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livetrax/libs/audiographer/private/gdither/gdither.h

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/*
* Copyright (C) 2002 Steve Harris <steve@plugin.org.uk>
*
* 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*/
#ifndef GDITHER_H
#define GDITHER_H
#ifdef __cplusplus
extern "C" {
#endif
#include "gdither_types.h"
/* Create and initialise a state structure, takes a dither type, a number of
* channels and a bit depth as input
*
* The Dither type is one of
*
* GDitherNone - straight nearest neighbour rounding. Theres no pressing
* reason to do this at 8 or 16 bit, but you might want to at 24, for some
* reason. At the lest it will save you writing int->float conversion code,
* which is arder than it sounds.
*
* GDitherRect - mathematically most accurate, lowest noise floor, but not
* that good for audio. It is the fastest though.
*
* GDitherTri - a happy medium between Rectangular and Shaped, reasonable
* noise floor, not too obvious, quite fast.
*
* GDitherShaped - should have the least audible impact, but has the highest
* noise floor, fairly CPU intensive. Not advisible if your going to apply
* any frequency manipulation afterwards.
*
* channels, sets the number of channels in the output data, output data will
* be written interleaved into the area given to gdither_run(). Set to 1
* if you are not working with interleaved buffers.
*
* bit depth, sets the bit width of the output sample data, it can be one of:
*
* GDither8bit - 8 bit unsiged
* GDither16bit - 16 bit signed
* GDither32bit - 24+bits in upper bits of a 32 bit word
* GDitherFloat - IEEE floating point (32bits)
* GDitherDouble - Double precision IEEE floating point (64bits)
*
* dither_depth, set the number of bits before the signal will be truncated to,
* eg. 16 will produce an output stream with 16bits-worth of signal. Setting to
* zero or greater than the width of the output format will dither to the
* maximum precision allowed by the output format.
*/
GDither gdither_new(GDitherType type, uint32_t channels,
GDitherSize bit_depth, int dither_depth);
/* Frees memory used by gdither_new.
*/
void gdither_free(GDither s);
/* Applies dithering to the supplied signal.
*
* channel is the channel number you are processing (0 - channles-1), length is
* the length of the input, in samples, x is the input samples (float), y is
* where the output samples will be written, it should have the approaprate
* type for the chosen bit depth
*/
void gdither_runf(GDither s, uint32_t channel, uint32_t length,
float const *x, void *y);
/* see gdither_runf, vut input argument is double format */
void gdither_run(GDither s, uint32_t channel, uint32_t length,
double const *x, void *y);
#ifdef __cplusplus
}
#endif
#endif