Mercurial > sdl-ios-xcode
view docs/man3/SDL_MixAudio.3 @ 689:5bb080d35049
Date: Tue, 19 Aug 2003 17:57:00 +0200
From: Stephane Marchesin
Subject: Re: [SDL] [patch] MMX alpha blit patches with MMX detection
I think everything is correct now. I've done as much testing as I could,
but some real-world testing wouldn't hurt, I think.
The patch is here : http://icps.u-strasbg.fr/~marchesin/sdl_mmxblit.patch
If you do byte-by-byte comparison of the output between C and MMX
functions, you'll notice that the results for 555 and 565 RGB alpha
blits aren't exactly the same. This is because MMX functions for 555 and
565 RGB have an higher accuracy. If you want the exact same behaviour
that's possible by masking the three lower alpha bits in the MMX
functions. Just ask !
I removed one MMX function because after I fixed it to match its C
equivalent, it revealed to be slower than the C version on a PIII
(although a bit faster on an Athlon XP).
I've also added MMX and PIII replacements for SDL_memcpy. Those provide
some speed up in testvidinfo -benchmark (at least for me, under linux &
X11).
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Fri, 22 Aug 2003 05:51:19 +0000 (2003-08-22) |
parents | e5bc29de3f0a |
children | 546f7c1eb755 |
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.TH "SDL_MixAudio" "3" "Tue 11 Sep 2001, 22:58" "SDL" "SDL API Reference" .SH "NAME" SDL_MixAudio\- Mix audio data .SH "SYNOPSIS" .PP \fB#include "SDL\&.h" .sp \fBvoid \fBSDL_MixAudio\fP\fR(\fBUint8 *dst, Uint8 *src, Uint32 len, int volume\fR); .SH "DESCRIPTION" .PP This function takes two audio buffers of \fBlen\fR bytes each of the playing audio format and mixes them, performing addition, volume adjustment, and overflow clipping\&. The \fBvolume\fR ranges from 0 to \fBSDL_MIX_MAXVOLUME\fP and should be set to the maximum value for full audio volume\&. Note this does not change hardware volume\&. This is provided for convenience -- you can mix your own audio data\&. .PP .RS \fBNote: .PP Do not use this function for mixing together more than two streams of sample data\&. The output from repeated application of this function may be distorted by clipping, because there is no accumulator with greater range than the input (not to mention this being an inefficient way of doing it)\&. Use mixing functions from SDL_mixer, OpenAL, or write your own mixer instead\&. .RE .SH "SEE ALSO" .PP \fI\fBSDL_OpenAudio\fP\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 22:58