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-rw-r--r--src/pcm_channels.c102
1 files changed, 102 insertions, 0 deletions
diff --git a/src/pcm_channels.c b/src/pcm_channels.c
new file mode 100644
index 000000000..6555a3b74
--- /dev/null
+++ b/src/pcm_channels.c
@@ -0,0 +1,102 @@
+/* the Music Player Daemon (MPD)
+ * Copyright (C) 2008 Max Kellermann <max@duempel.org>
+ * This project's homepage is: 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
+ */
+
+#include "pcm_channels.h"
+#include "utils.h"
+#include "log.h"
+
+#include <assert.h>
+
+static void
+pcm_convert_channels_16_1_to_2(int16_t *dest, const int16_t *src,
+ unsigned num_frames)
+{
+ while (num_frames-- > 0) {
+ int16_t value = *src++;
+
+ *dest++ = value;
+ *dest++ = value;
+ }
+}
+
+static void
+pcm_convert_channels_16_2_to_1(int16_t *dest, const int16_t *src,
+ unsigned num_frames)
+{
+ while (num_frames-- > 0) {
+ int32_t a = *src++, b = *src++;
+
+ *dest++ = (a + b) / 2;
+ }
+}
+
+static void
+pcm_convert_channels_16_n_to_2(int16_t *dest,
+ unsigned src_channels, const int16_t *src,
+ unsigned num_frames)
+{
+ unsigned c;
+
+ assert(src_channels > 0);
+
+ while (num_frames-- > 0) {
+ int32_t sum = 0;
+ int16_t value;
+
+ for (c = 0; c < src_channels; ++c)
+ sum += *src++;
+ value = sum / (int)src_channels;
+
+ /* XXX this is actually only mono ... */
+ *dest++ = value;
+ *dest++ = value;
+ }
+}
+
+const int16_t *
+pcm_convert_channels_16(int8_t dest_channels,
+ int8_t src_channels, const int16_t *src,
+ size_t src_size, size_t *dest_size_r)
+{
+ static int16_t *buf;
+ static size_t len;
+ unsigned num_frames = src_size / src_channels / sizeof(*src);
+ unsigned dest_size = num_frames * dest_channels * sizeof(*src);
+
+ if (dest_size > len) {
+ len = dest_size;
+ buf = xrealloc(buf, len);
+ }
+
+ *dest_size_r = dest_size;
+
+ if (src_channels == 1 && dest_channels == 2)
+ pcm_convert_channels_16_1_to_2(buf, src, num_frames);
+ else if (src_channels == 2 && dest_channels == 1)
+ pcm_convert_channels_16_2_to_1(buf, src, num_frames);
+ else if (dest_channels == 2)
+ pcm_convert_channels_16_n_to_2(buf, src_channels, src,
+ num_frames);
+ else {
+ ERROR("conversion %u->%u channels is not supported\n",
+ src_channels, dest_channels);
+ return NULL;
+ }
+
+ return buf;
+}