git.sesse.net Git - nageru/blob - alsa_input.cpp

   1 #include "alsa_input.h"
   2 #include "audio_mixer.h"
   3 #include "defs.h"
   4
   5 #include <sys/inotify.h>
   6
   7 #include <functional>
   8 #include <unordered_map>
   9
  10 using namespace std;
  11 using namespace std::placeholders;
  12
  13 namespace {
  14
  15 bool set_base_params(const char *device_name, snd_pcm_t *pcm_handle, snd_pcm_hw_params_t *hw_params, unsigned *sample_rate)
  16 {
  17         int err;
  18         err = snd_pcm_hw_params_any(pcm_handle, hw_params);
  19         if (err < 0) {
  20                 fprintf(stderr, "[%s] snd_pcm_hw_params_any(): %s\n", device_name, snd_strerror(err));
  21                 return false;
  22         }
  23         err = snd_pcm_hw_params_set_access(pcm_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
  24         if (err < 0) {
  25                 fprintf(stderr, "[%s] snd_pcm_hw_params_set_access(): %s\n", device_name, snd_strerror(err));
  26                 return false;
  27         }
  28         snd_pcm_format_mask_t *format_mask;
  29         snd_pcm_format_mask_alloca(&format_mask);
  30         snd_pcm_format_mask_set(format_mask, SND_PCM_FORMAT_S16_LE);
  31         snd_pcm_format_mask_set(format_mask, SND_PCM_FORMAT_S24_LE);
  32         snd_pcm_format_mask_set(format_mask, SND_PCM_FORMAT_S32_LE);
  33         err = snd_pcm_hw_params_set_format_mask(pcm_handle, hw_params, format_mask);
  34         if (err < 0) {
  35                 fprintf(stderr, "[%s] snd_pcm_hw_params_set_format_mask(): %s\n", device_name, snd_strerror(err));
  36                 return false;
  37         }
  38         err = snd_pcm_hw_params_set_rate_near(pcm_handle, hw_params, sample_rate, 0);
  39         if (err < 0) {
  40                 fprintf(stderr, "[%s] snd_pcm_hw_params_set_rate_near(): %s\n", device_name, snd_strerror(err));
  41                 return false;
  42         }
  43         return true;
  44 }
  45
  46 }  // namespace
  47
  48 #define RETURN_ON_ERROR(msg, expr) do {                                                    \
  49         int err = (expr);                                                                  \
  50         if (err < 0) {                                                                     \
  51                 fprintf(stderr, "[%s] " msg ": %s\n", device.c_str(), snd_strerror(err));  \
  52                 if (err == -ENODEV) return CaptureEndReason::DEVICE_GONE;                  \
  53                 return CaptureEndReason::OTHER_ERROR;                                      \
  54         }                                                                                  \
  55 } while (false)
  56
  57 #define RETURN_FALSE_ON_ERROR(msg, expr) do {                                              \
  58         int err = (expr);                                                                  \
  59         if (err < 0) {                                                                     \
  60                 fprintf(stderr, "[%s] " msg ": %s\n", device.c_str(), snd_strerror(err));  \
  61                 return false;                                                              \
  62         }                                                                                  \
  63 } while (false)
  64
  65 #define WARN_ON_ERROR(msg, expr) do {                                                      \
  66         int err = (expr);                                                                  \
  67         if (err < 0) {                                                                     \
  68                 fprintf(stderr, "[%s] " msg ": %s\n", device.c_str(), snd_strerror(err));  \
  69         }                                                                                  \
  70 } while (false)
  71
  72 ALSAInput::ALSAInput(const char *device, unsigned sample_rate, unsigned num_channels, audio_callback_t audio_callback, ALSAPool *parent_pool, unsigned internal_dev_index)
  73         : device(device),
  74           sample_rate(sample_rate),
  75           num_channels(num_channels),
  76           audio_callback(audio_callback),
  77           parent_pool(parent_pool),
  78           internal_dev_index(internal_dev_index)
  79 {
  80 }
  81
  82 bool ALSAInput::open_device()
  83 {
  84         RETURN_FALSE_ON_ERROR("snd_pcm_open()", snd_pcm_open(&pcm_handle, device.c_str(), SND_PCM_STREAM_CAPTURE, 0));
  85
  86         // Set format.
