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

   1
   2 #include "alsa_input.h"
   3
   4 using namespace std;
   5
   6 ALSAInput::ALSAInput(const char *device, unsigned sample_rate, unsigned num_channels, audio_callback_t audio_callback)
   7         : device(device), sample_rate(sample_rate), num_channels(num_channels), audio_callback(audio_callback)
   8 {
   9         die_on_error(device, snd_pcm_open(&pcm_handle,device, SND_PCM_STREAM_CAPTURE, 0));
  10
  11         // Set format.
  12         snd_pcm_hw_params_t *hw_params;
  13         snd_pcm_hw_params_alloca(&hw_params);
  14         die_on_error("snd_pcm_hw_params_any()", snd_pcm_hw_params_any(pcm_handle, hw_params));
  15         die_on_error("snd_pcm_hw_params_set_access()", snd_pcm_hw_params_set_access(pcm_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED));
  16         snd_pcm_format_mask_t *format_mask;
  17         snd_pcm_format_mask_alloca(&format_mask);
  18         snd_pcm_format_mask_set(format_mask, SND_PCM_FORMAT_S16_LE);
  19         snd_pcm_format_mask_set(format_mask, SND_PCM_FORMAT_S24_LE);
  20         snd_pcm_format_mask_set(format_mask, SND_PCM_FORMAT_S32_LE);
  21         die_on_error("snd_pcm_hw_params_set_format()", snd_pcm_hw_params_set_format_mask(pcm_handle, hw_params, format_mask));
  22         die_on_error("snd_pcm_hw_params_set_rate_near()", snd_pcm_hw_params_set_rate_near(pcm_handle, hw_params, &sample_rate, 0));
  23         die_on_error("snd_pcm_hw_params_set_channels()", snd_pcm_hw_params_set_channels(pcm_handle, hw_params, num_channels));
  24
  25         die_on_error("snd_pcm_hw_params_set_channels()", snd_pcm_hw_params_set_channels(pcm_handle, hw_params, num_channels));
  26
  27         // Fragment size of 64 samples (about 1 ms at 48 kHz; a frame at 60
  28         // fps/48 kHz is 800 samples.) We ask for 64 such periods in our buffer
  29         // (~85 ms buffer); more than that, and our jitter is probably so high
  30         // that the resampling queue can't keep up anyway.
  31         // The entire thing with periods and such is a bit mysterious to me;
  32         // seemingly I can get 96 frames at a time with no problems even if
  33         // the period size is 64 frames. And if I set num_periods to e.g. 1,
  34         // I can't have a big buffer.
  35         num_periods = 16;
  36         int dir = 0;
  37         die_on_error("snd_pcm_hw_params_set_periods_near()", snd_pcm_hw_params_set_periods_near(pcm_handle, hw_params, &num_periods, &dir));
  38         period_size = 64;
  39         dir = 0;
  40         die_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));
  41         buffer_frames = 64 * 64;
  42         die_on_error("snd_pcm_hw_params_set_buffer_size_near()", snd_pcm_hw_params_set_buffer_size_near(pcm_handle, hw_params, &buffer_frames));
  43         die_on_error("snd_pcm_hw_params()", snd_pcm_hw_params(pcm_handle, hw_params));
  44         //snd_pcm_hw_params_free(hw_params);
  45
  46         // Figure out which format the card actually chose.
  47         die_on_error("snd_pcm_hw_params_current()", snd_pcm_hw_params_current(pcm_handle, hw_params));
  48         snd_pcm_format_t chosen_format;
  49         die_on_error("snd_pcm_hw_params_get_format()", snd_pcm_hw_params_get_format(hw_params, &chosen_format));
  50
  51         audio_format.num_channels = num_channels;
  52         audio_format.bits_per_sample = 0;
  53         switch (chosen_format) {
  54         case SND_PCM_FORMAT_S16_LE:
  55                 audio_format.bits_per_sample = 16;
  56                 break;
  57         case SND_PCM_FORMAT_S24_LE:
  58                 audio_format.bits_per_sample = 24;
  59                 break;
  60         case SND_PCM_FORMAT_S32_LE:
  61                 audio_format.bits_per_sample = 32;
  62                 break;
  63         default:
  64                 assert(false);
  65         }
  66         //printf("num_periods=%u period_size=%u buffer_frames=%u sample_rate=%u bits_per_sample=%d\n",
  67         //      num_periods, unsigned(period_size), unsigned(buffer_frames), sample_rate, audio_format.bits_per_sample);
  68
  69         buffer.reset(new uint8_t[buffer_frames * num_channels * audio_format.bits_per_sample / 8]);
  70
  71         snd_pcm_sw_params_t *sw_params;
  72         snd_pcm_sw_params_alloca(&sw_params);
  73         die_on_error("snd_pcm_sw_params_current()", snd_pcm_sw_params_current(pcm_handle, sw_params));
  74         die_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));
  75         die_on_error("snd_pcm_sw_params()", snd_pcm_sw_params(pcm_handle, sw_params));
  76
  77         die_on_error("snd_pcm_nonblock()", snd_pcm_nonblock(pcm_handle, 1));
  78         die_on_error("snd_pcm_prepare()", snd_pcm_prepare(pcm_handle));
  79 }
  80
  81 ALSAInput::~ALSAInput()
  82 {
  83         die_on_error("snd_pcm_close()", snd_pcm_close(pcm_handle));
  84 }
  85
  86 void ALSAInput::start_capture_thread()
  87 {
  88         should_quit = false;
  89         capture_thread = thread(&ALSAInput::capture_thread_func, this);
  90 }
  91
  92 void ALSAInput::stop_capture_thread()
  93 {
  94         should_quit = true;
  95         capture_thread.join();
  96 }
  97
  98 void ALSAInput::capture_thread_func()
  99 {
 100         die_on_error("snd_pcm_start()", snd_pcm_start(pcm_handle));
 101         uint64_t num_frames_output = 0;
 102         while (!should_quit) {
 103                 int ret = snd_pcm_wait(pcm_handle, /*timeout=*/100);
 104                 if (ret == 0) continue;  // Timeout.
