Multimedia and canvas elements in HTML5

Multimedia and canvas elements in HTML5


The <canvas> element was originally developed by Apple® for use in Mac OS X
Dashboard widgets and in Safari, but was later adopted by Mozilla® and Opera® in
their Web browsers. The element has been standardized and included in the HTML5
specification, along with a series of 2D drawing APIs that can be used to create
shapes, text, transitions, and animations inside the element.
Many believe that the <canvas> element is one of the most important aspects of
HTML5 as it facilitates the production of graphs, interactive games, paint
applications, and other graphics on the fly without requiring external plug-ins such as
Adobe Flash.

The <canvas> element itself is quite basic, defining the width, height, and unique ID
for the object. The developer must then use a series of JavaScript APIs to actually
draw objects on the canvas, typically when the Web page has finished rendering.
These APIs allow the developer to draw shapes and lines; apply color, opacity, and
gradients; create text; transform canvas objects; and perform animation. The APIs
also allow the <canvas> to be interactive and respond to user input such as mouse
events and key events, facilitating the production of games and Web applications on
the canvas. You will see an example of the <canvas> element in action in the
sample HTML5/CSS3 Web site later in this tutorial.

<audio> and <video>

In recent years, the popularity of video sharing sites such as YouTube and content
delivery platforms like Hulu has seen a huge explosion in the use of the Web for
multimedia streaming. Unfortunately, the Web was not built with such content in
mind, and as a result, the provision of video and audio has by and large been
facilitated by the Flash Video (.flv) file format and the Adobe Flash platform.
HTML5, however, includes support for two new elements, <audio> and <video>,
which allow Web developers to include multimedia content without relying on the
user to have additional browser plug-ins installed. Several browsers, including
Mozilla Firefox, Apple Safari, and Google Chrome, have begun supporting these
new elements and providing standard browser playback controls, should the user
choose to use them. In addition, a set of standard JavaScript APIs has been
provided to allow developers to create their own playback controls, should they wish
to do so. A key advantage to native multimedia playback is that it theoretically
requires less CPU resources, which can lead to energy savings.
A key issue with these new multimedia elements, however, is the file formats
supported by each browser and the patent licensing issues that go along with the
various codecs that these files can be encoded with. Mozilla and Opera want to use
the open source Theora video container and codec, which does not require patent
licensing for the inclusion of the codecs in the Web browser. On the other hand,
Apple and Google are not happy with the quality of Theora, particularly for the
delivery of high definition (HD) content on the likes of YouTube. They prefer the
H.264 codec, typically contained in MP4, MOV, or MKV files.
The issue is not just with video however, as the same problems reside with audio
codecs. The MP3 and AAC formats are restricted by patents, whereas the Vorbis
format is not. The problem with Vorbis audio is that it is not in widespread use, as
portable media players and many media software applications do not support it.
There are many decisions to be made about HTML5 <video> and <audio> in the
near future, and it will be interesting to see what codecs and formats are facilitated in
the final recommendation. In the meantime, you can try to support all browsers by
making video available in a variety of formats and by providing Flash video as a
fallback. Let’s hope that a final decision is made, and that it is not left to browser
vendors to decide which formats to support, as that would essentially render these
new elements useless.
Again, you will see the <video> element in action later in this tutorial.

HTML 5 – Semantic elements

HTML 5 – Semantic elements

The HTML5 specification includes a series of new semantic elements that is used to
give some meaning to the various sections or parts of a Web page, such as a
header, footer, navigation, and so on. In previous versions of HTML (HTML4.01), you would
typically use <div> elements to create these parts, using ID or class attributes to
differentiate them from each other. The problem with this is that this has no semantic
meaning, as there are no strict rules defined that specify what class names or IDs
are to be used, making it extremely difficult for software to determine what the
particular area is doing. HTML5 should help alleviate these issues, making it easier
for Web browsers to parse the semantic structure of a document.
It is worth pointing out that continuing to use <div> elements in HTML5 is perfectly
valid, but in order to future-proof your work, it is recommended that you use
semantic elements where relevant.

Try avoid using these new elements for purposes other than their intended. For
example, the <nav> element should not be used for just any group of links; it is
intended to surround the main navigation block on the page.
The main semantic elements that HTML5 introduces are:


This element is used to define a header for some part of a Web page, be it the
entire page, an <article> element, or a <section> element.


Like the <header> element, this new element defines a footer for some part of
a page. A footer does not have to be included at the end of a page, article, or
section, but it typically does.


This is a container for the primary navigation links on a Web page. This
element is not intended for use with all groups of links and should be used for
major navigation blocks only. If you have a <footer> element that contains
navigation links, you do not need to wrap these links in a <nav> element, since
the <footer> element will suffice on its own.


The <article> element is used to define an independent item on the page that
can be distributed on its own, such as a news item, blog post, or comment.
Such items are typically syndicated using RSS feeds.


This element represents a section of a document or application, such as a
chapter or a section of an article or tutorial. For example, the section you are
reading now could be surrounded by a <section> element in HTML5. <section>
elements typically have a header, although it is not strictly required. The header
for the section you are reading now would contain the text "Semantic
elements," for example.


This new element can be used to mark up a sidebar or some other content that
is considered somewhat separate to the content around it. An example of this
might be advertising blocks.


In some cases, a page, article, or section may require more than one heading,
such as where you have a title and a subtitle. This tutorial, for example, has the
title "Create modern Web sites using HTML5 and CSS3" and the subtitle
"Implementing the canvas and video elements in HTML5." You could wrap
these in an <hgroup> element, using an <h1> element for the main title
Create modern Web sites using HTML5 <h2> element for the subtitle.
The sample Web site at the end of this tutorial includes several of these new
semantic elements, and I will explain their syntax and use in more detail at that