NOT test WEBRTC_WIN version

• based on https://github.com/open-webrtc-toolkit/owt-deps-webrtc/tree/70-sdk , https://github.com/open-webrtc-toolkit/owt-deps-webrtc/tree/59-server and https://gitlab.freedesktop.org/pulseaudio/webrtc-audio-processing/-/tree/v1.0
• add post-processing part like mixer/(part of)neteq/...
• try to make it more c like for embed use (eg. pure-c version)
  1. checks (in rtc_base, c part)
  2. spl
  3. vad-common/vad-isac/agc-legacy/ns-core/aec(m/core, delay_estimter)
  4. (cxx) rnn-vad/agc2/ns2/aec3 (and rtc_base, cxx part)
  5. (cxx) apm, mixer, neteq, ...

• apm

  // APM operates on two audio streams on a frame-by-frame basis. Frames of the 
  // primary stream, on which all processing is applied, are passed to 
  // |ProcessStream()|. Frames of the reverse direction stream are passed to 
  // |ProcessReverseStream()|. 
  // On the client-side, this will typically be the 
  // near-end (capture) and far-end (render) streams, respectively.
  // On the server-side, the reverse stream will normally 
  // not be used, with processing occurring on each incoming stream.

  • render uses

    std::unique_ptr<SwapQueue<std::vector<float>, RenderQueueItemVerifier<float>>>

    PackRenderAudioBuffer --> Insert --> Remove --> ProcessRenderAudio
  • capture uses

    AudioBuffer

    AnalyzeCaptureAudio --> ProcessCaptureAudio render before capture, EmptyQueuedRenderAudio(it calls ProcessRenderAudio) will be called
• agc
  • legacy/WebRtcAgc_xxx(gain applier) --> GainControl(gain applier)
  • LoudnessHistogram --> Agc(level estimator) --> MonoAgc(level estimator) --> AgcManagerDirect(GainControl::set_compression_gain_db) Combine these two (old version like m70 agc_manager set gain_control in it)

  if (submodules_.agc_manager) {
    submodules_.agc_manager->Process(capture_buffer);
  
    rtc::Optional<int> new_digital_gain =
        submodules_.agc_manager->GetDigitalComressionGain();
    if (new_digital_gain && submodules_.gain_control) {
      submodules_.gain_control->set_compression_gain_db(*new_digital_gain);
    }
  }
  
  if (submodules_.gain_control) {
    // TODO(peah): Add reporting from AEC3 whether there is echo.
    RETURN_ON_ERR(submodules_.gain_control->ProcessCaptureAudio(
        capture_buffer, /*stream_has_echo*/ false));
  }

  gain_control_for_experimental_agc using VolumeCallbacks in agc_manager_direct which is deprecated (use set_stream_analog_level instead)