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SDL_dmaaudio.c
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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,
but WITHOUT ANY WARRANTY; without even the implied warranty of
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
License along with this library; if not, write to the Free Software
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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*/
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#include "SDL_config.h"
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/* !!! FIXME: merge this driver with "dsp". */
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/* Allow access to a raw mixing buffer */
#include <stdio.h>
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#include <string.h> /* For strerror() */
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#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/mman.h>
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#if SDL_AUDIO_DRIVER_OSS_SOUNDCARD_H
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/* This is installed on some systems */
#include <soundcard.h>
#else
/* This is recommended by OSS */
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#include <sys/soundcard.h>
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#endif
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#ifndef MAP_FAILED
#define MAP_FAILED ((Uint8 *)-1)
#endif
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#include "SDL_timer.h"
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#include "SDL_audio.h"
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#include "../SDL_audio_c.h"
#include "../SDL_audiodev_c.h"
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#include "SDL_dmaaudio.h"
/* The tag name used by DMA audio */
#define DMA_DRIVER_NAME "dma"
/* Open the audio device for playback, and don't block if busy */
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#define OPEN_FLAGS_INPUT (O_RDWR|O_NONBLOCK)
#define OPEN_FLAGS_OUTPUT (O_RDWR|O_NONBLOCK)
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static char **outputDevices = NULL;
static int outputDeviceCount = 0;
static char **inputDevices = NULL;
static int inputDeviceCount = 0;
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static int
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test_for_mmap(int fd)
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{
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int caps = 0;
struct audio_buf_info info;
if ((ioctl(fd, SNDCTL_DSP_GETCAPS, &caps) == 0) &&
(caps & DSP_CAP_TRIGGER) && (caps & DSP_CAP_MMAP) &&
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(ioctl(fd, SNDCTL_DSP_GETOSPACE, &info) == 0)) {
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size_t len = info.fragstotal * info.fragsize;
Uint8 *buf = (Uint8 *) mmap(NULL, len, PROT_WRITE, MAP_SHARED, fd, 0);
if (buf != MAP_FAILED) {
munmap(buf, len);
return 1;
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}
}
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return 0;
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}
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static inline void
free_device_list(char ***devs, int *count)
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{
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SDL_FreeUnixAudioDevices(devs, count);
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}
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static inline void
build_device_list(int iscapture, char ***devs, int *count)
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{
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const int flags = ((iscapture) ? OPEN_FLAGS_INPUT : OPEN_FLAGS_OUTPUT);
free_device_list(devs, count);
SDL_EnumUnixAudioDevices(flags, 0, test_for_mmap, devs, count);
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}
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static inline void
build_device_lists(void)
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{
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build_device_list(0, &outputDevices, &outputDeviceCount);
build_device_list(1, &inputDevices, &inputDeviceCount);
}
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static inline void
free_device_lists(void)
{
free_device_list(&outputDevices, &outputDeviceCount);
free_device_list(&inputDevices, &inputDeviceCount);
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}
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static void
DMA_Deinitialize(void)
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{
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free_device_lists();
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}
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static int
DMA_DetectDevices(int iscapture)
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{
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if (iscapture) {
build_device_list(1, &inputDevices, &inputDeviceCount);
return inputDeviceCount;
} else {
build_device_list(0, &outputDevices, &outputDeviceCount);
return outputDeviceCount;
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}
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return 0; /* shouldn't ever hit this. */
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}
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static const char *
DMA_GetDeviceName(int index, int iscapture)
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{
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if ((iscapture) && (index < inputDeviceCount)) {
return inputDevices[index];
} else if ((!iscapture) && (index < outputDeviceCount)) {
return outputDevices[index];
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}
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SDL_SetError("No such device");
return NULL;
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}
