Multimedia comes in many different formats. It can be almost anything you can hear or see.
Examples: Pictures, music, sound, videos, records, films, animations, and more.
Web pages often contains multimedia elements of different types and formats.
In this chapter you will learn about the different multimedia formats.
The first web browsers had support for text only, limited to a single font in a single color.
Later came browsers with support for colors and fonts, and even support for pictures!
The support for sounds, animations, and videos is handled differently by various browsers. Different types and formats are supported, and some formats requires extra helper programs (plug-ins) to work.
Hopefully this will become history. HTML5 multimedia promises an easier future for multimedia.
Multimedia elements (like sounds or videos) are stored in media files.
The most common way to discover the type of a file, is to look at the file extension. When a browser sees the file extension .htm or .html, it will treat the file as an HTML file. The .xml extension indicates an XML file, and the .css extension indicates a style sheet file. Pictures are recognized by extensions like .gif, .png and .jpg.
Multimedia files also have their own formats and different extensions like: .swf, .wav, .mp3, .mp4, .mpg, .wmv, and .avi.
|
MP4 is the new and upcoming format for internet video. |
|
Format |
File |
Description |
|
MPEG |
.mpg |
MPEG. Developed by the Moving Pictures Expert Group. The first popular video format on the web. Used to be supported by all browsers, but it is not supported in HTML5 (See MP4). |
|
AVI |
.avi |
AVI (Audio Video Interleave). Developed by Microsoft. Commonly used in video cameras and TV hardware. Plays well on Windows computers, but not in web browsers. |
|
WMV |
.wmv |
WMV (Windows Media Video). Developed by Microsoft. Commonly used in video cameras and TV hardware. Plays well on Windows computers, but not in web browsers. |
|
QuickTime |
.mov |
QuickTime. Developed by Apple. Commonly used in video cameras and TV hardware. Plays well on Apple computers, but not in web browsers. (See MP4) |
|
RealVideo |
.rm |
RealVideo. Developed by Real Media to allow video streaming with low bandwidths. It is still used for online video and Internet TV, but does not play in web browsers. |
|
Flash |
.swf |
Flash. Developed by Macromedia. Often requires an extra component (plug-in) to play in web browsers. |
|
Ogg |
.ogg |
Theora Ogg. Developed by the Xiph.Org Foundation. Supported by HTML5. |
|
WebM |
.webm |
WebM. Developed by the web giants, Mozilla, Opera, Adobe, and Google. Supported by HTML5. |
|
MPEG-4 |
.mp4 |
MP4. Developed by the Moving Pictures Expert Group. Based on QuickTime. Commonly used in newer video cameras and TV hardware. Supported by all HTML5 browsers. Recommended by YouTube. |
|
Only MP4, WebM, and Ogg video is supported by the newest HTML5 standard. |
MP3 is the newest format for compressed recorded music. The term MP3 has become synonymous with digital music.
If your website is about recorded music, MP3 is the choice.
|
Format |
File |
Description |
|
MIDI |
.mid |
MIDI (Musical Instrument Digital Interface). Main format for all electronic music devices like synthesizers and PC sound cards. MIDI files do not contain sound, but digital notes that can be played by electronics. Plays well on all computers and music hardware, but not in web browsers. |
|
RealAudio |
.rm |
RealAudio. Developed by Real Media to allow streaming of audio with low bandwidths. Does not play in web browsers. |
|
WMA |
.wma |
WMA (Windows Media Audio). Developed by Microsoft. Commonly used in music players. Plays well on Windows computers, but not in web browsers. |
|
AAC |
.aac |
AAC (Advanced Audio Coding). Developed by Apple as the default format for iTunes. Plays well on Apple computers, but not in web browsers. |
|
WAV |
.wav |
WAV. Developed by IBM and Microsoft. Plays well on Windows, Macintosh, and Linux operating systems. Supported by HTML5. |
|
Ogg |
.ogg |
Ogg. Developed by the Xiph.Org Foundation. Supported by HTML5. |
|
MP3 |
.mp3 |
MP3 files are actually the sound part of MPEG files. MP3 is the most popular format for music players. Combines good compression (small files) with high quality. Supported by all browsers. |
|
MP4 |
.mp4 |
MP4 is a video format, but can also be used for audio. MP4 video is the upcoming video format on the internet. This leads to automatic support for MP4 audio by all browsers. |
|
Only MP3, WAV, and Ogg audio is supported by the newest HTML5 standard. |
Before HTML5, there was no standard for showing videos on a web page.
