enabled, but I'm not sure if Windows was
>>lying 
>>about that.
> 
> 
> DVD (and videos in general) can be accelerated using the Xvideo (Xv)
> extention.  This extension handles the scaling and colorspace
> conversion in hardware.  It also has nothing to do with 3D
> acceleration.  Xv should just work in the r128 driver assuming your dvd
> software uses that extension.  run "xvinfo" from a command prompt to
> see if the extension is available. 
> 

Yes, I checked DVD playback works fine with ColorDepth 24 using xine. 
Thanks for explaining (I can add all this to the DRI wiki if you like). 
  It doesn't work if the only change I make in my xorg.conf is to use 
ColorDepth 16 instead of ColorDepth 24 (I get a blue screen instead, 
although sound works and xine-check doesn't report anything wrong), but 
I guess this isn't the right place to be asking about that.

I've also noticed, after using depth 24 for a while (I'd previously 
given up), that images look a lot nicer because there are no banding 
effects.

glxinfo in depth 24 gives me the following table

    visual  x  bf lv rg d st colorbuffer ax dp st accumbuffer  ms  cav
  id dep cl sp sz l  ci b ro  r  g  b  a bf th cl  r  g  b  a ns b eat
----------------------------------------------------------------------
0x23 24 tc  0 24  0 r  y  .  8  8  8  0  0 16  0  0  0  0  0  0 0 None
0x24 24 tc  0 24  0 r  y  .  8  8  8  0  0 16  8 16 16 16  0  0 0 None
0x25 24 tc  0 32  0 r  y  .  8  8  8  8  0 16  8 16 16 16 16  0 0 None
0x26 24 tc  0 32  0 r  .  .  8  8  8  8  0 16  8 16 16 16 16  0 0 None
0x27 24 dc  0 24  0 r  y  .  8  8  8  0  0 16  0  0  0  0  0  0 0 None
0x28 24 dc  0 24  0 r  y  .  8  8  8  0  0 16  8 16 16 16  0  0 0 None
0x29 24 dc  0 32  0 r  y  .  8  8  8  8  0 16  8 16 16 16 16  0 0 None
0x2a 24 dc  0 32  0 r  .  .  8  8  8  8  0 16  8 16 16 16 16  0 0 None

There seem to be several modes that don't require 32-bit buffers because 
the alpha channel is disabled.  Using a buffer size of 24 bits instead 
of 32, there is enough memory on my video card for my panel at full 
resolution: 1400*1050*(24/8)*3*(1/1024) = 12920 kB (plus a little for 
the extra pixels), whereas my card can handle up to 16384 kB.

That would be fantastic, because then I could get 2D and 3D hardware 
acceleration with 24 bits, which if I understand correctly will always 
look nicer than 16 bits, even if the alpha channel is disabled.

Is this something worth pursuing?  It seems from an outsider's 
perspective that relatively minor changes would be required.  I'm 
willing to help out but I don't know where to get started.

Cheers,
Chris