0
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/*
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SDL - Simple DirectMedia Layer
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Copyright (C) 1997, 1998, 1999, 2000, 2001 Sam Lantinga
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with this library; if not, write to the Free
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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Sam Lantinga
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slouken@devolution.com
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*/
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#ifdef SAVE_RCSID
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static char rcsid =
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"@(#) $Id$";
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#endif
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/* Functions for audio drivers to perform runtime conversion of audio format */
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#include <stdio.h>
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#include "SDL_error.h"
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#include "SDL_audio.h"
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/* Effectively mix right and left channels into a single channel */
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void SDL_ConvertMono(SDL_AudioCVT *cvt, Uint16 format)
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{
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int i;
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Sint32 sample;
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#ifdef DEBUG_CONVERT
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fprintf(stderr, "Converting to mono\n");
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#endif
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switch (format&0x8018) {
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case AUDIO_U8: {
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Uint8 *src, *dst;
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src = cvt->buf;
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dst = cvt->buf;
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for ( i=cvt->len_cvt/2; i; --i ) {
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sample = src[0] + src[1];
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if ( sample > 255 ) {
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*dst = 255;
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} else {
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*dst = sample;
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}
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src += 2;
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dst += 1;
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}
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}
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break;
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case AUDIO_S8: {
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Sint8 *src, *dst;
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src = (Sint8 *)cvt->buf;
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dst = (Sint8 *)cvt->buf;
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for ( i=cvt->len_cvt/2; i; --i ) {
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sample = src[0] + src[1];
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if ( sample > 127 ) {
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*dst = 127;
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} else
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if ( sample < -128 ) {
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*dst = -128;
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} else {
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*dst = sample;
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}
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src += 2;
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dst += 1;
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}
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}
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break;
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case AUDIO_U16: {
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Uint8 *src, *dst;
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src = cvt->buf;
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dst = cvt->buf;
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if ( (format & 0x1000) == 0x1000 ) {
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for ( i=cvt->len_cvt/4; i; --i ) {
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sample = (Uint16)((src[0]<<8)|src[1])+
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(Uint16)((src[2]<<8)|src[3]);
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if ( sample > 65535 ) {
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dst[0] = 0xFF;
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dst[1] = 0xFF;
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} else {
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dst[1] = (sample&0xFF);
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sample >>= 8;
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dst[0] = (sample&0xFF);
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}
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src += 4;
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dst += 2;
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}
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} else {
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for ( i=cvt->len_cvt/4; i; --i ) {
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sample = (Uint16)((src[1]<<8)|src[0])+
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(Uint16)((src[3]<<8)|src[2]);
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if ( sample > 65535 ) {
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dst[0] = 0xFF;
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dst[1] = 0xFF;
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} else {
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dst[0] = (sample&0xFF);
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sample >>= 8;
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dst[1] = (sample&0xFF);
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}
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src += 4;
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dst += 2;
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}
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}
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}
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break;
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case AUDIO_S16: {
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Uint8 *src, *dst;
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src = cvt->buf;
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dst = cvt->buf;
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if ( (format & 0x1000) == 0x1000 ) {
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for ( i=cvt->len_cvt/4; i; --i ) {
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sample = (Sint16)((src[0]<<8)|src[1])+
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(Sint16)((src[2]<<8)|src[3]);
