src/audio/dsp/SDL_dspaudio.c
author Ryan C. Gordon
Thu, 04 Aug 2011 00:31:11 -0400
changeset 5593 ab22ca13c47f
parent 5535 96594ac5fd1a
child 5594 e741303e08a8
permissions -rw-r--r--
Cleaned up audio device detection. Cleared out a lot of cut-and-paste.
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/*
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  Simple DirectMedia Layer
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  Copyright (C) 1997-2011 Sam Lantinga <slouken@libsdl.org>
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  This software is provided 'as-is', without any express or implied
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  warranty.  In no event will the authors be held liable for any damages
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  arising from the use of this software.
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  Permission is granted to anyone to use this software for any purpose,
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  including commercial applications, and to alter it and redistribute it
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  freely, subject to the following restrictions:
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  1. The origin of this software must not be misrepresented; you must not
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     claim that you wrote the original software. If you use this software
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     in a product, an acknowledgment in the product documentation would be
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     appreciated but is not required.
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  2. Altered source versions must be plainly marked as such, and must not be
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     misrepresented as being the original software.
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  3. This notice may not be removed or altered from any source distribution.
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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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static void
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DSP_Deinitialize(void)
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{
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}
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static void
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DSP_DetectDevices(int iscapture)
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{
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    SDL_EnumUnixAudioDevices(iscapture, 0, NULL);
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}
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static void
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DSP_CloseDevice(_THIS)
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{
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    if (this->hidden != NULL) {
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        if (this->hidden->mixbuf != NULL) {
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            SDL_FreeAudioMem(this->hidden->mixbuf);
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            this->hidden->mixbuf = NULL;
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        }
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        if (this->hidden->audio_fd >= 0) {
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            close(this->hidden->audio_fd);
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            this->hidden->audio_fd = -1;
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        }
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        SDL_free(this->hidden);
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        this->hidden = NULL;
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    }
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}
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static int
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DSP_OpenDevice(_THIS, const char *devname, int iscapture)
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{
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    const int flags = ((iscapture) ? OPEN_FLAGS_INPUT : OPEN_FLAGS_OUTPUT);
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    int format;
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    int value;
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    int frag_spec;
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    SDL_AudioFormat test_format;
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    /* We don't care what the devname is...we'll try to open anything. */
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    /*  ...but default to first name in the list... */
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    if (devname == NULL) {
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        devname = SDL_GetAudioDeviceName(0, iscapture);
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        if (devname == NULL) {
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            SDL_SetError("No such audio device");
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            return 0;
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        }
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    }
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    /* Make sure fragment size stays a power of 2, or OSS fails. */
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    /* I don't know which of these are actually legal values, though... */
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    if (this->spec.channels > 8)
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        this->spec.channels = 8;
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    else if (this->spec.channels > 4)
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        this->spec.channels = 4;
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    else if (this->spec.channels > 2)
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        this->spec.channels = 2;
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    /* Initialize all variables that we clean on shutdown */
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    this->hidden = (struct SDL_PrivateAudioData *)
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        SDL_malloc((sizeof *this->hidden));
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    if (this->hidden == NULL) {
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        SDL_OutOfMemory();
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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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    /* Open the audio device */
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    this->hidden->audio_fd = open(devname, flags, 0);
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    if (this->hidden->audio_fd < 0) {
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        DSP_CloseDevice(this);
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        SDL_SetError("Couldn't open %s: %s", devname, strerror(errno));
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        return 0;
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    }
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    this->hidden->mixbuf = NULL;
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    /* Make the file descriptor use blocking writes with fcntl() */
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    {
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        long ctlflags;
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        ctlflags = fcntl(this->hidden->audio_fd, F_GETFL);
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        ctlflags &= ~O_NONBLOCK;
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        if (fcntl(this->hidden->audio_fd, F_SETFL, ctlflags) < 0) {
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            DSP_CloseDevice(this);
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            SDL_SetError("Couldn't set audio blocking mode");
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            return 0;
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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(this->hidden->audio_fd, SNDCTL_DSP_GETFMTS, &value) < 0) {
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        perror("SNDCTL_DSP_GETFMTS");
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        DSP_CloseDevice(this);
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        SDL_SetError("Couldn't get audio format list");
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        return 0;
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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(this->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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        DSP_CloseDevice(this);
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        SDL_SetError("Couldn't find any hardware audio formats");
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        return 0;
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    }
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    this->spec.format = test_format;
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    /* Set the audio format */
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    value = format;
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    if ((ioctl(this->hidden->audio_fd, SNDCTL_DSP_SETFMT, &value) < 0) ||
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        (value != format)) {
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        perror("SNDCTL_DSP_SETFMT");
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        DSP_CloseDevice(this);
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        SDL_SetError("Couldn't set audio format");
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        return 0;
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    }
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    /* Set the number of channels of output */
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    value = this->spec.channels;
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    if (ioctl(this->hidden->audio_fd, SNDCTL_DSP_CHANNELS, &value) < 0) {
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        perror("SNDCTL_DSP_CHANNELS");
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        DSP_CloseDevice(this);
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        SDL_SetError("Cannot set the number of channels");
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        return 0;
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    }
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    this->spec.channels = value;
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    /* Set the DSP frequency */
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    value = this->spec.freq;
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    if (ioctl(this->hidden->audio_fd, SNDCTL_DSP_SPEED, &value) < 0) {
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        perror("SNDCTL_DSP_SPEED");
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        DSP_CloseDevice(this);
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        SDL_SetError("Couldn't set audio frequency");
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        return 0;
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    }
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    this->spec.freq = value;
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    /* Calculate the final parameters for this audio specification */
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    SDL_CalculateAudioSpec(&this->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) < this->spec.size; ++frag_spec);
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    if ((0x01U << frag_spec) != this->spec.size) {
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        DSP_CloseDevice(this);
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        SDL_SetError("Fragment size must be a power of two");
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        return 0;
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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(this->hidden->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(this->hidden->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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    this->hidden->mixlen = this->spec.size;
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    this->hidden->mixbuf = (Uint8 *) SDL_AllocAudioMem(this->hidden->mixlen);
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    if (this->hidden->mixbuf == NULL) {
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        DSP_CloseDevice(this);
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        SDL_OutOfMemory();
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        return 0;
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    }
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    SDL_memset(this->hidden->mixbuf, this->spec.silence, this->spec.size);
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    /* We're ready to rock and roll. :-) */
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    return 1;
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}
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static void
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DSP_PlayDevice(_THIS)
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{
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    const Uint8 *mixbuf = this->hidden->mixbuf;
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    const int mixlen = this->hidden->mixlen;
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    if (write(this->hidden->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_GetDeviceBuf(_THIS)
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{
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    return (this->hidden->mixbuf);
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}
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static int
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DSP_Init(SDL_AudioDriverImpl * impl)
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{
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    /* Set the function pointers */
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    impl->DetectDevices = DSP_DetectDevices;
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    impl->OpenDevice = DSP_OpenDevice;
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    impl->PlayDevice = DSP_PlayDevice;
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    impl->GetDeviceBuf = DSP_GetDeviceBuf;
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    impl->CloseDevice = DSP_CloseDevice;
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    impl->Deinitialize = DSP_Deinitialize;
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    return 1;   /* this audio target is available. */
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}
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AudioBootStrap DSP_bootstrap = {
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    DSP_DRIVER_NAME, "OSS /dev/dsp standard audio", DSP_Init, 0
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};
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/* vi: set ts=4 sw=4 expandtab: */