libao2/ao_oss.c

   1 /*
   2  * OSS audio output driver
   3  *
   4  * This file is part of MPlayer.
   5  *
   6  * MPlayer is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * MPlayer is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with MPlayer; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19  */
  20
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23
  24 #include <sys/ioctl.h>
  25 #include <unistd.h>
  26 #include <sys/time.h>
  27 #include <sys/types.h>
  28 #include <sys/stat.h>
  29 #include <fcntl.h>
  30 #include <errno.h>
  31 #include <string.h>
  32
  33 #include "config.h"
  34 #include "mp_msg.h"
  35 #include "mixer.h"
  36 #include "help_mp.h"
  37
  38 #ifdef HAVE_SYS_SOUNDCARD_H
  39 #include <sys/soundcard.h>
  40 #else
  41 #ifdef HAVE_SOUNDCARD_H
  42 #include <soundcard.h>
  43 #endif
  44 #endif
  45
  46 #include "libaf/af_format.h"
  47
  48 #include "audio_out.h"
  49 #include "audio_out_internal.h"
  50
  51 static const ao_info_t info =
  52 {
  53         "OSS/ioctl audio output",
  54         "oss",
  55         "A'rpi",
  56         ""
  57 };
  58
  59 /* Support for >2 output channels added 2001-11-25 - Steve Davies <steve@daviesfam.org> */
  60
  61 LIBAO_EXTERN(oss)
  62
  63 static int format2oss(int format)
  64 {
  65     switch(format)
  66     {
  67     case AF_FORMAT_U8: return AFMT_U8;
  68     case AF_FORMAT_S8: return AFMT_S8;
  69     case AF_FORMAT_U16_LE: return AFMT_U16_LE;
  70     case AF_FORMAT_U16_BE: return AFMT_U16_BE;
  71     case AF_FORMAT_S16_LE: return AFMT_S16_LE;
  72     case AF_FORMAT_S16_BE: return AFMT_S16_BE;
  73 #ifdef AFMT_S24_PACKED
  74     case AF_FORMAT_S24_LE: return AFMT_S24_PACKED;
  75 #endif
  76 #ifdef AFMT_U32_LE
  77     case AF_FORMAT_U32_LE: return AFMT_U32_LE;
  78 #endif
  79 #ifdef AFMT_U32_BE
  80     case AF_FORMAT_U32_BE: return AFMT_U32_BE;
  81 #endif
  82 #ifdef AFMT_S32_LE
  83     case AF_FORMAT_S32_LE: return AFMT_S32_LE;
  84 #endif
  85 #ifdef AFMT_S32_BE
  86     case AF_FORMAT_S32_BE: return AFMT_S32_BE;
  87 #endif
  88 #ifdef AFMT_FLOAT
  89     case AF_FORMAT_FLOAT_NE: return AFMT_FLOAT;
  90 #endif
  91     // SPECIALS
  92     case AF_FORMAT_MU_LAW: return AFMT_MU_LAW;
  93     case AF_FORMAT_A_LAW: return AFMT_A_LAW;
  94     case AF_FORMAT_IMA_ADPCM: return AFMT_IMA_ADPCM;
  95 #ifdef AFMT_MPEG
  96     case AF_FORMAT_MPEG2: return AFMT_MPEG;
  97 #endif
  98 #ifdef AFMT_AC3
  99     case AF_FORMAT_AC3_NE: return AFMT_AC3;
 100 #endif
 101     }
 102     mp_msg(MSGT_AO, MSGL_V, "OSS: Unknown/not supported internal format: %s\n", af_fmt2str_short(format));
 103     return -1;
 104 }
 105
 106 static int oss2format(int format)
 107 {
 108     switch(format)
 109     {
 110     case AFMT_U8: return AF_FORMAT_U8;
 111     case AFMT_S8: return AF_FORMAT_S8;
 112     case AFMT_U16_LE: return AF_FORMAT_U16_LE;
 113     case AFMT_U16_BE: return AF_FORMAT_U16_BE;
 114     case AFMT_S16_LE: return AF_FORMAT_S16_LE;
 115     case AFMT_S16_BE: return AF_FORMAT_S16_BE;
 116 #ifdef AFMT_S24_PACKED
 117     case AFMT_S24_PACKED: return AF_FORMAT_S24_LE;
 118 #endif
 119 #ifdef AFMT_U32_LE
 120     case AFMT_U32_LE: return AF_FORMAT_U32_LE;
