+ // Find all channel maps for this device, and pick out the one
+ // with the most channels.
+ snd_pcm_chmap_query_t **cmaps = snd_pcm_query_chmaps_from_hw(card_index, dev_index, 0, SND_PCM_STREAM_CAPTURE);
+ if (cmaps != nullptr) {
+ for (snd_pcm_chmap_query_t **ptr = cmaps; *ptr; ++ptr) {
+ num_channels = max(num_channels, (*ptr)->map.channels);
+ }
+ snd_pcm_free_chmaps(cmaps);
+ }
+ if (num_channels == 0) {
+ // Device had no channel maps. We need to open it to query.
+ // TODO: Do this asynchronously.
+ snd_pcm_t *pcm_handle;
+ int err = snd_pcm_open(&pcm_handle, address, SND_PCM_STREAM_CAPTURE, 0);
+ if (err < 0) {
+ // TODO: When we go to hotplug support, we should support some
+ // retry here, as the device could legitimately be busy.
+ printf("%s: %s\n", address, snd_strerror(err));
+ return false;
+ }
+ snd_pcm_hw_params_t *hw_params;
+ snd_pcm_hw_params_alloca(&hw_params);
+ unsigned sample_rate;
+ if (!set_base_params(address, pcm_handle, hw_params, &sample_rate)) {
+ snd_pcm_close(pcm_handle);
+ return false;
+ }
+ err = snd_pcm_hw_params_get_channels_max(hw_params, &num_channels);
+ if (err < 0) {
+ fprintf(stderr, "[%s] snd_pcm_hw_params_get_channels_max(): %s\n",
+ address, snd_strerror(err));
+ snd_pcm_close(pcm_handle);
+ return false;
+ }
+ snd_pcm_close(pcm_handle);
+ }
+
+ if (num_channels == 0) {
+ printf("%s: No channel maps with channels\n", address);
+ return true;
+ }
+
+ snd_ctl_card_info_t *card_info;
+ snd_ctl_card_info_alloca(&card_info);
+ snd_ctl_card_info(ctl, card_info);
+
+ Device dev;
+ dev.address = address;
+ dev.name = snd_ctl_card_info_get_name(card_info);
+ dev.info = snd_pcm_info_get_name(pcm_info);
+ dev.num_channels = num_channels;
+ dev.state = Device::State::RUNNING;
+
+ lock_guard<mutex> lock(mu);
+ devices.push_back(std::move(dev));
+ return true;
+}
+
+void ALSAPool::init()
+{
+ enumerate_devices();
+}
+
+void ALSAPool::reset_device(unsigned index)
+{
+ lock_guard<mutex> lock(mu);
+ Device *device = &devices[index];
+ if (inputs[index] != nullptr) {
+ inputs[index]->stop_capture_thread();
+ }
+ if (!device->held) {
+ inputs[index].reset();
+ } else {
+ // TODO: Put on a background thread instead of locking?
+ inputs[index].reset(new ALSAInput(device->address.c_str(), OUTPUT_FREQUENCY, device->num_channels, bind(&AudioMixer::add_audio, global_audio_mixer, DeviceSpec{InputSourceType::ALSA_INPUT, index}, _1, _2, _3, _4)));
+ inputs[index]->start_capture_thread();
+ }
+ device->input = inputs[index].get();
+}
+
+unsigned ALSAPool::get_capture_frequency(unsigned index)
+{
+ lock_guard<mutex> lock(mu);
+ assert(devices[index].held);
+ if (devices[index].input)
+ return devices[index].input->get_sample_rate();
+ else
+ return OUTPUT_FREQUENCY;