src/audio/alsa/SDL_alsa_audio.c
author Sam Lantinga
Sat, 17 Oct 2009 07:04:58 +0000
branchSDL-1.2
changeset 4348 b312352d8c8d
parent 4347 38f22ed3a433
child 4349 471dac4b41dd
permissions -rw-r--r--
Enable the ALSA debug code via environment variable
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/*
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    SDL - Simple DirectMedia Layer
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    Copyright (C) 1997-2009 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@libsdl.org
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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 <sys/types.h>
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#include <signal.h>	/* For kill() */
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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_alsa_audio.h"
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#ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC
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#include "SDL_name.h"
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#include "SDL_loadso.h"
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#else
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#define SDL_NAME(X)	X
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#endif
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/* The tag name used by ALSA audio */
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#define DRIVER_NAME         "alsa"
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/*#define DEBUG_PERIOD_SIZE*/
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/* Audio driver functions */
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static int ALSA_OpenAudio(_THIS, SDL_AudioSpec *spec);
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static void ALSA_WaitAudio(_THIS);
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static void ALSA_PlayAudio(_THIS);
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static Uint8 *ALSA_GetAudioBuf(_THIS);
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static void ALSA_CloseAudio(_THIS);
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#ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC
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static const char *alsa_library = SDL_AUDIO_DRIVER_ALSA_DYNAMIC;
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static void *alsa_handle = NULL;
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static int alsa_loaded = 0;
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static int (*SDL_NAME(snd_pcm_open))(snd_pcm_t **pcm, const char *name, snd_pcm_stream_t stream, int mode);
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static int (*SDL_NAME(snd_pcm_close))(snd_pcm_t *pcm);
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static snd_pcm_sframes_t (*SDL_NAME(snd_pcm_writei))(snd_pcm_t *pcm, const void *buffer, snd_pcm_uframes_t size);
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static int (*SDL_NAME(snd_pcm_resume))(snd_pcm_t *pcm);
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static int (*SDL_NAME(snd_pcm_prepare))(snd_pcm_t *pcm);
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static int (*SDL_NAME(snd_pcm_drain))(snd_pcm_t *pcm);
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static const char *(*SDL_NAME(snd_strerror))(int errnum);
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static size_t (*SDL_NAME(snd_pcm_hw_params_sizeof))(void);
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static size_t (*SDL_NAME(snd_pcm_sw_params_sizeof))(void);
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static int (*SDL_NAME(snd_pcm_hw_params_any))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params);
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static int (*SDL_NAME(snd_pcm_hw_params_set_access))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_access_t access);
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static int (*SDL_NAME(snd_pcm_hw_params_set_format))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_format_t val);
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static int (*SDL_NAME(snd_pcm_hw_params_set_channels))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val);
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static int (*SDL_NAME(snd_pcm_hw_params_get_channels))(const snd_pcm_hw_params_t *params, unsigned int *val);
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static int (*SDL_NAME(snd_pcm_hw_params_set_rate_near))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir);
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static int (*SDL_NAME(snd_pcm_hw_params_set_period_size_near))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val, int *dir);
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static int (*SDL_NAME(snd_pcm_hw_params_get_period_size))(const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *frames, int *dir);
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static int (*SDL_NAME(snd_pcm_hw_params_set_periods_near))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir);
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static int (*SDL_NAME(snd_pcm_hw_params_get_periods))(const snd_pcm_hw_params_t *params, unsigned int *val, int *dir);
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static int (*SDL_NAME(snd_pcm_hw_params_set_buffer_size_near))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val);
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static int (*SDL_NAME(snd_pcm_hw_params_get_buffer_size))(const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val);
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static int (*SDL_NAME(snd_pcm_hw_params))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params);
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/*
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*/
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static int (*SDL_NAME(snd_pcm_sw_params_current))(snd_pcm_t *pcm, snd_pcm_sw_params_t *swparams);
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static int (*SDL_NAME(snd_pcm_sw_params_set_start_threshold))(snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_uframes_t val);
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static int (*SDL_NAME(snd_pcm_sw_params))(snd_pcm_t *pcm, snd_pcm_sw_params_t *params);
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static int (*SDL_NAME(snd_pcm_nonblock))(snd_pcm_t *pcm, int nonblock);
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#define snd_pcm_hw_params_sizeof SDL_NAME(snd_pcm_hw_params_sizeof)
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#define snd_pcm_sw_params_sizeof SDL_NAME(snd_pcm_sw_params_sizeof)
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/* cast funcs to char* first, to please GCC's strict aliasing rules. */
