From 86f860a7a40e2047fd04500e4d197fca68525962 Mon Sep 17 00:00:00 2001
From: Simon Schubert <simon.schubert@epfl.ch>
Date: Thu, 23 Jul 2009 16:09:15 +0200
Subject: [PATCH] pcm: perform stereo volume mixing for vchans

The vchan code before only performed an average volume mix for both
channels, thus not allowing to pan between left and right vchan channel.
Now we perform actual stereo volume mixing for left and right channel.
---
 sys/dev/sound/pcm/vchan.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/sys/dev/sound/pcm/vchan.c b/sys/dev/sound/pcm/vchan.c
index d484e83388..83e9ee68c2 100644
--- a/sys/dev/sound/pcm/vchan.c
+++ b/sys/dev/sound/pcm/vchan.c
@@ -75,20 +75,21 @@ vchan_mix_s16(int16_t *to, int16_t *tmp, unsigned int count, int volume)
 	/*
 	 * to is the output buffer, tmp is the input buffer
 	 * count is the number of 16bit samples to mix
-	 * volume is in range 0-100
+	 * volume is in range 0-100, (left || (right << 8))
 	 */
 	int i;
 	int x;
-	int scale;
+	int scale[2];
 	int doscale;
 
-	scale = log_mix_cvt[volume];
-	doscale = volume != 100;
+	scale[0] = log_mix_cvt[volume & 0xff];
+	scale[1] = log_mix_cvt[(volume >> 8) & 0xff];
+	doscale = volume != (100 || (100 << 8));
 
 	for(i = 0; i < count; i++) {
 		x = to[i];
 		if (doscale)
-			x += ((int)tmp[i] * scale) >> 16;
+			x += ((int)tmp[i] * scale[i % 2]) >> 16;
 		else
 			x += tmp[i];
 		if (x < -32768) {
@@ -114,7 +115,6 @@ feed_vchan_s16(struct pcm_feeder *f, struct pcm_channel *c, u_int8_t *b, u_int32
 	uint32_t sz;
 	int16_t *tmp, *dst;
 	unsigned int cnt, rcnt = 0;
-	int volume;
 
 	#if 0
 	if (sndbuf_getsize(src) < count)
@@ -145,10 +145,7 @@ feed_vchan_s16(struct pcm_feeder *f, struct pcm_channel *c, u_int8_t *b, u_int32
 			if (ch->flags & CHN_F_MAPPED)
 				sndbuf_acquire(ch->bufsoft, NULL, sndbuf_getfree(ch->bufsoft));
 			cnt = FEEDER_FEED(ch->feeder, ch, (u_int8_t *)tmp, count, ch->bufsoft);
-			volume = ch->volume & 0xff;	/* XXX do special stereo processing? */
-			volume += (ch->volume >> 8) & 0xff;
-			volume >>= 1;
-			vchan_mix_s16(dst, tmp, cnt >> 1, volume);
+			vchan_mix_s16(dst, tmp, cnt >> 1, ch->volume);
 			if (cnt > rcnt)
 				rcnt = cnt;
 		}
-- 
2.11.4.GIT