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To: Randall Hopper <rhh@ct.picker.com>
cc: multimedia@freebsd.org
Subject: Re: The "BT848 RISC Challenge" 
In-reply-to: Your message of "Thu, 24 Apr 1997 21:15:46 EDT."
             <19970424211546.22989@ct.picker.com> 
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Date: Thu, 24 Apr 1997 19:05:46 -0700
From: Amancio Hasty <hasty@rah.star-gate.com>
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Hi,

First of, the Bt848 driver operates in RGB mode and has been that way since
the beginning. What is currently out in beta in 
ftp://rah.star-gate.com/pub/bt848-clip.tar.gz is the swapping of pixel
orders and clip list support. 

The Bt848 supports RGB32, RGB24, RGB16, and RGB15.

The supported modes are RGB32 (METEOR_GEO_RGB24) and RGB15 ( METEOR_GEO_RGB16)
needless to say that the METEOR_GEO_RGBXXX are misnomers.

the following table hopefully will make all this clear, from the
Bt848 databook:

FIFO Input	Output of Fifo
31:24		[31:24]	[23:16]	[15:8]	[7:0]
23:16		[23:16] [31:24]	[7:0]	[15:8]
15:8		[15:8]	[7:0]	[31:24]	[23:16]
7:0		[7:0]	[15:8]	[23:16]	[31:24]

If RGB24 is desired, then we can add an ioctl to tell the driver 
to dma the video using rgb24.

A few ways of accomplishing this is to:

1.  to create a bt848 ioctl call with the appropriate correct color depth.
    bt848SETRGB and pass a value of the color depth desired 

2.  we can generalized the mechanism for setting the pixel order to also
    determine the color depth. 

3.  Create a new bt848 ioctl call which has geometry, color depth, pixel
    order and video frame buffer info .

----


Briefly, we can do it.

	Amancio


>From The Desk Of Randall Hopper :
> Thought that'd grab your attention   :-)
> 
> 
> THE CHALLENGE:  Figure out how to get the BT848 to DMA pixels in
>                 RGBRGB packed 24bpp (3Bpp) format to the frame buffer or
>                 memory.
> 
> 
>      It'd be cool if we could do this to support those of us whose Xservers
> config the card for this format.  For now, the driver limits direct video
> in 24bpp to those folks that have BGRBGR packed 24bpp organization.
> 
> SOME OPTIONS:
>     
>     1. Put the chip in RGB32 pixel FIFO mode with byte and short swapping 
>        enabled (ARGBARGB).  For each pixel, write 2 RISC instructions:  a
>        SKIP to skip the Alpha, and a WRITE to blast the RGB.  
> 
>        Hmmmmmm, let's see....that's only 2.5 Megs for a 640x480 image.  :-)
> 
>     2. Rotate the HUE 90 deg.  (I'm not kidding.  It works.  It's ugly but
>        it works!)
> 
> Anybody know a kindler, gentler way to do this on the chip? :-)
> 
> Randall
>