owncast/build/javascript/node_modules/mux.js/lib/flv/coalesce-stream.js

/**
 * mux.js
 *
 * Copyright (c) Brightcove
 * Licensed Apache-2.0 https://github.com/videojs/mux.js/blob/master/LICENSE
 */
'use strict';

var Stream = require('../utils/stream.js');

/**
 * The final stage of the transmuxer that emits the flv tags
 * for audio, video, and metadata. Also tranlates in time and
 * outputs caption data and id3 cues.
 */
var CoalesceStream = function(options) {
  // Number of Tracks per output segment
  // If greater than 1, we combine multiple
  // tracks into a single segment
  this.numberOfTracks = 0;
  this.metadataStream = options.metadataStream;

  this.videoTags = [];
  this.audioTags = [];
  this.videoTrack = null;
  this.audioTrack = null;
  this.pendingCaptions = [];
  this.pendingMetadata = [];
  this.pendingTracks = 0;
  this.processedTracks = 0;

  CoalesceStream.prototype.init.call(this);

  // Take output from multiple
  this.push = function(output) {
    // buffer incoming captions until the associated video segment
    // finishes
    if (output.text) {
      return this.pendingCaptions.push(output);
    }
    // buffer incoming id3 tags until the final flush
    if (output.frames) {
      return this.pendingMetadata.push(output);
    }

    if (output.track.type === 'video') {
      this.videoTrack = output.track;
      this.videoTags = output.tags;
      this.pendingTracks++;
    }
    if (output.track.type === 'audio') {
      this.audioTrack = output.track;
      this.audioTags = output.tags;
      this.pendingTracks++;
    }
  };
};

CoalesceStream.prototype = new Stream();
CoalesceStream.prototype.flush = function(flushSource) {
  var
    id3,
    caption,
    i,
    timelineStartPts,
    event = {
      tags: {},
      captions: [],
      captionStreams: {},
      metadata: []
    };

  if (this.pendingTracks < this.numberOfTracks) {
    if (flushSource !== 'VideoSegmentStream' &&
        flushSource !== 'AudioSegmentStream') {
      // Return because we haven't received a flush from a data-generating
      // portion of the segment (meaning that we have only recieved meta-data
      // or captions.)
      return;
    } else if (this.pendingTracks === 0) {
      // In the case where we receive a flush without any data having been
      // received we consider it an emitted track for the purposes of coalescing
      // `done` events.
      // We do this for the case where there is an audio and video track in the
      // segment but no audio data. (seen in several playlists with alternate
      // audio tracks and no audio present in the main TS segments.)
      this.processedTracks++;

      if (this.processedTracks < this.numberOfTracks) {
        return;
      }
    }
  }

  this.processedTracks += this.pendingTracks;
  this.pendingTracks = 0;

  if (this.processedTracks < this.numberOfTracks) {
    return;
  }

  if (this.videoTrack) {
    timelineStartPts = this.videoTrack.timelineStartInfo.pts;
  } else if (this.audioTrack) {
    timelineStartPts = this.audioTrack.timelineStartInfo.pts;
  }

  event.tags.videoTags = this.videoTags;
  event.tags.audioTags = this.audioTags;

  // Translate caption PTS times into second offsets into the
  // video timeline for the segment, and add track info
  for (i = 0; i < this.pendingCaptions.length; i++) {
    caption = this.pendingCaptions[i];
    caption.startTime = caption.startPts - timelineStartPts;
    caption.startTime /= 90e3;
    caption.endTime = caption.endPts - timelineStartPts;
    caption.endTime /= 90e3;
    event.captionStreams[caption.stream] = true;
    event.captions.push(caption);
  }

  // Translate ID3 frame PTS times into second offsets into the
  // video timeline for the segment
  for (i = 0; i < this.pendingMetadata.length; i++) {
    id3 = this.pendingMetadata[i];
    id3.cueTime = id3.pts - timelineStartPts;
    id3.cueTime /= 90e3;
    event.metadata.push(id3);
  }
  // We add this to every single emitted segment even though we only need
  // it for the first
  event.metadata.dispatchType = this.metadataStream.dispatchType;

  // Reset stream state
  this.videoTrack = null;
  this.audioTrack = null;
  this.videoTags = [];
  this.audioTags = [];
  this.pendingCaptions.length = 0;
  this.pendingMetadata.length = 0;
  this.pendingTracks = 0;
  this.processedTracks = 0;

  // Emit the final segment
  this.trigger('data', event);

  this.trigger('done');
};

module.exports = CoalesceStream;