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dmix: add S24_3LE support

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Add to the dmix plugin support for the S24_3LE sample format which is
used by 24-bit USB devices.

The optimized assembler version uses only 23 bits for sample data so
that the lowest bit can be used for synchronization because there is no
24-bit cmpxchg instruction.
This commit is contained in:
Clemens Ladisch 2005-12-19 07:39:03 +00:00
parent 46f81f994b
commit 45f63a8735
8 changed files with 404 additions and 7 deletions
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35
src/pcm/pcm_dmix_generic.c
View file

@ -121,7 +121,8 @@ static void mix_select_callbacks(snd_pcm_direct_t *dmix)
/* non-concurrent version, supporting both endians */
static unsigned long long 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_S16_BE) | (1ULL << SND_PCM_FORMAT_S32_BE) |
(1ULL << SND_PCM_FORMAT_S24_3LE);
#include <byteswap.h>
@ -245,6 +246,37 @@ static void mix_areas2_swap(unsigned int size,
}
}
/* always little endian */
static void mix_areas3(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)
{
register signed int sample;
for (;;) {
sample = src[0] | (src[1] << 8) | (((signed char *)src)[2] << 16);
if (!(dst[0] | dst[1] | dst[2])) {
*sum = sample;
} else {
sample += *sum;
*sum = sample;
if (sample > 0x7fffff)
sample = 0x7fffff;
else if (sample < -0x800000)
sample = -0x800000;
}
dst[0] = sample;
dst[1] = sample >> 8;
dst[2] = sample >> 16;
if (!--size)
return;
dst += dst_step;
src += src_step;
sum = (signed int *) ((char *)sum + sum_step);
}
}
static void mix_select_callbacks(snd_pcm_direct_t *dmix)
{
@ -255,6 +287,7 @@ static void mix_select_callbacks(snd_pcm_direct_t *dmix)
dmix->u.dmix.mix_areas1 = mix_areas1_swap;
dmix->u.dmix.mix_areas2 = mix_areas2_swap;
}
dmix->u.dmix.mix_areas3 = mix_areas3;
}
#endif