When choosing the best video format for the web, the underlying question, from a media content provider's point of view, is not related to quality of the format as much as the universal accessibility of its intended route. An audience's experience matters more than anything else.

Many video file formats can be used with a variety of codecs, so choosing a format and choosing a codec are often separate steps. For Web delivery, many combinations of player, codec, and format are possible. Currently in the video/web marketplace, there are only four major competitors seeking your content: Flash, Windows Media, QuickTime, and Real Media.

This is the modern format of choice because it's the most universal. Flash reaches the greatest proportion of computer users with its distribution. Flash brings unmatched ease of use, and the player technology is essentially invisible to the user. Flash has a digital rights management (DRM) component within Flash Media Server 3, and now gives users the ability to download videos to their desktops with the Adobe Media Player (http://labs.adobe.com).

Windows Media offers a mainstream solution for streaming at all bandwidths. The Windows Media 9 codec plays on WM Player 7 or later. The latest Windows Media (version 11) has the excellent VC-1 codec at HD (16:9) quality. Compatibility has improved greatly since the introduction of "Silverlight," a browser plug-in which is now available to all users on alternative operating systems or browsers. Windows Media supports full DRM capability through Windows Media DRM services.

Real Video requires software from Real Networks to run in Mac or PC browsers. Real Video can be a fair choice for streaming at all bitrates.

QuickTime is a container format, which means you can use several different codecs for compressing the video (e.g., H.264, DV/DVCPro, etc.). QuickTime is a solid solution for streaming at all bitrates. The Quick- Time player has wide, but not universal, distribution. H.264 is the native format for video on the iPod and Apple TV. QuickTime supports DRM through Apple's iTunes Music Store.

There are a wide variety of tools for encoding video. Each encoding tool's codec implementation is slightly different. Encoding performance and image quality will vary depending on which tools are being used, frame rates, and types of content. You should always encode from the highest-quality video source, such as an uncompressed .DV, .MOV, .MPEG2 at 6-10 Mbs, or .AVI file. Do not use compressed video because it contains visual artifacts. Encoding from a compressed video will produce a poor quality output. If your source is analog videotape, use original masters and encode to a high-quality digital format first. Then transcode to the video formats you'll deliver on the Web. Grass Valley ProCoder 3 is the encoding tool of choice for me and will be the tool we'll focus on for these examples.

These settings apply to all video and are codec-independent:

Deinterlacing: The process of converting interlaced video, like common analog television signals, into a non-interlaced form. Deinterlacing extracts a clean digital-friendly progressive video from the interlaced source.

Color Correction: Vivid color and good contrast can help the codec produce good results at lower bitrates.

Cropping and Resizing: When cropping or resizing video, it is good practice to select dimensions that are divisible by 16 (use 8 or 4 for small images). Common encoded video sizes are 320x240, 400x300, 240x180, and 120x190. Other aspect ratios for importing digital video sources are 720x480 or 486 - 4:3 (Standard TV) and 1.85:1 or 2.4:1 - 16:9 (High-Def TV).

Encoding: These settings set parameters for the encoding process itself. Some of the available options will vary from codec to encoder tool, but the general principles apply.

CBR is useful for streaming multimedia content on limited capacity channels. Since it is the maximum bitrate, not the average, that matters, CBR should be used to take advantage of all of the capacity. CBR encoding maintains a fixed bitrate over the duration of the video. CBR encoding is fast, generally done in one pass, and sometimes in two-pass encoding tools.

VBR alternates the amount of output data per time segment. VBR allows a higher bitrate to be allocated to the more complex segments of media files while less space is allocated to less complex segments. The average of these rates is calculated to produce an average bitrate for the file that will represent its overall quality.

In most encoding tools, two-pass VBR trots through the video twice. The first time it runs through the video, it analyzes the changes in motion and so on. In the second pass, it does the actual compression.

Video codecs capture a complete image of one frame (a "key frame") and then encode subsequent frames by calculating the differences between them. A video with more scene changes will require more keyframes for optimal results. Accept the default values.

The number of still images that make up one second of video; .30fps is full motion video for NTSC, .25fps for PAL. When a video is encoded to a frame rate of less than fifteen frames per second, it becomes noticeably jumpy, but it is good for low-bitrate encoding. Targeted frame rates are 7.5, 10, 15, and 30.

The measurement of the number of data bits per second in a file. Eight bits form one byte. Video files are normally measured in thousands of bits, or kilobits per second (kbps). The higher the bitrate, the larger the resulting file for a specified amount of time. The user's Internet bandwidth will affect their experience. If the user's bandwidth is higher than the video's bitrate, they'll get quick-loading, smooth-running video. If the bitrate is higher than the available bandwidth, the user will be waiting for the video to buffer or download before they can start to view it.

Three separate dimensions of video quality all compete for bits from the total bitrate—accurately reproducing fine detail in a video image, frame rate, and frame size. Reducing one of these will let you increase another, while increasing any one decreases the others. Testing different options with your own media content is essential.

Streaming and downloading are distinct methods of Internet delivery, each with its own benefits and limitations. No matter if you're delivering Windows Media, Real Media, QuickTime, or Flash, the user cannot tell whether the video they're watching is downloading or streaming.

Delivering your video file using a web server is called "HTTP download" or "Progressive download." You place a video or audio file on your Web server, then put a link to the file on your web page and it begins to download to the user's computers. The entire video file is delivered, so the video arrives with the same quality at which it was encoded. The "progressive download" feature in most media players allows them to begin playing the file as soon as enough data has been downloaded. Of course, you can't fast-forward to the end of the file until it has completely downloaded from the web server. In this case, the user will receive the file only as fast as their connection will support. If the bitrate of the video significantly exceeds the available bandwidth, the user will have to wait for enough video to download before they can play it. Once the file is completely downloaded, it is cached into the temporary folder of the user's computer, so they can play it again without repeating the download.

Alternatively, when a media file is streamed via a media streaming server, a measured stream of data is delivered to users as the video plays. There are two sides to this conversation—one to transfer the video and one for control messages between the player and the server.

Windows Media Server and Adobe Flash Media Server can adjust to changing network conditions as the video plays, improving the viewing experience. Users can skip ahead in a video, or begin playback at a point somewhere in the middle.

It also lets you monitor exactly what people are watching, and for how long they are watching it. The video file is not stored on the user's computer.

So which video format for the web is the best format to use? Audience experience matters more than anything else. To determine which formats are best for an intended audience, experiment with a few encoding tools, formats, and calculated bitrates, then playback the file locally to see and hear which format produces the most desirable results. Test those formats via a web server or streaming server with the appropriate web player and ask a few colleagues take a look at the video and provide some feedback on their web experience.

Marcus is a Digital Media Consultant and also the Digital Media Coordinator for Breath of Life Christian Center (Memphis, Tennessee), where he helps to spread the gospel via media technology. Singleton launched a 24-hour Global Network, providing a variety of Internet streaming and downloading possibilities for ministries.

This article originally appeared in Technologies for Worship Magazine, a magazine dedicated to educating churches on how technology can help them minister to a modern world.