Transcript Using Multimedia on the Web

Using Multimedia on the Web
Enhancing a Web Site with
Sound, Video, and Applets
Objectives
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Working with Multimedia
Working with Audio and Audio Clip
Working with Video and Video Clip
Using a Dynamic Source
Introducing Java
Working with Applets
Creating a Marquee with Internet Explorer
Working with the Object Element
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Working with Multimedia
• Bandwidth is a measure of the
amount of data that can be sent
through a communication pipeline
each second
– Consider bandwidth when working with
multimedia on a Web site
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Working with Multimedia
• Multimedia can be added to a Web
page two different ways:
– External media is a sound of video file
that’s accessed through a link
• Useful for a low bandwidth
– Inline media is placed within a Web
page as an embedded object
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Working with Multimedia
Inline media
External media
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Working with Audio
• Every sound wave is composed of two
components:
– Amplitude- the height of the wave. Amplitude
relates to the sound’s volume (the higher the
amplitude, the louder the sound).
– Frequency- the speed at which the sound
wave moves. Frequency relates to sound
pitch (high frequencies have high pitches).
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Working with Audio
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Sampling Rate, Sample
Resolution, and Channels
• Sound waves are analog functions
(represent a continuously varying signal)
– To store the information, however, it must be
converted to pieces of information.
• Digital recording measures the sound’s
amplitude at discrete moments in time
– Each measurement is called a sample
• Samples per second taken is called the sampling
rate
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Sampling Rate
Low sampling rate
Medium sampling
rate
High sampling rate
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Sampling Rate, Sample
Resolution, and Channels
• Sampling resolution indicates the
precision in measuring the sound
within each sample
– 8-bit
– 16-bit
– 32-bit
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Sample Resolution
Low sample resolution
High sample resolution
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Sample Rates and Resolution
Sampling rate and sample resolution as
related to sound quality:
Sampling Rate and Sample Resolution
Sound Quality
8 KHz, 8-bit, mono
22 KHz, 16-bit, stereo
44 KHz, 16-bit, stereo
48 KHz, 16-bit, stereo
(DAT)
Telephone
Radio
CD
Digital Audio Tape
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Sound File Formats
• There are different sound file formats
used for different operating systems
• Different file formats provide varying
levels of sound quality and sound
compression
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Sound File Formats
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WAV
Nonstreaming media
Streaming media
MIDI
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Sound File Formats
• MP3 is a version of the MPEG format,
which compresses audio files with
minor impact on sound quality
– One controversy around the MP3 format
involves copyrighted material that has
been copied as MP3 without the
permission of the artist or producers
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Sound File Formats
• Nonstreaming media must be
completely downloaded by users
before being played
– May produce lengthy delays
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Sound File Formats
• Streaming media are processed in a
steady and continuous stream as they
are downloaded by the browser
– Both sound and video
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Sound File Formats
• MIDI (Musical Instrument Digital
Interface) converts an analog signal
to a series of functions describing the
pitch, length, and volume of each
note
– MIDI format is limited to instrumental
music and cannot be used for general
sounds, such as speech
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Linking to an Audio Clip
Inserting links to the sound clips
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Embedding an Audio Clip
• An embedded object is any media
clip, file, program, or other object that
can be run or viewed from within a
Web page
– Browsers need the appropriate plug-ins
to run embedded objects
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Embedding an Audio Clip
(Internet Explorer and Netscape)
To embed a sound or video clip, use the
embed element:
<embed src=“url” width=“value”
height=“value” autostart=“type” />
Where url is the location of the object, the width and height
attributes specify the width and the height of the object in
pixels, and type is either true (to start the clip
automatically when the page loads) or false (to start the
clip manually).
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Playing Background Sounds
• Internet Explorer (with Version 3.0)
introduced an element to play background
sounds:
<bgsound src=“url” balance=“value”
loop=“value” volume=“value” />
Where url is the URL of the sound file, the balance attribute
defines how the sound should be balanced between left and
right speakers, loop defines how many times the sound clip is
played, and the volume attribute indicates the background
sound volume.