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static struct {
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	const char *name;
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	void **func;
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} alsa_functions[] = {
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	{ "snd_pcm_open",	(void**)(char*)&SDL_NAME(snd_pcm_open)		},
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	{ "snd_pcm_close",	(void**)(char*)&SDL_NAME(snd_pcm_close)	},
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	{ "snd_pcm_writei",	(void**)(char*)&SDL_NAME(snd_pcm_writei)	},
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	{ "snd_pcm_resume",	(void**)(char*)&SDL_NAME(snd_pcm_resume)	},
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	{ "snd_pcm_prepare",	(void**)(char*)&SDL_NAME(snd_pcm_prepare)	},
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	{ "snd_pcm_drain",	(void**)(char*)&SDL_NAME(snd_pcm_drain)	},
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	{ "snd_strerror",	(void**)(char*)&SDL_NAME(snd_strerror)		},
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	{ "snd_pcm_hw_params_sizeof",		(void**)(char*)&SDL_NAME(snd_pcm_hw_params_sizeof)		},
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	{ "snd_pcm_sw_params_sizeof",		(void**)(char*)&SDL_NAME(snd_pcm_sw_params_sizeof)		},
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	{ "snd_pcm_hw_params_any",		(void**)(char*)&SDL_NAME(snd_pcm_hw_params_any)		},
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	{ "snd_pcm_hw_params_set_access",	(void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_access)		},
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	{ "snd_pcm_hw_params_set_format",	(void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_format)		},
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	{ "snd_pcm_hw_params_set_channels",	(void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_channels)	},
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	{ "snd_pcm_hw_params_get_channels",	(void**)(char*)&SDL_NAME(snd_pcm_hw_params_get_channels)	},
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	{ "snd_pcm_hw_params_set_rate_near",	(void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_rate_near)	},
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	{ "snd_pcm_hw_params_set_period_size_near",	(void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_period_size_near)	},
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	{ "snd_pcm_hw_params_get_period_size",	(void**)(char*)&SDL_NAME(snd_pcm_hw_params_get_period_size)	},
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	{ "snd_pcm_hw_params_set_periods_near",	(void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_periods_near)	},
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	{ "snd_pcm_hw_params_get_periods",	(void**)(char*)&SDL_NAME(snd_pcm_hw_params_get_periods)	},
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	{ "snd_pcm_hw_params_set_buffer_size_near",	(void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_buffer_size_near) },
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	{ "snd_pcm_hw_params_get_buffer_size",	(void**)(char*)&SDL_NAME(snd_pcm_hw_params_get_buffer_size) },
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	{ "snd_pcm_hw_params",	(void**)(char*)&SDL_NAME(snd_pcm_hw_params)	},
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	{ "snd_pcm_sw_params_current",	(void**)(char*)&SDL_NAME(snd_pcm_sw_params_current)	},
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	{ "snd_pcm_sw_params_set_start_threshold",	(void**)(char*)&SDL_NAME(snd_pcm_sw_params_set_start_threshold)	},
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	{ "snd_pcm_sw_params",	(void**)(char*)&SDL_NAME(snd_pcm_sw_params)	},
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	{ "snd_pcm_nonblock",	(void**)(char*)&SDL_NAME(snd_pcm_nonblock)	},
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};
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static void UnloadALSALibrary(void) {
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	if (alsa_loaded) {
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		SDL_UnloadObject(alsa_handle);
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		alsa_handle = NULL;
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		alsa_loaded = 0;
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	}
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}
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static int LoadALSALibrary(void) {
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	int i, retval = -1;
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	alsa_handle = SDL_LoadObject(alsa_library);
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	if (alsa_handle) {
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		alsa_loaded = 1;
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		retval = 0;
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		for (i = 0; i < SDL_arraysize(alsa_functions); i++) {
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			*alsa_functions[i].func = SDL_LoadFunction(alsa_handle,alsa_functions[i].name);
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			if (!*alsa_functions[i].func) {
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				retval = -1;
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				UnloadALSALibrary();
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				break;
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			}
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		}
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	}
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	return retval;
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}
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#else
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static void UnloadALSALibrary(void) {
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	return;
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}
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static int LoadALSALibrary(void) {
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	return 0;
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}
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#endif /* SDL_AUDIO_DRIVER_ALSA_DYNAMIC */
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static const char *get_audio_device(int channels)
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{
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	const char *device;
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	device = SDL_getenv("AUDIODEV");	/* Is there a standard variable name? */
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	if ( device == NULL ) {
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		switch (channels) {