  87         snd_pcm_hw_params_t *hw_params;
  88         snd_pcm_hw_params_alloca(&hw_params);
  89         if (!set_base_params(device.c_str(), pcm_handle, hw_params, &sample_rate)) {
  90                 return false;
  91         }
  92
  93         RETURN_FALSE_ON_ERROR("snd_pcm_hw_params_set_channels()", snd_pcm_hw_params_set_channels(pcm_handle, hw_params, num_channels));
  94
  95         // Fragment size of 64 samples (about 1 ms at 48 kHz; a frame at 60
  96         // fps/48 kHz is 800 samples.) We ask for 64 such periods in our buffer
  97         // (~85 ms buffer); more than that, and our jitter is probably so high
  98         // that the resampling queue can't keep up anyway.
  99         // The entire thing with periods and such is a bit mysterious to me;
 100         // seemingly I can get 96 frames at a time with no problems even if
 101         // the period size is 64 frames. And if I set num_periods to e.g. 1,
 102         // I can't have a big buffer.
 103         num_periods = 16;
 104         int dir = 0;
 105         RETURN_FALSE_ON_ERROR("snd_pcm_hw_params_set_periods_near()", snd_pcm_hw_params_set_periods_near(pcm_handle, hw_params, &num_periods, &dir));
 106         period_size = 64;
 107         dir = 0;
 108         RETURN_FALSE_ON_ERROR("snd_pcm_hw_params_set_period_size_near()", snd_pcm_hw_params_set_period_size_near(pcm_handle, hw_params, &period_size, &dir));
 109         buffer_frames = 64 * 64;
 110         RETURN_FALSE_ON_ERROR("snd_pcm_hw_params_set_buffer_size_near()", snd_pcm_hw_params_set_buffer_size_near(pcm_handle, hw_params, &buffer_frames));
 111         RETURN_FALSE_ON_ERROR("snd_pcm_hw_params()", snd_pcm_hw_params(pcm_handle, hw_params));
 112         //snd_pcm_hw_params_free(hw_params);
 113
 114         // Figure out which format the card actually chose.
 115         RETURN_FALSE_ON_ERROR("snd_pcm_hw_params_current()", snd_pcm_hw_params_current(pcm_handle, hw_params));
 116         snd_pcm_format_t chosen_format;
 117         RETURN_FALSE_ON_ERROR("snd_pcm_hw_params_get_format()", snd_pcm_hw_params_get_format(hw_params, &chosen_format));
 118
 119         audio_format.num_channels = num_channels;
 120         audio_format.bits_per_sample = 0;
 121         switch (chosen_format) {
 122         case SND_PCM_FORMAT_S16_LE:
 123                 audio_format.bits_per_sample = 16;
 124                 break;
 125         case SND_PCM_FORMAT_S24_LE:
 126                 audio_format.bits_per_sample = 24;
 127                 break;
 128         case SND_PCM_FORMAT_S32_LE:
 129                 audio_format.bits_per_sample = 32;
 130                 break;
 131         default:
 132                 assert(false);
 133         }
 134         //printf("num_periods=%u period_size=%u buffer_frames=%u sample_rate=%u bits_per_sample=%d\n",
 135         //      num_periods, unsigned(period_size), unsigned(buffer_frames), sample_rate, audio_format.bits_per_sample);
 136
 137         buffer.reset(new uint8_t[buffer_frames * num_channels * audio_format.bits_per_sample / 8]);
 138
 139         snd_pcm_sw_params_t *sw_params;
 140         snd_pcm_sw_params_alloca(&sw_params);