Before HTML5, videos could only be played with a plug-in (like flash).
The HTML5 <video> element specifies a standard way to embed a video in a web page.
Internet Explorer 9+, Firefox, Opera, Chrome, and Safari support the <video> element.
Note: Internet Explorer 8 and earlier versions, do not support the <video> element.
To show a video in HTML, use the <video> element:
<video width="320" height="240" controls>
<source src="movie.mp4" type="video/mp4">
<source src="movie.ogg" type="video/ogg">
Your browser does not support the video tag.
</video>
The controls attribute adds video controls, like play, pause, and volume.
It is a good idea to always include width and height attributes.
If height and width are not set, the browser does not know the size of the video. The effect will be that the page will change (or flicker) while the video loads.
Text between the <video> and </video> tags will only display in browsers that do not support the <video> element.
Multiple <source> elements can link to different video files. The browser will use the first recognized format.
To start a video automatically use the autoplay attribute:
<video width="320" height="240" autoplay>
<source src="movie.mp4" type="video/mp4">
<source src="movie.ogg" type="video/ogg">
Your browser does not support the video tag.
</video>
Currently, there are 3 supported video formats for the <video> element: MP4, WebM, and Ogg:
|
Browser |
MP4 |
WebM |
Ogg |
|
Internet Explorer |
YES |
NO |
NO |
|
Chrome |
YES |
YES |
YES |
|
Firefox |
YES |
YES |
YES |
|
Safari |
YES |
NO |
NO |
|
Opera |
NO |
YES |
YES |
|
File Format |
Media Type |
|
MP4 |
video/mp4 |
|
WebM |
video/webm |
|
Ogg |
video/ogg |
HTML5 defines DOM methods, properties, and events for the <video> element.
This allows you to load, play, and pause videos, as well as setting duration and volume.
There are also DOM events that can notify you when a video begins to play, is paused, etc.
Your browser does not support HTML5 video.
Video courtesy of Big Buck Bunny.
For a full DOM reference, go to our HTML5 Audio/Video DOM Reference.
|
Tag |
Description |
|
Defines a video or movie |
|
|
Defines multiple media resources for media elements, such as <video> and <audio> |
|
|
Defines text tracks in media players |
Before HTML5, there was no standard for playing audio files on a web page.
Before HTML5, audio files could only be played with a plug-in (like flash).
The HTML5 <audio> element specifies a standard way to embed audio in a web page.
Internet Explorer 9+, Firefox, Opera, Chrome, and Safari support the <audio> element.
Note: Internet Explorer 8 and earlier versions, do not support the <audio> element.
To play an audio file in HTML, use the <audio> element:
<audio controls>
<source src="horse.ogg" type="audio/ogg">
<source src="horse.mp3" type="audio/mpeg">
Your browser does not support the audio element.
</audio>
The controls attribute adds audio controls, like play, pause, and volume.
Text between the <audio> and </audio> tags will display in browsers that do not support the <audio> element.
Multiple <source> elements can link to different audio files. The browser will use the first recognized format.
Currently, there are 3 supported file formats for the <audio> element: MP3, Wav, and Ogg:
|
Browser |
MP3 |
Wav |
Ogg |
|
Internet Explorer |
YES |
NO |
NO |
|
Chrome |
YES |
YES |
YES |
|
Firefox |
YES |
YES |
YES |
|
Safari |
YES |
YES |
NO |
|
Opera |
NO |
YES |
YES |
|
File Format |
Media Type |
|
MP3 |
audio/mpeg |
|
Ogg |
audio/ogg |
|
Wav |
audio/wav |
HTML5 defines DOM methods, properties, and events for the <audio> element.
This allows you to load, play, and pause audios, as well as setting duration and volume.
There are also DOM events that can notify you when an audio begins to play, is paused, etc.
For a full DOM reference, go to our HTML5 Audio/Video DOM Reference.
|
Tag |
Description |
|
Defines sound content |
|
|
Defines multiple media resources for media elements, such as <video> and <audio> |
Different versions of different browsers support different video formats.
Earlier in this tutorial, you have seen that you might have to convert your videos to different video formats, to make sure they play in all browsers.
Converting videos to different format can be difficult and time consuming.
An easier solution might be to let YouTube play the videos in your web pages.