 121 #endif
 122 #ifdef AFMT_U32_BE
 123     case AFMT_U32_BE: return AF_FORMAT_U32_BE;
 124 #endif
 125 #ifdef AFMT_S32_LE
 126     case AFMT_S32_LE: return AF_FORMAT_S32_LE;
 127 #endif
 128 #ifdef AFMT_S32_BE
 129     case AFMT_S32_BE: return AF_FORMAT_S32_BE;
 130 #endif
 131 #ifdef AFMT_FLOAT
 132     case AFMT_FLOAT: return AF_FORMAT_FLOAT_NE;
 133 #endif
 134     // SPECIALS
 135     case AFMT_MU_LAW: return AF_FORMAT_MU_LAW;
 136     case AFMT_A_LAW: return AF_FORMAT_A_LAW;
 137     case AFMT_IMA_ADPCM: return AF_FORMAT_IMA_ADPCM;
 138 #ifdef AFMT_MPEG
 139     case AFMT_MPEG: return AF_FORMAT_MPEG2;
 140 #endif
 141 #ifdef AFMT_AC3
 142     case AFMT_AC3: return AF_FORMAT_AC3_NE;
 143 #endif
 144     }
 145     mp_tmsg(MSGT_GLOBAL,MSGL_ERR,"[AO OSS] Unknown/Unsupported OSS format: %x.\n", format);
 146     return -1;
 147 }
 148
 149 static char *dsp=PATH_DEV_DSP;
 150 static audio_buf_info zz;
 151 static int audio_fd=-1;
 152 static int prepause_space;
 153
 154 static const char *oss_mixer_device = PATH_DEV_MIXER;
 155 static int oss_mixer_channel = SOUND_MIXER_PCM;
 156
 157 #ifdef SNDCTL_DSP_GETPLAYVOL
 158 static int volume_oss4(ao_control_vol_t *vol, int cmd) {
 159     int v;
 160
 161     if (audio_fd < 0)
 162         return CONTROL_ERROR;
 163
 164     if (cmd == AOCONTROL_GET_VOLUME) {
 165         if (ioctl(audio_fd, SNDCTL_DSP_GETPLAYVOL, &v) == -1)
 166             return CONTROL_ERROR;
 167         vol->right = (v & 0xff00) >> 8;
 168         vol->left = v & 0x00ff;
 169         return CONTROL_OK;
 170     } else if (cmd == AOCONTROL_SET_VOLUME) {
 171         v = ((int) vol->right << 8) | (int) vol->left;
 172         if (ioctl(audio_fd, SNDCTL_DSP_SETPLAYVOL, &v) == -1)
 173             return CONTROL_ERROR;
 174         return CONTROL_OK;
 175     } else
 176         return CONTROL_UNKNOWN;
 177 }
 178 #endif
 179
 180 // to set/get/query special features/parameters
 181 static int control(int cmd,void *arg){
 182     switch(cmd){
 183         case AOCONTROL_SET_DEVICE:
 184             dsp=(char*)arg;
 185             return CONTROL_OK;
 186         case AOCONTROL_GET_DEVICE:
 187             *(char**)arg=dsp;
 188             return CONTROL_OK;
 189 #ifdef SNDCTL_DSP_GETFMTS
 190         case AOCONTROL_QUERY_FORMAT:
 191         {
 192             int format;
 193             if (!ioctl(audio_fd, SNDCTL_DSP_GETFMTS, &format))
 194                 if ((unsigned int)format & (unsigned long)arg)
 195                     return CONTROL_TRUE;
 196             return CONTROL_FALSE;
 197         }
 198 #endif
 199         case AOCONTROL_GET_VOLUME:
 200         case AOCONTROL_SET_VOLUME:
 201         {
 202             ao_control_vol_t *vol = (ao_control_vol_t *)arg;
 203             int fd, v, devs;
 204
 205 #ifdef SNDCTL_DSP_GETPLAYVOL
 206         // Try OSS4 first
 207         if (volume_oss4(vol, cmd) == CONTROL_OK)
 208             return CONTROL_OK;
 209 #endif
 210
 211             if(AF_FORMAT_IS_AC3(ao_data.format))
 212                 return CONTROL_TRUE;
 213
 214             if ((fd = open(oss_mixer_device, O_RDONLY)) > 0)
 215             {
