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-rw-r--r--src/pcm_utils.c46
1 files changed, 28 insertions, 18 deletions
diff --git a/src/pcm_utils.c b/src/pcm_utils.c
index 90856fa1d..077010062 100644
--- a/src/pcm_utils.c
+++ b/src/pcm_utils.c
@@ -24,6 +24,26 @@
#include "conf.h"
#include "os_compat.h"
+static inline int
+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)
{
@@ -44,12 +64,10 @@ 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 :
- (temp32 < -32768 ? -32768 : temp32);
+ *buffer16 = pcm_range(temp32, 16);
buffer16++;
bufferSize -= 2;
}
@@ -58,12 +76,10 @@ 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 :
- (temp32 < -128 ? -128 : temp32);
+ *buffer8 = pcm_range(temp32, 8);
buffer8++;
bufferSize--;
}
@@ -90,13 +106,10 @@ 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 =
- temp32 > 32767 ? 32767 : (temp32 <
- -32768 ? -32768 : temp32);
+ *buffer16_1 = pcm_range(temp32, 16);
buffer16_1++;
buffer16_2++;
bufferSize1 -= 2;
@@ -109,13 +122,10 @@ 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 =
- temp32 > 127 ? 127 : (temp32 <
- -128 ? -128 : temp32);
+ *buffer8_1 = pcm_range(temp32, 8);
buffer8_1++;
buffer8_2++;
bufferSize1--;