sdl_audiocvt.c

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						dst[1] = (lf&0xFF);
						dst[0] = ((lf>>8)&0xFF);
						dst[3] = (rf&0xFF);
						dst[2] = ((rf>>8)&0xFF);

						dst[1+4] = (lr&0xFF);
						dst[0+4] = ((lr>>8)&0xFF);
						dst[3+4] = (rr&0xFF);
						dst[2+4] = ((rr>>8)&0xFF);

						dst[1+8] = (ce&0xFF);
						dst[0+8] = ((ce>>8)&0xFF);
						dst[3+8] = (ce&0xFF);
						dst[2+8] = ((ce>>8)&0xFF);
				}
			} else {
				for ( i=cvt->len_cvt/4; i; --i ) {
					dst -= 12;
					src -= 4;
					lf = (Uint16)((src[1]<<8)|src[0]);
					rf = (Uint16)((src[3]<<8)|src[2]);
					ce = (lf/2) + (rf/2);
					rr = lf - ce;
					lr = rf - ce;
						dst[0] = (lf&0xFF);
						dst[1] = ((lf>>8)&0xFF);
						dst[2] = (rf&0xFF);
						dst[3] = ((rf>>8)&0xFF);

						dst[0+4] = (lr&0xFF);
						dst[1+4] = ((lr>>8)&0xFF);
						dst[2+4] = (rr&0xFF);
						dst[3+4] = ((rr>>8)&0xFF);

						dst[0+8] = (ce&0xFF);
						dst[1+8] = ((ce>>8)&0xFF);
						dst[2+8] = (ce&0xFF);
						dst[3+8] = ((ce>>8)&0xFF);
				}
			}
		}
		break;

		case AUDIO_S16: {
			Uint8 *src, *dst;
			Sint16 lf, rf, ce, lr, rr;

			src = cvt->buf+cvt->len_cvt;
			dst = cvt->buf+cvt->len_cvt*3;

			if ( (format & 0x1000) == 0x1000 ) {
				for ( i=cvt->len_cvt/4; i; --i ) {
					dst -= 12;
					src -= 4;
					lf = (Sint16)((src[0]<<8)|src[1]);
					rf = (Sint16)((src[2]<<8)|src[3]);
					ce = (lf/2) + (rf/2);
					rr = lf - ce;
					lr = rf - ce;
						dst[1] = (lf&0xFF);
						dst[0] = ((lf>>8)&0xFF);
						dst[3] = (rf&0xFF);
						dst[2] = ((rf>>8)&0xFF);

						dst[1+4] = (lr&0xFF);
						dst[0+4] = ((lr>>8)&0xFF);
						dst[3+4] = (rr&0xFF);
						dst[2+4] = ((rr>>8)&0xFF);

						dst[1+8] = (ce&0xFF);
						dst[0+8] = ((ce>>8)&0xFF);
						dst[3+8] = (ce&0xFF);
						dst[2+8] = ((ce>>8)&0xFF);
				}
			} else {
				for ( i=cvt->len_cvt/4; i; --i ) {
					dst -= 12;
					src -= 4;
					lf = (Sint16)((src[1]<<8)|src[0]);
					rf = (Sint16)((src[3]<<8)|src[2]);
					ce = (lf/2) + (rf/2);
					rr = lf - ce;
					lr = rf - ce;
						dst[0] = (lf&0xFF);
						dst[1] = ((lf>>8)&0xFF);
						dst[2] = (rf&0xFF);
						dst[3] = ((rf>>8)&0xFF);

						dst[0+4] = (lr&0xFF);
						dst[1+4] = ((lr>>8)&0xFF);
						dst[2+4] = (rr&0xFF);
						dst[3+4] = ((rr>>8)&0xFF);

						dst[0+8] = (ce&0xFF);
						dst[1+8] = ((ce>>8)&0xFF);
						dst[2+8] = (ce&0xFF);
						dst[3+8] = ((ce>>8)&0xFF);
				}
			}
		}
		break;
	}
	cvt->len_cvt *= 3;
	if ( cvt->filters[++cvt->filter_index] ) {
		cvt->filters[cvt->filter_index](cvt, format);
	}
}


/* Duplicate a stereo channel to a pseudo-4.0 stream */
void SDL_ConvertSurround_4(SDL_AudioCVT *cvt, Uint16 format)
{
	int i;

