5b82ffc291
After we've been hit by Large File Support problems several times in the past week (which only occur on 32 bit platforms, which I don't have), this is yet another attempt to fix the issue.
96 lines
2.3 KiB
C
96 lines
2.3 KiB
C
/*
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* Copyright (C) 2003-2009 The Music Player Daemon Project
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* http://www.musicpd.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "config.h"
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#include "pcm_dither.h"
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#include "pcm_prng.h"
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static int16_t
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pcm_dither_sample_24_to_16(int32_t sample, struct pcm_dither *dither)
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{
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int32_t output, rnd;
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enum {
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from_bits = 24,
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to_bits = 16,
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scale_bits = from_bits - to_bits,
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round = 1 << (scale_bits - 1),
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mask = (1 << scale_bits) - 1,
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ONE = 1 << (from_bits - 1),
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MIN = -ONE,
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MAX = ONE - 1
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};
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sample += dither->error[0] - dither->error[1] + dither->error[2];
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dither->error[2] = dither->error[1];
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dither->error[1] = dither->error[0] / 2;
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/* round */
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output = sample + round;
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rnd = pcm_prng(dither->random);
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output += (rnd & mask) - (dither->random & mask);
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dither->random = rnd;
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/* clip */
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if (output > MAX) {
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output = MAX;
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if (sample > MAX)
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sample = MAX;
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} else if (output < MIN) {
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output = MIN;
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if (sample < MIN)
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sample = MIN;
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}
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output &= ~mask;
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dither->error[0] = sample - output;
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return (int16_t)(output >> scale_bits);
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}
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void
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pcm_dither_24_to_16(struct pcm_dither *dither,
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int16_t *dest, const int32_t *src,
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unsigned num_samples)
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{
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while (num_samples-- > 0)
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*dest++ = pcm_dither_sample_24_to_16(*src++, dither);
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}
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static int16_t
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pcm_dither_sample_32_to_16(int32_t sample, struct pcm_dither *dither)
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{
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return pcm_dither_sample_24_to_16(sample >> 8, dither);
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}
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void
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pcm_dither_32_to_16(struct pcm_dither *dither,
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int16_t *dest, const int32_t *src,
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unsigned num_samples)
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{
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while (num_samples-- > 0)
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*dest++ = pcm_dither_sample_32_to_16(*src++, dither);
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}
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