 216                 ioctl(fd, SOUND_MIXER_READ_DEVMASK, &devs);
 217                 if (devs & (1 << oss_mixer_channel))
 218                 {
 219                     if (cmd == AOCONTROL_GET_VOLUME)
 220                     {
 221                         ioctl(fd, MIXER_READ(oss_mixer_channel), &v);
 222                         vol->right = (v & 0xFF00) >> 8;
 223                         vol->left = v & 0x00FF;
 224                     }
 225                     else
 226                     {
 227                         v = ((int)vol->right << 8) | (int)vol->left;
 228                         ioctl(fd, MIXER_WRITE(oss_mixer_channel), &v);
 229                     }
 230                 }
 231                 else
 232                 {
 233                     close(fd);
 234                     return CONTROL_ERROR;
 235                 }
 236                 close(fd);
 237                 return CONTROL_OK;
 238             }
 239         }
 240         return CONTROL_ERROR;
 241     }
 242     return CONTROL_UNKNOWN;
 243 }
 244
 245 // open & setup audio device
 246 // return: 1=success 0=fail
 247 static int init(int rate,int channels,int format,int flags){
 248   char *mixer_channels [SOUND_MIXER_NRDEVICES] = SOUND_DEVICE_NAMES;
 249   int oss_format;
 250   char *mdev = mixer_device, *mchan = mixer_channel;
 251
 252   mp_msg(MSGT_AO,MSGL_V,"ao2: %d Hz  %d chans  %s\n",rate,channels,
 253     af_fmt2str_short(format));
 254
 255   if (ao_subdevice) {
 256     char *m,*c;
 257     m = strchr(ao_subdevice,':');
 258     if(m) {
 259       c = strchr(m+1,':');
 260       if(c) {
 261         mchan = c+1;
 262         c[0] = '\0';
 263       }
 264       mdev = m+1;
 265       m[0] = '\0';
 266     }
 267     dsp = ao_subdevice;
 268   }
 269
 270   if(mdev)
 271     oss_mixer_device=mdev;
 272   else
 273     oss_mixer_device=PATH_DEV_MIXER;
 274
 275   if(mchan){
 276     int fd, devs, i;
 277
 278     if ((fd = open(oss_mixer_device, O_RDONLY)) == -1){
 279       mp_tmsg(MSGT_AO,MSGL_ERR,"[AO OSS] audio_setup: Can't open mixer device %s: %s\n",
 280         oss_mixer_device, strerror(errno));
 281     }else{
 282       ioctl(fd, SOUND_MIXER_READ_DEVMASK, &devs);
 283       close(fd);
 284
 285       for (i=0; i<SOUND_MIXER_NRDEVICES; i++){
 286         if(!strcasecmp(mixer_channels[i], mchan)){
 287           if(!(devs & (1 << i))){
 288             mp_tmsg(MSGT_AO,MSGL_ERR,"[AO OSS] audio_setup: Audio card mixer does not have channel '%s', using default.\n",mchan);
 289             i = SOUND_MIXER_NRDEVICES+1;
 290             break;
 291           }
 292           oss_mixer_channel = i;
 293           break;
 294         }
 295       }
 296       if(i==SOUND_MIXER_NRDEVICES){
 297         mp_tmsg(MSGT_AO,MSGL_ERR,"[AO OSS] audio_setup: Audio card mixer does not have channel '%s', using default.\n",mchan);
 298       }
 299     }
 300   } else
 301     oss_mixer_channel = SOUND_MIXER_PCM;
 302
 303   mp_msg(MSGT_AO,MSGL_V,"audio_setup: using '%s' dsp device\n", dsp);
 304   mp_msg(MSGT_AO,MSGL_V,"audio_setup: using '%s' mixer device\n", oss_mixer_device);
 305   mp_msg(MSGT_AO,MSGL_V,"audio_setup: using '%s' mixer device\n", mixer_channels[oss_mixer_channel]);