 105                 if (ret == -EPIPE) {
 106                         fprintf(stderr, "[%s] ALSA overrun\n", device.c_str());
 107                         snd_pcm_prepare(pcm_handle);
 108                         snd_pcm_start(pcm_handle);
 109                         continue;
 110                 }
 111                 die_on_error("snd_pcm_wait()", ret);
 112
 113                 snd_pcm_sframes_t frames = snd_pcm_readi(pcm_handle, buffer.get(), buffer_frames);
 114                 if (frames == -EPIPE) {
 115                         fprintf(stderr, "[%s] ALSA overrun\n", device.c_str());
 116                         snd_pcm_prepare(pcm_handle);
 117                         snd_pcm_start(pcm_handle);
 118                         continue;
 119                 }
 120                 if (frames == 0) {
 121                         fprintf(stderr, "snd_pcm_readi() returned 0\n");
 122                         break;
 123                 }
 124                 die_on_error("snd_pcm_readi()", frames);
 125
 126                 const int64_t prev_pts = frames_to_pts(num_frames_output);
 127                 const int64_t pts = frames_to_pts(num_frames_output + frames);
 128                 bool success;
 129                 do {
 130                         if (should_quit) return;
 131                         success = audio_callback(buffer.get(), frames, audio_format, pts - prev_pts);
 132                 } while (!success);
 133                 num_frames_output += frames;
 134         }
 135 }
 136
 137 int64_t ALSAInput::frames_to_pts(uint64_t n) const
 138 {
 139         return (n * TIMEBASE) / sample_rate;
 140 }
 141
 142 void ALSAInput::die_on_error(const char *func_name, int err)
 143 {
 144         if (err < 0) {
 145                 fprintf(stderr, "[%s] %s: %s\n", device.c_str(), func_name, snd_strerror(err));
 146                 exit(1);
 147         }
 148 }
 149
 150 vector<ALSAInput::Device> ALSAInput::enumerate_devices()
 151 {
 152         vector<Device> ret;
 153
 154         // Enumerate all cards.
 155         for (int card_index = -1; snd_card_next(&card_index) == 0 && card_index >= 0; ) {
 156                 char address[256];
 157                 snprintf(address, sizeof(address), "hw:%d", card_index);
 158
 159                 snd_ctl_t *ctl;
 160                 int err = snd_ctl_open(&ctl, address, 0);
 161                 if (err < 0) {
 162                         printf("%s: %s\n", address, snd_strerror(err));
 163                         continue;
 164                 }
 165                 snd_ctl_card_info_t *card_info;
 166                 snd_ctl_card_info_alloca(&card_info);
 167                 snd_ctl_card_info(ctl, card_info);
 168
 169                 string card_name = snd_ctl_card_info_get_name(card_info);
 170
 171                 // Enumerate all devices on this card.
 172                 for (int dev_index = -1; snd_ctl_pcm_next_device(ctl, &dev_index) == 0 && dev_index >= 0; ) {
 173                         snd_pcm_info_t *pcm_info;
 174                         snd_pcm_info_alloca(&pcm_info);
 175                         snd_pcm_info_set_device(pcm_info, dev_index);
 176                         snd_pcm_info_set_subdevice(pcm_info, 0);
 177                         snd_pcm_info_set_stream(pcm_info, SND_PCM_STREAM_CAPTURE);
 178                         if (snd_ctl_pcm_info(ctl, pcm_info) < 0) {
 179                                 // Not available for capture.
 180                                 continue;
 181                         }
 182
 183                         snprintf(address, sizeof(address), "hw:%d,%d", card_index, dev_index);
 184
 185                         // Find all channel maps for this device, and pick out the one
 186                         // with the most channels.
 187                         snd_pcm_chmap_query_t **cmaps = snd_pcm_query_chmaps_from_hw(card_index, dev_index, 0, SND_PCM_STREAM_CAPTURE);
 188                         unsigned num_channels = 0;
 189                         for (snd_pcm_chmap_query_t **ptr = cmaps; *ptr; ++ptr) {
 190                                 num_channels = max(num_channels, (*ptr)->map.channels);
 191                         }
 192
 193                         snd_pcm_free_chmaps(cmaps);
 194
 195                         if (num_channels == 0) {
 196                                 printf("%s: No channel maps with channels\n", address);
 197                                 continue;
 198                         }
 199
 200                         Device dev;
 201                         dev.address = address;
 202                         dev.name = card_name;
 203                         dev.info = snd_pcm_info_get_name(pcm_info);
 204                         dev.num_channels = num_channels;
 205
 206                         ret.push_back(dev);
 207                 }
 208                 snd_ctl_close(ctl);
 209         }
 210
 211         return ret;
 212 }