 141         RETURN_FALSE_ON_ERROR("snd_pcm_sw_params_current()", snd_pcm_sw_params_current(pcm_handle, sw_params));
 142         RETURN_FALSE_ON_ERROR("snd_pcm_sw_params_set_start_threshold", snd_pcm_sw_params_set_start_threshold(pcm_handle, sw_params, num_periods * period_size / 2));
 143         RETURN_FALSE_ON_ERROR("snd_pcm_sw_params()", snd_pcm_sw_params(pcm_handle, sw_params));
 144
 145         RETURN_FALSE_ON_ERROR("snd_pcm_nonblock()", snd_pcm_nonblock(pcm_handle, 1));
 146         RETURN_FALSE_ON_ERROR("snd_pcm_prepare()", snd_pcm_prepare(pcm_handle));
 147         return true;
 148 }
 149
 150 ALSAInput::~ALSAInput()
 151 {
 152         WARN_ON_ERROR("snd_pcm_close()", snd_pcm_close(pcm_handle));
 153 }
 154
 155 void ALSAInput::start_capture_thread()
 156 {
 157         should_quit = false;
 158         capture_thread = thread(&ALSAInput::capture_thread_func, this);
 159 }
 160
 161 void ALSAInput::stop_capture_thread()
 162 {
 163         should_quit = true;
 164         capture_thread.join();
 165 }
 166
 167 void ALSAInput::capture_thread_func()
 168 {
 169         // If the device hasn't been opened already, we need to do so
 170         // before we can capture.
 171         while (!should_quit && pcm_handle == nullptr) {
 172                 if (!open_device()) {
 173                         fprintf(stderr, "[%s] Waiting one second and trying again...\n",
 174                                 device.c_str());
 175                         sleep(1);
 176                 }
 177         }
 178
 179         if (should_quit) {
 180                 // Don't call free_card(); that would be a deadlock.
 181                 return;
 182         }
 183
 184         // Do the actual capture. (Termination condition within loop.)
 185         for ( ;; ) {
 186                 switch (do_capture()) {
 187                 case CaptureEndReason::REQUESTED_QUIT:
 188                         // Don't call free_card(); that would be a deadlock.
 189                         return;
 190                 case CaptureEndReason::DEVICE_GONE:
 191                         parent_pool->free_card(internal_dev_index);
 192                         return;
 193                 case CaptureEndReason::OTHER_ERROR:
 194                         parent_pool->set_card_state(internal_dev_index, ALSAPool::Device::State::STARTING);
 195                         fprintf(stderr, "[%s] Sleeping one second and restarting capture...\n",
 196                                 device.c_str());
 197                         sleep(1);
 198                         break;
 199                 }
 200         }
 201 }
 202
 203 ALSAInput::CaptureEndReason ALSAInput::do_capture()
 204 {
 205         parent_pool->set_card_state(internal_dev_index, ALSAPool::Device::State::STARTING);
 206         RETURN_ON_ERROR("snd_pcm_start()", snd_pcm_start(pcm_handle));
 207         parent_pool->set_card_state(internal_dev_index, ALSAPool::Device::State::RUNNING);
 208
 209         uint64_t num_frames_output = 0;
 210         while (!should_quit) {
 211                 int ret = snd_pcm_wait(pcm_handle, /*timeout=*/100);
 212                 if (ret == 0) continue;  // Timeout.
