src/audio/dsp/SDL_dspaudio.c
author Sam Lantinga
Mon, 10 Jul 2006 21:04:37 +0000
changeset 1895 c121d94672cb
parent 1612 97d0966f4bf7
child 1982 3b4ce57c6215
permissions -rw-r--r--
SDL 1.2 is moving to a branch, and SDL 1.3 is becoming the head.
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/*
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    SDL - Simple DirectMedia Layer
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    Copyright (C) 1997-2006 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 Lesser General Public
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    License as published by the Free Software Foundation; either
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    version 2.1 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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    Lesser General Public License for more details.
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    You should have received a copy of the GNU Lesser General Public
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    License along with this library; if not, write to the Free Software
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    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
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    Sam Lantinga
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    slouken@libsdl.org
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    Modified in Oct 2004 by Hannu Savolainen 
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    hannu@opensound.com
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*/
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#include "SDL_config.h"
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/* Allow access to a raw mixing buffer */
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#include <stdio.h>              /* For perror() */
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#include <string.h>             /* For strerror() */
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#include <errno.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <sys/time.h>
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#include <sys/ioctl.h>
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#include <sys/stat.h>
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#if SDL_AUDIO_DRIVER_OSS_SOUNDCARD_H
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/* This is installed on some systems */
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#include <soundcard.h>
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#else
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/* This is recommended by OSS */
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#include <sys/soundcard.h>
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#endif
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#include "SDL_timer.h"
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#include "SDL_audio.h"
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#include "../SDL_audiomem.h"
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#include "../SDL_audio_c.h"
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#include "../SDL_audiodev_c.h"
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#include "SDL_dspaudio.h"
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/* The tag name used by DSP audio */
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#define DSP_DRIVER_NAME         "dsp"
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/* Open the audio device for playback, and don't block if busy */
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#define OPEN_FLAGS	(O_WRONLY|O_NONBLOCK)
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/* Audio driver functions */
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static int DSP_OpenAudio(_THIS, SDL_AudioSpec * spec);
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static void DSP_WaitAudio(_THIS);
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static void DSP_PlayAudio(_THIS);
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static Uint8 *DSP_GetAudioBuf(_THIS);
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static void DSP_CloseAudio(_THIS);
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/* Audio driver bootstrap functions */
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static int
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Audio_Available(void)
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{
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    int fd;
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    int available;
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    available = 0;
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    fd = SDL_OpenAudioPath(NULL, 0, OPEN_FLAGS, 0);
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    if (fd >= 0) {
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        available = 1;
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        close(fd);
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    }
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    return (available);
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}
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static void
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Audio_DeleteDevice(SDL_AudioDevice * device)
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{
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    SDL_free(device->hidden);
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    SDL_free(device);
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}
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static SDL_AudioDevice *
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Audio_CreateDevice(int devindex)
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{
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    SDL_AudioDevice *this;
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    /* Initialize all variables that we clean on shutdown */
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    this = (SDL_AudioDevice *) SDL_malloc(sizeof(SDL_AudioDevice));
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    if (this) {
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        SDL_memset(this, 0, (sizeof *this));
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        this->hidden = (struct SDL_PrivateAudioData *)
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            SDL_malloc((sizeof *this->hidden));
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    }
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    if ((this == NULL) || (this->hidden == NULL)) {
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        SDL_OutOfMemory();
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        if (this) {
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            SDL_free(this);
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        }
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        return (0);
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    }
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    SDL_memset(this->hidden, 0, (sizeof *this->hidden));
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    audio_fd = -1;
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    /* Set the function pointers */
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    this->OpenAudio = DSP_OpenAudio;
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    this->WaitAudio = DSP_WaitAudio;
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    this->PlayAudio = DSP_PlayAudio;
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    this->GetAudioBuf = DSP_GetAudioBuf;
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    this->CloseAudio = DSP_CloseAudio;
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    this->free = Audio_DeleteDevice;
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    return this;
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}
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AudioBootStrap DSP_bootstrap = {
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    DSP_DRIVER_NAME, "OSS /dev/dsp standard audio",
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    Audio_Available, Audio_CreateDevice
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};
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/* This function waits until it is possible to write a full sound buffer */
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static void
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DSP_WaitAudio(_THIS)
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{
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    /* Not needed at all since OSS handles waiting automagically */
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}
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static void
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DSP_PlayAudio(_THIS)
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{
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    if (write(audio_fd, mixbuf, mixlen) == -1) {
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        perror("Audio write");
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        this->enabled = 0;
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    }
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#ifdef DEBUG_AUDIO
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    fprintf(stderr, "Wrote %d bytes of audio data\n", mixlen);
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#endif
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}
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static Uint8 *
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DSP_GetAudioBuf(_THIS)
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{
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    return (mixbuf);
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}
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static void
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DSP_CloseAudio(_THIS)
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{
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    if (mixbuf != NULL) {
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        SDL_FreeAudioMem(mixbuf);
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        mixbuf = NULL;
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    }
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    if (audio_fd >= 0) {
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        close(audio_fd);
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        audio_fd = -1;
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    }
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}
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static int
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DSP_OpenAudio(_THIS, SDL_AudioSpec * spec)
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{
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    char audiodev[1024];
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    int format;
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    int value;
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    int frag_spec;
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    Uint16 test_format;
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    /* Open the audio device */
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    audio_fd = SDL_OpenAudioPath(audiodev, sizeof(audiodev), OPEN_FLAGS, 0);
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    if (audio_fd < 0) {
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        SDL_SetError("Couldn't open %s: %s", audiodev, strerror(errno));
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        return (-1);
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    }
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    mixbuf = NULL;
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    /* Make the file descriptor use blocking writes with fcntl() */
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    {
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        long flags;
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        flags = fcntl(audio_fd, F_GETFL);
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        flags &= ~O_NONBLOCK;
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        if (fcntl(audio_fd, F_SETFL, flags) < 0) {
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            SDL_SetError("Couldn't set audio blocking mode");
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            DSP_CloseAudio(this);
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            return (-1);
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        }
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    }
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    /* Get a list of supported hardware formats */
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    if (ioctl(audio_fd, SNDCTL_DSP_GETFMTS, &value) < 0) {
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        perror("SNDCTL_DSP_GETFMTS");
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        SDL_SetError("Couldn't get audio format list");
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        DSP_CloseAudio(this);
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        return (-1);
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    }
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    /* Try for a closest match on audio format */
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    format = 0;
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    for (test_format = SDL_FirstAudioFormat(spec->format);
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         !format && test_format;) {
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#ifdef DEBUG_AUDIO
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        fprintf(stderr, "Trying format 0x%4.4x\n", test_format);
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#endif
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        switch (test_format) {
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        case AUDIO_U8:
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            if (value & AFMT_U8) {
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                format = AFMT_U8;
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            }
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            break;
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        case AUDIO_S16LSB:
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            if (value & AFMT_S16_LE) {
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                format = AFMT_S16_LE;
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            }
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            break;
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        case AUDIO_S16MSB:
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            if (value & AFMT_S16_BE) {
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                format = AFMT_S16_BE;
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            }
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            break;
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#if 0
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/*
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 * These formats are not used by any real life systems so they are not 
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 * needed here.