 306
 307 #ifdef __linux__
 308   audio_fd=open(dsp, O_WRONLY | O_NONBLOCK);
 309 #else
 310   audio_fd=open(dsp, O_WRONLY);
 311 #endif
 312   if(audio_fd<0){
 313     mp_tmsg(MSGT_AO,MSGL_ERR,"[AO OSS] audio_setup: Can't open audio device %s: %s\n", dsp, strerror(errno));
 314     return 0;
 315   }
 316
 317 #ifdef __linux__
 318   /* Remove the non-blocking flag */
 319   if(fcntl(audio_fd, F_SETFL, 0) < 0) {
 320    mp_tmsg(MSGT_AO,MSGL_ERR,"[AO OSS] audio_setup: Can't make file descriptor blocking: %s\n", strerror(errno));
 321    return 0;
 322   }
 323 #endif
 324
 325 #if defined(FD_CLOEXEC) && defined(F_SETFD)
 326   fcntl(audio_fd, F_SETFD, FD_CLOEXEC);
 327 #endif
 328
 329   if(AF_FORMAT_IS_AC3(format)) {
 330     ao_data.samplerate=rate;
 331     ioctl (audio_fd, SNDCTL_DSP_SPEED, &ao_data.samplerate);
 332   }
 333
 334 ac3_retry:
 335   if (AF_FORMAT_IS_AC3(format))
 336     format = AF_FORMAT_AC3_NE;
 337   ao_data.format=format;
 338   oss_format=format2oss(format);
 339   if (oss_format == -1) {
 340 #if HAVE_BIGENDIAN
 341     oss_format=AFMT_S16_BE;
 342 #else
 343     oss_format=AFMT_S16_LE;
 344 #endif
 345     format=AF_FORMAT_S16_NE;
 346   }
 347   if( ioctl(audio_fd, SNDCTL_DSP_SETFMT, &oss_format)<0 ||
 348       oss_format != format2oss(format)) {
 349     mp_tmsg(MSGT_AO,MSGL_WARN, "[AO OSS] Can't set audio device %s to %s output, trying %s...\n", dsp,
 350             af_fmt2str_short(format), af_fmt2str_short(AF_FORMAT_S16_NE) );
 351     format=AF_FORMAT_S16_NE;
 352     goto ac3_retry;
 353   }
 354 #if 0
 355   if(oss_format!=format2oss(format))
 356         mp_msg(MSGT_AO,MSGL_WARN,"WARNING! Your soundcard does NOT support %s sample format! Broken audio or bad playback speed are possible! Try with '-af format'\n",audio_out_format_name(format));
 357 #endif
 358
 359   ao_data.format = oss2format(oss_format);
 360   if (ao_data.format == -1) return 0;
 361
 362   mp_msg(MSGT_AO,MSGL_V,"audio_setup: sample format: %s (requested: %s)\n",
 363     af_fmt2str_short(ao_data.format), af_fmt2str_short(format));
 364
 365   ao_data.channels = channels;
 366   if(!AF_FORMAT_IS_AC3(format)) {
 367     // We only use SNDCTL_DSP_CHANNELS for >2 channels, in case some drivers don't have it
 368     if (ao_data.channels > 2) {
 369       if ( ioctl(audio_fd, SNDCTL_DSP_CHANNELS, &ao_data.channels) == -1 ||
 370            ao_data.channels != channels ) {
 371         mp_tmsg(MSGT_AO,MSGL_ERR,"[AO OSS] audio_setup: Failed to set audio device to %d channels.\n", channels);
 372         return 0;
 373       }
 374     }
 375     else {
 376       int c = ao_data.channels-1;
 377       if (ioctl (audio_fd, SNDCTL_DSP_STEREO, &c) == -1) {
 378         mp_tmsg(MSGT_AO,MSGL_ERR,"[AO OSS] audio_setup: Failed to set audio device to %d channels.\n", ao_data.channels);
 379         return 0;
 380       }
 381       ao_data.channels=c+1;
 382     }
 383     mp_msg(MSGT_AO,MSGL_V,"audio_setup: using %d channels (requested: %d)\n", ao_data.channels, channels);
 384     // set rate
 385     ao_data.samplerate=rate;
 386     ioctl (audio_fd, SNDCTL_DSP_SPEED, &ao_data.samplerate);
