前言

分为外部AudioState和内部AudioState

RefCountedObject

代码分析

WebRtcVoiceEngine::Init

H:\webrtc-20210315\webrtc-20210315\webrtc\webrtc-checkout\src\media\engine\webrtc_voice_engine.cc

void WebRtcVoiceEngine::Init() {
  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
  RTC_LOG(LS_INFO) << "WebRtcVoiceEngine::Init";
  // 1、 TaskQueue expects to be created/destroyed on the same thread.
  low_priority_worker_queue_.reset(
      new rtc::TaskQueue(task_queue_factory_->CreateTaskQueue(
          "rtc-low-prio", webrtc::TaskQueueFactory::Priority::LOW)));
  // 2、 收集音频编码器
  RTC_LOG(LS_VERBOSE) << "Supported send codecs in order of preference:";
  send_codecs_ = CollectCodecs(encoder_factory_->GetSupportedEncoders());
  for (const AudioCodec& codec : send_codecs_) {
    RTC_LOG(LS_VERBOSE) << ToString(codec);
  }
  // 3、 收集音频解码器
  RTC_LOG(LS_VERBOSE) << "Supported recv codecs in order of preference:";
  recv_codecs_ = CollectCodecs(decoder_factory_->GetSupportedDecoders());
  for (const AudioCodec& codec : recv_codecs_) {
    RTC_LOG(LS_VERBOSE) << ToString(codec);
  }
  // 4、创建ADM
#if defined(WEBRTC_INCLUDE_INTERNAL_AUDIO_DEVICE)
  // No ADM supplied? Create a default one.
  if (!adm_) {
    adm_ = webrtc::AudioDeviceModule::Create(
        webrtc::AudioDeviceModule::kPlatformDefaultAudio, task_queue_factory_);
  }
#endif  // WEBRTC_INCLUDE_INTERNAL_AUDIO_DEVICE
  RTC_CHECK(adm());
  // 5、 初始化adm
  webrtc::adm_helpers::Init(adm());
  // 6、 Set up AudioState. 当前讲解这一步
  {
    webrtc::AudioState::Config config;
    if (audio_mixer_) {
      config.audio_mixer = audio_mixer_;
    } else {
      config.audio_mixer = webrtc::AudioMixerImpl::Create();
    }
    config.audio_processing = apm_;
    config.audio_device_module = adm_;
    if (audio_frame_processor_)
      config.async_audio_processing_factory =
          new rtc::RefCountedObject<webrtc::AsyncAudioProcessing::Factory>(
              *audio_frame_processor_, *task_queue_factory_);
    audio_state_ = webrtc::AudioState::Create(config);
  }
  // 7、 Connect the ADM to our audio path. 
  // 注册回调，采集到音频数据后，由audio_transport()传输
  adm()->RegisterAudioCallback(audio_state()->audio_transport());
  // 8、 Set default engine options.
  {
    AudioOptions options;
    options.echo_cancellation = true;
    options.auto_gain_control = true;
#if defined(WEBRTC_IOS)
    // On iOS, VPIO provides built-in NS.
    options.noise_suppression = false;
    options.typing_detection = false;
#else
    options.noise_suppression = true;
    options.typing_detection = true;
#endif
    options.experimental_ns = false;
    options.highpass_filter = true;
    options.stereo_swapping = false;
    options.audio_jitter_buffer_max_packets = 200;
    options.audio_jitter_buffer_fast_accelerate = false;
    options.audio_jitter_buffer_min_delay_ms = 0;
    options.audio_jitter_buffer_enable_rtx_handling = false;
    options.experimental_agc = false;
    options.residual_echo_detector = true;
    bool error = ApplyOptions(options);
    RTC_DCHECK(error);
  }
  initialized_ = true;
}

—》
// 6、 Set up AudioState. 当前讲解这一步
{
webrtc::AudioState::Config config;
if (audiomixer) {
config.audiomixer = audio_mixer;
} else {
config.audiomixer = webrtc::AudioMixerImpl::Create();
}
config.audio_processing = apm;
config.audiodevice_module = adm;
if (audioframe_processor)
config.asyncaudio_processing_factory =
new rtc::RefCountedObject(
*audio_frame_processor, *taskqueue_factory);
audiostate = webrtc::AudioState::Create(config);
}
当前堆栈

—》

AudioState::Create

rtc::scoped_refptr<AudioState> AudioState::Create(
    const AudioState::Config& config) {
  return new rtc::RefCountedObject<internal::AudioState>(config);
}

—》

internal::AudioState::AudioState

namespace webrtc {
namespace internal {
AudioState::AudioState(const AudioState::Config& config)
    : config_(config),
      audio_transport_(config_.audio_mixer,
                       config_.audio_processing.get(),
                       config_.async_audio_processing_factory.get()) {
  process_thread_checker_.Detach();
  RTC_DCHECK(config_.audio_mixer);
  RTC_DCHECK(config_.audio_device_module);
}
    ****