Module Name: src
Committed By: isaki
Date: Mon Jun 10 13:49:39 UTC 2019
Modified Files:
src/sys/dev/audio: audio.c audiodef.h
Log Message:
Use AUDIO_SCALEDOWN() macro rather than seemingly strange ifdefs.
Discussed on source-changes-d.
To generate a diff of this commit:
cvs rdiff -u -r1.15 -r1.16 src/sys/dev/audio/audio.c
cvs rdiff -u -r1.3 -r1.4 src/sys/dev/audio/audiodef.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/dev/audio/audio.c
diff -u src/sys/dev/audio/audio.c:1.15 src/sys/dev/audio/audio.c:1.16
--- src/sys/dev/audio/audio.c:1.15 Mon Jun 10 13:28:08 2019
+++ src/sys/dev/audio/audio.c Mon Jun 10 13:49:39 2019
@@ -1,4 +1,4 @@
-/* $NetBSD: audio.c,v 1.15 2019/06/10 13:28:08 isaki Exp $ */
+/* $NetBSD: audio.c,v 1.16 2019/06/10 13:49:39 isaki Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -142,7 +142,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: audio.c,v 1.15 2019/06/10 13:28:08 isaki Exp $");
+__KERNEL_RCSID(0, "$NetBSD: audio.c,v 1.16 2019/06/10 13:49:39 isaki Exp $");
#ifdef _KERNEL_OPT
#include "audio.h"
@@ -458,6 +458,28 @@ audio_track_bufstat(audio_track_t *track
#define SPECIFIED(x) ((x) != ~0)
#define SPECIFIED_CH(x) ((x) != (u_char)~0)
+/*
+ * AUDIO_SCALEDOWN()
+ * This macro should be used for audio wave data only.
+ *
+ * The arithmetic shift right (ASR) (in other words, floor()) is good for
+ * this purpose, and will be faster than division on the most platform.
+ * The division (in other words, truncate()) is not so bad alternate for
+ * this purpose, and will be fast enough.
+ * (Using ASR is 1.9 times faster than division on my amd64, and 1.3 times
+ * faster on my m68k. -- isaki 201801.)
+ *
+ * However, the right shift operator ('>>') for negative integer is
+ * "implementation defined" behavior in C (note that it's not "undefined"
+ * behavior). So only if implementation defines '>>' as ASR, we use it.
+ */
+#if defined(__GNUC__)
+/* gcc defines '>>' as ASR. */
+#define AUDIO_SCALEDOWN(value, bits) ((value) >> (bits))
+#else
+#define AUDIO_SCALEDOWN(value, bits) ((value) / (1 << (bits)))
+#endif
+
/* Device timeout in msec */
#define AUDIO_TIMEOUT (3000)
@@ -3200,11 +3222,7 @@ audio_track_chvol(audio_filter_arg_t *ar
for (ch = 0; ch < channels; ch++) {
aint2_t val;
val = *s++;
-#if defined(AUDIO_USE_C_IMPLEMENTATION_DEFINED_BEHAVIOR) && defined(__GNUC__)
- val = val * ch_volume[ch] >> 8;
-#else
- val = val * ch_volume[ch] / 256;
-#endif
+ val = AUDIO_SCALEDOWN(val * ch_volume[ch], 8);
*d++ = (aint_t)val;
}
}
@@ -3226,11 +3244,7 @@ audio_track_chmix_mixLR(audio_filter_arg
d = arg->dst;
for (i = 0; i < arg->count; i++) {
-#if defined(AUDIO_USE_C_IMPLEMENTATION_DEFINED_BEHAVIOR) && defined(__GNUC__)
- *d++ = (s[0] >> 1) + (s[1] >> 1);
-#else
- *d++ = (s[0] / 2) + (s[1] / 2);
-#endif
+ *d++ = AUDIO_SCALEDOWN(s[0], 1) + AUDIO_SCALEDOWN(s[1], 1);
s += arg->srcfmt->channels;
}
}
@@ -5027,11 +5041,7 @@ audio_pmixer_process(struct audio_softc
if (vol != 256) {
m = mixer->mixsample;
for (i = 0; i < sample_count; i++) {
-#if defined(AUDIO_USE_C_IMPLEMENTATION_DEFINED_BEHAVIOR) && defined(__GNUC__)
- *m = *m * vol >> 8;
-#else
- *m = *m * vol / 256;
-#endif
+ *m = AUDIO_SCALEDOWN(*m * vol, 8);
m++;
}
}
@@ -5119,11 +5129,9 @@ audio_pmixer_mix_track(audio_trackmixer_
#if defined(AUDIO_SUPPORT_TRACK_VOLUME)
if (track->volume != 256) {
for (i = 0; i < sample_count; i++) {
-#if defined(AUDIO_USE_C_IMPLEMENTATION_DEFINED_BEHAVIOR) && defined(__GNUC__)
- *d++ = ((aint2_t)*s++) * track->volume >> 8;
-#else
- *d++ = ((aint2_t)*s++) * track->volume / 256;
-#endif
+ aint2_t v;
+ v = *s++;
+ *d++ = AUDIO_SCALEDOWN(v * track->volume, 8)
}
} else
#endif
@@ -5137,11 +5145,9 @@ audio_pmixer_mix_track(audio_trackmixer_
#if defined(AUDIO_SUPPORT_TRACK_VOLUME)
if (track->volume != 256) {
for (i = 0; i < sample_count; i++) {
-#if defined(AUDIO_USE_C_IMPLEMENTATION_DEFINED_BEHAVIOR) && defined(__GNUC__)
- *d++ += ((aint2_t)*s++) * track->volume >> 8;
-#else
- *d++ += ((aint2_t)*s++) * track->volume / 256;
-#endif
+ aint2_t v;
+ v = *s++;
+ *d++ += AUDIO_SCALEDOWN(v * track->volume, 8);
}
} else
#endif
Index: src/sys/dev/audio/audiodef.h
diff -u src/sys/dev/audio/audiodef.h:1.3 src/sys/dev/audio/audiodef.h:1.4
--- src/sys/dev/audio/audiodef.h:1.3 Thu May 23 12:20:27 2019
+++ src/sys/dev/audio/audiodef.h Mon Jun 10 13:49:39 2019
@@ -1,4 +1,4 @@
-/* $NetBSD: audiodef.h,v 1.3 2019/05/23 12:20:27 isaki Exp $ */
+/* $NetBSD: audiodef.h,v 1.4 2019/06/10 13:49:39 isaki Exp $ */
/*
* Copyright (C) 2017 Tetsuya Isaki. All rights reserved.
@@ -63,12 +63,6 @@
*/
/* #define AUDIO_SUPPORT_TRACK_VOLUME */
-/*
- * Whether use C language's "implementation defined" behavior (note that
- * it's not "undefined" behavior). It improves performance well.
- */
-#define AUDIO_USE_C_IMPLEMENTATION_DEFINED_BEHAVIOR
-
/* conversion stage */
typedef struct {
audio_ring_t srcbuf;