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if ( sample > 32767 ) {
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dst[0] = 0x7F;
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dst[1] = 0xFF;
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} else
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if ( sample < -32768 ) {
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dst[0] = 0x80;
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dst[1] = 0x00;
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} else {
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dst[1] = (sample&0xFF);
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sample >>= 8;
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dst[0] = (sample&0xFF);
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}
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src += 4;
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dst += 2;
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}
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} else {
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for ( i=cvt->len_cvt/4; i; --i ) {
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sample = (Sint16)((src[1]<<8)|src[0])+
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(Sint16)((src[3]<<8)|src[2]);
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if ( sample > 32767 ) {
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dst[1] = 0x7F;
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dst[0] = 0xFF;
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} else
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if ( sample < -32768 ) {
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dst[1] = 0x80;
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dst[0] = 0x00;
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} else {
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dst[0] = (sample&0xFF);
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sample >>= 8;
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dst[1] = (sample&0xFF);
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}
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src += 4;
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dst += 2;
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}
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}
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}
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break;
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}
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cvt->len_cvt /= 2;
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if ( cvt->filters[++cvt->filter_index] ) {
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cvt->filters[cvt->filter_index](cvt, format);
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}
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}
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/* Duplicate a mono channel to both stereo channels */
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void SDL_ConvertStereo(SDL_AudioCVT *cvt, Uint16 format)
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{
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int i;
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#ifdef DEBUG_CONVERT
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fprintf(stderr, "Converting to stereo\n");
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#endif
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if ( (format & 0xFF) == 16 ) {
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Uint16 *src, *dst;
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src = (Uint16 *)(cvt->buf+cvt->len_cvt);
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dst = (Uint16 *)(cvt->buf+cvt->len_cvt*2);
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for ( i=cvt->len_cvt/2; i; --i ) {
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dst -= 2;
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src -= 1;
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dst[0] = src[0];
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dst[1] = src[0];
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}
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} else {
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Uint8 *src, *dst;
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src = cvt->buf+cvt->len_cvt;
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dst = cvt->buf+cvt->len_cvt*2;
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for ( i=cvt->len_cvt; i; --i ) {
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dst -= 2;
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src -= 1;
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dst[0] = src[0];
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dst[1] = src[0];
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}
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}
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cvt->len_cvt *= 2;
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if ( cvt->filters[++cvt->filter_index] ) {
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cvt->filters[cvt->filter_index](cvt, format);
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}
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}
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/* Convert 8-bit to 16-bit - LSB */
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void SDL_Convert16LSB(SDL_AudioCVT *cvt, Uint16 format)
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{
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int i;
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Uint8 *src, *dst;
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#ifdef DEBUG_CONVERT
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fprintf(stderr, "Converting to 16-bit LSB\n");
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#endif
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src = cvt->buf+cvt->len_cvt;
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dst = cvt->buf+cvt->len_cvt*2;
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for ( i=cvt->len_cvt; i; --i ) {
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src -= 1;
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dst -= 2;
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dst[1] = *src;
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dst[0] = 0;
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}
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format = ((format & ~0x0008) | AUDIO_U16LSB);
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cvt->len_cvt *= 2;
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if ( cvt->filters[++cvt->filter_index] ) {
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cvt->filters[cvt->filter_index](cvt, format);
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}
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}
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/* Convert 8-bit to 16-bit - MSB */
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void SDL_Convert16MSB(SDL_AudioCVT *cvt, Uint16 format)
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{
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int i;
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Uint8 *src, *dst;
