Ensure sample delta adjusts with object distance

2 files changed, 30 insertions, 16 deletions

diff --git a/include/xas/spatial.h b/include/xas/spatial.h
index 581543c..864770b 100644
--- a/include/xas/spatial.h
+++ b/include/xas/spatial.h
@@ -50,8 +50,8 @@ struct _xas_spatial_object {
     size_t delta_l,
            delta_r;
 
-    size_t shift_l,
-           shift_r;
+    ssize_t shift_l,
+            shift_r;
 
     xas_spatial_coord coord;
     xas_audio_stream *source;
diff --git a/src/spatial.c b/src/spatial.c
index f35749c..1c09be7 100644
--- a/src/spatial.c
+++ b/src/spatial.c
@@ -184,18 +184,27 @@ ssize_t scene_fill(xas_spatial_scene *scene,
 
             index_l = index_r = buffer->index;
 
-            if (obj->shift_l) {
-                index_l += obj->delta_l;
-                obj->shift_l--;
+            if (obj->shift_l < 0) {
+                obj->shift_l++;
+            } else {
+                if (obj->shift_l > 0) {
+                    index_l += obj->delta_l;
+                    obj->shift_l--;
+                }
+
+                dest[XAS_AUDIO_STEREO*index_l] += value_l;
             }
 
-            if (obj->shift_r) {
-                index_r += obj->delta_r;
-                obj->shift_r--;
-            }
+            if (obj->shift_r < 0) {
+                obj->shift_r++;
+            } else {
+                if (obj->shift_r > 0) {
+                    index_r += obj->delta_r;
+                    obj->shift_r--;
+                }
 
-            dest[XAS_AUDIO_STEREO*index_l]   += value_l;
-            dest[XAS_AUDIO_STEREO*index_r+1] += value_r;
+                dest[XAS_AUDIO_STEREO*index_r+1] += value_r;
+            }
 
             buffer->index++;
         }
@@ -273,14 +282,17 @@ void xas_spatial_scene_set_observer(xas_spatial_scene *scene,
 static void object_position(xas_spatial_scene *scene,
                             xas_spatial_object *object,
                             xas_spatial_coord coord) {
+    size_t delta_l_old = object->delta_l,
+           delta_r_old = object->delta_r;
+
     object->coord = coord;
 
     object->distance_l = dist(scene->speaker_l, coord);
     object->distance_r = dist(scene->speaker_r, coord);
     object->delta_l    = sample_delta(scene, object->distance_l);
     object->delta_r    = sample_delta(scene, object->distance_r);
-    object->shift_l    = object->delta_l;
-    object->shift_r    = object->delta_r;
+    object->shift_l    = object->delta_l - delta_l_old;
+    object->shift_r    = object->delta_r - delta_r_old;
 }
 
 void xas_spatial_scene_set_speaker_coords(xas_spatial_scene *scene,
@@ -327,9 +339,11 @@ xas_spatial_object *xas_spatial_scene_add_object(xas_spatial_scene *scene,
         goto error_malloc_object;
     }
 
-    object->coord  = coord;
-    object->source = source;
-    object->next   = NULL;
+    object->coord   = coord;
+    object->source  = source;
+    object->next    = NULL;
+    object->delta_l = 0;
+    object->delta_r = 0;
 
     object_position(scene, object, coord);