#ifdef DEBUG_CONVERT
	fprintf(stderr, "Converting stereo to quad\n");
#endif
	switch (format&0x8018) {

		case AUDIO_U8: {
			Uint8 *src, *dst, lf, rf, ce;

			src = (Uint8 *)(cvt->buf+cvt->len_cvt);
			dst = (Uint8 *)(cvt->buf+cvt->len_cvt*2);
			for ( i=cvt->len_cvt; i; --i ) {
				dst -= 4;
				src -= 2;
				lf = src[0];
				rf = src[1];
				ce = (lf/2) + (rf/2);
				dst[0] = lf;
				dst[1] = rf;
				dst[2] = lf - ce;
				dst[3] = rf - ce;
			}
		}
		break;

		case AUDIO_S8: {
			Sint8 *src, *dst, lf, rf, ce;

			src = cvt->buf+cvt->len_cvt;
			dst = cvt->buf+cvt->len_cvt*2;
			for ( i=cvt->len_cvt; i; --i ) {
				dst -= 4;
				src -= 2;
				lf = src[0];
				rf = src[1];
				ce = (lf/2) + (rf/2);
				dst[0] = lf;
				dst[1] = rf;
				dst[2] = lf - ce;
				dst[3] = rf - ce;
			}
		}
		break;

		case AUDIO_U16: {
			Uint8 *src, *dst;
			Uint16 lf, rf, ce, lr, rr;

			src = cvt->buf+cvt->len_cvt;
			dst = cvt->buf+cvt->len_cvt*2;

			if ( (format & 0x1000) == 0x1000 ) {
				for ( i=cvt->len_cvt/4; i; --i ) {
					dst -= 8;
					src -= 4;
					lf = (Uint16)((src[0]<<8)|src[1]);
					rf = (Uint16)((src[2]<<8)|src[3]);
					ce = (lf/2) + (rf/2);
					rr = lf - ce;
					lr = rf - ce;
						dst[1] = (lf&0xFF);
						dst[0] = ((lf>>8)&0xFF);
						dst[3] = (rf&0xFF);
						dst[2] = ((rf>>8)&0xFF);

						dst[1+4] = (lr&0xFF);
						dst[0+4] = ((lr>>8)&0xFF);
						dst[3+4] = (rr&0xFF);
						dst[2+4] = ((rr>>8)&0xFF);
				}
			} else {
				for ( i=cvt->len_cvt/4; i; --i ) {
					dst -= 8;
					src -= 4;
					lf = (Uint16)((src[1]<<8)|src[0]);
					rf = (Uint16)((src[3]<<8)|src[2]);
					ce = (lf/2) + (rf/2);
					rr = lf - ce;
					lr = rf - ce;
						dst[0] = (lf&0xFF);
						dst[1] = ((lf>>8)&0xFF);
						dst[2] = (rf&0xFF);
						dst[3] = ((rf>>8)&0xFF);

						dst[0+4] = (lr&0xFF);
						dst[1+4] = ((lr>>8)&0xFF);
						dst[2+4] = (rr&0xFF);
						dst[3+4] = ((rr>>8)&0xFF);
				}
			}
		}
		break;

		case AUDIO_S16: {
			Uint8 *src, *dst;
			Sint16 lf, rf, ce, lr, rr;

			src = cvt->buf+cvt->len_cvt;
			dst = cvt->buf+cvt->len_cvt*2;

			if ( (format & 0x1000) == 0x1000 ) {
				for ( i=cvt->len_cvt/4; i; --i ) {
					dst -= 8;
					src -= 4;
					lf = (Sint16)((src[0]<<8)|src[1]);
					rf = (Sint16)((src[2]<<8)|src[3]);
					ce = (lf/2) + (rf/2);
					rr = lf - ce;
					lr = rf - ce;
						dst[1] = (lf&0xFF);
						dst[0] = ((lf>>8)&0xFF);
						dst[3] = (rf&0xFF);
						dst[2] = ((rf>>8)&0xFF);

						dst[1+4] = (lr&0xFF);
						dst[0+4] = ((lr>>8)&0xFF);
						dst[3+4] = (rr&0xFF);
						dst[2+4] = ((rr>>8)&0xFF);
				}
			} else {
				for ( i=cvt->len_cvt/4; i; --i ) {
					dst -= 8;
					src -= 4;
					lf = (Sint16)((src[1]<<8)|src[0]);
					rf = (Sint16)((src[3]<<8)|src[2]);
					ce = (lf/2) + (rf/2);
					rr = lf - ce;
					lr = rf - ce;
						dst[0] = (lf&0xFF);
						dst[1] = ((lf>>8)&0xFF);
						dst[2] = (rf&0xFF);
						dst[3] = ((rf>>8)&0xFF);

