Section 34.3. Video File Formats

34.3. Video File Formats

As with audio, in the early days of the Web, adding video to a web page meant using one of the currently available video formats (such as QuickTime or AVI) and linking it to a page for download. The evolution of streaming media has changed that, and now adding video content like movie trailers, news broadcasts, even live programming to a web site is much more practical and widespread.

This section looks at the video formats that are most common for web delivery.

34.3.1. Windows Media (.wmv or .asf)

Windows Media is a new standard for audio and video, created by Microsoft and therefore very closely integrated with the Windows OS. The Windows Media Player is capable of playing Microsoft's proprietary Windows Media Video (.wmv) and Advanced Streaming Format (.asf), as well as a number of other formats such as AVI, MPEG, MP3, and QuickTime.

Windows Media movies are encoded using the proprietary Windows Media Video codec designed especially for the Windows Media system. They may also feature DRM (digital rights management) capabilities.

In addition to the player, the Windows Media 9 Series platform includes Windows Media Encoder, Windows Media Rights Manager 9 Series SDK, Windows Media Services, and a collection of audio and video codecs.

For more general information about Window Media, visit Microsoft's site at www.microsoft.com/windows/windowsmedia/. Resources related specifically to codecs (video and audio) are available at www.microsoft.com/windows/windowsmedia/mp10/codecs.aspx. If you want to create and stream Windows media, the book Microsoft Windows Media Resource Kit, by Tricia Gill, Bill Birney, and the Microsoft Windows Media Team (Microsoft Press) offers a comprehensive overview.

The following summarizes the Windows Media format:

Good for...	Delivering video to a wide audience (very good support).
Delivery	Streaming or download.
Creation tools	Windows Media Encoder for converting to Windows Media format, Windows Movie Maker for making simple movies on a PC. A growing number of third-party video editors support Windows Media, including Avid, Adobe Premiere, Autodesk Cleaner XL, and Sorenson Squeeze.
Player	Windows Media Player (shipped with Windows OS), also available as a download for the Mac as well as a variety of handheld devices.

34.3.2. QuickTime Movie (.mov)

QuickTime is a highly versatile and well-supported media format. While originally developed as a video format, it has evolved into a container format capable of storing all sorts of media (still images, audio, video, Flash, and SMIL presentations).

QuickTime, a system extension that makes it possible to view audio/video information on a computer, was introduced by Apple Computer in 1991. Although developed for the Macintosh, it is also supported on PCs via QuickTime for Windows. QuickTime has grown to be an industry standard for multimedia development, and most hardware and software offer QuickTime support.

34.3.2.1. Streaming

QuickTime movies may be downloaded (via HTTP) or streamed using a number of streaming server packages, including Apple's QuickTime Streaming Server for Mac OS X or its open source Darwin Streaming Server for Unix, Linux, and Windows. To give the illusion of streaming from an HTTP server (pseudostreaming ), create FastStart QuickTime movies that begin playing right away and continue playing as the file downloads.

34.3.2.2. Creating QuickTime movies

You can take care of rudimentary video editing, such as deleting and rearranging, right in Apple's free QuickTime Player. The QuickTime Pro version ($29.95) offers more features and is sufficient for most basic tasks.

For advanced video editing, use a professional video editing tool such as Apple Final Cut Pro, Adobe Premiere or Adobe After Effects (most video editors support QuickTime). You may also use a file converter, such as Cleaner from Autodesk (www.autodesk.com) or Sorenson Squeeze from Sorenson Communications (www.sorenson.com), to convert existing files to QuickTime format.

An important step to remember when saving a movie is to make it self-contained. This process resolves all data references and prepares the file to go out on the Internet on its own. You will also be asked to pick a codec. QuickTime supports several codecs including the advanced H.264 codec (see earlier description) introduced in QuickTime 7.

34.3.2.3. Reference movies

Another interesting feature of QuickTime is its support for reference movies . Reference movies are used as pointers to alternate versions (or "tracks") of a movie, each optimized for a different connection speed. When a user downloads the reference movie, the plug-in ensures that the best track for the current connection speed is played.

34.3.2.4. For more information

The process for adding QuickTime to a web page is discussed later in this chapter. For general information on QuickTime, see Apple's site at www.apple.com/quicktime/. For complete information on all aspects of QuickTime creation and delivery, I recommend the book QuickTime for the Web for Windows and Macintosh by Steven Gulie (Morgan Kaufmann).

The following summarizes the QuickTime format:

Good for...	Delivering video to a wide audience (very good support).
Delivery	True streaming via RTP or RTSP (using QuickTime Server on Mac OS X Server or the open source Darwin Streaming Server on Unix and Windows), pseudostreaming on HTTP servers, download.
Creation tools	Most video editing and conversion tools support QuickTime, or use Apple's basic editing tool, QuickTime Pro, for $29.95.
Player	QuickTime plug-in (part of Netscape Navigator and Internet Explorer) for viewing within a web browser or QuickTime Player (standalone utility).