If you want to play a video in a web page, you can upload the video to YouTube and insert the proper HTML code, in your web page, to display the video:
<iframe width="420" height="315"
src="http://www.youtube.com/embed/XGSy3_Czz8k">
</iframe>
<object width="420" height="315"
data="http://www.youtube.com/v/XGSy3_Czz8k">
</object>
<embed width="420" height="315"
src="http://www.youtube.com/v/XGSy3_Czz8k">
|
YouTube will display the code to use (like:XGSy3_Czz8k), when you click share under the video. |
The HTML Geolocation API is used to get the geographical position of a user.
Since this can compromise user privacy, the position is not available unless the user approves it.
Internet Explorer 9+, Firefox, Chrome, Safari and Opera support Geolocation.
Note: Geolocation is much more accurate for devices with GPS, like iPhone.
Use the getCurrentPosition() method to get the user's position.
The example below is a simple Geolocation example returning the latitude and longitude of the user's position:
<script>
var x = document.getElementById("demo");
function getLocation() {
if (navigator.geolocation) {
navigator.geolocation.getCurrentPosition(showPosition);
} else {
x.innerHTML = "Geolocation is not supported by this browser.";
}
}
function showPosition(position) {
x.innerHTML = "Latitude: " + position.coords.latitude +
"<br>Longitude: " + position.coords.longitude;
}
</script>
Example explained:
The example above is a very basic Geolocation script, with no error handling.
The second parameter of the getCurrentPosition() method is used to handle errors. It specifies a function to run if it fails to get the user's location:
function showError(error) {
switch(error.code) {
case error.PERMISSION_DENIED:
x.innerHTML = "User denied the request for Geolocation."
break;
case error.POSITION_UNAVAILABLE:
x.innerHTML = "Location information is unavailable."
break;
case error.TIMEOUT:
x.innerHTML = "The request to get user location timed out."
break;
case error.UNKNOWN_ERROR:
x.innerHTML = "An unknown error occurred."
break;
}
}
Error Codes:
To display the result in a map, you need access to a map service that can use latitude and longitude, like Google Maps:
function showPosition(position) {
var latlon = position.coords.latitude + "," + position.coords.longitude;
var img_url = "http://maps.googleapis.com/maps/api/staticmap?center=
"+latlon+"&zoom=14&size=400x300&sensor=false";
document.getElementById("mapholder").innerHTML = "<img src='"+img_url+"'>";
}
In the example above we use the returned latitude and longitude data to show the location in a Google map (using a static image).
Google Map Script
How to use a script to show an interactive map with a marker, zoom and drag options.
This page demonstrated how to show a user's position on a map. However, Geolocation is also very useful for location-specific information.
Examples:
The getCurrentPosition() method returns an object if it is successful. The latitude, longitude and accuracy properties are always returned. The other properties below are returned if available.
|
Property |
Description |
|
coords.latitude |
The latitude as a decimal number |
|
coords.longitude |
The longitude as a decimal number |
|
coords.accuracy |
The accuracy of position |
|
coords.altitude |
The altitude in meters above the mean sea level |
|
coords.altitudeAccuracy |
The altitude accuracy of position |
|
coords.heading |
The heading as degrees clockwise from North |
|
coords.speed |
The speed in meters per second |
|
timestamp |
The date/time of the response |
watchPosition() - Returns the current position of the user and continues to return updated position as the user moves (like the GPS in a car).
clearWatch() - Stops the watchPosition() method.
The example below shows the watchPosition() method. You need an accurate GPS device to test this (like iPhone):
<script>
var x = document.getElementById("demo");
function getLocation() {
if (navigator.geolocation) {
navigator.geolocation.watchPosition(showPosition);
} else {
x.innerHTML = "Geolocation is not supported by this browser.";
}
}
function showPosition(position) {
x.innerHTML = "Latitude: " + position.coords.latitude +
"<br>Longitude: " + position.coords.longitude;
}
</script>
Drag and drop is a very common feature. It is when you "grab" an object and drag it to a different location.
In HTML5, drag and drop is part of the standard, and any element can be draggable.
Internet Explorer 9+, Firefox, Opera, Chrome, and Safari support drag and drop.
Note: Drag and drop does not work in Safari 5.1.7 and earlier versions.
The example below is a simple drag and drop example:
<!DOCTYPE HTML>
<html>
<head>
<script>
function allowDrop(ev) {
ev.preventDefault();
}
function drag(ev) {
ev.dataTransfer.setData("text/html", ev.target.id);
}
function drop(ev) {
ev.preventDefault();
var data = ev.dataTransfer.getData("text/html");
ev.target.appendChild(document.getElementById(data));
}
</script>
</head>
<body>
<div id="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<img id="drag1" src="img_logo.gif" draggable="true"
ondragstart="drag(event)" width="336" height="69">
</body>
</html>
It might seem complicated, but lets go through all the different parts of a drag and drop event.
