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Editor’s note: The following tip on encoding for the web in Compressor is excerpted from Apple Pro Training Series: Compressor 3 Quick-Reference Guide, by Brian Gary, published by Peachpit Press.

Working With Bit Rates
From: Digital Distribution in Final Cut Studio; pgs. 80 - 81 No magic number or setting works to encode all source media. Every job is unique and has individual requirements that you will need to address both objectively (Will a DVD-5 provide enough space?) and subjectively (Does that high-motion section look good enough for prime time?). Encoding is both a science and an art. Here are some elements to consider when adjusting the bit rate:

• 10.08 Mbps is the maximum bit rate allowed by the standard-definition DVD specification. That limit, however, applies to the combined bit rates of all audio and video content. If a movie is playing concurrently with its soundtrack and an additional commentary track, these three streams combined cannot exceed the 10.08 Mbps rate. Use caution when manually adjusting bit rate so that you do not exceed this allowable limit for DVD players.
• Audio bit rates, whether AIFF or Dolby 2.0, are not variable, so they are much easier to calculate. AIFF has a constant bit rate of 1.5 Mbps, and Dolby 2.0 can deliver similar quality at about one-tenth that rate. Therefore, when you're combining a single AIFF stream with a single video stream, the Maximum Bit Rate slider should not exceed 7.8 Mbps. When using Dolby 2.0, you can safely increase the rate to 8.5 Mbps on the Maximum Bit Rate slider.
• Keep a spread of at least 1 Mbps between the average bit rate and maximum bit rate to allow Compressor enough room to implement the variable bit rate modes and deliver consistent quality.
• Bit rates between 3 Mbps and 4.5 Mbps are the most challenging in terms of quality control. The two-pass modes produce better results and are definitely worth the increased encoding times.

TIP: Although a constant bit rate of 2 Mbps will produce movies with reduced quality, it also allows up to 4 hours of media to be stored on a single DVD-5 (with properly encoded Dolby 2.0 audio). You can use this bit rate to create long-duration, low-resolution DVDs (such as screener DVDs). During a project's editorial phase, these discs work well for dailies or rough cuts, where quality is not as significant as the amount of content on the disc. Excerpted from Apple Pro Training Series: Compressor 3 Quick-Reference Guide by Brian Gary. Copyright © 2007. Used with permission of Pearson Education, Inc. and Peachpit Press.