chrome/browser/media/audio_ducker.cc

// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "chrome/browser/media/audio_ducker.h"

#include "content/public/browser/media_session.h"
#include "content/public/browser/media_session_service.h"

AudioDucker::AudioDucker(content::Page& page)
    : content::PageUserData<AudioDucker>(page),
      content::WebContentsObserver(GetWebContents()) {}

AudioDucker::~AudioDucker() {
  StopDuckingOtherAudio();
}

bool AudioDucker::StartDuckingOtherAudio() {
  if (ducking_state_ == AudioDuckingState::kDucking) {
    return true;
  }
  if (!BindToAudioFocusManagerIfNecessary()) {
    return false;
  }
  StartDuckingImpl();
  ducking_state_ = AudioDuckingState::kDucking;
  return true;
}

bool AudioDucker::StopDuckingOtherAudio() {
  if (ducking_state_ == AudioDuckingState::kNoDucking) {
    return true;
  }
  if (!BindToAudioFocusManagerIfNecessary()) {
    return false;
  }
  audio_focus_remote_->StopDuckingAllAudio();
  ducking_state_ = AudioDuckingState::kNoDucking;
  return true;
}

void AudioDucker::MediaSessionCreated(content::MediaSession*) {
  // When a MediaSession is created and we're already ducking, we need to tell
  // the AudioFocusManager to start ducking again while exempting the new
  // request ID. This will supercede the previous request and replace it with a
  // request that has an exempted MediaSession.
  if (ducking_state_ == AudioDuckingState::kDucking &&
      BindToAudioFocusManagerIfNecessary()) {
    StartDuckingImpl();
  }
}

void AudioDucker::StartDuckingImpl() {
  // Null base::UnguessableTokens cannot be passed via mojo, so convert to an
  // empty optional if the request ID is null.
  const base::UnguessableToken& request_id =
      content::MediaSession::GetRequestIdFromWebContents(GetWebContents());
  std::optional<base::UnguessableToken> optional_request_id;
  if (!request_id.is_empty()) {
    optional_request_id = request_id;
  }

  audio_focus_remote_->StartDuckingAllAudio(optional_request_id);
}

content::WebContents* AudioDucker::GetWebContents() const {
  return content::WebContents::FromRenderFrameHost(&page().GetMainDocument());
}

bool AudioDucker::BindToAudioFocusManagerIfNecessary() {
  if (audio_focus_remote_.is_bound()) {
    return true;
  }
  content::GetMediaSessionService().BindAudioFocusManager(
      audio_focus_remote_.BindNewPipeAndPassReceiver());
  audio_focus_remote_.reset_on_disconnect();
  return audio_focus_remote_.is_bound();
}

PAGE_USER_DATA_KEY_IMPL(AudioDucker);