media/mojo/mojom/audio_processing.mojom

// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

module media.mojom;

// Stats from software audio processing in the audio service. Are passed upon
// request from the renderer, see AudioProcessorControls::GetStats() in this
// file.
struct AudioProcessingStats {

  // TODO(https://crbug.com/657632): Numeric values cannot be optional, so add
  // flags for each of them.
  bool has_echo_return_loss;
  double echo_return_loss;

  bool has_echo_return_loss_enhancement;
  double echo_return_loss_enhancement;
};

// Settings for the software audio processing performed in the audio service.
// The settings are determined in the renderer from media constraints passed by
// JavaScript clients and platform capabilities, and are passed to the audio
// service where the actual processing is applied.
struct AudioProcessingSettings {
  bool echo_cancellation;
  bool noise_suppression;
  bool transient_noise_suppression;
  bool automatic_gain_control;
  bool high_pass_filter;
  bool multi_channel_capture_processing;
  bool stereo_mirroring;
  bool force_apm_creation;
};

// This interface is hosted in the audio service and called from the renderer.
// It is only used when the audio processing is performed in the audio service.
interface AudioProcessorControls {

  // Request the latest stats from the audio processor. At the farthest level,
  // this is triggered by calls from JavaScript, through some levels of
  // indirection. (See: https://www.w3.org/TR/webrtc-stats/). Since there are no
  // guarantees in the standard about the rate at which stats change, it is
  // reasonable to let multiple user-facing calls result in just one call to
  // this function.
  GetStats() => (AudioProcessingStats stats);

  // Sets a preferred number of capture audio channels. This allows the audio
  // processor to avoid unnecessary computational load when the number of input
  // audio channels exceeds what is used by the input consumers.
  // Values less than 1 and greater than the input stream capacity are adjusted
  // to the nearest valid number.
  SetPreferredNumCaptureChannels(int32 num_preferred_channels);
};

struct AudioProcessingConfig {
  // Used for getting stats and controlling diagnostic audio recordings (AEC
  // dumps).
  pending_receiver<AudioProcessorControls> controls_receiver;

  // Used for determining which kind of audio processing is enabled.
  AudioProcessingSettings settings;
};