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implemented 'Int24_To_Int16_Dither' converter to allow 24-bit audio be played (before was silence for WMME and DirectSound)

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dmitrykos 2010-04-16 19:08:00 +00:00
commit bd2bfe985e
1 changed files with 31 additions and 7 deletions
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38
src/common/pa_converters.c
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@ -1163,15 +1163,39 @@ static void Int24_To_Int16_Dither(
void *sourceBuffer, signed int sourceStride,
unsigned int count, struct PaUtilTriangularDitherGenerator *ditherGenerator )
{
(void) destinationBuffer; /* unused parameters */
(void) destinationStride; /* unused parameters */
(void) sourceBuffer; /* unused parameters */
(void) sourceStride; /* unused parameters */
(void) count; /* unused parameters */
(void) ditherGenerator; /* unused parameters */
/* IMPLEMENT ME */
#define _PA_CNV_RESCALE(__max_from,__max_to,g) ((1.0f/(float)(__max_from/2+1))*((float)((__max_to/2+1)+g)))
#ifndef PA_BIG_ENDIAN
#define _PA_INT24_TO_INT32(v) ((int)(((int)v[2] << 24)|((int)v[1] << 16)|((int)v[0] << 8)) >> 8)
#else
#define _PA_INT24_TO_INT32(v) ((int)(((int)v[0] << 24)|((int)v[1] << 16)|((int)v[2] << 8)) >> 8)
#endif
#define _PA_INT24_TO_FLOAT(v,g) ((float)(_PA_INT24_TO_INT32(v)) * _PA_CNV_RESCALE(0xffffff,0xffff,g))
unsigned char *src = (unsigned char *)sourceBuffer;
PaInt16 *dest = (PaInt16 *)destinationBuffer;
float dither, dithered;
while( count-- )
{
dither = PaUtil_GenerateFloatTriangularDither( ditherGenerator );
/* upscale 24-bit int to 16-bit float, decrease scaler by 2 to leave space for dither
in order to not overflow
*/
dithered = _PA_INT24_TO_FLOAT(src, -2.0f) + dither;
#ifdef PA_USE_C99_LRINTF
*dest = lrintf(dithered-0.5f);
#else
*dest = (PaInt16) dithered;
#endif
src += sourceStride * 3;
dest += destinationStride;
}
}
/* -------------------------------------------------------------------------- */
static void Int24_To_Int8(