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Working with Video
• Video files add a visual element to a
Web page as well as provide
information
• Video files are composed of a series
of single images called frames
• The number of frames shown in a
period of time is the frame rate
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Frame Rates and Codecs
• Reducing the frame rate reduces the size
of your file
– This is one way to control file size of video
files
• Using a Codec
(compression/decompression) is another
way to control the file size
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Video File Formats
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Linking to a Video Clip
• Follow the same procedure to link a
video clip as you would to link a
sound clip
– Include information about the size of
each video file so that users can
determine whether they want to retrieve
the clip
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Embedding a Video Clip
• Use the same embed element to
embed a video file as you did to
embed a sound clip
– You must specify a source for an
embedded video clip with the src
attribute and a size for the clip using the
height and width attributes
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Using a Dynamic Source
• To turn inline images into dynamic video clips,
use the following syntax:
<img src=“url” dynsrc=“url” start=“type”
loop=“value” control=“control” />
Where the dynsrc attribute specifies the URL of a
dynamic (video) version of the inline image. The start attribute
tells the browser when to start the clip, the loop attribute
specifies the number of times the video will play, and the
control attribute specifies whether IE should display player
controls below the inline image to start and stop the video clip.
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Supporting Non-Embedded
Elements
• If you want to support older
browsers, you can add the noembed
element
• The noembed element works like the
noframe element for frames,
providing a way to support older
browsers that do not recognize
embedded objects
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Using Non-Embedded Content
To provide alternate content for browsers that
don’t support embedded objects, use the code
<embed attributes />
<noembed>
alternate content
</noembed>
where alternate content is the content displayed by browsers that
don’t support embedded objects
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Introducing Java
• Oak was developed by Sun Microsystems
as an operating system intended to be
used by common appliances and devices
• Oak was renamed Java in 1995
• HotJava runs programs written in the Java
language
– HotJava is a Java interpreter (it understands
and runs Java languages)
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Applets and Java Interpreters
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Applets
• Applets are displayed as embedded
objects on a Web page in an applet
window
• Use a Java Developer’s Kit (JDK) to write
your own Java applet
• Compiling changes the file into an
executable file that can run by itself
without the JDK
– The executable file is called a class file
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Working with Applets
Attributes of the applet element
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Inserting a Java Applet
• To insert a Java applet, use the code
<applet code=“file”>
<param name=“text” value=“value” />
<param name=“text” value=“value” ?>
…
</applet>
Where file is the name of the Java class file, text is the
name of an applet parameter, and value is the
parameter’s value.
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Creating a Marquee with
Internet Explorer
• An alternative to using an applet to create
a box with scrolling text is to create a
marquee element
<marquee
attributes>content</marquee>
Where attributes is one or more of the marquee
elements, and content is the page content that appears
in the marquee box.
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Working with the Object
Element
• The object element is the generic element
for any object whose content is stored in a
file separate from the current Web page
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Inline images
Sound clips
Video clips
Program applets
Other HTML documents
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Working with the Object
Element
Specific and generic elements
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Working with the Object
Element
• MIME
(Multipurpose
Internet Mail
Extension)
names are
used to indicate
the type of data
using the type
attribute in an
object element.
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ActiveX
• ActiveX attaches desktop applications to
Web pages
• ActiveX objects are referred to as
ActiveX controls
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Tips for Using Multimedia
• When linking to multimedia, provide a
variety of media formats to ensure that all
users have access to formats they can
use
• Include the file size in links to large
multimedia files to notify users with low
bandwidth connections
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Tips for Using Multimedia
• Do not embed multimedia clips in your Web
pages unless you are sure that users will be
accessing the pages through a high-speed
connection
• Do not insert media clips unless you provide a
method for users to turn off the clips; if a clip
plays automatically, allow it to play only once
• Use the embed and applet elements in
preference to the object element because of
the broader browser support
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