sp-streams/dist/constant-fps-stream.js

Streamplace Streams for Piping Video Around and Stuff

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = constantFpsStream;

var _mpegMungerStream = require("./mpeg-munger-stream");

var _mpegMungerStream2 = _interopRequireDefault(_mpegMungerStream);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

/**
 * Takes in a mpegts stream and emits e.g. 30 frames per real-time second. Like
 * ffmpeg's "-re" flag.
 * @param {{fps}} fps
 */
function constantFpsStream() {
  var _ref = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {},
      fps = _ref.fps;

  if (typeof fps !== "number") {
    throw new Error(fps + " is not a valid fps");
  }
  var mpegMunger = (0, _mpegMungerStream2.default)();
  var frames = 0;
  var firstFrameTime = void 0;
  mpegMunger.on("pts", function (_ref2) {
    var pts = _ref2.pts,
        streamId = _ref2.streamId;

    if (!(0, _mpegMungerStream.streamIsVideo)(streamId)) {
      return;
    }
    if (!firstFrameTime) {
      firstFrameTime = Date.now();
    }
    frames += 1;
    check();
  });
  var check = function check() {
    if (firstFrameTime === undefined) {
      return;
    }
    var expectedFrames = Math.ceil((Date.now() - firstFrameTime) / 1000 * fps);
    // console.log(`Expected ${expectedFrames}, found ${frames}`);
    if (expectedFrames > frames) {
      mpegMunger.resume();
    } else if (expectedFrames < frames) {
      mpegMunger.pause();
    }
  };
  var interval = setInterval(check, 250);
  mpegMunger.on("end", function () {
    clearInterval(interval);
  });
  return mpegMunger;
}