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         if (pcm_handle) {
 153                 WARN_ON_ERROR("snd_pcm_close()", snd_pcm_close(pcm_handle));
 154         }
 155 }
 156
 157 void ALSAInput::start_capture_thread()
 158 {
 159         should_quit = false;
 160         capture_thread = thread(&ALSAInput::capture_thread_func, this);
 161 }
 162
 163 void ALSAInput::stop_capture_thread()
 164 {
 165         should_quit = true;
 166         capture_thread.join();
 167 }
 168
 169 void ALSAInput::capture_thread_func()
 170 {
 171         parent_pool->set_card_state(internal_dev_index, ALSAPool::Device::State::STARTING);
 172
 173         // If the device hasn't been opened already, we need to do so
 174         // before we can capture.
 175         while (!should_quit && pcm_handle == nullptr) {
 176                 if (!open_device()) {
 177                         fprintf(stderr, "[%s] Waiting one second and trying again...\n",
 178                                 device.c_str());
 179                         sleep(1);
 180                 }
 181         }
 182
 183         if (should_quit) {
 184                 // Don't call free_card(); that would be a deadlock.
 185                 WARN_ON_ERROR("snd_pcm_close()", snd_pcm_close(pcm_handle));
 186                 pcm_handle = nullptr;
 187                 return;
 188         }
 189
 190         // Do the actual capture. (Termination condition within loop.)
 191         for ( ;; ) {
 192                 switch (do_capture()) {
 193                 case CaptureEndReason::REQUESTED_QUIT:
 194                         // Don't call free_card(); that would be a deadlock.
 195                         WARN_ON_ERROR("snd_pcm_close()", snd_pcm_close(pcm_handle));
 196                         pcm_handle = nullptr;
 197                         return;
 198                 case CaptureEndReason::DEVICE_GONE:
 199                         parent_pool->free_card(internal_dev_index);
 200                         WARN_ON_ERROR("snd_pcm_close()", snd_pcm_close(pcm_handle));
 201                         pcm_handle = nullptr;
 202                         return;
 203                 case CaptureEndReason::OTHER_ERROR:
 204                         parent_pool->set_card_state(internal_dev_index, ALSAPool::Device::State::STARTING);
 205                         fprintf(stderr, "[%s] Sleeping one second and restarting capture...\n",
 206                                 device.c_str());
 207                         sleep(1);
 208                         break;
 209                 }
 210         }
 211 }
 212
 213 ALSAInput::CaptureEndReason ALSAInput::do_capture()
 214 {
 215         parent_pool->set_card_state(internal_dev_index, ALSAPool::Device::State::STARTING);
 216         RETURN_ON_ERROR("snd_pcm_start()", snd_pcm_start(pcm_handle));
 217         parent_pool->set_card_state(internal_dev_index, ALSAPool::Device::State::RUNNING);
 218
 219         uint64_t num_frames_output = 0;
 220         while (!should_quit) {
 221                 int ret = snd_pcm_wait(pcm_handle, /*timeout=*/100);
 222                 if (ret == 0) continue;  // Timeout.