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static int
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DMA_ReopenAudio(_THIS, const char *audiodev, int format, int stereo)
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{
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int frag_spec;
int value;
/* Close and then reopen the audio device */
close(audio_fd);
audio_fd = open(audiodev, O_RDWR, 0);
if (audio_fd < 0) {
SDL_SetError("Couldn't open %s: %s", audiodev, strerror(errno));
return (-1);
}
/* 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; (0x01 << frag_spec) < this->spec.size; ++frag_spec);
if ((0x01 << frag_spec) != this->spec.size) {
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SDL_SetError("Fragment size must be a power of two");
return (-1);
}
/* Set the audio buffering parameters */
if (ioctl(audio_fd, SNDCTL_DSP_SETFRAGMENT, &frag_spec) < 0) {
SDL_SetError("Couldn't set audio fragment spec");
return (-1);
}
/* Set the audio format */
value = format;
if ((ioctl(audio_fd, SNDCTL_DSP_SETFMT, &value) < 0) || (value != format)) {
SDL_SetError("Couldn't set audio format");
return (-1);
}
/* Set mono or stereo audio */
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value = (this->spec.channels > 1);
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if ((ioctl(audio_fd, SNDCTL_DSP_STEREO, &stereo) < 0) ||
(value != stereo)) {
SDL_SetError("Couldn't set audio channels");
return (-1);
}
/* Set the DSP frequency */
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value = this->spec.freq;
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if (ioctl(audio_fd, SNDCTL_DSP_SPEED, &value) < 0) {
SDL_SetError("Couldn't set audio frequency");
return (-1);
}
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this->spec.freq = value;
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/* We successfully re-opened the audio */
return (0);
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}
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static void
DMA_CloseDevice(_THIS)
{
if (this->hidden != NULL) {
if (dma_buf != NULL) {
munmap(dma_buf, dma_len);
dma_buf = NULL;
}
if (audio_fd >= 0) {
close(audio_fd);
audio_fd = -1;
}
SDL_free(this->hidden);
this->hidden = NULL;
}
}
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static int
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DMA_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;
int stereo;
int value;
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SDL_AudioFormat test_format;
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struct audio_buf_info info;
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/* We don't care what the devname is...we'll try to open anything. */
/* ...but default to first name in the list... */
if (devname == NULL) {
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if (((iscapture) && (inputDeviceCount == 0)) ||
((!iscapture) && (outputDeviceCount == 0))) {
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SDL_SetError("No such audio device");
return 0;
}
devname = ((iscapture) ? inputDevices[0] : outputDevices[0]);
}
/* Initialize all variables that we clean on shutdown */
this->hidden = (struct SDL_PrivateAudioData *)
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SDL_malloc((sizeof *this->hidden));
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if (this->hidden == NULL) {
SDL_OutOfMemory();
return 0;
}
SDL_memset(this->hidden, 0, (sizeof *this->hidden));
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/* Open the audio device */
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audio_fd = open(devname, flags, 0);
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if (audio_fd < 0) {
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DMA_CloseDevice(this);
SDL_SetError("Couldn't open %s: %s", devname, strerror(errno));
return 0;
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}
dma_buf = NULL;
ioctl(audio_fd, SNDCTL_DSP_RESET, 0);
/* Get a list of supported hardware formats */
if (ioctl(audio_fd, SNDCTL_DSP_GETFMTS, &value) < 0) {
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DMA_CloseDevice(this);
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SDL_SetError("Couldn't get audio format list");
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return 0;
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}
/* Try for a closest match on audio format */
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) {
case AUDIO_U8:
if (value & AFMT_U8) {
format = AFMT_U8;
}
break;
case AUDIO_S8:
if (value & AFMT_S8) {
format = AFMT_S8;
}
break;
case AUDIO_S16LSB:
if (value & AFMT_S16_LE) {
format = AFMT_S16_LE;
}
break;
case AUDIO_S16MSB:
if (value & AFMT_S16_BE) {
format = AFMT_S16_BE;
}
break;
case AUDIO_U16LSB:
if (value & AFMT_U16_LE) {
format = AFMT_U16_LE;
}
break;
case AUDIO_U16MSB:
if (value & AFMT_U16_BE) {
format = AFMT_U16_BE;
}
break;
default:
format = 0;
break;
}
if (!format) {
test_format = SDL_NextAudioFormat();
}
}
if (format == 0) {
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DMA_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 */
value = format;
if ((ioctl(audio_fd, SNDCTL_DSP_SETFMT, &value) < 0) || (value != format)) {
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DMA_CloseDevice(this);
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SDL_SetError("Couldn't set audio format");
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return 0;
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}
/* Set mono or stereo audio (currently only two channels supported) */
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stereo = (this->spec.channels > 1);
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ioctl(audio_fd, SNDCTL_DSP_STEREO, &stereo);
if (stereo) {
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this->spec.channels = 2;
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} else {