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 */
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        case AUDIO_S8:
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            if (value & AFMT_S8) {
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                format = AFMT_S8;
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            }
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            break;
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        case AUDIO_U16LSB:
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            if (value & AFMT_U16_LE) {
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                format = AFMT_U16_LE;
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            }
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            break;
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        case AUDIO_U16MSB:
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            if (value & AFMT_U16_BE) {
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                format = AFMT_U16_BE;
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            }
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            break;
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#endif
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        default:
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            format = 0;
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            break;
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        }
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        if (!format) {
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            test_format = SDL_NextAudioFormat();
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        }
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    }
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    if (format == 0) {
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        SDL_SetError("Couldn't find any hardware audio formats");
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        DSP_CloseAudio(this);
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        return (-1);
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    }
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    spec->format = test_format;
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    /* Set the audio format */
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    value = format;
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    if ((ioctl(audio_fd, SNDCTL_DSP_SETFMT, &value) < 0) || (value != format)) {
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        perror("SNDCTL_DSP_SETFMT");
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        SDL_SetError("Couldn't set audio format");
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        DSP_CloseAudio(this);
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        return (-1);
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    }
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    /* Set the number of channels of output */
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    value = spec->channels;
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    if (ioctl(audio_fd, SNDCTL_DSP_CHANNELS, &value) < 0) {
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        perror("SNDCTL_DSP_CHANNELS");
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        SDL_SetError("Cannot set the number of channels");
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        DSP_CloseAudio(this);
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        return (-1);
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    }
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    spec->channels = value;
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    /* Set the DSP frequency */
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    value = spec->freq;
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    if (ioctl(audio_fd, SNDCTL_DSP_SPEED, &value) < 0) {
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        perror("SNDCTL_DSP_SPEED");
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        SDL_SetError("Couldn't set audio frequency");
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        DSP_CloseAudio(this);
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        return (-1);
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    }
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    spec->freq = value;
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    /* Calculate the final parameters for this audio specification */
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    SDL_CalculateAudioSpec(spec);
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    /* Determine the power of two of the fragment size */
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    for (frag_spec = 0; (0x01U << frag_spec) < spec->size; ++frag_spec);
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    if ((0x01U << frag_spec) != spec->size) {
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        SDL_SetError("Fragment size must be a power of two");
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        DSP_CloseAudio(this);
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        return (-1);
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    }
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    frag_spec |= 0x00020000;    /* two fragments, for low latency */
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    /* Set the audio buffering parameters */
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#ifdef DEBUG_AUDIO
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    fprintf(stderr, "Requesting %d fragments of size %d\n",
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            (frag_spec >> 16), 1 << (frag_spec & 0xFFFF));
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#endif
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    if (ioctl(audio_fd, SNDCTL_DSP_SETFRAGMENT, &frag_spec) < 0) {
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        perror("SNDCTL_DSP_SETFRAGMENT");
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    }
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#ifdef DEBUG_AUDIO
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    {
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        audio_buf_info info;
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        ioctl(audio_fd, SNDCTL_DSP_GETOSPACE, &info);
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        fprintf(stderr, "fragments = %d\n", info.fragments);
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        fprintf(stderr, "fragstotal = %d\n", info.fragstotal);
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        fprintf(stderr, "fragsize = %d\n", info.fragsize);
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        fprintf(stderr, "bytes = %d\n", info.bytes);
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    }
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#endif
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    /* Allocate mixing buffer */
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    mixlen = spec->size;
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    mixbuf = (Uint8 *) SDL_AllocAudioMem(mixlen);
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    if (mixbuf == NULL) {
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        DSP_CloseAudio(this);
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        return (-1);
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    }
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    SDL_memset(mixbuf, spec->silence, spec->size);
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    /* Get the parent process id (we're the parent of the audio thread) */
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    parent = getpid();
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    /* We're ready to rock and roll. :-) */
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    return (0);
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}
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/* vi: set ts=4 sw=4 expandtab: */