 223                 if (ret == -EPIPE) {
 224                         fprintf(stderr, "[%s] ALSA overrun\n", device.c_str());
 225                         snd_pcm_prepare(pcm_handle);
 226                         snd_pcm_start(pcm_handle);
 227                         continue;
 228                 }
 229                 RETURN_ON_ERROR("snd_pcm_wait()", ret);
 230
 231                 snd_pcm_sframes_t frames = snd_pcm_readi(pcm_handle, buffer.get(), buffer_frames);
 232                 if (frames == -EPIPE) {
 233                         fprintf(stderr, "[%s] ALSA overrun\n", device.c_str());
 234                         snd_pcm_prepare(pcm_handle);
 235                         snd_pcm_start(pcm_handle);
 236                         continue;
 237                 }
 238                 if (frames == 0) {
 239                         fprintf(stderr, "snd_pcm_readi() returned 0\n");
 240                         break;
 241                 }
 242                 RETURN_ON_ERROR("snd_pcm_readi()", frames);
 243
 244                 const int64_t prev_pts = frames_to_pts(num_frames_output);
 245                 const int64_t pts = frames_to_pts(num_frames_output + frames);
 246                 bool success;
 247                 do {
 248                         if (should_quit) return CaptureEndReason::REQUESTED_QUIT;
 249                         success = audio_callback(buffer.get(), frames, audio_format, pts - prev_pts);
 250                 } while (!success);
 251                 num_frames_output += frames;
 252         }
 253         return CaptureEndReason::REQUESTED_QUIT;
 254 }
 255
 256 int64_t ALSAInput::frames_to_pts(uint64_t n) const
 257 {
 258         return (n * TIMEBASE) / sample_rate;
 259 }
 260
 261 ALSAPool::~ALSAPool()
 262 {
 263         for (Device &device : devices) {
 264                 if (device.input != nullptr) {
 265                         device.input->stop_capture_thread();
 266                 }
 267         }
 268 }
 269
 270 std::vector<ALSAPool::Device> ALSAPool::get_devices()
 271 {
 272         lock_guard<mutex> lock(mu);
 273         for (Device &device : devices) {
 274                 device.held = true;
 275         }
 276         return devices;
 277 }
 278
 279 void ALSAPool::hold_device(unsigned index)
 280 {
 281         lock_guard<mutex> lock(mu);
 282         assert(index < devices.size());
 283         devices[index].held = true;
 284 }
 285
 286 void ALSAPool::release_device(unsigned index)
 287 {
 288         lock_guard<mutex> lock(mu);
 289         if (index < devices.size()) {
 290                 devices[index].held = false;
 291         }
 292 }
 293
 294 void ALSAPool::enumerate_devices()
 295 {
 296         // Enumerate all cards.
 297         for (int card_index = -1; snd_card_next(&card_index) == 0 && card_index >= 0; ) {
 298                 char address[256];
 299                 snprintf(address, sizeof(address), "hw:%d", card_index);
 300
 301                 snd_ctl_t *ctl;
 302                 int err = snd_ctl_open(&ctl, address, 0);
 303                 if (err < 0) {
 304                         printf("%s: %s\n", address, snd_strerror(err));
 305                         continue;
 306                 }
 307                 unique_ptr<snd_ctl_t, decltype(snd_ctl_close)*> ctl_closer(ctl, snd_ctl_close);
 308
 309                 // Enumerate all devices on this card.
 310                 for (int dev_index = -1; snd_ctl_pcm_next_device(ctl, &dev_index) == 0 && dev_index >= 0; ) {
 311                         probe_device_with_retry(card_index, dev_index);
 312                 }
 313         }
 314 }
 315
 316 void ALSAPool::probe_device_with_retry(unsigned card_index, unsigned dev_index)
 317 {
 318         char address[256];
 319         snprintf(address, sizeof(address), "hw:%d,%d", card_index, dev_index);
 320
 321         lock_guard<mutex> lock(add_device_mutex);
 322         if (add_device_tries_left.count(address)) {
 323                 // Some thread is already busy retrying this,
 324                 // so just reset its count.
 325                 add_device_tries_left[address] = num_retries;
 326                 return;
 327         }
 328
 329         // Try (while still holding the lock) to add the device synchronously.
 330         ProbeResult result = probe_device_once(card_index, dev_index);
 331         if (result == ProbeResult::SUCCESS) {
 332                 return;
 333         } else if (result == ProbeResult::FAILURE) {
 334                 return;
 335         }
 336         assert(result == ProbeResult::DEFER);
 337
 338         // Add failed for whatever reason (probably just that the device
 339         // isn't up yet. Set up a count so that nobody else starts a thread,
 340         // then start it ourselves.
 341         fprintf(stderr, "Trying %s again in one second...\n", address);
 342         add_device_tries_left[address] = num_retries;
 343         thread(&ALSAPool::probe_device_retry_thread_func, this, card_index, dev_index).detach();
 344 }
 345
 346 void ALSAPool::probe_device_retry_thread_func(unsigned card_index, unsigned dev_index)
 347 {
 348         char address[256];
 349         snprintf(address, sizeof(address), "hw:%d,%d", card_index, dev_index);
 350
 351         for ( ;; ) {  // Termination condition within the loop.
 352                 sleep(1);
 353
 354                 // See if there are any retries left.