 213                 if (ret == -EPIPE) {
 214                         fprintf(stderr, "[%s] ALSA overrun\n", device.c_str());
 215                         snd_pcm_prepare(pcm_handle);
 216                         snd_pcm_start(pcm_handle);
 217                         continue;
 218                 }
 219                 RETURN_ON_ERROR("snd_pcm_wait()", ret);
 220
 221                 snd_pcm_sframes_t frames = snd_pcm_readi(pcm_handle, buffer.get(), buffer_frames);
 222                 if (frames == -EPIPE) {
 223                         fprintf(stderr, "[%s] ALSA overrun\n", device.c_str());
 224                         snd_pcm_prepare(pcm_handle);
 225                         snd_pcm_start(pcm_handle);
 226                         continue;
 227                 }
 228                 if (frames == 0) {
 229                         fprintf(stderr, "snd_pcm_readi() returned 0\n");
 230                         break;
 231                 }
 232                 RETURN_ON_ERROR("snd_pcm_readi()", frames);
 233
 234                 const int64_t prev_pts = frames_to_pts(num_frames_output);
 235                 const int64_t pts = frames_to_pts(num_frames_output + frames);
 236                 bool success;
 237                 do {
 238                         if (should_quit) return CaptureEndReason::REQUESTED_QUIT;
 239                         success = audio_callback(buffer.get(), frames, audio_format, pts - prev_pts);
 240                 } while (!success);
 241                 num_frames_output += frames;
 242         }
 243         return CaptureEndReason::REQUESTED_QUIT;
 244 }
 245
 246 int64_t ALSAInput::frames_to_pts(uint64_t n) const
 247 {
 248         return (n * TIMEBASE) / sample_rate;
 249 }
 250
 251 ALSAPool::~ALSAPool()
 252 {
 253         for (Device &device : devices) {
 254                 if (device.input != nullptr) {
 255                         device.input->stop_capture_thread();
 256                 }
 257         }
 258 }
 259
 260 std::vector<ALSAPool::Device> ALSAPool::get_devices()
 261 {
 262         lock_guard<mutex> lock(mu);
 263         for (Device &device : devices) {
 264                 device.held = true;
 265         }
 266         return devices;
 267 }
 268
 269 void ALSAPool::hold_device(unsigned index)
 270 {
 271         lock_guard<mutex> lock(mu);
 272         assert(index < devices.size());
 273         devices[index].held = true;
 274 }
 275
 276 void ALSAPool::release_device(unsigned index)
 277 {
 278         lock_guard<mutex> lock(mu);
 279         if (index < devices.size()) {
 280                 devices[index].held = false;
 281         }
 282 }
 283
 284 void ALSAPool::enumerate_devices()
 285 {
 286         // Enumerate all cards.
 287         for (int card_index = -1; snd_card_next(&card_index) == 0 && card_index >= 0; ) {
 288                 char address[256];
 289                 snprintf(address, sizeof(address), "hw:%d", card_index);
 290
 291                 snd_ctl_t *ctl;
 292                 int err = snd_ctl_open(&ctl, address, 0);
 293                 if (err < 0) {
 294                         printf("%s: %s\n", address, snd_strerror(err));
 295                         continue;
 296                 }
 297                 unique_ptr<snd_ctl_t, decltype(snd_ctl_close)*> ctl_closer(ctl, snd_ctl_close);
 298
 299                 // Enumerate all devices on this card.
 300                 for (int dev_index = -1; snd_ctl_pcm_next_device(ctl, &dev_index) == 0 && dev_index >= 0; ) {
 301                         probe_device_with_retry(card_index, dev_index);
 302                 }
 303         }
 304 }
 305
 306 void ALSAPool::probe_device_with_retry(unsigned card_index, unsigned dev_index)
 307 {
 308         char address[256];
 309         snprintf(address, sizeof(address), "hw:%d,%d", card_index, dev_index);
 310
 311         lock_guard<mutex> lock(add_device_mutex);
 312         if (add_device_tries_left.count(address)) {
 313                 // Some thread is already busy retrying this,
 314                 // so just reset its count.
 315                 add_device_tries_left[address] = num_retries;
 316                 return;
 317         }
 318
 319         // Try (while still holding the lock) to add the device synchronously.
