Some of our web pages include video and audio elements. We generally use the MPEG-4 format for videos, and MP3 for audio, sometimes with other formats as fallbacks (eg MPEG-1 for those without MPEG-4 playback capability).
For novices, there is a section at the bottom of this page which explains what MPEG-4 is, along with concepts such as plugins and streaming.
Each video we provide is usually available in a variety of different qualities. For videos which are primary content (eg promotional videos, television clips etc), the user is generally asked to select from different versions at differing qualities.
For videos that are not primary content (eg headings/banners), the quality of the videos you'll see is determined by automatically checking the speed of your Internet link. You can change your preferred quality for those (automatically-selected) videos here.
With regard to software, in some cases you may need to install additional software to add MPEG-4 functionality to your system. In particular, Microsoft currently does not supply standard MPEG-4 playback functionality with Windows Media Player :-(
The recommended plugins for each operating system are listed below...
NOTE: The information in these help pages assumes you are running recent versions of your web browser and operating system. Older versions may not have the same features, and thus may behave differently.
WindowsUnfortunately, Microsoft has (so far) elected not to support the MPEG-4 standard in Windows Media Player, so at present, standard MPEG-4 video files cannot be played out-of-the-box on Windows :-(
However, there is an excellent solution - we recommend installing QuickTime, which (starting with version 6) can play MPEG-4 video and audio with superb quality. QuickTime provides a powerful and well-designed plugin which also supports many other formats (MOV, QTVR, AVI, AIFF, WAV, AU, MIDI etc), and it fits seamlessly into the end-user's web browsing experience.
MacOSOn the Macintosh things are wonderful because of QuickTime, which is part of the operating system and (starting with version 6) can play MPEG-4 video and audio with superb quality. QuickTime provides a powerful and well-designed plugin which also supports many other formats (MOV, QTVR, AVI, AIFF, WAV, AU, MIDI etc), and it fits seamlessly into the end-user's web browsing experience.
NOTE: Although QuickTime is included as a standard part of MacOS, you may need to upgrade to version 6 if you have an older version (QuickTime version 6 was shipped as part of MacOS X version 10.2). Versions of QuickTime prior to 6.0 cannot play MPEG-4.
NOTE: Apple also makes a version of QuickTime for Windows (see above).
UNIXAt the present time most UNIX systems do not have MPEG-4 playback capability. However, MPEG-4 support is actively under development in the freeware/open-source community, so you can expect MPEG-4 playback to be possible on UNIX systems in the near future.
Regarding MPEG-1 video and MP3 audio, most versions of Netscape for UNIX cannot play MPEG-1 video or MP3 audio with just their standard installations, so you will need to install some additional tools.
The exception is Silicon Graphics systems, which come with tools suitable for playback of most multimedia formats, including MPEG-1 video playback via a plugin form of the movieplayer tool and MP3 audio playback via the soundplayer tool. Even on SGI systems, however, we still recommend that you install the tools listed below because they provide additional features (such as streaming).
For MPEG-1 video we recommend MpegTV, which is an external helper application that can be made to work as a plugin with Plugger. MpegTV is available for Solaris, IRIX, Linux and other UNIX systems. It supports MPEG-1 video and video+audio, but not just audio-only.
Plugger Configuration for MpegTV: We recommend the following settings (in your pluggerrc config file)...
video/mpeg: mpg,mpeg,mpe: MPEG-1 Video
video/x-mpeg: mpg,mpeg,mpe: MPEG-1 Video
video/mpeg-system: mpg,mpeg,mpe: MPEG-1 Video
video/x-mpeg-system: mpg,mpeg,mpe: MPEG-1 Video
stream: mtv -i -W$window -
loop: mtv -i -W$window -l $file
: mtv -i -W$window $file
For MPEG-1 audio (MP2/MP3) we recommend Xaudio, which is an external helper application that can be made to work as a plugin with Plugger. Xaudio is available for Solaris, IRIX, Linux and other UNIX systems.
Plugger Configuration for Xaudio: We recommend the following settings (in your pluggerrc config file)...
audio/mpeg: mp2,mp3,mpa: MPEG Audio
audio/x-mpeg: mp2,mp3,mpa: MPEG Audio
audio/mpeg2: mp2: MPEG Audio
audio/x-mpeg2: mp2: MPEG Audio
audio/mpeg3: mp3: MPEG Audio
audio/x-mpeg3: mp3: MPEG Audio
stream,preload: mxaudio -iconic -
: mxaudio -iconic $file
The HTML web page format allows for much more than just simple text and pictures on a page. In fact, the combination of JavaScript, the EMBED tag, and other HTML extensions allow for a rich multimedia presentation to be delivered, including video and audio.
Just as with images, there are many ways to compress video and audio, resulting in many different file formats. Some of these formats only contain audio (MP3, AU, AIFF, WAV), while others can contain both video and audio (MPEG, MOV, AVI, WMV). Two of these formats (MOV & AVI) support several different types of compression (codecs), such as Cinepak, Indeo, Sorenson etc.
We provide our video elements in MPEG-4 format and our audio in MP3 format. MPEG-4 is the successor to the popular MPEG-1 and MPEG-2 video formats, which were used for VideoCD and DVD respectively. MP3 is widely used to distribute music on the Internet, and is actually an enhanced form of the audio compression used in MPEG-1 video files (which was called MP2).
We choose to use MPEG-4 and MP3 for two main reasons...
Unfortunately, some operating systems do not come with suitable software to play the MPEG-4 video and MP3 audio formats. In particular, Microsoft currently does not supply standard MPEG-4 playback functionality with Windows Media Player :-( In such cases, you will need to install additional software to provide MPEG-4 playback capability (see above).
Unlike static images, a user can be watching a video or listening to some audio while it is still downloading. That is, the video or audio can start playing while the file is downloading. Such "streaming" behavior (playback while downloading) works very smoothly, and means that the end user doesn't have to wait for the entire file to download before playing it. With such technology, the total size of the file is not so important, only the data rate, ie the rate at which data must keep coming in to achieve smooth uninterrupted playback.
To avoid stop-start playback, smart plugins such as Apple's QuickTime usually measure the speed of the download and use this information, in combination with knowledge of the length of the file, to determine how much should be downloaded before playback should start so that playback ends just as the final bytes of the file are coming in.
Obviously, when the downloading speed is less than the video clip's data rate there will be an initial delay before streaming playback can begin. During this delay the plugin loads enough of the file so that once playback starts the rest of the file will download in roughly the same time as the file takes to play.
Some types of streaming continually re-negotiate the quality of the video and audio to compensate for the speed of your Internet link. That is, rather than delaying the initial playback they reduce the quality of the material (resolution, frame rate etc) until it is able to be played in realtime with no delay. Since this type of streaming often results in very low quality video, we do not use it.
Playing a high quality MPEG-4 video requires a reasonably fast computer (Pentium-II, PowerMac G3). Playing while downloading (streaming) requires even more power. Slower machines will drop frames and/or lose audio sync. Scaling or zooming to full screen requires even more power again.
Streaming at high data rates requires a recent version of your browser and operating system. Bottlenecks in older OS versions mean they will often struggle to push the data up through the networking system, into the browser, and into the MPEG plugin fast enough.
Some Internet service providers use web caches which have problems with very large files such as video clips. If you find your downloading suddenly just stops, you may need to bypass your ISP's web cache by changing the proxy preferences in your web browser.
This document was last updated on