 355                 lock_guard<mutex> lock(add_device_mutex);
 356                 if (!add_device_tries_left.count(address) ||
 357                     add_device_tries_left[address] == 0) {
 358                         add_device_tries_left.erase(address);
 359                         fprintf(stderr, "Giving up probe of %s.\n", address);
 360                         return;
 361                 }
 362
 363                 // Seemingly there were. Give it a try (we still hold the mutex).
 364                 ProbeResult result = probe_device_once(card_index, dev_index);
 365                 if (result == ProbeResult::SUCCESS) {
 366                         add_device_tries_left.erase(address);
 367                         fprintf(stderr, "Probe of %s succeeded.\n", address);
 368                         return;
 369                 } else if (result == ProbeResult::FAILURE || --add_device_tries_left[address] == 0) {
 370                         add_device_tries_left.erase(address);
 371                         fprintf(stderr, "Giving up probe of %s.\n", address);
 372                         return;
 373                 }
 374
 375                 // Failed again.
 376                 assert(result == ProbeResult::DEFER);
 377                 fprintf(stderr, "Trying %s again in one second (%d tries left)...\n",
 378                         address, add_device_tries_left[address]);
 379         }
 380 }
 381
 382 ALSAPool::ProbeResult ALSAPool::probe_device_once(unsigned card_index, unsigned dev_index)
 383 {
 384         char address[256];
 385         snprintf(address, sizeof(address), "hw:%d", card_index);
 386         snd_ctl_t *ctl;
 387         int err = snd_ctl_open(&ctl, address, 0);
 388         if (err < 0) {
 389                 printf("%s: %s\n", address, snd_strerror(err));
 390                 return ALSAPool::ProbeResult::DEFER;
 391         }
 392         unique_ptr<snd_ctl_t, decltype(snd_ctl_close)*> ctl_closer(ctl, snd_ctl_close);
 393
 394         snd_pcm_info_t *pcm_info;
 395         snd_pcm_info_alloca(&pcm_info);
 396         snd_pcm_info_set_device(pcm_info, dev_index);
 397         snd_pcm_info_set_subdevice(pcm_info, 0);
 398         snd_pcm_info_set_stream(pcm_info, SND_PCM_STREAM_CAPTURE);
 399         if (snd_ctl_pcm_info(ctl, pcm_info) < 0) {
 400                 // Not available for capture.
 401                 printf("%s: Not available for capture.\n", address);
 402                 return ALSAPool::ProbeResult::DEFER;
 403         }
 404
 405         snprintf(address, sizeof(address), "hw:%d,%d", card_index, dev_index);
 406
 407         unsigned num_channels = 0;
 408
 409         // Find all channel maps for this device, and pick out the one
 410         // with the most channels.
 411         snd_pcm_chmap_query_t **cmaps = snd_pcm_query_chmaps_from_hw(card_index, dev_index, 0, SND_PCM_STREAM_CAPTURE);
 412         if (cmaps != nullptr) {
 413                 for (snd_pcm_chmap_query_t **ptr = cmaps; *ptr; ++ptr) {
 414                         num_channels = max(num_channels, (*ptr)->map.channels);
 415                 }
 416                 snd_pcm_free_chmaps(cmaps);
 417         }
 418         if (num_channels == 0) {
 419                 // Device had no channel maps. We need to open it to query.
 420                 // TODO: Do this asynchronously.
