From 0d34142f7e1509f2d8c896eb8cec90ed8c745d50 Mon Sep 17 00:00:00 2001
From: "Kevin P. Fleming" <kpfleming@digium.com>
Date: Fri, 28 Oct 2005 16:20:44 +0000
Subject: [PATCH] add API function to perform volume adjustment on a frame of
 SLINEAR data documentation cleanup

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@6874 65c4cc65-6c06-0410-ace0-fbb531ad65f3
---
 frame.c                  | 19 +++++++++++++++++++
 include/asterisk/frame.h | 14 +++++++++++---
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/frame.c b/frame.c
index 5d9ddab118..7b4fa4ddf5 100755
--- a/frame.c
+++ b/frame.c
@@ -1252,3 +1252,22 @@ int ast_codec_get_len(int format, int samples)
 
 	return len;
 }
+
+int ast_frame_adjust_volume(struct ast_frame *f, int adjustment)
+{
+	int count;
+	short *fdata = f->data;
+
+	if ((f->frametype != AST_FRAME_VOICE) || (f->subclass != AST_FORMAT_SLINEAR))
+		return -1;
+
+	for (count = 0; count < f->samples; count++) {
+		if (adjustment > 0) {
+			fdata[count] *= abs(adjustment);
+		} else if (adjustment < 0) {
+			fdata[count] /= abs(adjustment);
+		}
+	}
+
+	return 0;
+}
diff --git a/include/asterisk/frame.h b/include/asterisk/frame.h
index 48a2bbebb0..c17e2eecbe 100755
--- a/include/asterisk/frame.h
+++ b/include/asterisk/frame.h
@@ -49,7 +49,7 @@ struct ast_frame {
 	int samples;				
 	/*! Was the data malloc'd?  i.e. should we free it when we discard the frame? */
 	int mallocd;				
-	/*! How far into "data" the data really starts */
+	/*! How many bytes exist _before_ "data" that can be used if needed */
 	int offset;				
 	/*! Optional source of frame for debugging */
 	const char *src;				
@@ -64,8 +64,8 @@ struct ast_frame {
 };
 
 #define AST_FRIENDLY_OFFSET 	64		/*! It's polite for a a new frame to
-						    				have this number of bytes for additional
-											headers.  */
+						  have this number of bytes for additional
+						  headers.  */
 #define AST_MIN_OFFSET 		32		/*! Make sure we keep at least this much handy */
 
 /*! Need the header be free'd? */
@@ -419,6 +419,14 @@ static inline int ast_codec_interp_len(int format)
 	return (format == AST_FORMAT_ILBC) ? 30 : 20;
 }
 
+/*!
+  \brief Adjusts the volume of the audio samples contained in a frame.
+  \param f The frame containing the samples (must be AST_FRAME_VOICE and AST_FORMAT_SLINEAR)
+  \param adjustment The number of dB to adjust up or down.
+  \return 0 for success, non-zero for an error
+ */
+int ast_frame_adjust_volume(struct ast_frame *f, int adjustment);
+
 #if defined(__cplusplus) || defined(c_plusplus)
 }
 #endif