pcm_volume: added constant PCM_VOLUME_1

It may be desirable to change the range of integer volume levels
(e.g. to 1024, which may utilize shifts instead of expensive integer
divisions).  Introduce the constant PCM_VOLUME_1 which describes the
integer value for "100% volume".  This is currently 1000.

4 files changed, 27 insertions, 14 deletions

diff --git a/src/pcm_utils.c b/src/pcm_utils.c
index c06c7e1ab..a68542f4a 100644
--- a/src/pcm_utils.c
+++ b/src/pcm_utils.c
@@ -53,7 +53,8 @@ pcm_volume_change_8(int8_t *buffer, unsigned num_samples, int volume)
 	while (num_samples > 0) {
 		int32_t sample = *buffer;
 
-		sample = (sample * volume + pcm_dither() + 500) / 1000;
+		sample = (sample * volume + pcm_dither() + PCM_VOLUME_1 / 2)
+			/ PCM_VOLUME_1;
 
 		*buffer++ = pcm_range(sample, 8);
 		--num_samples;
@@ -66,7 +67,8 @@ pcm_volume_change_16(int16_t *buffer, unsigned num_samples, int volume)
 	while (num_samples > 0) {
 		int32_t sample = *buffer;
 
-		sample = (sample * volume + pcm_dither() + 500) / 1000;
+		sample = (sample * volume + pcm_dither() + PCM_VOLUME_1 / 2)
+			/ PCM_VOLUME_1;
 
 		*buffer++ = pcm_range(sample, 16);
 		--num_samples;
@@ -79,7 +81,8 @@ pcm_volume_change_24(int32_t *buffer, unsigned num_samples, int volume)
 	while (num_samples > 0) {
 		int64_t sample = *buffer;
 
-		sample = (sample * volume + pcm_dither() + 500) / 1000;
+		sample = (sample * volume + pcm_dither() + PCM_VOLUME_1 / 2)
+			/ PCM_VOLUME_1;
 
 		*buffer++ = pcm_range(sample, 24);
 		--num_samples;
@@ -90,7 +93,7 @@ void pcm_volume(char *buffer, int bufferSize,
 		const struct audio_format *format,
 		int volume)
 {
-	if (volume >= 1000)
+	if (volume >= PCM_VOLUME_1)
 		return;
 
 	if (volume <= 0) {
@@ -128,7 +131,7 @@ pcm_add_8(int8_t *buffer1, const int8_t *buffer2,
 		int32_t sample2 = *buffer2++;
 
 		sample1 = ((sample1 * volume1 + sample2 * volume2) +
-			   pcm_dither() + 500) / 1000;
+			   pcm_dither() + PCM_VOLUME_1 / 2) / PCM_VOLUME_1;
 
 		*buffer1++ = pcm_range(sample1, 8);
 		--num_samples;
@@ -144,7 +147,7 @@ pcm_add_16(int16_t *buffer1, const int16_t *buffer2,
 		int32_t sample2 = *buffer2++;
 
 		sample1 = ((sample1 * volume1 + sample2 * volume2) +
-			   pcm_dither() + 500) / 1000;
+			   pcm_dither() + PCM_VOLUME_1 / 2) / PCM_VOLUME_1;
 
 		*buffer1++ = pcm_range(sample1, 16);
 		--num_samples;
@@ -160,7 +163,7 @@ pcm_add_24(int32_t *buffer1, const int32_t *buffer2,
 		int64_t sample2 = *buffer2++;
 
 		sample1 = ((sample1 * volume1 + sample2 * volume2) +
-			   pcm_dither() + 500) / 1000;
+			   pcm_dither() + PCM_VOLUME_1 / 2) / PCM_VOLUME_1;
 
 		*buffer1++ = pcm_range(sample1, 24);
 		--num_samples;
@@ -200,10 +203,10 @@ void pcm_mix(char *buffer1, const char *buffer2, size_t size,
 	float s = sin(M_PI_2 * portion1);
 	s *= s;
 
-	vol1 = s * 1000 + 0.5;
-	vol1 = vol1 > 1000 ? 1000 : (vol1 < 0 ? 0 : vol1);
+	vol1 = s * PCM_VOLUME_1 + 0.5;
+	vol1 = vol1 > PCM_VOLUME_1 ? PCM_VOLUME_1 : (vol1 < 0 ? 0 : vol1);
 
-	pcm_add(buffer1, buffer2, size, vol1, 1000 - vol1, format);
+	pcm_add(buffer1, buffer2, size, vol1, PCM_VOLUME_1 - vol1, format);
 }
 
 void pcm_convert_init(struct pcm_convert_state *state)
diff --git a/src/pcm_utils.h b/src/pcm_utils.h
index 069fb9f53..71398c015 100644
--- a/src/pcm_utils.h
+++ b/src/pcm_utils.h
@@ -27,6 +27,11 @@
 
 struct audio_format;
 
+enum {
+	/** this value means "100% volume" */
+	PCM_VOLUME_1 = 1000,
+};
+
 struct pcm_convert_state {
 	struct pcm_resample_state resample;
 
@@ -43,7 +48,7 @@ struct pcm_convert_state {
 static inline int
 pcm_float_to_volume(float volume)
 {
-	return volume * 1000.0 + 0.5;
+	return volume * PCM_VOLUME_1 + 0.5;
 }
 
 void pcm_volume(char *buffer, int bufferSize,
diff --git a/src/player_control.c b/src/player_control.c
index f65ba7c08..1d5c76aa0 100644
--- a/src/player_control.c
+++ b/src/player_control.c
@@ -22,6 +22,7 @@
 #include "tag.h"
 #include "song.h"
 #include "idle.h"
+#include "pcm_utils.h"
 #include "os_compat.h"
 #include "main_notify.h"
 
@@ -35,7 +36,7 @@ void pc_init(unsigned int buffered_before_play)
 	pc.error = PLAYER_ERROR_NOERROR;
 	pc.state = PLAYER_STATE_STOP;
 	pc.cross_fade_seconds = 0;
-	pc.software_volume = 1000;
+	pc.software_volume = PCM_VOLUME_1;
 }
 
 void pc_deinit(void)
@@ -220,7 +221,11 @@ void setPlayerCrossFade(float crossFadeInSeconds)
 
 void setPlayerSoftwareVolume(int volume)
 {
-	volume = (volume > 1000) ? 1000 : (volume < 0 ? 0 : volume);
+	if (volume > PCM_VOLUME_1)
+		volume = PCM_VOLUME_1;
+	else if (volume < 0)
+		volume = 0;
+
 	pc.software_volume = volume;
 }
 
diff --git a/src/volume.c b/src/volume.c
index 8d497ed44..4b619f916 100644
--- a/src/volume.c
+++ b/src/volume.c
@@ -480,7 +480,7 @@ static int changeSoftwareVolume(int change, int rel)
 
 	/*new = 100.0*(exp(new/50.0)-1)/(M_E*M_E-1)+0.5; */
 	if (new >= 100)
-		new = 1000;
+		new = PCM_VOLUME_1;
 	else if (new <= 0)
 		new = 0;
 	else