From 6e6f4b9c9347277dce66c342f1eceb2fbab558e2 Mon Sep 17 00:00:00 2001
From: Clemens Ladisch <clemens@ladisch.de>
Date: Mon, 10 Dec 2007 12:35:08 +0100
Subject: [PATCH] dmix: add U8 support

Add support for direct mixing of U8 samples (for devices like some USB
headsets or the Tux Droid).
---
 src/pcm/pcm_direct.c       |  1 +
 src/pcm/pcm_direct.h       |  6 ++++++
 src/pcm/pcm_dmix.c         |  4 ++++
 src/pcm/pcm_dmix_generic.c | 33 ++++++++++++++++++++++++++++++++-
 4 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/src/pcm/pcm_direct.c b/src/pcm/pcm_direct.c
index 64003a0d..3f908e26 100644
--- a/src/pcm/pcm_direct.c
+++ b/src/pcm/pcm_direct.c
@@ -885,6 +885,7 @@ int snd_pcm_direct_initialize_slave(snd_pcm_direct_t *dmix, snd_pcm_t *spcm, str
 			SND_PCM_FORMAT_S16,
 			SND_PCM_FORMAT_S16 ^ SND_PCM_FORMAT_S16_LE ^ SND_PCM_FORMAT_S16_BE,
 			SND_PCM_FORMAT_S24_3LE,
+			SND_PCM_FORMAT_U8,
 		};
 		snd_pcm_format_t format;
 		unsigned int i;
diff --git a/src/pcm/pcm_direct.h b/src/pcm/pcm_direct.h
index a96fb4e6..b51ca851 100644
--- a/src/pcm/pcm_direct.h
+++ b/src/pcm/pcm_direct.h
@@ -44,6 +44,11 @@ typedef void (mix_areas_24_t)(unsigned int size,
 			      volatile signed int *sum, size_t dst_step,
 			      size_t src_step, size_t sum_step);
 
+typedef void (mix_areas_u8_t)(unsigned int size,
+			      volatile unsigned char *dst, unsigned char *src,
+			      volatile signed int *sum, size_t dst_step,
+			      size_t src_step, size_t sum_step);
+
 struct slave_params {
 	snd_pcm_format_t format;
 	int rate;
@@ -156,6 +161,7 @@ struct snd_pcm_direct {
 			mix_areas_16_t *mix_areas_16;
 			mix_areas_32_t *mix_areas_32;
 			mix_areas_24_t *mix_areas_24;
+			mix_areas_u8_t *mix_areas_u8;
 		} dmix;
 		struct {
 		} dsnoop;
diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c
index b2c200d5..b9fb1c7a 100644
--- a/src/pcm/pcm_dmix.c
+++ b/src/pcm/pcm_dmix.c
@@ -176,6 +176,10 @@ static void mix_areas(snd_pcm_direct_t *dmix,
 		sample_size = 3;
 		do_mix_areas = (mix_areas_t *)dmix->u.dmix.mix_areas_24;
 		break;
+	case SND_PCM_FORMAT_U8:
+		sample_size = 1;
+		do_mix_areas = (mix_areas_t *)dmix->u.dmix.mix_areas_u8;
+		break;
 	default:
 		return;
 	}
diff --git a/src/pcm/pcm_dmix_generic.c b/src/pcm/pcm_dmix_generic.c
index 492f5f7d..9bef18d6 100644
--- a/src/pcm/pcm_dmix_generic.c
+++ b/src/pcm/pcm_dmix_generic.c
@@ -122,7 +122,8 @@ static void mix_select_callbacks(snd_pcm_direct_t *dmix)
 #define generic_dmix_supported_format \
 	((1ULL << SND_PCM_FORMAT_S16_LE) | (1ULL << SND_PCM_FORMAT_S32_LE) |\
 	 (1ULL << SND_PCM_FORMAT_S16_BE) | (1ULL << SND_PCM_FORMAT_S32_BE) |\
-	 (1ULL << SND_PCM_FORMAT_S24_3LE))
+	 (1ULL << SND_PCM_FORMAT_S24_3LE) | \
+	 (1ULL << SND_PCM_FORMAT_U8))
 
 #include <byteswap.h>
 
@@ -292,6 +293,35 @@ static void generic_mix_areas_24(unsigned int size,
 	}
 }
 
+static void generic_mix_areas_u8(unsigned int size,
+				 volatile unsigned char *dst,
+				 unsigned char *src,
+				 volatile signed int *sum,
+				 size_t dst_step,
+				 size_t src_step,
+				 size_t sum_step)
+{
+	for (;;) {
+		register int sample = *src - 0x80;
+		if (*dst == 0x80) {
+			*sum = sample;
+		} else {
+			sample += *sum;
+			*sum = sample;
+			if (sample > 0x7f)
+				sample = 0x7f;
+			else if (sample < -0x80)
+				sample = -0x80;
+		}
+		*dst = sample + 0x80;
+		if (!--size)
+			return;
+		dst += dst_step;
+		src += src_step;
+		sum = (signed int *) ((char *)sum + sum_step);
+	}
+}
+
 
 static void generic_mix_select_callbacks(snd_pcm_direct_t *dmix)
 {
@@ -303,6 +333,7 @@ static void generic_mix_select_callbacks(snd_pcm_direct_t *dmix)
 		dmix->u.dmix.mix_areas_32 = generic_mix_areas_32_swap;
 	}
 	dmix->u.dmix.mix_areas_24 = generic_mix_areas_24;
+	dmix->u.dmix.mix_areas_u8 = generic_mix_areas_u8;
 }
 
 #endif
-- 
2.47.1