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#ifdef DEBUG_CONVERT
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fprintf(stderr, "Converting to 16-bit MSB\n");
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#endif
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src = cvt->buf+cvt->len_cvt;
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dst = cvt->buf+cvt->len_cvt*2;
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for ( i=cvt->len_cvt; i; --i ) {
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src -= 1;
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dst -= 2;
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dst[0] = *src;
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dst[1] = 0;
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}
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format = ((format & ~0x0008) | AUDIO_U16MSB);
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cvt->len_cvt *= 2;
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if ( cvt->filters[++cvt->filter_index] ) {
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cvt->filters[cvt->filter_index](cvt, format);
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}
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}
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/* Convert 16-bit to 8-bit */
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void SDL_Convert8(SDL_AudioCVT *cvt, Uint16 format)
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{
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int i;
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Uint8 *src, *dst;
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#ifdef DEBUG_CONVERT
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fprintf(stderr, "Converting to 8-bit\n");
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#endif
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src = cvt->buf;
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dst = cvt->buf;
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if ( (format & 0x1000) != 0x1000 ) { /* Little endian */
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++src;
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}
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for ( i=cvt->len_cvt/2; i; --i ) {
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*dst = *src;
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src += 2;
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dst += 1;
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}
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format = ((format & ~0x9010) | AUDIO_U8);
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cvt->len_cvt /= 2;
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if ( cvt->filters[++cvt->filter_index] ) {
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cvt->filters[cvt->filter_index](cvt, format);
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}
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}
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/* Toggle signed/unsigned */
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void SDL_ConvertSign(SDL_AudioCVT *cvt, Uint16 format)
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{
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int i;
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Uint8 *data;
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#ifdef DEBUG_CONVERT
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fprintf(stderr, "Converting audio signedness\n");
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#endif
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data = cvt->buf;
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if ( (format & 0xFF) == 16 ) {
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if ( (format & 0x1000) != 0x1000 ) { /* Little endian */
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++data;
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}
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for ( i=cvt->len_cvt/2; i; --i ) {
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*data ^= 0x80;
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data += 2;
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}
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} else {
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for ( i=cvt->len_cvt; i; --i ) {
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*data++ ^= 0x80;
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}
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}
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format = (format ^ 0x8000);
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if ( cvt->filters[++cvt->filter_index] ) {
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cvt->filters[cvt->filter_index](cvt, format);
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}
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}
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/* Toggle endianness */
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void SDL_ConvertEndian(SDL_AudioCVT *cvt, Uint16 format)
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{
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int i;
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Uint8 *data, tmp;
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#ifdef DEBUG_CONVERT
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fprintf(stderr, "Converting audio endianness\n");
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#endif
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data = cvt->buf;
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for ( i=cvt->len_cvt/2; i; --i ) {
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tmp = data[0];
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data[0] = data[1];
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data[1] = tmp;
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data += 2;
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}
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format = (format ^ 0x1000);
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if ( cvt->filters[++cvt->filter_index] ) {
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cvt->filters[cvt->filter_index](cvt, format);
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}
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}
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/* Convert rate up by multiple of 2 */
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void SDL_RateMUL2(SDL_AudioCVT *cvt, Uint16 format)
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{
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int i;
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Uint8 *src, *dst;
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#ifdef DEBUG_CONVERT
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fprintf(stderr, "Converting audio rate * 2\n");
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#endif
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src = cvt->buf+cvt->len_cvt;
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dst = cvt->buf+cvt->len_cvt*2;
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switch (format & 0xFF) {
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case 8:
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for ( i=cvt->len_cvt; i; --i ) {