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		case 6:
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			device = "plug:surround51";
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			break;
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		case 4:
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			device = "plug:surround40";
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			break;
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		default:
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			device = "default";
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			break;
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		}
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	}
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	return device;
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}
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/* Audio driver bootstrap functions */
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static int Audio_Available(void)
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{
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	int available;
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	int status;
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	snd_pcm_t *handle;
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	available = 0;
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	if (LoadALSALibrary() < 0) {
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		return available;
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	}
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	status = SDL_NAME(snd_pcm_open)(&handle, get_audio_device(2), SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
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	if ( status >= 0 ) {
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		available = 1;
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        	SDL_NAME(snd_pcm_close)(handle);
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	}
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	UnloadALSALibrary();
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	return(available);
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}
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static void 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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	UnloadALSALibrary();
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}
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static SDL_AudioDevice *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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	LoadALSALibrary();
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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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	/* Set the function pointers */
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	this->OpenAudio = ALSA_OpenAudio;
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	this->WaitAudio = ALSA_WaitAudio;
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	this->PlayAudio = ALSA_PlayAudio;
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	this->GetAudioBuf = ALSA_GetAudioBuf;
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	this->CloseAudio = ALSA_CloseAudio;
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	this->free = Audio_DeleteDevice;
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	return this;
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}
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AudioBootStrap ALSA_bootstrap = {
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	DRIVER_NAME, "ALSA PCM 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 ALSA_WaitAudio(_THIS)
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{
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	/* Check to see if the thread-parent process is still alive */
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	{ static int cnt = 0;
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		/* Note that this only works with thread implementations 
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		   that use a different process id for each thread.
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		*/
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		if (parent && (((++cnt)%10) == 0)) { /* Check every 10 loops */
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			if ( kill(parent, 0) < 0 ) {
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				this->enabled = 0;
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			}
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		}
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	}
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}
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/*
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 * http://bugzilla.libsdl.org/show_bug.cgi?id=110
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 * "For Linux ALSA, this is FL-FR-RL-RR-C-LFE
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 *  and for Windows DirectX [and CoreAudio], this is FL-FR-C-LFE-RL-RR"
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 */
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#define SWIZ6(T) \
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    T *ptr = (T *) mixbuf; \
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    const Uint32 count = (this->spec.samples / 6); \
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    Uint32 i; \
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    for (i = 0; i < count; i++, ptr += 6) { \
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        T tmp; \
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        tmp = ptr[2]; ptr[2] = ptr[4]; ptr[4] = tmp; \
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        tmp = ptr[3]; ptr[3] = ptr[5]; ptr[5] = tmp; \
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    }
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static __inline__ void swizzle_alsa_channels_6_64bit(_THIS) { SWIZ6(Uint64); }
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static __inline__ void swizzle_alsa_channels_6_32bit(_THIS) { SWIZ6(Uint32); }
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static __inline__ void swizzle_alsa_channels_6_16bit(_THIS) { SWIZ6(Uint16); }
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static __inline__ void swizzle_alsa_channels_6_8bit(_THIS) { SWIZ6(Uint8); }
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#undef SWIZ6
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/*
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 * Called right before feeding this->mixbuf to the hardware. Swizzle channels
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 *  from Windows/Mac order to the format alsalib will want.
