sdl_paudio.c

jpeg and mpeg 编解码技术源代码

/*
    AIX support for the SDL - Simple DirectMedia Layer
    Copyright (C) 2000  Carsten Griwodz

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    Carsten Griwodz
    [e-mail]

    based on linux/SDL_dspaudio.c by Sam Lantinga
*/

#ifdef SAVE_RCSID
static char rcsid =
 "@(#) $Id: SDL_paudio.c,v 1.4 2002/04/22 21:38:02 wmay Exp $";
#endif

/* Allow access to a raw mixing buffer */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/time.h>
#include <sys/ioctl.h>
#include <sys/stat.h>

#include "SDL_audio.h"
#include "SDL_error.h"
#include "SDL_audiomem.h"
#include "SDL_audio_c.h"
#include "SDL_timer.h"
#include "SDL_audiodev_c.h"
#include "SDL_paudio.h"

#define DEBUG_AUDIO 1

/* A conflict within AIX 4.3.3 <sys/> headers and probably others as well.
 * I guess nobody ever uses audio... Shame over AIX header files.  */
#include <sys/machine.h>
#undef BIG_ENDIAN
#include <sys/audio.h>

/* The tag name used by paud audio */
#define Paud_DRIVER_NAME         "paud"

/* Open the audio device for playback, and don't block if busy */
/* #define OPEN_FLAGS	(O_WRONLY|O_NONBLOCK) */
#define OPEN_FLAGS	O_WRONLY

/* Audio driver functions */
static int Paud_OpenAudio(_THIS, SDL_AudioSpec *spec);
static void Paud_WaitAudio(_THIS);
static void Paud_PlayAudio(_THIS);
static Uint8 *Paud_GetAudioBuf(_THIS);
static void Paud_CloseAudio(_THIS);

/* Audio driver bootstrap functions */

static int Audio_Available(void)
{
	int fd;
	int available;

	available = 0;
	fd = SDL_OpenAudioPath(NULL, 0, OPEN_FLAGS, 0);
	if ( fd >= 0 ) {
		available = 1;
		close(fd);
	}
	return(available);
}

static void Audio_DeleteDevice(SDL_AudioDevice *device)
{
	free(device->hidden);
	free(device);
}

static SDL_AudioDevice *Audio_CreateDevice(int devindex)
{
	SDL_AudioDevice *this;

	/* Initialize all variables that we clean on shutdown */
	this = (SDL_AudioDevice *)malloc(sizeof(SDL_AudioDevice));
	if ( this ) {
		memset(this, 0, (sizeof *this));
		this->hidden = (struct SDL_PrivateAudioData *)
				malloc((sizeof *this->hidden));
	}
	if ( (this == NULL) || (this->hidden == NULL) ) {
		SDL_OutOfMemory();
		if ( this ) {
			free(this);
		}
		return(0);
	}
	memset(this->hidden, 0, (sizeof *this->hidden));
	audio_fd = -1;

	/* Set the function pointers */
	this->OpenAudio = Paud_OpenAudio;
	this->WaitAudio = Paud_WaitAudio;
	this->PlayAudio = Paud_PlayAudio;
	this->GetAudioBuf = Paud_GetAudioBuf;
	this->CloseAudio = Paud_CloseAudio;

	this->free = Audio_DeleteDevice;

	return this;
}

AudioBootStrap Paud_bootstrap = {
	Paud_DRIVER_NAME, "AIX Paudio",
	Audio_Available, Audio_CreateDevice
};

/* This function waits until it is possible to write a full sound buffer */
static void Paud_WaitAudio(_THIS)
{
    fd_set fdset;

    /* See if we need to use timed audio synchronization */
    if ( frame_ticks ) {
        /* Use timer for general audio synchronization */
        Sint32 ticks;

        ticks = ((Sint32)(next_frame - SDL_GetTicks()))-FUDGE_TICKS;
        if ( ticks > 0 ) {
	    SDL_Delay(ticks);
        }
    } else {
        audio_buffer  paud_bufinfo;

