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We are trying to use MSE (Media Source Extensions) to show real time video on a website. We are sending frames over websocket and trying our hardest to keep latency down. Our current prototype is streaming very well in IE, Edge, Chrome, Safari etc. The issue we have is that IE and Edge insists on buffering around 3-5 seconds before starting to play the video. This is not acceptable in our use case (live video from security cameras). We are wondering if there is some property or similar (we have tried setting preload=none, with no success) which removes this buffering? All other browsers happily starts playing when the first frame is added to the sourceBuffer, and we want the same behavior from IE/Edge. Is there any other workaround you can suggest for us?
The frames are in the ISO BMFF format
Here is a reproducing example I have created that measures the time from the first frame is appended to the video starts playing.It uses an interval to spoof data arriving over a websocket.
Results:
Browser Delay(ms)
-----------------------
Chrome: ~300
Safari @ Mac: ~7
Chrome @ Android: ~30
IE11 @ Win10: ~3200
Edge: ~3200
Here is the mp4 file, if you want to examine it.
549
When you serve the video to IE or to Edge, use the following Javascript. It worked for me. Here it is in GitHub as a simplified version of this MSDN example. On my computer, the video plays almost instantly.
mp4box -dash 10000 -frag 1000 -rap path\to\ie_5s.mp4
You will now have a bunch of files alongside your original .mp4.
ie_5s.mp4
ie_5s_dash.mpd
ie_5s_dashinit.mp4
out_ie_5s.mp4
Rename the .mpd file to a .xml file.
Then create a new .html file is the same directory. Paste the following code:
<!DOCTYPE html>
<html>
<!-- Media streaming example
Reads an .mpd file created using mp4box and plays the file
-->
<head>
<meta charset="utf-8" />
<title>Media streaming example</title>
</head>
<body>
<input type="text" id="filename" value="ie_5s_dash.xml" />
<button id="load">Play</button>
<br />
<video id="myVideo" autoplay="autoplay">No video available</video>
<script src="index.js"></script>
</body>
</html>
Also create a new .js file in the same directory.
/*globals window, console, XMLHttpRequest, document, Uint8Array, DOMParser, URL*/
(function () { /* code */
'use strict';
// Global Parameters from .mpd file
var file; // MP4 file
var width; // Native width and height
var height;
// Elements
var videoElement = document.getElementById('myVideo');
var playButton = document.getElementById("load");
videoElement.poster = "poster.png";
// Description of initialization segment, and approx segment lengths
var initialization;
// Video parameters
var bandwidth; // bitrate of video
// Parameters to drive segment loop
var index = 0; // Segment to get
var segments;
// Source and buffers
var mediaSource;
var videoSource;
// Parameters to drive fetch loop
var segCheck;
var lastTime = 0;
var bufferUpdated = false;
// Flags to keep things going
var lastMpd = "";
var requestId = 0;
// Logs messages to the console
function log(s) {
// send to console
// you can also substitute UI here
console.log(s);
}
// Clears the log
function clearLog() {
console.clear();
}
function timeToDownload(range) {
var vidDur = range.split("-");
// Time = size * 8 / bitrate
return (((vidDur[1] - vidDur[0]) * 8) / bandwidth);
}
// Play segment plays a byte range (format nnnn-nnnnn) of a media file
function playSegment(range, url) {
var xhr = new XMLHttpRequest();
if (range || url) { // Make sure we've got incoming params
xhr.open('GET', url);
xhr.setRequestHeader("Range", "bytes=" + range);
xhr.send();
xhr.responseType = 'arraybuffer';
try {
xhr.addEventListener("readystatechange", function () {
if (xhr.readyState === xhr.DONE) { //wait for video to load
// Calculate when to get next segment based on time of current one
segCheck = (timeToDownload(range) * 0.8).toFixed(3); // Use point eight as fudge factor
// Add received content to the buffer
try {
videoSource.appendBuffer(new Uint8Array(xhr.response));
} catch (e) {
log('Exception while appending', e);
}
}
}, false);
} catch (e) {
log(e);
return; // No value for range
}
}
}
// Get video segments
function fileChecks() {
// If we're ok on the buffer, then continue
if (bufferUpdated === true) {
if (index < segments.length) {
// Loads next segment when time is close to the end of the last loaded segment
if ((videoElement.currentTime - lastTime) >= segCheck) {
playSegment(segments[index].getAttribute("mediaRange").toString(), file);
lastTime = videoElement.currentTime;
index++;
}
} else {
videoElement.removeEventListener("timeupdate", fileChecks, false);
}
}
}
// Play our file segments
function getStarted(url) {
// Start by loading the first segment of media
playSegment(segments[index].getAttribute("mediaRange").toString(), url);
// Display current index
index++;
// Continue in a loop where approximately every x seconds reload the buffer
videoElement.addEventListener("timeupdate", fileChecks, false);
}
function updateFunct() {
// This is a one shot function, when init segment finishes loading,
// update the buffer flag, call getStarted, and then remove this event.
