From 962f2407d2a3579b7125f937d93d04ccbeb9a453 Mon Sep 17 00:00:00 2001 From: Max Kellermann Date: Sat, 3 Jan 2009 14:51:47 +0100 Subject: pcm_utils: use the custom PRNG for volume dithering Don't use libc's rand() function, because it is slow. Our own trivial linear congruential generator is good enough for dithering. --- src/pcm_prng.h | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) create mode 100644 src/pcm_prng.h (limited to 'src/pcm_prng.h') diff --git a/src/pcm_prng.h b/src/pcm_prng.h new file mode 100644 index 000000000..e961baacd --- /dev/null +++ b/src/pcm_prng.h @@ -0,0 +1,31 @@ +/* + * Copyright (C) 2003-2009 The Music Player Daemon Project + * http://www.musicpd.org + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + +#ifndef PCM_PRNG_H +#define PCM_PRNG_H + +/** + * A very simple linear congruential PRNG. It's good enough for PCM + * dithering. + */ +static unsigned long prng(unsigned long state) +{ + return (state * 0x0019660dL + 0x3c6ef35fL) & 0xffffffffL; +} + +#endif -- cgit v1.2.3