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this->spec.channels = 1;
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}
/* Because some drivers don't allow setting the buffer size
after setting the format, we must re-open the audio device
once we know what format and channels are supported
*/
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if (DMA_ReopenAudio(this, devname, format, stereo) < 0) {
DMA_CloseDevice(this);
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/* Error is set by DMA_ReopenAudio() */
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return 0;
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}
/* Memory map the audio buffer */
if (ioctl(audio_fd, SNDCTL_DSP_GETOSPACE, &info) < 0) {
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DMA_CloseDevice(this);
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SDL_SetError("Couldn't get OSPACE parameters");
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return 0;
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}
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this->spec.size = info.fragsize;
this->spec.samples = this->spec.size / ((this->spec.format & 0xFF) / 8);
this->spec.samples /= this->spec.channels;
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num_buffers = info.fragstotal;
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dma_len = num_buffers * this->spec.size;
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dma_buf = (Uint8 *) mmap(NULL, dma_len, PROT_WRITE, MAP_SHARED,
audio_fd, 0);
if (dma_buf == MAP_FAILED) {
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DMA_CloseDevice(this);
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SDL_SetError("DMA memory map failed");
dma_buf = NULL;
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return 0;
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}
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SDL_memset(dma_buf, this->spec.silence, dma_len);
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/* Check to see if we need to use select() workaround */
{
char *workaround;
workaround = SDL_getenv("SDL_DSP_NOSELECT");
if (workaround) {
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frame_ticks =
(float) (this->spec.samples * 1000) / this->spec.freq;
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next_frame = SDL_GetTicks() + frame_ticks;
}
}
/* Trigger audio playback */
value = 0;
ioctl(audio_fd, SNDCTL_DSP_SETTRIGGER, &value);
value = PCM_ENABLE_OUTPUT;
if (ioctl(audio_fd, SNDCTL_DSP_SETTRIGGER, &value) < 0) {
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DMA_CloseDevice(this);
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SDL_SetError("Couldn't trigger audio output");
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return 0;
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}
/* Get the parent process id (we're the parent of the audio thread) */
parent = getpid();
/* We're ready to rock and roll. :-) */
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return 1;
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}
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/* This function waits until it is possible to write a full sound buffer */
static void
DMA_WaitDevice(_THIS)
{
fd_set fdset;
/* Check to see if the thread-parent process is still alive */
{
static int cnt = 0;
/* Note that this only works with thread implementations
that use a different process id for each thread.
*/
if (parent && (((++cnt) % 10) == 0)) { /* Check every 10 loops */
if (kill(parent, 0) < 0) {
this->enabled = 0;
}
}
}
/* 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 {
/* Use select() for audio synchronization */
struct timeval timeout;
FD_ZERO(&fdset);
FD_SET(audio_fd, &fdset);
timeout.tv_sec = 10;
timeout.tv_usec = 0;
#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 =
#ifdef AUDIO_OSPACE_HACK
"Audio timeout - buggy audio driver? (trying ospace)";
#else
"Audio timeout - buggy audio driver? (disabled)";
#endif
/* 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\n", message);
#ifdef AUDIO_OSPACE_HACK
/* We may be able to use GET_OSPACE trick */
frame_ticks = (float) (this->spec.samples * 1000) /
this->spec.freq;
next_frame = SDL_GetTicks() + frame_ticks;
#else
this->enabled = 0;
/* Don't try to close - may hang */
audio_fd = -1;
#ifdef DEBUG_AUDIO
fprintf(stderr, "Done disabling audio\n");
#endif
#endif /* AUDIO_OSPACE_HACK */
}
#ifdef DEBUG_AUDIO
fprintf(stderr, "Ready!\n");
#endif
}
}
static void
DMA_PlayDevice(_THIS)
{
/* If timer synchronization is enabled, set the next write frame */
if (frame_ticks) {
next_frame += frame_ticks;
}
return;
}
static Uint8 *
DMA_GetDeviceBuf(_THIS)
{
count_info info;
int playing;
int filling;
/* Get number of blocks, looping if we're not using select() */
do {
if (ioctl(audio_fd, SNDCTL_DSP_GETOPTR, &info) < 0) {
/* Uh oh... */
this->enabled = 0;
return (NULL);
}
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} while (frame_ticks && (info.blocks < 1));
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#ifdef DEBUG_AUDIO
if (info.blocks > 1) {
printf("Warning: audio underflow (%d frags)\n", info.blocks - 1);
}
#endif
playing = info.ptr / this->spec.size;
filling = (playing + 1) % num_buffers;
return (dma_buf + (filling * this->spec.size));
}
static int
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DMA_Init(SDL_AudioDriverImpl * impl)
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{
/* Set the function pointers */
impl->DetectDevices = DMA_DetectDevices;
impl->GetDeviceName = DMA_GetDeviceName;
impl->OpenDevice = DMA_OpenDevice;
impl->WaitDevice = DMA_WaitDevice;
impl->PlayDevice = DMA_PlayDevice;
impl->GetDeviceBuf = DMA_GetDeviceBuf;
impl->CloseDevice = DMA_CloseDevice;
impl->Deinitialize = DMA_Deinitialize;
build_device_lists();
return 1;
}
AudioBootStrap DMA_bootstrap = {
DMA_DRIVER_NAME, "OSS /dev/dsp DMA audio", DMA_Init, 0
};
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/* vi: set ts=4 sw=4 expandtab: */