 320         ProbeResult result = probe_device_once(card_index, dev_index);
 321         if (result == ProbeResult::SUCCESS) {
 322                 return;
 323         } else if (result == ProbeResult::FAILURE) {
 324                 return;
 325         }
 326         assert(result == ProbeResult::DEFER);
 327
 328         // Add failed for whatever reason (probably just that the device
 329         // isn't up yet. Set up a count so that nobody else starts a thread,
 330         // then start it ourselves.
 331         fprintf(stderr, "Trying %s again in one second...\n", address);
 332         add_device_tries_left[address] = num_retries;
 333         thread(&ALSAPool::probe_device_retry_thread_func, this, card_index, dev_index).detach();
 334 }
 335
 336 void ALSAPool::probe_device_retry_thread_func(unsigned card_index, unsigned dev_index)
 337 {
 338         char address[256];
 339         snprintf(address, sizeof(address), "hw:%d,%d", card_index, dev_index);
 340
 341         for ( ;; ) {  // Termination condition within the loop.
 342                 sleep(1);
 343
 344                 // See if there are any retries left.
 345                 lock_guard<mutex> lock(add_device_mutex);
 346                 if (!add_device_tries_left.count(address) ||
 347                     add_device_tries_left[address] == 0) {
 348                         add_device_tries_left.erase(address);
 349                         fprintf(stderr, "Giving up probe of %s.\n", address);
 350                         return;
 351                 }
 352
 353                 // Seemingly there were. Give it a try (we still hold the mutex).
 354                 ProbeResult result = probe_device_once(card_index, dev_index);
 355                 if (result == ProbeResult::SUCCESS) {
 356                         add_device_tries_left.erase(address);
 357                         fprintf(stderr, "Probe of %s succeeded.\n", address);
 358                         return;
 359                 } else if (result == ProbeResult::FAILURE || --add_device_tries_left[address] == 0) {
 360                         add_device_tries_left.erase(address);
 361                         fprintf(stderr, "Giving up probe of %s.\n", address);
 362                         return;
 363                 }
 364
 365                 // Failed again.
 366                 assert(result == ProbeResult::DEFER);
 367                 fprintf(stderr, "Trying %s again in one second (%d tries left)...\n",
 368                         address, add_device_tries_left[address]);
 369         }
 370 }
 371
 372 ALSAPool::ProbeResult ALSAPool::probe_device_once(unsigned card_index, unsigned dev_index)
 373 {
 374         char address[256];
 375         snprintf(address, sizeof(address), "hw:%d", card_index);
 376         snd_ctl_t *ctl;
 377         int err = snd_ctl_open(&ctl, address, 0);
 378         if (err < 0) {
 379                 printf("%s: %s\n", address, snd_strerror(err));
 380                 return ALSAPool::ProbeResult::DEFER;
 381         }
 382         unique_ptr<snd_ctl_t, decltype(snd_ctl_close)*> ctl_closer(ctl, snd_ctl_close);
 383
 384         snd_pcm_info_t *pcm_info;
 385         snd_pcm_info_alloca(&pcm_info);
 386         snd_pcm_info_set_device(pcm_info, dev_index);
 387         snd_pcm_info_set_subdevice(pcm_info, 0);
 388         snd_pcm_info_set_stream(pcm_info, SND_PCM_STREAM_CAPTURE);
 389         if (snd_ctl_pcm_info(ctl, pcm_info) < 0) {
 390                 // Not available for capture.
 391                 printf("%s: Not available for capture.\n", address);
 392                 return ALSAPool::ProbeResult::DEFER;
 393         }
 394
 395         snprintf(address, sizeof(address), "hw:%d,%d", card_index, dev_index);
 396
 397         unsigned num_channels = 0;
 398
 399         // Find all channel maps for this device, and pick out the one
 400         // with the most channels.
 401         snd_pcm_chmap_query_t **cmaps = snd_pcm_query_chmaps_from_hw(card_index, dev_index, 0, SND_PCM_STREAM_CAPTURE);
 402         if (cmaps != nullptr) {
 403                 for (snd_pcm_chmap_query_t **ptr = cmaps; *ptr; ++ptr) {
 404                         num_channels = max(num_channels, (*ptr)->map.channels);
 405                 }
 406                 snd_pcm_free_chmaps(cmaps);
 407         }
 408         if (num_channels == 0) {
 409                 // Device had no channel maps. We need to open it to query.