						dst[0+4] = (lr&0xFF);
						dst[1+4] = ((lr>>8)&0xFF);
						dst[2+4] = (rr&0xFF);
						dst[3+4] = ((rr>>8)&0xFF);
				}
			}
		}
		break;
	}
	cvt->len_cvt *= 2;
	if ( cvt->filters[++cvt->filter_index] ) {
		cvt->filters[cvt->filter_index](cvt, format);
	}
}


/* Convert 8-bit to 16-bit - LSB */
void SDL_Convert16LSB(SDL_AudioCVT *cvt, Uint16 format)
{
	int i;
	Uint8 *src, *dst;

#ifdef DEBUG_CONVERT
	fprintf(stderr, "Converting to 16-bit LSB\n");
#endif
	src = cvt->buf+cvt->len_cvt;
	dst = cvt->buf+cvt->len_cvt*2;
	for ( i=cvt->len_cvt; i; --i ) {
		src -= 1;
		dst -= 2;
		dst[1] = *src;
		dst[0] = 0;
	}
	format = ((format & ~0x0008) | AUDIO_U16LSB);
	cvt->len_cvt *= 2;
	if ( cvt->filters[++cvt->filter_index] ) {
		cvt->filters[cvt->filter_index](cvt, format);
	}
}
/* Convert 8-bit to 16-bit - MSB */
void SDL_Convert16MSB(SDL_AudioCVT *cvt, Uint16 format)
{
	int i;
	Uint8 *src, *dst;

#ifdef DEBUG_CONVERT
	fprintf(stderr, "Converting to 16-bit MSB\n");
#endif
	src = cvt->buf+cvt->len_cvt;
	dst = cvt->buf+cvt->len_cvt*2;
	for ( i=cvt->len_cvt; i; --i ) {
		src -= 1;
		dst -= 2;
		dst[0] = *src;
		dst[1] = 0;
	}
	format = ((format & ~0x0008) | AUDIO_U16MSB);
	cvt->len_cvt *= 2;
	if ( cvt->filters[++cvt->filter_index] ) {
		cvt->filters[cvt->filter_index](cvt, format);
	}
}

/* Convert 16-bit to 8-bit */
void SDL_Convert8(SDL_AudioCVT *cvt, Uint16 format)
{
	int i;
	Uint8 *src, *dst;

#ifdef DEBUG_CONVERT
	fprintf(stderr, "Converting to 8-bit\n");
#endif
	src = cvt->buf;
	dst = cvt->buf;
	if ( (format & 0x1000) != 0x1000 ) { /* Little endian */
		++src;
	}
	for ( i=cvt->len_cvt/2; i; --i ) {
		*dst = *src;
		src += 2;
		dst += 1;
	}
	format = ((format & ~0x9010) | AUDIO_U8);
	cvt->len_cvt /= 2;
	if ( cvt->filters[++cvt->filter_index] ) {
		cvt->filters[cvt->filter_index](cvt, format);
	}
}

/* Toggle signed/unsigned */
void SDL_ConvertSign(SDL_AudioCVT *cvt, Uint16 format)
{
	int i;
	Uint8 *data;

#ifdef DEBUG_CONVERT
	fprintf(stderr, "Converting audio signedness\n");
#endif
	data = cvt->buf;
	if ( (format & 0xFF) == 16 ) {
		if ( (format & 0x1000) != 0x1000 ) { /* Little endian */
			++data;
		}
		for ( i=cvt->len_cvt/2; i; --i ) {
			*data ^= 0x80;
			data += 2;
		}
	} else {
		for ( i=cvt->len_cvt; i; --i ) {
			*data++ ^= 0x80;
		}
	}
	format = (format ^ 0x8000);
	if ( cvt->filters[++cvt->filter_index] ) {
		cvt->filters[cvt->filter_index](cvt, format);
	}
}

/* Toggle endianness */
void SDL_ConvertEndian(SDL_AudioCVT *cvt, Uint16 format)
{
	int i;
	Uint8 *data, tmp;

