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/* plugin_common - Routines common to several plugins
* Copyright (C) 2002,2003,2004 Josh Coalson
*
* dithering routine derived from (other GPLed source):
* mad - MPEG audio decoder
* Copyright (C) 2000-2001 Robert Leslie
*
* 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.
*/
#include "include/common.h"
#include "include/dither.h"
#include "FLAC/assert.h"
/* 32-bit pseudo-random number generator
*
* @@@ According to Miroslav, this one is poor quality, the one from the
* @@@ original replaygain code is much better
*/
static FLAC__INLINE FLAC__uint32 prng(FLAC__uint32 state)
{
return (state * 0x0019660dL + 0x3c6ef35fL) & 0xffffffffL;
}
/* dither routine derived from MAD winamp plugin */
typedef struct {
FLAC__int32 error[3];
FLAC__int32 random;
} dither_state;
static FLAC__INLINE FLAC__int32 linear_dither(
unsigned source_bps, unsigned target_bps, FLAC__int32 sample,
dither_state *dither, const FLAC__int32 MIN, const FLAC__int32 MAX) {
unsigned scalebits;
FLAC__int32 output, mask, random;
FLAC__ASSERT(source_bps < 32);
FLAC__ASSERT(target_bps <= 24);
FLAC__ASSERT(target_bps <= source_bps);
/* noise shape */
sample += dither->error[0] - dither->error[1] + dither->error[2];
dither->error[2] = dither->error[1];
dither->error[1] = dither->error[0] / 2;
/* bias */
output = sample + (1L << (source_bps - target_bps - 1));
scalebits = source_bps - target_bps;
mask = (1L << scalebits) - 1;
/* dither */
random = (FLAC__int32)prng(dither->random);
output += (random & mask) - (dither->random & mask);
dither->random = random;
/* clip */
if (output > MAX) {
output = MAX;
if (sample > MAX) {
sample = MAX;
}
} else if (output < MIN) {
output = MIN;
if (sample < MIN) {
sample = MIN;
}
}
/* quantize */
output &= ~mask;
/* error feedback */
dither->error[0] = sample - output;
/* scale */
return output >> scalebits;
}
size_t pack_pcm_signed_big_endian(FLAC__byte *data, FLAC__int32 *input,
unsigned wide_samples, unsigned channels, unsigned source_bps, unsigned target_bps) {
static dither_state dither[FLAC__MAX_SUPPORTED_CHANNELS];
FLAC__byte * const start = data;
FLAC__int32 sample;
unsigned samples, channel;
const unsigned bytes_per_sample = target_bps / 8;
const unsigned incr = bytes_per_sample * channels;
const FLAC__int32 MIN = -(1L << (source_bps - 1));
const FLAC__int32 MAX = ~MIN; /*(1L << (source_bps-1)) - 1 */
FLAC__ASSERT(channels > 0 && channels <= FLAC__MAX_SUPPORTED_CHANNELS);
FLAC__ASSERT(source_bps < 32);
FLAC__ASSERT(target_bps <= 24);
FLAC__ASSERT(target_bps <= source_bps);
FLAC__ASSERT((source_bps & 7) == 0);
FLAC__ASSERT((target_bps & 7) == 0);
for (channel = 0; channel < channels; channel++) {
samples = wide_samples;
data = start + bytes_per_sample * channel;
while (samples--) {
if (source_bps != target_bps) {
sample = linear_dither(source_bps, target_bps, *input++, &dither[channel], MIN, MAX);
} else {
sample = *input++;
}
switch (target_bps) {
case 8:
data[0] = sample ^ 0x80;
break;
case 16:
data[0] = (FLAC__byte)(sample >> 8);
data[1] = (FLAC__byte)sample;
break;
case 24:
data[0] = (FLAC__byte)(sample >> 16);
data[1] = (FLAC__byte)(sample >> 8);
data[2] = (FLAC__byte)sample;
break;
}
data += incr;
}
}
return wide_samples * channels * (target_bps/8);
}
size_t pack_pcm_signed_little_endian(FLAC__byte *data, FLAC__int32 *input,
unsigned wide_samples, unsigned channels, unsigned source_bps, unsigned target_bps) {
static dither_state dither[FLAC__MAX_SUPPORTED_CHANNELS];
FLAC__byte * const start = data;
FLAC__int32 sample;
unsigned samples, channel;
const unsigned bytes_per_sample = target_bps / 8;
const unsigned incr = bytes_per_sample * channels;
const FLAC__int32 MIN = -(1L << (source_bps - 1));
const FLAC__int32 MAX = ~MIN; /*(1L << (source_bps-1)) - 1 */
FLAC__ASSERT(channels > 0 && channels <= FLAC__MAX_SUPPORTED_CHANNELS);
FLAC__ASSERT(source_bps < 32);
FLAC__ASSERT(target_bps <= 24);
FLAC__ASSERT(target_bps <= source_bps);
FLAC__ASSERT((source_bps & 7) == 0);
FLAC__ASSERT((target_bps & 7) == 0);
for (channel = 0; channel < channels; channel++) {
samples = wide_samples;
data = start + bytes_per_sample * channel;
while (samples--) {
if (source_bps != target_bps) {
sample = linear_dither(source_bps, target_bps, *input++, &dither[channel], MIN, MAX);
} else {
sample = *input++;
}
switch(target_bps) {
case 8:
data[0] = sample ^ 0x80;
break;
case 24:
data[2] = (FLAC__byte)(sample >> 16);
/* fall through */
case 16:
data[1] = (FLAC__byte)(sample >> 8);
data[0] = (FLAC__byte)sample;
}
data += incr;
}
}
return wide_samples * channels * (target_bps/8);
}
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