Re: what's 32 bpp?
On Mon, Feb 08, 1999 at 18:26 -0500, Branden Robinson wrote: On Mon, Feb 08, 1999 at 12:06:30PM -0800, Kenneth Scharf wrote: What happens in 32bpp?? I do not believe that video dac's are available wider than 8 bits. If they are, are 3 10 bit dac's used, with the extra 2 bits thrown away? Or is a 12 bit dac used for the green Or is this only a maping thing, 24 bits are used, and a whole byte is thrown away, but using 32bits per pixel cleans up the dma access some how? As far as I know, the latter is the case. Kind of a shame. I wish the last 8 bits could be used for an alpha channel. I seem to recall reading somewhere (I think it was in the xfree86 docs for the matrox driver) that using 32bpp was faster than using 24bpp, probably because it can blit stuff along a longword boundary...But what do I know? Cheers Dave -- Dave Swegen | Debian 2.0 on Linux i386 2.2.1 [EMAIL PROTECTED] | PGP key available on request [EMAIL PROTECTED] | Linux: The Choice of a GNU Generation --
what's 32 bpp?
I see that X servers can be set to run at 8,16,24, or 32 BPP. (also 2 and 4 but that's yuck!). I know that the 8 bpp mode uses a map table to select 256 out of 2**16 or 2**18 colors, assuming that the card has 3 6 bit dac's, one for each color. In 16 or 15 bit mode the access to the dac's is direct. 5 bits are used for each dac, with the lsb set to 0. In 16 bbp mode the extra bit is given to the green dac. In 24bpp mode 8 bit dac's are used, 8*3=24 bits. What happens in 32bpp?? I do not believe that video dac's are available wider than 8 bits. If they are, are 3 10 bit dac's used, with the extra 2 bits thrown away? Or is a 12 bit dac used for the green Or is this only a maping thing, 24 bits are used, and a whole byte is thrown away, but using 32bits per pixel cleans up the dma access some how? == Amateur Radio, when all else fails! http://www.qsl.net/wa2mze Debian Gnu Linux, Live Free or . _ DO YOU YAHOO!? Get your free @yahoo.com address at http://mail.yahoo.com
Re: what's 32 bpp?
On Mon, Feb 08, 1999 at 12:06:30PM -0800, Kenneth Scharf wrote: What happens in 32bpp?? I do not believe that video dac's are available wider than 8 bits. If they are, are 3 10 bit dac's used, with the extra 2 bits thrown away? Or is a 12 bit dac used for the green Or is this only a maping thing, 24 bits are used, and a whole byte is thrown away, but using 32bits per pixel cleans up the dma access some how? As far as I know, the latter is the case. Kind of a shame. I wish the last 8 bits could be used for an alpha channel. -- G. Branden Robinson | Human beings rarely imagine a god that Debian GNU/Linux | behaves any better than a spoiled child. [EMAIL PROTECTED] | -- Robert Heinlein cartoon.ecn.purdue.edu/~branden/ | pgpU923fBYBSr.pgp Description: PGP signature
