pcm_volume: implemented 32 bit support

Support 32 bit samples with software mixer.

NEWS

@@ -71,6 +71,7 @@ ver 0.16 (20??/??/??)
 * database: eliminated maximum line length
 * log: redirect stdout/stderr to /dev/null if syslog is used
 * set the close-on-exec flag on all file descriptors
+* pcm_volume: implemented 32 bit support
 * obey $(sysconfdir) for default mpd.conf location
 * build with large file support by default
 * require GLib 2.12

src/pcm_utils.h

@@ -38,4 +38,18 @@ pcm_range(int32_t sample, unsigned bits)
 	return sample;
 }
 
+/**
+ * Check if the value is within the range of the provided bit size,
+ * and caps it if necessary.
+ */
+static inline int64_t
+pcm_range_64(int64_t sample, unsigned bits)
+{
+	if (G_UNLIKELY(sample < ((int64_t)-1 << (bits - 1))))
+		return (int64_t)-1 << (bits - 1);
+	if (G_UNLIKELY(sample >= ((int64_t)1 << (bits - 1))))
+		return ((int64_t)1 << (bits - 1)) - 1;
+	return sample;
+}
+
 #endif

src/pcm_volume.c

@@ -114,6 +114,29 @@ pcm_volume_change_24(int32_t *buffer, unsigned num_samples, int volume)
 	}
 }
 
+static void
+pcm_volume_change_32(int32_t *buffer, unsigned num_samples, int volume)
+{
+	while (num_samples > 0) {
+#ifdef __i386__
+		/* assembly version for i386 */
+		int32_t sample = *buffer;
+
+		*buffer++ = pcm_volume_sample_24(sample, volume, 0);
+#else
+		/* portable version */
+		int64_t sample = *buffer;
+
+		sample = (sample * volume + pcm_volume_dither() +
+			  PCM_VOLUME_1 / 2)
+			/ PCM_VOLUME_1;
+		*buffer++ = pcm_range_64(sample, 32);
+#endif
+
+		--num_samples;
+	}
+}
+
 bool
 pcm_volume(void *buffer, int length,
 	   const struct audio_format *format,
@@ -142,6 +165,11 @@ pcm_volume(void *buffer, int length,
 				     volume);
 		return true;
 
+	case 32:
+		pcm_volume_change_32((int32_t*)buffer, length / 4,
+				     volume);
+		return true;
+
 	default:
 		return false;
 	}