7f701744a7
Added an inline assembly function for the 64 bit multiplication.
Benchmark results on a Pentium II 266 MHz, 512 MB of 24 bit PCM data:
dd if=/dev/zero bs=64k count=8k |
time ./test/software_volume 48000:24:2 >/dev/null
Before this patch 22.94s, after this patch 7.24s.
148 lines
3.3 KiB
C
148 lines
3.3 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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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include "pcm_volume.h"
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#include "pcm_utils.h"
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#include "audio_format.h"
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#include <glib.h>
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#include <stdint.h>
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#include <string.h>
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#undef G_LOG_DOMAIN
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#define G_LOG_DOMAIN "pcm_volume"
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static void
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pcm_volume_change_8(int8_t *buffer, unsigned num_samples, int volume)
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{
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while (num_samples > 0) {
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int32_t sample = *buffer;
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sample = (sample * volume + pcm_volume_dither() +
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PCM_VOLUME_1 / 2)
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/ PCM_VOLUME_1;
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*buffer++ = pcm_range(sample, 8);
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--num_samples;
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}
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}
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static void
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pcm_volume_change_16(int16_t *buffer, unsigned num_samples, int volume)
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{
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while (num_samples > 0) {
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int32_t sample = *buffer;
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sample = (sample * volume + pcm_volume_dither() +
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PCM_VOLUME_1 / 2)
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/ PCM_VOLUME_1;
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*buffer++ = pcm_range(sample, 16);
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--num_samples;
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}
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}
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#if __i386__
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/**
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* Optimized volume function for i386. Use the EDX:EAX 2*32 bit
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* multiplication result instead of emulating 64 bit multiplication.
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*/
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static inline int32_t
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pcm_volume_sample_24(int32_t sample, int32_t volume, int32_t dither)
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{
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int32_t result;
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asm(/* edx:eax = sample * volume */
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"imul %2\n"
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/* "add %3, %1\n" dithering disabled for now, because we
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have no overflow check - is dithering really important
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here? */
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/* eax = edx:eax / PCM_VOLUME_1 */
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"sal $22, %%edx\n"
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"shr $10, %1\n"
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"or %%edx, %1\n"
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: "=a"(result)
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: "0"(sample), "r"(volume) /* , "r"(dither) */
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: "edx"
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);
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return result;
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}
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#endif
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static void
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pcm_volume_change_24(int32_t *buffer, unsigned num_samples, int volume)
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{
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while (num_samples > 0) {
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#if __i386__
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/* assembly version for i386 */
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int32_t sample = *buffer;
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sample = pcm_volume_sample_24(sample, volume,
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pcm_volume_dither());
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#else
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/* portable version */
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int64_t sample = *buffer;
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sample = (sample * volume + pcm_volume_dither() +
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PCM_VOLUME_1 / 2)
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/ PCM_VOLUME_1;
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#endif
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*buffer++ = pcm_range(sample, 24);
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--num_samples;
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}
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}
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void
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pcm_volume(void *buffer, int bufferSize,
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const struct audio_format *format,
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int volume)
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{
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if (volume == PCM_VOLUME_1)
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return;
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if (volume <= 0) {
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memset(buffer, 0, bufferSize);
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return;
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}
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switch (format->bits) {
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case 8:
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pcm_volume_change_8((int8_t *)buffer, bufferSize, volume);
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break;
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case 16:
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pcm_volume_change_16((int16_t *)buffer, bufferSize / 2,
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volume);
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break;
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case 24:
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pcm_volume_change_24((int32_t*)buffer, bufferSize / 4,
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volume);
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break;
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default:
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g_error("%u bits not supported by pcm_volume!\n",
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format->bits);
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}
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}
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