 387     mp_msg(MSGT_AO,MSGL_V,"audio_setup: using %d Hz samplerate (requested: %d)\n",ao_data.samplerate,rate);
 388   }
 389
 390   if(ioctl(audio_fd, SNDCTL_DSP_GETOSPACE, &zz)==-1){
 391       int r=0;
 392       mp_tmsg(MSGT_AO,MSGL_WARN,"[AO OSS] audio_setup: driver doesn't support SNDCTL_DSP_GETOSPACE :-(\n");
 393       if(ioctl(audio_fd, SNDCTL_DSP_GETBLKSIZE, &r)==-1){
 394           mp_msg(MSGT_AO,MSGL_V,"audio_setup: %d bytes/frag (config.h)\n",ao_data.outburst);
 395       } else {
 396           ao_data.outburst=r;
 397           mp_msg(MSGT_AO,MSGL_V,"audio_setup: %d bytes/frag (GETBLKSIZE)\n",ao_data.outburst);
 398       }
 399   } else {
 400       mp_msg(MSGT_AO,MSGL_V,"audio_setup: frags: %3d/%d  (%d bytes/frag)  free: %6d\n",
 401           zz.fragments, zz.fragstotal, zz.fragsize, zz.bytes);
 402       if(ao_data.buffersize==-1) ao_data.buffersize=zz.bytes;
 403       ao_data.outburst=zz.fragsize;
 404   }
 405
 406   if(ao_data.buffersize==-1){
 407     // Measuring buffer size:
 408     void* data;
 409     ao_data.buffersize=0;
 410 #ifdef HAVE_AUDIO_SELECT
 411     data=malloc(ao_data.outburst); memset(data,0,ao_data.outburst);
 412     while(ao_data.buffersize<0x40000){
 413       fd_set rfds;
 414       struct timeval tv;
 415       FD_ZERO(&rfds); FD_SET(audio_fd,&rfds);
 416       tv.tv_sec=0; tv.tv_usec = 0;
 417       if(!select(audio_fd+1, NULL, &rfds, NULL, &tv)) break;
 418       write(audio_fd,data,ao_data.outburst);
 419       ao_data.buffersize+=ao_data.outburst;
 420     }
 421     free(data);
 422     if(ao_data.buffersize==0){
 423         mp_tmsg(MSGT_AO,MSGL_ERR,"[AO OSS]\n   ***  Your audio driver DOES NOT support select()  ***\n Recompile MPlayer with #undef HAVE_AUDIO_SELECT in config.h !\n\n");
 424         return 0;
 425     }
 426 #endif
 427   }
 428
 429   ao_data.bps=ao_data.channels;
 430   switch (ao_data.format & AF_FORMAT_BITS_MASK) {
 431   case AF_FORMAT_8BIT:
 432     break;
 433   case AF_FORMAT_16BIT:
 434     ao_data.bps*=2;
 435     break;
 436   case AF_FORMAT_24BIT:
 437     ao_data.bps*=3;
 438     break;
 439   case AF_FORMAT_32BIT:
 440     ao_data.bps*=4;
 441     break;
 442   }
 443
 444   ao_data.outburst-=ao_data.outburst % ao_data.bps; // round down
 445   ao_data.bps*=ao_data.samplerate;
 446
 447     return 1;
 448 }
 449
 450 // close audio device
 451 static void uninit(int immed){
 452     if(audio_fd == -1) return;
 453 #ifdef SNDCTL_DSP_SYNC
 454     // to get the buffer played
 455     if (!immed)
 456         ioctl(audio_fd, SNDCTL_DSP_SYNC, NULL);
 457 #endif
 458 #ifdef SNDCTL_DSP_RESET
 459     if (immed)
 460         ioctl(audio_fd, SNDCTL_DSP_RESET, NULL);
 461 #endif
 462     close(audio_fd);
 463     audio_fd = -1;
 464 }
 465
 466 // stop playing and empty buffers (for seeking/pause)
 467 static void reset(void){
 468   int oss_format;
 469     uninit(1);
 470     audio_fd=open(dsp, O_WRONLY);
 471     if(audio_fd < 0){
 472         mp_tmsg(MSGT_AO,MSGL_ERR,"[AO OSS]\nFatal error: *** CANNOT RE-OPEN / RESET AUDIO DEVICE *** %s\n", strerror(errno));
 473         return;
 474     }
 475
 476 #if defined(FD_CLOEXEC) && defined(F_SETFD)
 477   fcntl(audio_fd, F_SETFD, FD_CLOEXEC);
