author Marian-Vasile Laza <>
Wed, 01 Dec 2021 07:02:05 +0200
changeset 600693 89800efd9e5cfcf0146767961a63d5c4e2a86e2c
parent 515082 bb1ce9b0e5f64889ff6faa732414afe81f229e11
permissions -rw-r--r--
Merge autoland to mozilla-central. a=merge

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at */

#if !defined(MediaMetadataManager_h__)
#  define MediaMetadataManager_h__

#  include "mozilla/AbstractThread.h"
#  include "mozilla/LinkedList.h"

#  include "MediaEventSource.h"
#  include "TimeUnits.h"
#  include "VideoUtils.h"

namespace mozilla {

class TimedMetadata;
typedef MediaEventProducerExc<TimedMetadata> TimedMetadataEventProducer;
typedef MediaEventSourceExc<TimedMetadata> TimedMetadataEventSource;

// A struct that contains the metadata of a media, and the time at which those
// metadata should start to be reported.
class TimedMetadata : public LinkedListElement<TimedMetadata> {
  TimedMetadata(const media::TimeUnit& aPublishTime,
                UniquePtr<MetadataTags>&& aTags, UniquePtr<MediaInfo>&& aInfo)
      : mPublishTime(aPublishTime),
        mInfo(std::move(aInfo)) {}

  // Define our move constructor because we don't want to move the members of
  // LinkedListElement to change the list.
  TimedMetadata(TimedMetadata&& aOther)
      : mPublishTime(aOther.mPublishTime),
        mInfo(std::move(aOther.mInfo)) {}

  // The time, in microseconds, at which those metadata should be available.
  media::TimeUnit mPublishTime;
  // The metadata. The ownership is transfered to the element when dispatching
  // to the main threads.
  UniquePtr<MetadataTags> mTags;
  // The media info, including the info of audio tracks and video tracks.
  // The ownership is transfered to MediaDecoder when dispatching to the
  // main thread.
  UniquePtr<MediaInfo> mInfo;

// This class encapsulate the logic to give the metadata from the reader to
// the content, at the right time.
class MediaMetadataManager {
  ~MediaMetadataManager() {
    TimedMetadata* element;
    while ((element = mMetadataQueue.popFirst()) != nullptr) {
      delete element;

  // Connect to an event source to receive TimedMetadata events.
  void Connect(TimedMetadataEventSource& aEvent, AbstractThread* aThread) {
    mListener =
        aEvent.Connect(aThread, this, &MediaMetadataManager::OnMetadataQueued);

  // Stop receiving TimedMetadata events.
  void Disconnect() { mListener.Disconnect(); }

  // Return an event source through which we will send TimedMetadata events
  // when playback position reaches the publish time.
  TimedMetadataEventSource& TimedMetadataEvent() { return mTimedMetadataEvent; }

  void DispatchMetadataIfNeeded(const media::TimeUnit& aCurrentTime) {
    TimedMetadata* metadata = mMetadataQueue.getFirst();
    while (metadata && aCurrentTime >= metadata->mPublishTime) {
      // Our listener will figure out what to do with TimedMetadata.
      delete mMetadataQueue.popFirst();
      metadata = mMetadataQueue.getFirst();

  void OnMetadataQueued(TimedMetadata&& aMetadata) {
    mMetadataQueue.insertBack(new TimedMetadata(std::move(aMetadata)));

  LinkedList<TimedMetadata> mMetadataQueue;
  MediaEventListener mListener;
  TimedMetadataEventProducer mTimedMetadataEvent;

}  // namespace mozilla