Fixed bug with circlar buffer

 - Circular buffer code wasn't correctly handling the splitting of
   newly placed data segments, the code was untested and turned out to
   just be backwards.  It now copied the data to the back and front of
   the buffer properly.

libobs/util/circlebuf.h

@@ -132,12 +132,12 @@ static inline void circlebuf_place(struct circlebuf *cb, size_t position,
 
 	data_end_pos = position + size;
 	if (data_end_pos > cb->capacity) {
-		size_t back_size = cb->capacity - data_end_pos;
+		size_t back_size = data_end_pos - cb->capacity;
 		size_t loop_size = size - back_size;
 
 		if (back_size)
-			memcpy((uint8_t*)cb->data + position, data, back_size);
-		memcpy(cb->data, (uint8_t*)data + back_size, loop_size);
+			memcpy((uint8_t*)cb->data + position, data, loop_size);
+		memcpy(cb->data, (uint8_t*)data + loop_size, back_size);
 	} else {
 		memcpy((uint8_t*)cb->data + position, data, size);
 	}