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 */
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static __inline__ void swizzle_alsa_channels(_THIS)
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{
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    if (this->spec.channels == 6) {
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        const Uint16 fmtsize = (this->spec.format & 0xFF); /* bits/channel. */
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        if (fmtsize == 16)
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            swizzle_alsa_channels_6_16bit(this);
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        else if (fmtsize == 8)
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            swizzle_alsa_channels_6_8bit(this);
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        else if (fmtsize == 32)
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            swizzle_alsa_channels_6_32bit(this);
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        else if (fmtsize == 64)
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            swizzle_alsa_channels_6_64bit(this);
icculus@1878
   307
    }
icculus@1878
   308
icculus@1878
   309
    /* !!! FIXME: update this for 7.1 if needed, later. */
icculus@1878
   310
}
icculus@1878
   311
icculus@1878
   312
slouken@354
   313
static void ALSA_PlayAudio(_THIS)
slouken@0
   314
{
icculus@4320
   315
	int status;
slouken@4332
   316
	snd_pcm_uframes_t frames_left;
icculus@4320
   317
	const Uint8 *sample_buf = (const Uint8 *) mixbuf;
slouken@4336
   318
	const int frame_size = (((int) (this->spec.format & 0xFF)) / 8) * this->spec.channels;
slouken@765
   319
icculus@1878
   320
	swizzle_alsa_channels(this);
icculus@1878
   321
slouken@4332
   322
	frames_left = ((snd_pcm_uframes_t) this->spec.samples);
icculus@1878
   323
slouken@4337
   324
	while ( frames_left > 0 && this->enabled ) {
slouken@4332
   325
		status = SDL_NAME(snd_pcm_writei)(pcm_handle, sample_buf, frames_left);
slouken@354
   326
		if ( status < 0 ) {
slouken@354
   327
			if ( status == -EAGAIN ) {
slouken@765
   328
				SDL_Delay(1);
slouken@354
   329
				continue;
slouken@354
   330
			}
slouken@354
   331
			if ( status == -ESTRPIPE ) {
slouken@354
   332
				do {
slouken@765
   333
					SDL_Delay(1);
slouken@865
   334
					status = SDL_NAME(snd_pcm_resume)(pcm_handle);
slouken@354
   335
				} while ( status == -EAGAIN );
slouken@354
   336
			}
slouken@354
   337
			if ( status < 0 ) {
slouken@865
   338
				status = SDL_NAME(snd_pcm_prepare)(pcm_handle);
slouken@354
   339
			}
slouken@354
   340
			if ( status < 0 ) {
slouken@354
   341
				/* Hmm, not much we can do - abort */
slouken@354
   342
				this->enabled = 0;
slouken@354
   343
				return;
slouken@0
   344
			}
slouken@356
   345
			continue;
slouken@0
   346
		}
slouken@4336
   347
		sample_buf += status * frame_size;
slouken@4332
   348
		frames_left -= status;
slouken@0
   349
	}
slouken@0
   350
}
slouken@0
   351
slouken@354
   352
static Uint8 *ALSA_GetAudioBuf(_THIS)
slouken@0
   353
{
slouken@354
   354
	return(mixbuf);
slouken@0
   355
}
slouken@0
   356
slouken@354
   357
static void ALSA_CloseAudio(_THIS)
slouken@0
   358
{
slouken@354
   359
	if ( mixbuf != NULL ) {
slouken@354