 421                 snd_pcm_t *pcm_handle;
 422                 int err = snd_pcm_open(&pcm_handle, address, SND_PCM_STREAM_CAPTURE, 0);
 423                 if (err < 0) {
 424                         printf("%s: %s\n", address, snd_strerror(err));
 425                         return ALSAPool::ProbeResult::DEFER;
 426                 }
 427                 snd_pcm_hw_params_t *hw_params;
 428                 snd_pcm_hw_params_alloca(&hw_params);
 429                 unsigned sample_rate;
 430                 if (!set_base_params(address, pcm_handle, hw_params, &sample_rate)) {
 431                         snd_pcm_close(pcm_handle);
 432                         return ALSAPool::ProbeResult::DEFER;
 433                 }
 434                 err = snd_pcm_hw_params_get_channels_max(hw_params, &num_channels);
 435                 if (err < 0) {
 436                         fprintf(stderr, "[%s] snd_pcm_hw_params_get_channels_max(): %s\n",
 437                                 address, snd_strerror(err));
 438                         snd_pcm_close(pcm_handle);
 439                         return ALSAPool::ProbeResult::DEFER;
 440                 }
 441                 snd_pcm_close(pcm_handle);
 442         }
 443
 444         if (num_channels == 0) {
 445                 printf("%s: No channel maps with channels\n", address);
 446                 return ALSAPool::ProbeResult::FAILURE;
 447         }
 448
 449         snd_ctl_card_info_t *card_info;
 450         snd_ctl_card_info_alloca(&card_info);
 451         snd_ctl_card_info(ctl, card_info);
 452
 453         string name = snd_ctl_card_info_get_name(card_info);
 454         string info = snd_pcm_info_get_name(pcm_info);
 455
 456         unsigned internal_dev_index;
 457         {
 458                 lock_guard<mutex> lock(mu);
 459                 internal_dev_index = find_free_device_index(name, info, num_channels, address);
 460                 devices[internal_dev_index].address = address;
 461                 devices[internal_dev_index].name = name;
 462                 devices[internal_dev_index].info = info;
 463                 devices[internal_dev_index].num_channels = num_channels;
 464                 // Note: Purposefully does not overwrite held.
 465         }
 466
 467         fprintf(stderr, "%s: Probed successfully.\n", address);
 468
 469         reset_device(internal_dev_index);  // Restarts it if it is held (ie., we just replaced a dead card).
 470
 471         return ALSAPool::ProbeResult::SUCCESS;
 472 }
 473
 474 void ALSAPool::init()
 475 {
 476         thread(&ALSAPool::inotify_thread_func, this).detach();
 477         enumerate_devices();
 478 }
 479
 480 void ALSAPool::inotify_thread_func()
 481 {
 482         int inotify_fd = inotify_init();
 483         if (inotify_fd == -1) {
 484                 perror("inotify_init()");
 485                 fprintf(stderr, "No hotplug of ALSA devices available.\n");
 486                 return;
 487         }
 488
 489         int watch_fd = inotify_add_watch(inotify_fd, "/dev/snd", IN_MOVE | IN_CREATE | IN_DELETE);
 490         if (watch_fd == -1) {
 491                 perror("inotify_add_watch()");
 492                 fprintf(stderr, "No hotplug of ALSA devices available.\n");
 493                 close(inotify_fd);
 494                 return;
 495         }
 496
 497         int size = sizeof(inotify_event) + NAME_MAX + 1;
 498         unique_ptr<char[]> buf(new char[size]);
 499         for ( ;; ) {
 500                 int ret = read(inotify_fd, buf.get(), size);
 501                 if (ret < int(sizeof(inotify_event))) {
 502                         fprintf(stderr, "inotify read unexpectedly returned %d, giving up hotplug of ALSA devices.\n",
 503                                 int(ret));
 504                         close(watch_fd);
 505                         close(inotify_fd);
 506                         return;
 507                 }
 508
 509                 for (int i = 0; i < ret; ) {
 510                         const inotify_event *event = reinterpret_cast<const inotify_event *>(&buf[i]);
 511                         i += sizeof(inotify_event) + event->len;
 512
 513                         if (event->mask & IN_Q_OVERFLOW) {
 514                                 fprintf(stderr, "WARNING: inotify overflowed, may lose ALSA hotplug events.\n");
 515                                 continue;
 516                         }
 517                         unsigned card, device;
 518                         char type;
 519                         if (sscanf(event->name, "pcmC%uD%u%c", &card, &device, &type) == 3 && type == 'c') {
 520                                 if (event->mask & (IN_MOVED_FROM | IN_DELETE)) {
 521                                         printf("Deleted capture device: Card %u, device %u\n", card, device);
 522                                         // TODO: Unplug.
 523                                 }
 524                                 if (event->mask & (IN_MOVED_TO | IN_CREATE)) {
 525                                         printf("Adding capture device: Card %u, device %u\n", card, device);
 526                                         probe_device_with_retry(card, device);
 527                                 }
 528                         }
 529                 }
 530         }
 531 }
 532
 533 void ALSAPool::reset_device(unsigned index)
 534 {
 535         lock_guard<mutex> lock(mu);
 536         Device *device = &devices[index];
 537         if (inputs[index] != nullptr) {
 538                 inputs[index]->stop_capture_thread();
 539         }
 540         if (!device->held) {
 541                 inputs[index].reset();
 542         } else {
 543                 // TODO: Put on a background thread instead of locking?
