add API call to properly sum two frames of SLINEAR data

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@6883 65c4cc65-6c06-0410-ace0-fbb531ad65f3

frame.c

@@ -1271,3 +1271,25 @@ int ast_frame_adjust_volume(struct ast_frame *f, int adjustment)
 
 	return 0;
 }
+
+int ast_frame_slinear_sum(struct ast_frame *f1, struct ast_frame *f2)
+{
+	int count;
+	short *data1, *data2;
+
+	if ((f1->frametype != AST_FRAME_VOICE) || (f1->subclass != AST_FORMAT_SLINEAR))
+		return -1;
+
+	if ((f2->frametype != AST_FRAME_VOICE) || (f2->subclass != AST_FORMAT_SLINEAR))
+		return -1;
+
+	if (f1->samples != f2->samples)
+		return -1;
+
+	for (count = 0, data1 = f1->data, data2 = f2->data;
+	     count < f1->samples;
+	     count++, data1++, data2++)
+		ast_slinear_saturated_add(data1, *data2);
+
+	return 0;
+}

include/asterisk/frame.h

@@ -427,6 +427,17 @@ static inline int ast_codec_interp_len(int format)
  */
 int ast_frame_adjust_volume(struct ast_frame *f, int adjustment);
 
+/*!
+  \brief Sums two frames of audio samples.
+  \param f1 The first frame (which will contain the result)
+  \param f2 The second frame
+  \return 0 for success, non-zero for an error
+
+  The frames must be AST_FRAME_VOICE and must contain AST_FORMAT_SLINEAR samples,
+  and must contain the same number of samples.
+ */
+int ast_frame_slinear_sum(struct ast_frame *f1, struct ast_frame *f2);
+
 #if defined(__cplusplus) || defined(c_plusplus)
 }
 #endif