source: downloads/openal-0.0.8/src/audioconvert/ac_bits.c @ 17

/* -*- mode: C; tab-width:8; c-basic-offset:8 -*-
 * vi:set ts=8:
 *
 * ac_bits.c
 *
 * audioconvert functions related to bit depth.
 */
#include "al_siteconfig.h"

#include <AL/al.h>
#include <stdio.h>

#include "audioconvert/audioconvert.h"

/* Convert 8-bit to 16-bit - LSB */
void acConvert16LSB( acAudioCVT *cvt, ALushort format ) {
        int i;
        ALubyte *src, *dst;

        src = (ALubyte *) cvt->buf + cvt->len_cvt;
        dst = (ALubyte *) cvt->buf + cvt->len_cvt * 2;
        for(i = cvt->len_cvt; i; i-- ) {
                src -= 1;
                dst -= 2;
                dst[0] = 0;
                dst[1] = *src;
        }

        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 acConvert16MSB(acAudioCVT *cvt, ALushort format) {
        int i;
        ALubyte *src, *dst;

        src = (ALubyte *) cvt->buf + cvt->len_cvt;
        dst = (ALubyte *) cvt->buf + cvt->len_cvt * 2;
        for(i = cvt->len_cvt; i; i--) {
                src -= 1;
                dst -= 2;
                dst[1] = 0;
                dst[0] = *src;
        }

        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 acConvert8(acAudioCVT *cvt, ALushort format) {
        int i;
        ALubyte *src, *dst;

        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);
        }
}