 544                 auto callback = bind(&AudioMixer::add_audio, global_audio_mixer, DeviceSpec{InputSourceType::ALSA_INPUT, index}, _1, _2, _3, _4);
 545                 inputs[index].reset(new ALSAInput(device->address.c_str(), OUTPUT_FREQUENCY, device->num_channels, callback, this, index));
 546                 inputs[index]->start_capture_thread();
 547         }
 548         device->input = inputs[index].get();
 549 }
 550
 551 unsigned ALSAPool::get_capture_frequency(unsigned index)
 552 {
 553         lock_guard<mutex> lock(mu);
 554         assert(devices[index].held);
 555         if (devices[index].input)
 556                 return devices[index].input->get_sample_rate();
 557         else
 558                 return OUTPUT_FREQUENCY;
 559 }
 560
 561 ALSAPool::Device::State ALSAPool::get_card_state(unsigned index)
 562 {
 563         lock_guard<mutex> lock(mu);
 564         assert(devices[index].held);
 565         return devices[index].state;
 566 }
 567
 568 void ALSAPool::set_card_state(unsigned index, ALSAPool::Device::State state)
 569 {
 570         {
 571                 lock_guard<mutex> lock(mu);
 572                 devices[index].state = state;
 573         }
 574
 575         DeviceSpec spec{InputSourceType::ALSA_INPUT, index};
 576         bool silence = (state != ALSAPool::Device::State::RUNNING);
 577         while (!global_audio_mixer->silence_card(spec, silence))
 578                 ;
 579 }
 580
 581 unsigned ALSAPool::find_free_device_index(const string &name, const string &info, unsigned num_channels, const string &address)
 582 {
 583         // First try to find an exact match on a dead card.
 584         for (unsigned i = 0; i < devices.size(); ++i) {
 585                 if (devices[i].state == Device::State::DEAD &&
 586                     devices[i].address == address &&
 587                     devices[i].name == name &&
 588                     devices[i].info == info &&
 589                     devices[i].num_channels == num_channels) {
 590                         devices[i].state = Device::State::READY;
 591                         return i;
 592                 }
 593         }
 594
 595         // Then try to find a match on everything but the address
 596         // (probably that devices were plugged back in a different order).
 597         // If we have two cards that are equal, this might get them mixed up,
 598         // but we don't have anything better.
 599         for (unsigned i = 0; i < devices.size(); ++i) {
 600                 if (devices[i].state == Device::State::DEAD &&
 601                     devices[i].name == name &&
 602                     devices[i].info == info &&
 603                     devices[i].num_channels == num_channels) {
 604                         devices[i].state = Device::State::READY;
 605                         return i;
 606                 }
 607         }
 608
 609         // OK, so we didn't find a match; see if there are any empty slots.
 610         for (unsigned i = 0; i < devices.size(); ++i) {
 611                 if (devices[i].state == Device::State::EMPTY) {
 612                         devices[i].state = Device::State::READY;
 613                         devices[i].held = false;
 614                         return i;
 615                 }
 616         }
 617
 618         // Failing that, we just insert the new device at the end.
 619         Device new_dev;
 620         new_dev.state = Device::State::READY;
 621         new_dev.held = false;
 622         devices.push_back(new_dev);
 623         inputs.emplace_back(nullptr);
 624         return devices.size() - 1;
 625 }
 626
 627 void ALSAPool::free_card(unsigned index)
 628 {
 629         DeviceSpec spec{InputSourceType::ALSA_INPUT, index};
 630         while (!global_audio_mixer->silence_card(spec, true))
 631                 ;
 632
 633         lock_guard<mutex> lock(mu);
 634         if (devices[index].held) {
 635                 devices[index].state = Device::State::DEAD;
 636         } else {
 637                 devices[index].state = Device::State::EMPTY;
 638                 inputs[index].reset();
 639         }
 640         while (!devices.empty() && devices.back().state == Device::State::EMPTY) {
 641                 devices.pop_back();
 642                 inputs.pop_back();
 643         }
 644 }