 410                 // TODO: Do this asynchronously.
 411                 snd_pcm_t *pcm_handle;
 412                 int err = snd_pcm_open(&pcm_handle, address, SND_PCM_STREAM_CAPTURE, 0);
 413                 if (err < 0) {
 414                         printf("%s: %s\n", address, snd_strerror(err));
 415                         return ALSAPool::ProbeResult::DEFER;
 416                 }
 417                 snd_pcm_hw_params_t *hw_params;
 418                 snd_pcm_hw_params_alloca(&hw_params);
 419                 unsigned sample_rate;
 420                 if (!set_base_params(address, pcm_handle, hw_params, &sample_rate)) {
 421                         snd_pcm_close(pcm_handle);
 422                         return ALSAPool::ProbeResult::DEFER;
 423                 }
 424                 err = snd_pcm_hw_params_get_channels_max(hw_params, &num_channels);
 425                 if (err < 0) {
 426                         fprintf(stderr, "[%s] snd_pcm_hw_params_get_channels_max(): %s\n",
 427                                 address, snd_strerror(err));
 428                         snd_pcm_close(pcm_handle);
 429                         return ALSAPool::ProbeResult::DEFER;
 430                 }
 431                 snd_pcm_close(pcm_handle);
 432         }
 433
 434         if (num_channels == 0) {
 435                 printf("%s: No channel maps with channels\n", address);
 436                 return ALSAPool::ProbeResult::FAILURE;
 437         }
 438
 439         snd_ctl_card_info_t *card_info;
 440         snd_ctl_card_info_alloca(&card_info);
 441         snd_ctl_card_info(ctl, card_info);
 442
 443         lock_guard<mutex> lock(mu);
 444         unsigned internal_dev_index = find_free_device_index();
 445         devices[internal_dev_index].address = address;
 446         devices[internal_dev_index].name = snd_ctl_card_info_get_name(card_info);
 447         devices[internal_dev_index].info = snd_pcm_info_get_name(pcm_info);
 448         devices[internal_dev_index].num_channels = num_channels;
 449         devices[internal_dev_index].state = Device::State::READY;
 450
 451         fprintf(stderr, "%s: Probed successfully.\n", address);
 452
 453         return ALSAPool::ProbeResult::SUCCESS;
 454 }
 455
 456 void ALSAPool::init()
 457 {
 458         thread(&ALSAPool::inotify_thread_func, this).detach();
 459         enumerate_devices();
 460 }
 461
 462 void ALSAPool::inotify_thread_func()
 463 {
 464         int inotify_fd = inotify_init();
 465         if (inotify_fd == -1) {
 466                 perror("inotify_init()");
 467                 fprintf(stderr, "No hotplug of ALSA devices available.\n");
 468                 return;
 469         }
 470
 471         int watch_fd = inotify_add_watch(inotify_fd, "/dev/snd", IN_MOVE | IN_CREATE | IN_DELETE);
 472         if (watch_fd == -1) {
 473                 perror("inotify_add_watch()");
 474                 fprintf(stderr, "No hotplug of ALSA devices available.\n");
 475                 close(inotify_fd);
 476                 return;
 477         }
 478
 479         int size = sizeof(inotify_event) + NAME_MAX + 1;
 480         unique_ptr<char[]> buf(new char[size]);
 481         for ( ;; ) {
 482                 int ret = read(inotify_fd, buf.get(), size);
 483                 if (ret < int(sizeof(inotify_event))) {
 484                         fprintf(stderr, "inotify read unexpectedly returned %d, giving up hotplug of ALSA devices.\n",
 485                                 int(ret));
 486                         close(watch_fd);
 487                         close(inotify_fd);
 488                         return;
 489                 }
 490
 491                 for (int i = 0; i < ret; ) {
 492                         const inotify_event *event = reinterpret_cast<const inotify_event *>(&buf[i]);
 493                         i += sizeof(inotify_event) + event->len;
 494
 495                         if (event->mask & IN_Q_OVERFLOW) {
 496                                 fprintf(stderr, "WARNING: inotify overflowed, may lose ALSA hotplug events.\n");
 497                                 continue;
 498                         }
 499                         unsigned card, device;
 500                         char type;
 501                         if (sscanf(event->name, "pcmC%uD%u%c", &card, &device, &type) == 3 && type == 'c') {
 502                                 if (event->mask & (IN_MOVED_FROM | IN_DELETE)) {
 503                                         printf("Deleted capture device: Card %u, device %u\n", card, device);
 504                                         // TODO: Unplug.
