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dmix: add U8 support

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Add support for direct mixing of U8 samples (for devices like some USB
headsets or the Tux Droid).
This commit is contained in:
Clemens Ladisch 2007-12-10 12:35:08 +01:00
parent a3fe1f7800
commit 6e6f4b9c93
4 changed files with 43 additions and 1 deletions
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33
src/pcm/pcm_dmix_generic.c
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@ -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