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src -= 1;
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dst -= 2;
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dst[0] = src[0];
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dst[1] = src[0];
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}
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break;
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case 16:
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for ( i=cvt->len_cvt/2; i; --i ) {
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src -= 2;
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dst -= 4;
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dst[0] = src[0];
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dst[1] = src[1];
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dst[2] = src[0];
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dst[3] = src[1];
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}
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break;
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370 |
}
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371 |
cvt->len_cvt *= 2;
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372 |
if ( cvt->filters[++cvt->filter_index] ) {
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cvt->filters[cvt->filter_index](cvt, format);
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}
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375 |
}
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376 |
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377 |
/* Convert rate down by multiple of 2 */
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378 |
void SDL_RateDIV2(SDL_AudioCVT *cvt, Uint16 format)
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379 |
{
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380 |
int i;
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381 |
Uint8 *src, *dst;
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382 |
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383 |
#ifdef DEBUG_CONVERT
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384 |
fprintf(stderr, "Converting audio rate / 2\n");
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385 |
#endif
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386 |
src = cvt->buf;
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dst = cvt->buf;
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388 |
switch (format & 0xFF) {
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389 |
case 8:
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390 |
for ( i=cvt->len_cvt/2; i; --i ) {
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dst[0] = src[0];
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src += 2;
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dst += 1;
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}
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break;
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case 16:
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for ( i=cvt->len_cvt/4; i; --i ) {
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398 |
dst[0] = src[0];
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dst[1] = src[1];
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src += 4;
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dst += 2;
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}
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403 |
break;
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}
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405 |
cvt->len_cvt /= 2;
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406 |
if ( cvt->filters[++cvt->filter_index] ) {
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407 |
cvt->filters[cvt->filter_index](cvt, format);
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}
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409 |
}
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410 |
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411 |
/* Very slow rate conversion routine */
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412 |
void SDL_RateSLOW(SDL_AudioCVT *cvt, Uint16 format)
|
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413 |
{
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|
414 |
double ipos;
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415 |
int i, clen;
|
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416 |
|
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417 |
#ifdef DEBUG_CONVERT
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418 |
fprintf(stderr, "Converting audio rate * %4.4f\n", 1.0/cvt->rate_incr);
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419 |
#endif
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420 |
clen = (int)((double)cvt->len_cvt / cvt->rate_incr);
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421 |
if ( cvt->rate_incr > 1.0 ) {
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422 |
switch (format & 0xFF) {
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423 |
case 8: {
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424 |
Uint8 *output;
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|
425 |
|
|
426 |
output = cvt->buf;
|
|
427 |
ipos = 0.0;
|
|
428 |
for ( i=clen; i; --i ) {
|
|
429 |
*output = cvt->buf[(int)ipos];
|
|
430 |
ipos += cvt->rate_incr;
|
|
431 |
output += 1;
|
|
432 |
}
|
|
433 |
}
|
|
434 |
break;
|
|
435 |
|
|
436 |
case 16: {
|
|
437 |
Uint16 *output;
|
|
438 |
|
|
439 |
clen &= ~1;
|
|
440 |
output = (Uint16 *)cvt->buf;
|
|
441 |
ipos = 0.0;
|
|
442 |
for ( i=clen/2; i; --i ) {
|
|
443 |
*output=((Uint16 *)cvt->buf)[(int)ipos];
|
|
444 |
ipos += cvt->rate_incr;
|
|
445 |
output += 1;
|
|
446 |
}
|
|
447 |
}
|
|
448 |
break;
|
|
449 |
}
|
|
450 |
} else {
|
|
451 |
switch (format & 0xFF) {
|
|
452 |
case 8: {
|
|
453 |
Uint8 *output;
|
|
454 |
|
|
455 |
output = cvt->buf+clen;
|
|
456 |
ipos = (double)cvt->len_cvt;
|
|
457 |
for ( i=clen; i; --i ) {
|
|
458 |
ipos -= cvt->rate_incr;
|
|
459 |
output -= 1;
|
|
460 |
*output = cvt->buf[(int)ipos];
|
|
461 |
}
|
|
462 |
}
|
|
463 |
break;
|
|
464 |
|
|
465 |
case 16: {
|
|
466 |
Uint16 *output;
|
|
467 |
|
|
468 |
clen &= ~1;
|
|
469 |
output = (Uint16 *)(cvt->buf+clen);
|
|
470 |
ipos = (double)cvt->len_cvt/2;
|
|
471 |
for ( i=clen/2; i; --i ) {
|
|
472 |
ipos -= cvt->rate_incr;
|
|
473 |
output -= 1;
|
|
474 |
*output=((Uint16 *)cvt->buf)[(int)ipos];
|
|
475 |
}
|
|
476 |
}
|
|
477 |
break;
|
|
478 |
}
|
|
479 |
}
|
|
480 |
cvt->len_cvt = clen;
|
|
481 |
if ( cvt->filters[++cvt->filter_index] ) {
|
|
482 |
cvt->filters[cvt->filter_index](cvt, format);
|
|
483 |
}
|
|
484 |
}
|
|
485 |
|
|
486 |
int SDL_ConvertAudio(SDL_AudioCVT *cvt)
|
|
487 |
{
|
|
488 |
/* Make sure there's data to convert */
|
|
489 |
if ( cvt->buf == NULL ) {
|
|
490 |
SDL_SetError("No buffer allocated for conversion");
|
|
491 |
return(-1);
|
|
492 |
}
|
|
493 |
/* Return okay if no conversion is necessary */
|
|
494 |
cvt->len_cvt = cvt->len;
|
|
495 |
if ( cvt->filters[0] == NULL ) {
|
|
496 |
return(0);
|
|
497 |
}
|
|
498 |
|
|
499 |
/* Set up the conversion and go! */
|
|
500 |
cvt->filter_index = 0;
|
|
501 |
cvt->filters[0](cvt, cvt->src_format);
|
|
502 |
return(0);
|
|
503 |
}
|
|
504 |
|
|
505 |
/* Creates a set of audio filters to convert from one format to another.