 505                                 }
 506                                 if (event->mask & (IN_MOVED_TO | IN_CREATE)) {
 507                                         printf("Adding capture device: Card %u, device %u\n", card, device);
 508                                         probe_device_with_retry(card, device);
 509                                 }
 510                         }
 511                 }
 512         }
 513 }
 514
 515 void ALSAPool::reset_device(unsigned index)
 516 {
 517         lock_guard<mutex> lock(mu);
 518         Device *device = &devices[index];
 519         if (inputs[index] != nullptr) {
 520                 inputs[index]->stop_capture_thread();
 521         }
 522         if (!device->held) {
 523                 inputs[index].reset();
 524         } else {
 525                 // TODO: Put on a background thread instead of locking?
 526                 auto callback = bind(&AudioMixer::add_audio, global_audio_mixer, DeviceSpec{InputSourceType::ALSA_INPUT, index}, _1, _2, _3, _4);
 527                 inputs[index].reset(new ALSAInput(device->address.c_str(), OUTPUT_FREQUENCY, device->num_channels, callback, this, index));
 528                 inputs[index]->start_capture_thread();
 529         }
 530         device->input = inputs[index].get();
 531 }
 532
 533 unsigned ALSAPool::get_capture_frequency(unsigned index)
 534 {
 535         lock_guard<mutex> lock(mu);
 536         assert(devices[index].held);
 537         if (devices[index].input)
 538                 return devices[index].input->get_sample_rate();
 539         else
 540                 return OUTPUT_FREQUENCY;
 541 }
 542
 543 ALSAPool::Device::State ALSAPool::get_card_state(unsigned index)
 544 {
 545         lock_guard<mutex> lock(mu);
 546         assert(devices[index].held);
 547         return devices[index].state;
 548 }
 549
 550 void ALSAPool::set_card_state(unsigned index, ALSAPool::Device::State state)
 551 {
 552         lock_guard<mutex> lock(mu);
 553         devices[index].state = state;
 554 }
 555
 556 unsigned ALSAPool::find_free_device_index()
 557 {
 558         for (unsigned i = 0; i < devices.size(); ++i) {
 559                 if (devices[i].state == Device::State::EMPTY) {
 560                         devices[i].state = Device::State::READY;
 561                         return i;
 562                 }
 563         }
 564         Device new_dev;
 565         new_dev.state = Device::State::READY;
 566         devices.push_back(new_dev);
 567         inputs.emplace_back(nullptr);
 568         return devices.size() - 1;
 569 }
 570
 571 void ALSAPool::free_card(unsigned index)
 572 {
 573         lock_guard<mutex> lock(mu);
 574         if (devices[index].held) {
 575                 devices[index].state = Device::State::DEAD;
 576         } else {
 577                 devices[index].state = Device::State::EMPTY;
 578                 inputs[index].reset();
 579         }
 580         while (!devices.empty() && devices.back().state == Device::State::EMPTY) {
 581                 devices.pop_back();
 582                 inputs.pop_back();
 583         }
 584 }