#ifdef DEBUG_CONVERT
	fprintf(stderr, "Converting audio endianness\n");
#endif
	data = cvt->buf;
	for ( i=cvt->len_cvt/2; i; --i ) {
		tmp = data[0];
		data[0] = data[1];
		data[1] = tmp;
		data += 2;
	}
	format = (format ^ 0x1000);
	if ( cvt->filters[++cvt->filter_index] ) {
		cvt->filters[cvt->filter_index](cvt, format);
	}
}

/* Convert rate up by multiple of 2 */
void SDL_RateMUL2(SDL_AudioCVT *cvt, Uint16 format)
{
	int i;
	Uint8 *src, *dst;

#ifdef DEBUG_CONVERT
	fprintf(stderr, "Converting audio rate * 2\n");
#endif
	src = cvt->buf+cvt->len_cvt;
	dst = cvt->buf+cvt->len_cvt*2;
	switch (format & 0xFF) {
		case 8:
			for ( i=cvt->len_cvt; i; --i ) {
				src -= 1;
				dst -= 2;
				dst[0] = src[0];
				dst[1] = src[0];
			}
			break;
		case 16:
			for ( i=cvt->len_cvt/2; i; --i ) {
				src -= 2;
				dst -= 4;
				dst[0] = src[0];
				dst[1] = src[1];
				dst[2] = src[0];
				dst[3] = src[1];
			}
			break;
	}
	cvt->len_cvt *= 2;
	if ( cvt->filters[++cvt->filter_index] ) {
		cvt->filters[cvt->filter_index](cvt, format);
	}
}


/* Convert rate up by multiple of 2, for stereo */
void SDL_RateMUL2_c2(SDL_AudioCVT *cvt, Uint16 format)
{
	int i;
	Uint8 *src, *dst;

#ifdef DEBUG_CONVERT
	fprintf(stderr, "Converting audio rate * 2\n");
#endif
	src = cvt->buf+cvt->len_cvt;
	dst = cvt->buf+cvt->len_cvt*2;
	switch (format & 0xFF) {
		case 8:
			for ( i=cvt->len_cvt/2; i; --i ) {
				src -= 2;
				dst -= 4;
				dst[0] = src[0];
				dst[1] = src[1];
				dst[2] = src[0];
				dst[3] = src[1];
			}
			break;
		case 16:
			for ( i=cvt->len_cvt/4; i; --i ) {
				src -= 4;
				dst -= 8;
				dst[0] = src[0];
				dst[1] = src[1];
				dst[2] = src[2];
				dst[3] = src[3];
				dst[4] = src[0];
				dst[5] = src[1];
				dst[6] = src[2];
				dst[7] = src[3];
			}
			break;
	}
	cvt->len_cvt *= 2;
	if ( cvt->filters[++cvt->filter_index] ) {
		cvt->filters[cvt->filter_index](cvt, format);
	}
}

/* Convert rate up by multiple of 2, for quad */
void SDL_RateMUL2_c4(SDL_AudioCVT *cvt, Uint16 format)
{
	int i;
	Uint8 *src, *dst;

#ifdef DEBUG_CONVERT
	fprintf(stderr, "Converting audio rate * 2\n");
#endif
	src = cvt->buf+cvt->len_cvt;
	dst = cvt->buf+cvt->len_cvt*2;
	switch (format & 0xFF) {
		case 8:
			for ( i=cvt->len_cvt/4; i; --i ) {
				src -= 4;
				dst -= 8;
				dst[0] = src[0];
				dst[1] = src[1];
				dst[2] = src[2];
				dst[3] = src[3];
				dst[4] = src[0];
				dst[5] = src[1];
				dst[6] = src[2];
				dst[7] = src[3];
			}
			break;
		case 16:
			for ( i=cvt->len_cvt/8; i; --i ) {
				src -= 8;
				dst -= 16;
				dst[0] = src[0];
				dst[1] = src[1];
				dst[2] = src[2];
				dst[3] = src[3];
				dst[4] = src[4];
				dst[5] = src[5];
				dst[6] = src[6];
				dst[7] = src[7];
				dst[8] = src[0];
				dst[9] = src[1];
				dst[10] = src[2];
				dst[11] = src[3];
				dst[12] = src[4];
				dst[13] = src[5];
				dst[14] = src[6];
				dst[15] = src[7];
			}
			break;
	}
	cvt->len_cvt *= 2;
	if ( cvt->filters[++cvt->filter_index] ) {
		cvt->filters[cvt->filter_index](cvt, format);
	}