   360
		SDL_FreeAudioMem(mixbuf);
slouken@354
   361
		mixbuf = NULL;
slouken@0
   362
	}
slouken@354
   363
	if ( pcm_handle ) {
slouken@865
   364
		SDL_NAME(snd_pcm_drain)(pcm_handle);
slouken@865
   365
		SDL_NAME(snd_pcm_close)(pcm_handle);
slouken@354
   366
		pcm_handle = NULL;
slouken@0
   367
	}
slouken@0
   368
}
slouken@0
   369
slouken@354
   370
static int ALSA_OpenAudio(_THIS, SDL_AudioSpec *spec)
slouken@0
   371
{
slouken@354
   372
	int                  status;
slouken@1552
   373
	snd_pcm_hw_params_t *hwparams;
slouken@1552
   374
	snd_pcm_sw_params_t *swparams;
slouken@354
   375
	snd_pcm_format_t     format;
slouken@354
   376
	snd_pcm_uframes_t    frames;
icculus@4292
   377
	unsigned int         rate;
icculus@4292
   378
	unsigned int         periods;
slouken@4333
   379
	unsigned int 	     channels;
slouken@354
   380
	Uint16               test_format;
slouken@0
   381
slouken@0
   382
	/* Open the audio device */
slouken@942
   383
	/* Name of device should depend on # channels in spec */
slouken@942
   384
	status = SDL_NAME(snd_pcm_open)(&pcm_handle, get_audio_device(spec->channels), SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
slouken@942
   385
slouken@354
   386
	if ( status < 0 ) {
slouken@865
   387
		SDL_SetError("Couldn't open audio device: %s", SDL_NAME(snd_strerror)(status));
slouken@354
   388
		return(-1);
slouken@354
   389
	}
slouken@354
   390
slouken@354
   391
	/* Figure out what the hardware is capable of */
slouken@1552
   392
	snd_pcm_hw_params_alloca(&hwparams);
slouken@1552
   393
	status = SDL_NAME(snd_pcm_hw_params_any)(pcm_handle, hwparams);
slouken@354
   394
	if ( status < 0 ) {
slouken@865
   395
		SDL_SetError("Couldn't get hardware config: %s", SDL_NAME(snd_strerror)(status));
slouken@354
   396
		ALSA_CloseAudio(this);
slouken@354
   397
		return(-1);
slouken@354
   398
	}
slouken@354
   399
slouken@354
   400
	/* SDL only uses interleaved sample output */
slouken@1552
   401
	status = SDL_NAME(snd_pcm_hw_params_set_access)(pcm_handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED);
slouken@354
   402
	if ( status < 0 ) {
slouken@865
   403
		SDL_SetError("Couldn't set interleaved access: %s", SDL_NAME(snd_strerror)(status));
slouken@354
   404
		ALSA_CloseAudio(this);
slouken@0
   405
		return(-1);
slouken@0
   406
	}
slouken@0
   407
slouken@0
   408
	/* Try for a closest match on audio format */
slouken@354
   409
	status = -1;
slouken@0
   410
	for ( test_format = SDL_FirstAudioFormat(spec->format);
slouken@354
   411
	      test_format && (status < 0); ) {
slouken@354
   412
		switch ( test_format ) {
slouken@0
   413
			case AUDIO_U8:
slouken@354
   414
				format = SND_PCM_FORMAT_U8;
slouken@0
   415
				break;
slouken@0
   416
			case AUDIO_S8:
slouken@354
   417
				format = SND_PCM_FORMAT_S8;
slouken@0
   418
				break;
slouken@0
   419
			case AUDIO_S16LSB:
slouken@354
   420
				format = SND_PCM_FORMAT_S16_LE;
slouken@0
   421
				break;
slouken@0
   422
			case AUDIO_S16MSB:
slouken@354
   423
				format = SND_PCM_FORMAT_S16_BE;
slouken@0
   424
				break;
slouken@0
   425
			case AUDIO_U16LSB:
slouken@354
   426
				format = SND_PCM_FORMAT_U16_LE;
slouken@0
   427
				break;
slouken@0
   428
			case AUDIO_U16MSB:
slouken@354
   429
				format = SND_PCM_FORMAT_U16_BE;
slouken@0