 478 #endif
 479
 480   oss_format = format2oss(ao_data.format);
 481   if(AF_FORMAT_IS_AC3(ao_data.format))
 482     ioctl (audio_fd, SNDCTL_DSP_SPEED, &ao_data.samplerate);
 483   ioctl (audio_fd, SNDCTL_DSP_SETFMT, &oss_format);
 484   if(!AF_FORMAT_IS_AC3(ao_data.format)) {
 485     if (ao_data.channels > 2)
 486       ioctl (audio_fd, SNDCTL_DSP_CHANNELS, &ao_data.channels);
 487     else {
 488       int c = ao_data.channels-1;
 489       ioctl (audio_fd, SNDCTL_DSP_STEREO, &c);
 490     }
 491     ioctl (audio_fd, SNDCTL_DSP_SPEED, &ao_data.samplerate);
 492   }
 493 }
 494
 495 // stop playing, keep buffers (for pause)
 496 static void audio_pause(void)
 497 {
 498     prepause_space = get_space();
 499     uninit(1);
 500 }
 501
 502 // resume playing, after audio_pause()
 503 static void audio_resume(void)
 504 {
 505     int fillcnt;
 506     reset();
 507     fillcnt = get_space() - prepause_space;
 508     if (fillcnt > 0 && !(ao_data.format & AF_FORMAT_SPECIAL_MASK)) {
 509       void *silence = calloc(fillcnt, 1);
 510       play(silence, fillcnt, 0);
 511       free(silence);
 512     }
 513 }
 514
 515
 516 // return: how many bytes can be played without blocking
 517 static int get_space(void){
 518   int playsize=ao_data.outburst;
 519
 520 #ifdef SNDCTL_DSP_GETOSPACE
 521   if(ioctl(audio_fd, SNDCTL_DSP_GETOSPACE, &zz)!=-1){
 522       // calculate exact buffer space:
 523       playsize = zz.fragments*zz.fragsize;
 524       return playsize;
 525   }
 526 #endif
 527
 528     // check buffer
 529 #ifdef HAVE_AUDIO_SELECT
 530     {  fd_set rfds;
 531        struct timeval tv;
 532        FD_ZERO(&rfds);
 533        FD_SET(audio_fd, &rfds);
 534        tv.tv_sec = 0;
 535        tv.tv_usec = 0;
 536        if(!select(audio_fd+1, NULL, &rfds, NULL, &tv)) return 0; // not block!
 537     }
 538 #endif
 539
 540   return ao_data.outburst;
 541 }
 542
 543 // plays 'len' bytes of 'data'
 544 // it should round it down to outburst*n
 545 // return: number of bytes played
 546 static int play(void* data,int len,int flags){
 547     if(len==0)
 548         return len;
 549     if(len>ao_data.outburst || !(flags & AOPLAY_FINAL_CHUNK)) {
 550         len/=ao_data.outburst;
 551         len*=ao_data.outburst;
 552     }
 553     len=write(audio_fd,data,len);
 554     return len;
 555 }
 556
 557 static int audio_delay_method=2;
 558
 559 // return: delay in seconds between first and last sample in buffer
 560 static float get_delay(void){
 561   /* Calculate how many bytes/second is sent out */
 562   if(audio_delay_method==2){
 563 #ifdef SNDCTL_DSP_GETODELAY
 564       int r=0;
 565       if(ioctl(audio_fd, SNDCTL_DSP_GETODELAY, &r)!=-1)
 566          return ((float)r)/(float)ao_data.bps;
 567 #endif
 568       audio_delay_method=1; // fallback if not supported
 569   }
 570   if(audio_delay_method==1){
 571       // SNDCTL_DSP_GETOSPACE
 572       if(ioctl(audio_fd, SNDCTL_DSP_GETOSPACE, &zz)!=-1)
 573          return ((float)(ao_data.buffersize-zz.bytes))/(float)ao_data.bps;
 574       audio_delay_method=0; // fallback if not supported
 575   }
 576   return ((float)ao_data.buffersize)/(float)ao_data.bps;
 577 }