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-rw-r--r--src/pcm_channels.c79
-rw-r--r--src/pcm_channels.h5
2 files changed, 84 insertions, 0 deletions
diff --git a/src/pcm_channels.c b/src/pcm_channels.c
index 6555a3b74..fca889c93 100644
--- a/src/pcm_channels.c
+++ b/src/pcm_channels.c
@@ -100,3 +100,82 @@ pcm_convert_channels_16(int8_t dest_channels,
return buf;
}
+
+static void
+pcm_convert_channels_24_1_to_2(int32_t *dest, const int32_t *src,
+ unsigned num_frames)
+{
+ while (num_frames-- > 0) {
+ int32_t value = *src++;
+
+ *dest++ = value;
+ *dest++ = value;
+ }
+}
+
+static void
+pcm_convert_channels_24_2_to_1(int32_t *dest, const int32_t *src,
+ unsigned num_frames)
+{
+ while (num_frames-- > 0) {
+ int32_t a = *src++, b = *src++;
+
+ *dest++ = (a + b) / 2;
+ }
+}
+
+static void
+pcm_convert_channels_24_n_to_2(int32_t *dest,
+ unsigned src_channels, const int32_t *src,
+ unsigned num_frames)
+{
+ unsigned c;
+
+ assert(src_channels > 0);
+
+ while (num_frames-- > 0) {
+ int32_t sum = 0;
+ int32_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 int32_t *
+pcm_convert_channels_24(int8_t dest_channels,
+ int8_t src_channels, const int32_t *src,
+ size_t src_size, size_t *dest_size_r)
+{
+ static int32_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_24_1_to_2(buf, src, num_frames);
+ else if (src_channels == 2 && dest_channels == 1)
+ pcm_convert_channels_24_2_to_1(buf, src, num_frames);
+ else if (dest_channels == 2)
+ pcm_convert_channels_24_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;
+}
diff --git a/src/pcm_channels.h b/src/pcm_channels.h
index 169fd3693..fa27fdb8f 100644
--- a/src/pcm_channels.h
+++ b/src/pcm_channels.h
@@ -27,4 +27,9 @@ 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);
+const int32_t *
+pcm_convert_channels_24(int8_t dest_channels,
+ int8_t src_channels, const int32_t *src,
+ size_t src_size, size_t *dest_size_r);
+
#endif