First of all: To make an element draggable, set the draggable attribute to true:
<img draggable="true">
Then, specify what should happen when the element is dragged.
In the example above, the ondragstart attribute calls a function, drag(event), that specifies what data to be dragged.
The dataTransfer.setData() method sets the data type and the value of the dragged data:
function drag(ev) {
ev.dataTransfer.setData("text/html", ev.target.id);
}
In this case, the data type is "text/html" and the value is the id of the draggable element ("drag1").
The ondragover event specifies where the dragged data can be dropped.
By default, data/elements cannot be dropped in other elements. To allow a drop, we must prevent the default handling of the element.
This is done by calling the event.preventDefault() method for the ondragover event:
event.preventDefault()
When the dragged data is dropped, a drop event occurs.
In the example above, the ondrop attribute calls a function, drop(event):
function drop(ev) {
ev.preventDefault();
var data = ev.dataTransfer.getData("text/html");
ev.target.appendChild(document.getElementById(data));
}
Code explained:
With local storage, web applications can store data locally within the user's browser.
Before HTML5, application data had to be stored in cookies, included in every server request. Local storage is more secure, and large amounts of data can be stored locally, without affecting website performance.
Unlike cookies, the storage limit is far larger (at least 5MB) and information is never transferred to the server.
Local storage is per domain. All pages, from one domain, can store and access the same data data.
Local storage is supported in Internet Explorer 8+, Firefox, Opera, Chrome, and Safari.
Note: Internet Explorer 7 and earlier versions, do not support Web Storage.
HTML local storage provides two objects for storing data on the client:
Before using local storage, check browser support for localStorage and sessionStorage:
if(typeof(Storage) !== "undefined") {
// Code for localStorage/sessionStorage.
} else {
// Sorry! No Web Storage support..
}
The localStorage object stores the data with no expiration date. The data will not be deleted when the browser is closed, and will be available the next day, week, or year.
// Store
localStorage.setItem("lastname", "Smith");
// Retrieve
document.getElementById("result").innerHTML = localStorage.getItem("lastname");
Example explained:
The example above could also be written like this:
// Store
localStorage.lastname = "Smith";
// Retrieve
document.getElementById("result").innerHTML = localStorage.lastname;
The syntax for removing the "lastname" localStorage item is as follows:
localStorage.removeItem("lastname");
Note: Name/value pairs are always stored as strings. Remember to convert them to another format when needed!
The following example counts the number of times a user has clicked a button. In this code the value string is converted to a number to be able to increase the counter:
if (localStorage.clickcount) {
localStorage.clickcount = Number(localStorage.clickcount) + 1;
} else {
localStorage.clickcount = 1;
}
document.getElementById("result").innerHTML = "You have clicked the button " +
localStorage.clickcount + " time(s).";
The sessionStorage object is equal to the localStorage object, except that it stores the data for only one session. The data is deleted when the user closes the browser window.
The following example counts the number of times a user has clicked a button, in the current session:
if (sessionStorage.clickcount) {
sessionStorage.clickcount = Number(sessionStorage.clickcount) + 1;
} else {
sessionStorage.clickcount = 1;
}
document.getElementById("result").innerHTML = "You have clicked the button " +
sessionStorage.clickcount + " time(s) in this session.";
HTML5 introduces application cache, which means that a web application is cached, and accessible without an internet connection.
Application cache gives an application three advantages:
Internet Explorer 10, Firefox, Chrome, Safari and Opera support Application cache.
The example below shows an HTML document with a cache manifest (for offline browsing):
<!DOCTYPE HTML>
<html manifest="demo.appcache">
<body>
The content of the document......
</body>
</html>
To enable application cache, include the manifest attribute in the document's <html> tag:
<!DOCTYPE HTML>
<html manifest="demo.appcache">
...
</html>
Every page with the manifest attribute specified will be cached when the user visits it. If the manifest attribute is not specified, the page will not be cached (unless the page is specified directly in the manifest file).
The recommended file extension for manifest files is: ".appcache"
|
A manifest file needs to be served with the correct media type, which is "text/cache-manifest". Must be configured on the web server. |
The manifest file is a simple text file, which tells the browser what to cache (and what to never cache).
The manifest file has three sections:
The first line, CACHE MANIFEST, is required:
CACHE MANIFEST
/theme.css
/logo.gif
/main.js
The manifest file above lists three resources: a CSS file, a GIF image, and a JavaScript file. When the manifest file is loaded, the browser will download the three files from the root directory of the web site. Then, whenever the user is not connected to the internet, the resources will still be available.