|
|
506 |
Returns -1 if the format conversion is not supported, or 1 if the
|
|
507 |
audio filter is set up.
|
|
508 |
*/
|
|
509 |
|
|
510 |
int SDL_BuildAudioCVT(SDL_AudioCVT *cvt,
|
|
511 |
Uint16 src_format, Uint8 src_channels, int src_rate,
|
|
512 |
Uint16 dst_format, Uint8 dst_channels, int dst_rate)
|
|
513 |
{
|
|
514 |
/* Start off with no conversion necessary */
|
|
515 |
cvt->needed = 0;
|
|
516 |
cvt->filter_index = 0;
|
|
517 |
cvt->filters[0] = NULL;
|
|
518 |
cvt->len_mult = 1;
|
|
519 |
cvt->len_ratio = 1.0;
|
|
520 |
|
|
521 |
/* First filter: Endian conversion from src to dst */
|
|
522 |
if ( (src_format & 0x1000) != (dst_format & 0x1000)
|
|
523 |
&& ((src_format & 0xff) != 8) ) {
|
|
524 |
cvt->filters[cvt->filter_index++] = SDL_ConvertEndian;
|
|
525 |
}
|
|
526 |
|
|
527 |
/* Second filter: Sign conversion -- signed/unsigned */
|
|
528 |
if ( (src_format & 0x8000) != (dst_format & 0x8000) ) {
|
|
529 |
cvt->filters[cvt->filter_index++] = SDL_ConvertSign;
|
|
530 |
}
|
|
531 |
|
|
532 |
/* Next filter: Convert 16 bit <--> 8 bit PCM */
|
|
533 |
if ( (src_format & 0xFF) != (dst_format & 0xFF) ) {
|
|
534 |
switch (dst_format&0x10FF) {
|
|
535 |
case AUDIO_U8:
|
|
536 |
cvt->filters[cvt->filter_index++] =
|
|
537 |
SDL_Convert8;
|
|
538 |
cvt->len_ratio /= 2;
|
|
539 |
break;
|
|
540 |
case AUDIO_U16LSB:
|
|
541 |
cvt->filters[cvt->filter_index++] =
|
|
542 |
SDL_Convert16LSB;
|
|
543 |
cvt->len_mult *= 2;
|
|
544 |
cvt->len_ratio *= 2;
|
|
545 |
break;
|
|
546 |
case AUDIO_U16MSB:
|
|
547 |
cvt->filters[cvt->filter_index++] =
|
|
548 |
SDL_Convert16MSB;
|
|
549 |
cvt->len_mult *= 2;
|
|
550 |
cvt->len_ratio *= 2;
|
|
551 |
break;
|
|
552 |
}
|
|
553 |
}
|
|
554 |
|
|
555 |
/* Last filter: Mono/Stereo conversion */
|
|
556 |
if ( src_channels != dst_channels ) {
|
|
557 |
while ( (src_channels*2) <= dst_channels ) {
|
|
558 |
cvt->filters[cvt->filter_index++] =
|
|
559 |
SDL_ConvertStereo;
|
|
560 |
cvt->len_mult *= 2;
|
|
561 |
src_channels *= 2;
|
|
562 |
cvt->len_ratio *= 2;
|
|
563 |
}
|
|
564 |
/* This assumes that 4 channel audio is in the format:
|
|
565 |
Left {front/back} + Right {front/back}
|
|
566 |
so converting to L/R stereo works properly.
|
|
567 |
*/
|
|
568 |
while ( ((src_channels%2) == 0) &&
|
|
569 |
((src_channels/2) >= dst_channels) ) {
|
|
570 |
cvt->filters[cvt->filter_index++] =
|
|
571 |
SDL_ConvertMono;
|
|
572 |
src_channels /= 2;
|
|
573 |
cvt->len_ratio /= 2;
|
|
574 |
}
|
|
575 |
if ( src_channels != dst_channels ) {
|
|
576 |
/* Uh oh.. */;
|
|
577 |
}
|
|
578 |
}
|
|
579 |
|
|
580 |
/* Do rate conversion */
|
|
581 |
cvt->rate_incr = 0.0;
|
|
582 |
if ( (src_rate/100) != (dst_rate/100) ) {
|
|
583 |
Uint32 hi_rate, lo_rate;
|
|
584 |
int len_mult;
|
|
585 |
double len_ratio;
|
|
586 |
void (*rate_cvt)(SDL_AudioCVT *cvt, Uint16 format);
|
|
587 |
|
|
588 |
if ( src_rate > dst_rate ) {
|
|
589 |
hi_rate = src_rate;
|
|
590 |
lo_rate = dst_rate;
|
|
591 |
rate_cvt = SDL_RateDIV2;
|
|
592 |
len_mult = 1;
|
|
593 |
len_ratio = 0.5;
|
|
594 |
} else {
|
|
595 |
hi_rate = dst_rate;
|
|
596 |
lo_rate = src_rate;
|
|
597 |
rate_cvt = SDL_RateMUL2;
|
|
598 |
len_mult = 2;
|
|
599 |
len_ratio = 2.0;
|
|
600 |
}
|
|
601 |
/* If hi_rate = lo_rate*2^x then conversion is easy */
|
|
602 |
while ( ((lo_rate*2)/100) <= (hi_rate/100) ) {
|
|
603 |
cvt->filters[cvt->filter_index++] = rate_cvt;
|
|
604 |
cvt->len_mult *= len_mult;
|
|
605 |
lo_rate *= 2;
|
|
606 |
cvt->len_ratio *= len_ratio;
|
|
607 |
}
|
|
608 |
/* We may need a slow conversion here to finish up */
|
|
609 |
if ( (lo_rate/100) != (hi_rate/100) ) {
|
|
610 |
#if 1
|
|
611 |
/* The problem with this is that if the input buffer is
|
|
612 |
say 1K, and the conversion rate is say 1.1, then the
|
|
613 |
output buffer is 1.1K, which may not be an acceptable
|
|
614 |
buffer size for the audio driver (not a power of 2)
|
|
615 |
*/
|
|
616 |
/* For now, punt and hope the rate distortion isn't great.
|
|
617 |
*/
|
|
618 |
#else
|
|
619 |
if ( src_rate < dst_rate ) {
|
|
620 |
cvt->rate_incr = (double)lo_rate/hi_rate;
|
|
621 |
cvt->len_mult *= 2;
|
|
622 |
cvt->len_ratio /= cvt->rate_incr;
|
|
623 |
} else {
|
|
624 |
cvt->rate_incr = (double)hi_rate/lo_rate;
|
|
625 |
cvt->len_ratio *= cvt->rate_incr;
|
|
626 |
}
|
|
627 |
cvt->filters[cvt->filter_index++] = SDL_RateSLOW;
|
|
628 |
#endif
|
|
629 |
}
|
|
630 |
}
|
|
631 |
|
|
632 |
/* Set up the filter information */
|
|
633 |
if ( cvt->filter_index != 0 ) {
|
|
634 |
cvt->needed = 1;
|
|
635 |
cvt->src_format = src_format;
|
|
636 |
cvt->dst_format = dst_format;
|
|
637 |
cvt->len = 0;
|
|
638 |
cvt->buf = NULL;
|
|
639 |
cvt->filters[cvt->filter_index] = NULL;
|
|
640 |
}
|
|
641 |
return(cvt->needed);
|
|
642 |
}
|