bufferUpdated = true;
getStarted(file); // Get video playback started
// Now that video has started, remove the event listener
videoSource.removeEventListener("update", updateFunct);
}
// Load video's initialization segment
function initVideo(range, url) {
var xhr = new XMLHttpRequest();
if (range || url) { // make sure we've got incoming params
// Set the desired range of bytes we want from the mp4 video file
xhr.open('GET', url);
xhr.setRequestHeader("Range", "bytes=" + range);
segCheck = (timeToDownload(range) * 0.8).toFixed(3); // use point eight as fudge factor
xhr.send();
xhr.responseType = 'arraybuffer';
try {
xhr.addEventListener("readystatechange", function () {
if (xhr.readyState === xhr.DONE) { // wait for video to load
// Add response to buffer
try {
videoSource.appendBuffer(new Uint8Array(xhr.response));
// Wait for the update complete event before continuing
videoSource.addEventListener("update", updateFunct, false);
} catch (e) {
log('Exception while appending initialization content', e);
}
}
}, false);
} catch (e) {
log(e);
}
} else {
return; // No value for range or url
}
}
// Create mediaSource and initialize video
function setupVideo() {
clearLog(); // Clear console log
// Create the media source
if (window.MediaSource) {
mediaSource = new window.MediaSource();
} else {
log("mediasource or syntax not supported");
return;
}
var url = URL.createObjectURL(mediaSource);
videoElement.pause();
videoElement.src = url;
videoElement.width = width;
videoElement.height = height;
// Wait for event that tells us that our media source object is
// ready for a buffer to be added.
mediaSource.addEventListener('sourceopen', function (e) {
try {
videoSource = mediaSource.addSourceBuffer('video/mp4');
initVideo(initialization, file);
} catch (ex) {
log('Exception calling addSourceBuffer for video', ex);
return;
}
}, false);
// Handler to switch button text to Play
videoElement.addEventListener("pause", function () {
playButton.innerText = "Play";
}, false);
// Handler to switch button text to pause
videoElement.addEventListener("playing", function () {
playButton.innerText = "Pause";
}, false);
}
// Retrieve parameters from our stored .mpd file
function getFileType(data) {
try {
file = data.querySelectorAll("BaseURL")[0].textContent.toString();
var rep = data.querySelectorAll("Representation");
width = rep[0].getAttribute("width");
height = rep[0].getAttribute("height");
bandwidth = rep[0].getAttribute("bandwidth");
var ini = data.querySelectorAll("Initialization");
initialization = ini[0].getAttribute("range");
segments = data.querySelectorAll("SegmentURL");
} catch (er) {
log(er);
return;
}
}
// Gets the mpd file and parses it
function getData(url) {
if (url !== "") {
var xhr = new XMLHttpRequest(); // Set up xhr request
xhr.open("GET", url, true); // Open the request
xhr.responseType = "text"; // Set the type of response expected
xhr.send();
// Asynchronously wait for the data to return
xhr.onreadystatechange = function () {
if (xhr.readyState === xhr.DONE) {
var tempoutput = xhr.response;
var parser = new DOMParser(); // Create a parser object
// Create an xml document from the .mpd file for searching
var xmlData = parser.parseFromString(tempoutput, "text/xml", 0);
log("parsing mpd file");
// Get and display the parameters of the .mpd file
getFileType(xmlData);
// Set up video object, buffers, etc
setupVideo();
}
};
// Report errors if they happen during xhr
xhr.addEventListener("error", function (e) {
log("Error: " + e + " Could not load url.");
}, false);
}
}
// Click event handler for load button
playButton.addEventListener("click", function () {
// If video is paused then check for file change
if (videoElement.paused === true) {
// Retrieve mpd file, and set up video
var curMpd = document.getElementById("filename").value;
// If current mpd file is different then last mpd file, load it.
if (curMpd !== lastMpd) {
// Cancel display of current video position
window.cancelAnimationFrame(requestId);
lastMpd = curMpd;
getData(curMpd);
} else {
// No change, just play
videoElement.play();
}
} else {
// Video was playing, now pause it
videoElement.pause();
}
}, false);
// Do a little trickery, start video when you click the video element
videoElement.addEventListener("click", function () {
playButton.click();
}, false);
// Event handler for the video element errors
document.getElementById("myVideo").addEventListener("error", function (e) {
log("video error: " + e.message);
}, false);
}());
When I serve the index.html file from a Web server to Edge or IE 11+ the video displays instantly. Time permitting and if you are interested, I will host the demo live for you to see.
79
IE buffering is done by looking at the sample duration in the MP4 TRUN box. You could perhaps solve it by adding ~5 seconds of fake data and then remove that once the video starts playing.
37
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