34.3.3. RealMedia (.rm)

RealNetworks (which used to be Progressive Networks) first launched its streaming video capabilities in Version 3.0 of its RealMedia line of products (of which RealAudio is the star component). RealMedia files (.rm) are viewed using RealPlayer. The wide distribution of RealPlayer makes RealMedia a popular choice for adding streaming media to a web site.

The components of the RealMedia system (RealPlayer for playback, Helix Server for serving simultaneous streams, and RealProducer and RealProducerPlus for creating .rm files) are the same as for RealAudio. RealMedia movies are encoded using a proprietary codec built into RealProducer and RealPlayer.

For more information, visit the RealNetworks site at www.realnetworks.com. For consumer-oriented information and downloads, see http://www.real.com.

The following summarizes the RealAudio format:

Good for...	Long-playing video clips and live broadcasts to large numbers of people.
Delivery	Streaming (via RTSP), pseudostreaming (via HTTP).
Creation tools	One of the RealNetworks encoders (such as RealProducer Plus or Basic) or a third-party tool such as Autodesk Cleaner. A plug-in is available for Final Cut Pro, Adobe After Effects, and Avid Xpress for exporting to RealMedia format.
Player	Freely available RealPlayer and commercial RealPlayer Enterprise.

34.3.4. AVI (.avi)

AVI (which stands for Audio/Video Interleaved) was introduced by Microsoft in 1992 as the standard movie format to work with its Video for Windows (VFW) multimedia architecture for Windows 95. In AVI files, the audio and video information is interleaved in every frame, which in theory produces smoother playback. The AVI format has been replaced by the more robust Windows Media as the standard media format for Windows. Macintosh users can view AVI files using the QuickTime player.

With the growing (and well-deserved) popularity of streaming media systems, AVI movies are becoming scarce for web distribution. More often, they serve as the high-quality video source file that is converted into a more web-friendly format.

The following summarizes the AVI format:

Good for...	Short web video clips, high-quality video source files.
Delivery	Download.
Creation tools	Most video editing tools support AVI.
Player	Windows Media Player, QuickTime Player.

34.3.5. MPEG (.mpg or .mpeg)

MPEG is a set of multimedia standards created by the Moving Picture Experts Group. It supports three types of information: video, audio, and streaming (which, in the context of MPEG compression, is synchronized video and audio).

MPEG was initially popular as a web format because it was the only format that could be produced on the Unix system.

MPEG files offer extremely high compression rates with little loss of quality. They accomplish this using a lossy compression technique that strips out data that is not discernible to the human ear or eye.

There are a number of MPEG standards. MPEG-1 was originally developed for video transfer at VHS quality. MPEG-2 is a higher-quality standard that was developed for television broadcast and DVD authoring. The most recent released standard is MPEG-4, made popular by its support by QuickTime (though MPEG-4 support is not limited to QuickTime).

MPEGs can be compressed using one of three schemes, Layer-I, -II, or -III. The complexity of the coding (and therefore the processor power needed to encode and decode) increases at each level. Due to this complexity, you need special encoding tools to produce MPEG videos.

MPEG-1 (which uses the .mpg or .mpeg suffix) is the most appropriate format for web purposes. MPEG-2 files are rare except in broadcast studios and on DVDs and are not well suited for web delivery. MPEG-4 is proving to be an attractive option for web video.

To learn more about MPEG, visit the MPEG web site (http://www.mpeg.org).

The following summarizes the MPEG movie format:

Good for...	High-quality video.
Delivery	Streaming, download.
Creation tools	QuickTime 7 Pro, professional video editing software such as Adobe Premiere and After Effects, Apple Final Cut Pro.
Player	Windows Media Player, QuickTime Player.

34.3.6. Which Format to Choose

To deliver long-playing video (like a full movie trailer) or live video broadcasts, you should definitely use one of the streaming media solutions (Windows Media, streaming QuickTime, or RealMedia). Which you choose will come down to the individual requirements of your site. If you expect heavy traffic and many simultaneous streams, definitely invest in a dedicated true streaming system.

If you have just a few short clips to share with a limited number of visitors, you may be able to get away with pseudostreaming RealMedia or FastStart QuickTime movies on your regular web server.

Because all streaming video formats are capable of supporting multiple file formats, are fairly stable, and feature well but not universally distributed players and plug-ins, the decision will likely come down to which server matches your budget or expertise.

For articles and news related to all matters of streaming media, see StreamingMedia.com.