   430
				break;
slouken@0
   431
			default:
slouken@354
   432
				format = 0;
slouken@0
   433
				break;
slouken@0
   434
		}
slouken@354
   435
		if ( format != 0 ) {
slouken@1552
   436
			status = SDL_NAME(snd_pcm_hw_params_set_format)(pcm_handle, hwparams, format);
slouken@354
   437
		}
slouken@354
   438
		if ( status < 0 ) {
slouken@0
   439
			test_format = SDL_NextAudioFormat();
slouken@0
   440
		}
slouken@0
   441
	}
slouken@354
   442
	if ( status < 0 ) {
slouken@0
   443
		SDL_SetError("Couldn't find any hardware audio formats");
slouken@354
   444
		ALSA_CloseAudio(this);
slouken@0
   445
		return(-1);
slouken@0
   446
	}
slouken@0
   447
	spec->format = test_format;
slouken@0
   448
slouken@354
   449
	/* Set the number of channels */
slouken@1552
   450
	status = SDL_NAME(snd_pcm_hw_params_set_channels)(pcm_handle, hwparams, spec->channels);
icculus@4292
   451
	channels = spec->channels;
slouken@354
   452
	if ( status < 0 ) {
icculus@4292
   453
		status = SDL_NAME(snd_pcm_hw_params_get_channels)(hwparams, &channels);
icculus@4292
   454
		if ( status < 0 ) {
slouken@354
   455
			SDL_SetError("Couldn't set audio channels");
slouken@354
   456
			ALSA_CloseAudio(this);
slouken@354
   457
			return(-1);
slouken@354
   458
		}
icculus@4292
   459
		spec->channels = channels;
slouken@354
   460
	}
slouken@0
   461
slouken@354
   462
	/* Set the audio rate */
icculus@4292
   463
	rate = spec->freq;
icculus@4292
   464
icculus@4292
   465
	status = SDL_NAME(snd_pcm_hw_params_set_rate_near)(pcm_handle, hwparams, &rate, NULL);
slouken@354
   466
	if ( status < 0 ) {
slouken@865
   467
		SDL_SetError("Couldn't set audio frequency: %s", SDL_NAME(snd_strerror)(status));
slouken@354
   468
		ALSA_CloseAudio(this);
slouken@354
   469
		return(-1);
slouken@354
   470
	}
icculus@4292
   471
	spec->freq = rate;
slouken@0
   472
slouken@354
   473
	/* Set the buffer size, in samples */
slouken@4347
   474
	if (getenv("SDL_AUDIO_ALSA_SET_PERIOD_SIZE")) {
slouken@4347
   475
		frames = spec->samples;
slouken@4347
   476
		status = SDL_NAME(snd_pcm_hw_params_set_period_size_near)(pcm_handle, hwparams, &frames, NULL);
slouken@4347
   477
		if ( status < 0 ) {
slouken@4347
   478
			SDL_SetError("Couldn't set period size: %s", SDL_NAME(snd_strerror)(status));
slouken@4347
   479
			ALSA_CloseAudio(this);
slouken@4347
   480
			return(-1);
slouken@4347
   481
		}
icculus@4292
   482
slouken@4347
   483
		spec->samples = frames;
icculus@4292
   484
slouken@4347
   485
		periods = 2;
slouken@4347
   486
		status = SDL_NAME(snd_pcm_hw_params_set_periods_near)(pcm_handle, hwparams, &periods, NULL);
slouken@4347
   487
		if ( status < 0 ) {
slouken@4347
   488
			SDL_SetError("Couldn't set period count: %s", SDL_NAME(snd_strerror)(status));
slouken@4347
   489
			ALSA_CloseAudio(this);
slouken@4347
   490
			return(-1);
slouken@4347
   491
		}
slouken@4347
   492
	} else {
slouken@4347
   493
		frames = spec->samples * 2;
slouken@4347
   494
		status = SDL_NAME(snd_pcm_hw_params_set_buffer_size_near)(pcm_handle, hwparams, &frames);
slouken@4347
   495
		if ( status < 0 ) {
slouken@4347
   496
			SDL_SetError("Couldn't set buffer size: %s", SDL_NAME(snd_strerror)(status));
slouken@4347
   497
			ALSA_CloseAudio(this);
slouken@4347
   498
			return(-1);
slouken@4347
