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pcm_dither: added generic 24 to 16 bit dithering

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Copied and adapted code from the mp3 decoder plugin.  This library now
replaces the old and low-quality function pcm_convert_24_to_16().
This commit is contained in:
Max Kellermann
2008-10-23 16:58:07 +02:00
parent 80603cf6f1
commit 0078837a97
5 changed files with 139 additions and 8 deletions
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18
src/pcm_utils.c
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@@ -208,6 +208,8 @@ void pcm_mix(char *buffer1, const char *buffer2, size_t size,
void pcm_convert_init(struct pcm_convert_state *state)
{
memset(state, 0, sizeof(*state));
pcm_dither_24_init(&state->dither);
}
#ifdef HAVE_LIBSAMPLERATE
@@ -457,17 +459,16 @@ pcm_convert_8_to_16(int16_t *out, const int8_t *in,
}
static void
pcm_convert_24_to_16(int16_t *out, const int32_t *in,
pcm_convert_24_to_16(struct pcm_dither_24 *dither,
int16_t *out, const int32_t *in,
unsigned num_samples)
{
while (num_samples > 0) {
*out++ = *in++ >> 8;
--num_samples;
}
pcm_dither_24_to_16(dither, out, in, num_samples);
}
static const int16_t *
pcm_convert_to_16(uint8_t bits, const void *src,
pcm_convert_to_16(struct pcm_convert_state *convert,
uint8_t bits, const void *src,
size_t src_size, size_t *dest_size_r)
{
static int16_t *buf;
@@ -500,7 +501,8 @@ pcm_convert_to_16(uint8_t bits, const void *src,
buf = xrealloc(buf, len);
}
pcm_convert_24_to_16((int16_t *)buf,
pcm_convert_24_to_16(&convert->dither,
(int16_t *)buf,
(const int32_t *)src,
num_samples);
return buf;
@@ -524,7 +526,7 @@ size_t pcm_convert(const struct audio_format *inFormat,
assert(outFormat->bits == 16);
/* everything else supports 16 bit only, so convert to that first */
buf = pcm_convert_to_16(inFormat->bits, src, src_size, &len);
buf = pcm_convert_to_16(convState, inFormat->bits, src, src_size, &len);
if (!buf)
exit(EXIT_FAILURE);