FS-11678: add/fix muxing to 2 channels (when audio file is multichannel - more than...

diff --git a/src/switch_resample.c b/src/switch_resample.c
index c9e1dc97596fcef7ebe849c02761a78786f5c689..0b763e597a0a3e77b5bd95138129a2a7bdcdd1da 100644 (file)
--- a/src/switch_resample.c
+++ b/src/switch_resample.c
@@ -279,14 +279,39 @@ SWITCH_DECLARE(void) switch_mux_channels(int16_t *data, switch_size_t samples, u
        switch_assert(channels < 11);
 
        if (orig_channels > channels) {
-               for (i = 0; i < samples; i++) {
-                       int32_t z = 0;
-                       for (j = 0; j < orig_channels; j++) {
-                               z += data[i * orig_channels + j];
+               if (channels == 1) {
+                       for (i = 0; i < samples; i++) {
+                               int32_t z = 0; int16_t y, last = 0;
+                               for (j = 0; j < orig_channels; j++) {
+                                       y = (int16_t) data[i * orig_channels + j];
+                                       if (y != last) z += y;
+                                       last = y;
+                               }
                                switch_normalize_to_16bit(z);
                                data[i] = (int16_t) z;
                        }
-               }
+               } else if (channels == 2) {
+                       int mark_buf = 0;
+                       for (i = 0; i < samples; i++) {
+                               int32_t z_left = 0, z_right = 0; int16_t y_left, y_right, last_left = 0, last_right = 0;
+                               for (j = 0; j < orig_channels; j++) {
+                                       if (j % 2) {
+                                               y_left = (int16_t) data[i * orig_channels + j];
+                                               if (y_left != last_left) z_left += y_left;
+                                               last_left = y_left;
+                                       } else {
+                                               y_right = (int16_t) data[i * orig_channels + j];
+                                               if (y_right != last_right) z_right += y_right;
+                                               last_right = y_right;
+                                       }
+                               }
+                               /* mark_buf will always be smaller than the size of data in bytes because orig_channels > channels */
+                               switch_normalize_to_16bit(z_left);
+                               data[mark_buf++] = (int16_t) z_left;
+                               switch_normalize_to_16bit(z_right);
+                               data[mark_buf++] = (int16_t) z_right;
+                       }
+               } 
        } else if (orig_channels < channels) {
 
                /* interesting problem... take a give buffer and double up every sample in the buffer without using any other buffer.....