   499
		}
slouken@4333
   500
	}
slouken@354
   501
slouken@354
   502
	/* "set" the hardware with the desired parameters */
slouken@1552
   503
	status = SDL_NAME(snd_pcm_hw_params)(pcm_handle, hwparams);
slouken@1552
   504
	if ( status < 0 ) {
slouken@1552
   505
		SDL_SetError("Couldn't set hardware audio parameters: %s", SDL_NAME(snd_strerror)(status));
slouken@1552
   506
		ALSA_CloseAudio(this);
slouken@1552
   507
		return(-1);
slouken@1552
   508
	}
slouken@1552
   509
slouken@4348
   510
	/* This is useful for debugging */
slouken@4348
   511
	if (getenv("SDL_AUDIO_ALSA_DEBUG_PERIOD_SIZE")) {
slouken@4348
   512
		snd_pcm_uframes_t bufsize;
slouken@4348
   513
		snd_pcm_sframes_t persize;
slouken@4348
   514
		unsigned int periods; int dir;
slouken@1552
   515
slouken@4348
   516
		SDL_NAME(snd_pcm_hw_params_get_buffer_size)(hwparams, &bufsize);
slouken@4348
   517
		SDL_NAME(snd_pcm_hw_params_get_period_size)(hwparams, &persize, &dir);
slouken@4348
   518
		SDL_NAME(snd_pcm_hw_params_get_periods)(hwparams, &periods, &dir);
slouken@4348
   519
slouken@4348
   520
		fprintf(stderr, "ALSA: period size = %ld, periods = %u, buffer size = %lu\n", persize, periods, bufsize);
slouken@4348
   521
	}
slouken@1552
   522
slouken@1552
   523
	/* Set the software parameters */
slouken@1552
   524
	snd_pcm_sw_params_alloca(&swparams);
slouken@1552
   525
	status = SDL_NAME(snd_pcm_sw_params_current)(pcm_handle, swparams);
slouken@354
   526
	if ( status < 0 ) {
slouken@1552
   527
		SDL_SetError("Couldn't get software config: %s", SDL_NAME(snd_strerror)(status));
slouken@1552
   528
		ALSA_CloseAudio(this);
slouken@1552
   529
		return(-1);
slouken@1552
   530
	}
slouken@4331
   531
	status = SDL_NAME(snd_pcm_sw_params_set_start_threshold)(pcm_handle, swparams, 1);
slouken@1552
   532
	if ( status < 0 ) {
slouken@1552
   533
		SDL_SetError("Couldn't set start threshold: %s", SDL_NAME(snd_strerror)(status));
slouken@1552
   534
		ALSA_CloseAudio(this);
slouken@1552
   535
		return(-1);
slouken@1552
   536
	}
slouken@1552
   537
	status = SDL_NAME(snd_pcm_sw_params)(pcm_handle, swparams);
slouken@1552
   538
	if ( status < 0 ) {
slouken@1552
   539
		SDL_SetError("Couldn't set software audio parameters: %s", SDL_NAME(snd_strerror)(status));
slouken@354
   540
		ALSA_CloseAudio(this);
slouken@0
   541
		return(-1);
slouken@0
   542
	}
slouken@0
   543
slouken@354
   544
	/* Calculate the final parameters for this audio specification */
slouken@354
   545
	SDL_CalculateAudioSpec(spec);
slouken@0
   546
slouken@354
   547
	/* Allocate mixing buffer */
slouken@354
   548
	mixlen = spec->size;
slouken@354
   549
	mixbuf = (Uint8 *)SDL_AllocAudioMem(mixlen);
slouken@354
   550
	if ( mixbuf == NULL ) {
slouken@354
   551
		ALSA_CloseAudio(this);
slouken@354
   552
		return(-1);
slouken@0
   553
	}
slouken@1336
   554
	SDL_memset(mixbuf, spec->silence, spec->size);
slouken@0
   555
slouken@0
   556
	/* Get the parent process id (we're the parent of the audio thread) */
slouken@0
   557
	parent = getpid();
slouken@0
   558
slouken@765
   559
	/* Switch to blocking mode for playback */
slouken@865
   560
	SDL_NAME(snd_pcm_nonblock)(pcm_handle, 0);
slouken@765
   561
slouken@0
   562
	/* We're ready to rock and roll. :-) */
slouken@0
   563
	return(0);
slouken@0
   564
}