        /* Use select() for audio synchronization */
        struct timeval timeout;
        FD_ZERO(&fdset);
        FD_SET(audio_fd, &fdset);

        if ( ioctl(audio_fd, AUDIO_BUFFER, &paud_bufinfo) < 0 ) {
#ifdef DEBUG_AUDIO
            fprintf(stderr, "Couldn't get audio buffer information\n");
#endif
            timeout.tv_sec  = 10;
            timeout.tv_usec = 0;
        } else {
	    long ms_in_buf = paud_bufinfo.write_buf_time;
            timeout.tv_sec  = ms_in_buf/1000;
	    ms_in_buf       = ms_in_buf - timeout.tv_sec*1000;
            timeout.tv_usec = ms_in_buf*1000;
#ifdef DEBUG_AUDIO
            fprintf( stderr,
		     "Waiting for write_buf_time=%ld,%ld\n",
		     timeout.tv_sec,
		     timeout.tv_usec );
#endif
	}

#ifdef DEBUG_AUDIO
        fprintf(stderr, "Waiting for audio to get ready\n");
#endif
        if ( select(audio_fd+1, NULL, &fdset, NULL, &timeout) <= 0 ) {
            const char *message = "Audio timeout - buggy audio driver? (disabled)";
            /*
	     * In general we should never print to the screen,
             * but in this case we have no other way of letting
             * the user know what happened.
             */
            fprintf(stderr, "SDL: %s - %s\n", strerror(errno), message);
            this->enabled = 0;
            /* Don't try to close - may hang */
            audio_fd = -1;
#ifdef DEBUG_AUDIO
            fprintf(stderr, "Done disabling audio\n");
#endif
        }
#ifdef DEBUG_AUDIO
        fprintf(stderr, "Ready!\n");
#endif
    }
}

static void Paud_PlayAudio(_THIS)
{
	int written;

	/* Write the audio data, checking for EAGAIN on broken audio drivers */
	do {
		written = write(audio_fd, mixbuf, mixlen);
		if ( (written < 0) && ((errno == 0) || (errno == EAGAIN)) ) {
			SDL_Delay(1);	/* Let a little CPU time go by */
		}
	} while ( (written < 0) && 
	          ((errno == 0) || (errno == EAGAIN) || (errno == EINTR)) );

	/* If timer synchronization is enabled, set the next write frame */
	if ( frame_ticks ) {
		next_frame += frame_ticks;
	}

	/* If we couldn't write, assume fatal error for now */
	if ( written < 0 ) {
		this->enabled = 0;
	}
#ifdef DEBUG_AUDIO
	fprintf(stderr, "Wrote %d bytes of audio data\n", written);
#endif
}

static Uint8 *Paud_GetAudioBuf(_THIS)
{
	return mixbuf;
}

static void Paud_CloseAudio(_THIS)
{
	if ( mixbuf != NULL ) {
		SDL_FreeAudioMem(mixbuf);
		mixbuf = NULL;
	}
	if ( audio_fd >= 0 ) {
		close(audio_fd);
		audio_fd = -1;
	}
}

static int Paud_OpenAudio(_THIS, SDL_AudioSpec *spec)
{
	char          audiodev[1024];
	int           format;
	int           bytes_per_sample;
	Uint16        test_format;
	audio_init    paud_init;
	audio_buffer  paud_bufinfo;
	audio_status  paud_status;
	audio_control paud_control;
	audio_change  paud_change;

	/* Reset the timer synchronization flag */
	frame_ticks = 0.0;

	/* Open the audio device */
	audio_fd = SDL_OpenAudioPath(audiodev, sizeof(audiodev), OPEN_FLAGS, 0);
	if ( audio_fd < 0 ) {
		SDL_SetError("Couldn't open %s: %s", audiodev, strerror(errno));
		return -1;