LIS 525 - Multimedia

Graphics Formats

Only a few graphics formats are generally supported by Web browsers. JPEG and GIF are generally supported. The newer PNG format is supported by newer browsers. Web graphics formats are generally bitmapped (raster), which makes them not particularly efficient for simple shapes, though compression can reduce file size considerably.

GIF (pronounced "jiff") (Graphics Interchange Format) supports up to 256 colors and allows one color to be defined as the transparent color. GIF includes data compression but is not lossy (except for the limitation on the number of colors). Because GIF generally used a patented data compression algorithm (called LZW), there was a move to replace it with PNG (though the patent has now either expired or is about to in most places). According to Security Space (October, 2007), about 62% of Web sites use GIF.

JPEG (Joint Photographic Experts Group) (pronounced "jay-peg") is a lossy compressed format for color images, which can reduce file sizes to about 5% of normal (.bmp) size (though a more normal reduction would be to about 35%). According to Security Space (October, 2007), about 55% of Web sites use JPEG.

PNG (Portable Network Graphics) (pronounced "ping") is a new format, similar to GIF, approved as a standard by the World Wide Web consortium. PNG is completely patent- and license-free and most features are supported by recent versions of popular browsers. A bug in the way Internet Explorer and Nescape for Solaris handle PNG files, however, represents a potential security threat at the browser end. Many tools still do not produce PNG files; but some newer software does, including Corel Photo House, Microsoft PowerPoint, Corel Presentations, GIMP, and some versions of Microsoft Paint. According to Security Space (October, 2007), about 11% of Web sites use PNG.

Audio Formats

WAV (Waveform) was developed for Microsoft Windows. It is the only form supported by Sound Recorder.

MIDI (Musical Instrument Digital Interface) is a format for electronic music. It can be produced by computers, electronic keyboards, and synthesizers. Inexpensive music editing software (not currently available on the FIMS LAN) may be used to produce MIDI files. Only a few programs are capable of converting MIDI to other sound formats.

AU (Sun Audio) was originally designed for Sun UNIX.

AIFF (Audio Interchange Format) was originally developed by Apple for music and high quality sound.

Sounds may also be encoded in various MPEG formats (.mpeg, .mpg, etc.).

WMA (Windows Media Audio) is a Microsoft format similar to MP3 (MPEG audio layer 3) but capable of higher compression.

An HTML page can use the embed tag to cause an audio file to be played while the page is being viewed; for example,

<embed SRC="drink.wma" height="100" width="140" autostart="true">
If plug-ins are disabled or a suitable plug-in has not been installed, the following embedded sound control will display as a default graphic, except in Opera which will just leave a blank space. In Opera, even with plug-ins enabled, the control is displayed, but the sound does not play, even when the "Play" button is clicked.

To see what plug-ins are available in your local installation, you can click on the "Plug-Ins..." button under "Downloads" in the "Options" dialog in Firefox or select "About Plug-ins" from the "Help" menu in Netscape Navigator; in Opera, select "Plug-Ins" under "Special" in the "Window" menu. For Internet Explorer, look in the "PLUGINS" subfolder in the "Internet Explorer" folder in the "Program Files" folder.

Unfortunately, there now appears to be no plug-in for Firefox and Netscape Navigator that will play .wav or .mid files. The Netscape plug-in finder link is bad; the plug-in list for FireFox suggests QuickTime, which plays .mov files as a plugin, but not audio files; for MIDI only, a no-longer-supported product called Crescendo, which appears to require ActiveX, and a product called Beatnik Player 2.2, which requires a "fake installation of Netscape 4.x"; and Yamaha MIDPLUG for XG, which is a bad link. So, relying on embedded .wav or .mid files in designing a Web site is not advisable.

For an audio file that could be safely embedded in this page, Windows Movie Maker was used to translate an existing .wav file into a .wma file.

As an alternative, a link can point to the audio file; for example,

<a href="creak.wav">Play Creak.wav</a>
Play Creak.wav.

Video

In their basic forms, current Web browsers do not support video. Plugins need to be added. Unfortunately, plugins may fail to install; for example, if someone uses the online get-plugin function in Firefox, Firefox may repeatedly say that it has installed a plugin when it has, in fact, done nothing. To install a plugin for a format such as Real Player, users may have to install the entire application, which comes with various extras that they may not want, including a somewhat intimidating EULA (end-user license agreement).

In practice, various formats are used for video on the Web, including Flash (for example, by Google Video and YouTube) and Real Player (for example, by CBC and EuroNews). Some sites make video available in more than one format; for example, Rotten Tomatoes provides clips in both high and low resolution in Flash, QuickTime, and Windows Media Player formats. For more information on video formats, see the page on Streaming Media.

Typical Sizes of Some Common Multimedia Formats

Category Format KBytes/sec.
Sound MIDI 0.1-0.4
MP3 16
WAV 86
WMA 8-16
Video (small window) AVI 40-160
QuickTime (MOV) 20-120
WMV 12-130

Codecs

To play a compressed multimedia format, users need to have the right CODEC (COmpressor/DECompressor) installed. Popular codecs for video include MPEG, Indeo and Cinepak.

Web page developers should generally use CODECs that are part of common players, such as Windows Media Player. Including a link to the download page for the current version of the appropriate player is also a good idea.

To see what CODECs are installed on a Windows XP workstation, select "Computer Management" from the "Administrative Tools" menu; click on "Device Manager" under "System Tools"; expand "Sound, video and game controllers"; then double-click on "Audio Codecs" or "Video Codecs" and go to the "Properties" tab.

Guidelines

To avoid excessive bandwidith consumption, you may want to place restrictions on content providers' use of multimedia files. Some examples:

For More Information


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Last updated October 31, 2007.
This page maintained by Prof. Tim Craven
E-mail (text/plain only): craven@uwo.ca
Faculty of Information and Media Studies
University of Western Ontario,
London, Ontario
Canada, N6A 5B7