The NETWORK section below specifies that the file "login.asp" should never be cached, and will not be available offline:
NETWORK:
login.asp
An asterisk can be used to indicate that all other resources/files require an internet connection:
NETWORK:
*
The FALLBACK section below specifies that "offline.html" will be served in place of all files in the /html/ catalog, in case an internet connection cannot be established:
FALLBACK:
/html/ /offline.html
Note: The first URI is the resource, the second is the fallback.
Once an application is cached, it remains cached until one of the following happens:
CACHE MANIFEST
# 2012-02-21 v1.0.0
/theme.css
/logo.gif
/main.js
NETWORK:
login.asp
FALLBACK:
/html/ /offline.html
|
Tip: Lines starting with a "#" are comment lines, but can also serve another purpose. An application's cache is only updated when its manifest file changes. If you edit an image or change a JavaScript function, those changes will not be re-cached. Updating the date and version in a comment line is one way to make the browser re-cache your files. |
Be careful with what you cache.
Once a file is cached, the browser will continue to show the cached version, even if you change the file on the server. To ensure the browser updates the cache, you need to change the manifest file.
Note: Browsers may have different size limits for cached data (some browsers have a 5MB limit per site).
When executing scripts in an HTML page, the page becomes unresponsive until the script is finished.
A web worker is a JavaScript that runs in the background, independently of other scripts, without affecting the performance of the page. You can continue to do whatever you want: clicking, selecting things, etc., while the web worker runs in the background.
Internet Explorer 10, Firefox, Chrome, Safari and Opera support Web workers.
The example below creates a simple web worker that count numbers in the background:
Count numbers:
Before creating a web worker, check whether the user's browser supports it:
if(typeof(Worker) !== "undefined") {
// Yes! Web worker support!
// Some code.....
} else {
// Sorry! No Web Worker support..
}
Now, let's create our web worker in an external JavaScript.
Here, we create a script that counts. The script is stored in the "demo_workers.js" file:
var i = 0;
function timedCount() {
i = i + 1;
postMessage(i);
setTimeout("timedCount()",500);
}
timedCount();
The important part of the code above is the postMessage() method - which is used to post a message back to the HTML page.
Note: Normally web workers are not used for such simple scripts, but for more CPU intensive tasks.
Now that we have the web worker file, we need to call it from an HTML page.
The following lines checks if the worker already exists, if not - it creates a new web worker object and runs the code in "demo_workers.js":
if(typeof(w) == "undefined") {
w = new Worker("demo_workers.js");
}
Then we can send and receive messages from the web worker.
Add an "onmessage" event listener to the web worker.
w.onmessage = function(event){
document.getElementById("result").innerHTML = event.data;
};
When the web worker posts a message, the code within the event listener is executed. The data from the web worker is stored in event.data.
When a web worker object is created, it will continue to listen for messages (even after the external script is finished) until it is terminated.
To terminate a web worker, and free browser/computer resources, use the terminate() method:
w.terminate();
If you set the worker variable to undefined, after it has been terminated, you can reuse the code:
w = undefined;
We have already seen the Worker code in the .js file. Below is the code for the HTML page:
<!DOCTYPE html>
<html>
<body>
<p>Count numbers: <output id="result"></output></p>
<button onclick="startWorker()">Start Worker</button>
<button onclick="stopWorker()">Stop Worker</button>
<br><br>
<script>
var w;
function startWorker() {
if(typeof(Worker) !== "undefined") {
if(typeof(w) == "undefined") {
w = new Worker("demo_workers.js");
}
w.onmessage = function(event) {
document.getElementById("result").innerHTML = event.data;
};
} else {
document.getElementById("result").innerHTML = "Sorry! No Web Worker support.";
}
}
function stopWorker() {
w.terminate();
w = undefined;
}
</script>
</body>
</html>
Since web workers are in external files, they do not have access to the following JavaScript objects:
A server-sent event is when a web page automatically gets updates from a server.
This was also possible before, but the web page would have to ask if any updates were available. With server-sent events, the updates come automatically.
Examples: Facebook/Twitter updates, stock price updates, news feeds, sport results, etc.
Server-Sent Events are supported in all major browsers, except Internet Explorer.
The EventSource object is used to receive server-sent event notifications:
var source = new EventSource("demo_sse.php");
source.onmessage = function(event) {
document.getElementById("result").innerHTML += event.data + "<br>";
};
Example explained: