From f471b4cfc5e4ad42e34f79daa81a2de217134517 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@duempel.org>
Date: Sun, 28 Sep 2008 18:35:42 +0200
Subject: pcm_utils: added inline function pcm_dither()

Merge some code into an inline function, so we can optimize it later
only once.
---
 src/pcm_utils.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

(limited to 'src')

diff --git a/src/pcm_utils.c b/src/pcm_utils.c
index 90856fa1d..3eb24d882 100644
--- a/src/pcm_utils.c
+++ b/src/pcm_utils.c
@@ -24,6 +24,12 @@
 #include "conf.h"
 #include "os_compat.h"
 
+static inline int
+pcm_dither(void)
+{
+	return (rand() & 511) - (rand() & 511);
+}
+
 void pcm_volumeChange(char *buffer, int bufferSize, const AudioFormat * format,
                       int volume)
 {
@@ -44,8 +50,7 @@ void pcm_volumeChange(char *buffer, int bufferSize, const AudioFormat * format,
 		while (bufferSize > 0) {
 			temp32 = *buffer16;
 			temp32 *= volume;
-			temp32 += rand() & 511;
-			temp32 -= rand() & 511;
+			temp32 += pcm_dither();
 			temp32 += 500;
 			temp32 /= 1000;
 			*buffer16 = temp32 > 32767 ? 32767 :
@@ -58,8 +63,7 @@ void pcm_volumeChange(char *buffer, int bufferSize, const AudioFormat * format,
 		while (bufferSize > 0) {
 			temp32 = *buffer8;
 			temp32 *= volume;
-			temp32 += rand() & 511;
-			temp32 -= rand() & 511;
+			temp32 += pcm_dither();
 			temp32 += 500;
 			temp32 /= 1000;
 			*buffer8 = temp32 > 127 ? 127 :
@@ -90,8 +94,7 @@ static void pcm_add(char *buffer1, const char *buffer2, size_t bufferSize1,
 			temp32 =
 			    (vol1 * (*buffer16_1) +
 			     vol2 * (*buffer16_2));
-			temp32 += rand() & 511;
-			temp32 -= rand() & 511;
+			temp32 += pcm_dither();
 			temp32 += 500;
 			temp32 /= 1000;
 			*buffer16_1 =
@@ -109,8 +112,7 @@ static void pcm_add(char *buffer1, const char *buffer2, size_t bufferSize1,
 		while (bufferSize1 > 0 && bufferSize2 > 0) {
 			temp32 =
 			    (vol1 * (*buffer8_1) + vol2 * (*buffer8_2));
-			temp32 += rand() & 511;
-			temp32 -= rand() & 511;
+			temp32 += pcm_dither();
 			temp32 += 500;
 			temp32 /= 1000;
 			*buffer8_1 =
-- 
cgit v1.2.3


From 33df4c65594384c32f91f0445d80fb2453d5ff7a Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@duempel.org>
Date: Sun, 28 Sep 2008 18:37:43 +0200
Subject: pcm_utils: added pcm_range()

Make the code more readable by moving the range checks to pcm_range().
gcc does quite a good job at optimizing it: the resulting binary is
exactly the same, although it contains a parametrized shift instead of
hard-coded boundaries.
---
 src/pcm_utils.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

(limited to 'src')

diff --git a/src/pcm_utils.c b/src/pcm_utils.c
index 3eb24d882..077010062 100644
--- a/src/pcm_utils.c
+++ b/src/pcm_utils.c
@@ -30,6 +30,20 @@ pcm_dither(void)
 	return (rand() & 511) - (rand() & 511);
 }
 
+/**
+ * Check if the value is within the range of the provided bit size,
+ * and caps it if necessary.
+ */
+static mpd_sint32
+pcm_range(mpd_sint32 sample, unsigned bits)
+{
+	if (mpd_unlikely(sample < (-1 << (bits - 1))))
+		return -1 << (bits - 1);
+	if (mpd_unlikely(sample >= (1 << (bits - 1))))
+		return (1 << (bits - 1)) - 1;
+	return sample;
+}
+
 void pcm_volumeChange(char *buffer, int bufferSize, const AudioFormat * format,
                       int volume)
 {
@@ -53,8 +67,7 @@ void pcm_volumeChange(char *buffer, int bufferSize, const AudioFormat * format,
 			temp32 += pcm_dither();
 			temp32 += 500;
 			temp32 /= 1000;
-			*buffer16 = temp32 > 32767 ? 32767 :
-			    (temp32 < -32768 ? -32768 : temp32);
+			*buffer16 = pcm_range(temp32, 16);
 			buffer16++;
 			bufferSize -= 2;
 		}
@@ -66,8 +79,7 @@ void pcm_volumeChange(char *buffer, int bufferSize, const AudioFormat * format,
 			temp32 += pcm_dither();
 			temp32 += 500;
 			temp32 /= 1000;
-			*buffer8 = temp32 > 127 ? 127 :
-			    (temp32 < -128 ? -128 : temp32);
+			*buffer8 = pcm_range(temp32, 8);
 			buffer8++;
 			bufferSize--;
 		}
@@ -97,9 +109,7 @@ static void pcm_add(char *buffer1, const char *buffer2, size_t bufferSize1,
 			temp32 += pcm_dither();
 			temp32 += 500;
 			temp32 /= 1000;
-			*buffer16_1 =
-			    temp32 > 32767 ? 32767 : (temp32 <
-						      -32768 ? -32768 : temp32);
+			*buffer16_1 = pcm_range(temp32, 16);
 			buffer16_1++;
 			buffer16_2++;
 			bufferSize1 -= 2;
@@ -115,9 +125,7 @@ static void pcm_add(char *buffer1, const char *buffer2, size_t bufferSize1,
 			temp32 += pcm_dither();
 			temp32 += 500;
 			temp32 /= 1000;
-			*buffer8_1 =
-			    temp32 > 127 ? 127 : (temp32 <
-						  -128 ? -128 : temp32);
+			*buffer8_1 = pcm_range(temp32, 8);
 			buffer8_1++;
 			buffer8_2++;
 			bufferSize1--;
-- 
cgit v1.2.3