Best Practices for Windows Media Encoding
Windows Media Video 9 Advanced Profile
Windows Media Video 9 Advanced Profile is a non-backwards compatible enhancement to WMV 9, focused primarily on much improved support for encoding content as interlaced, with other enhancements helpful for IPTV and HD DVD. For most web video, neither are needed.
WMV 9 AP was introduced with WMP 10 and the Format SDK 9.5 back in 2004. However, there have been a few format tweaks in the v11 implementation, meaning WMP 9 and 10 will require a codec download to play back v11-encoded WMV 9 AP.
Windows Media Video 9 Screen
The WMV 9 Screen codec is designed for efficient compression of screen recordings. It’s a special-use codec—very efficient for this task, but not appropriate for encoding normal video. Screen is the most efficient with simpler, flat graphics, so you can get efficient encoding out of the "Windows Classic" theme in XP and Vista. However, richer graphics environments, especially Vista, include a lot of gradients and transparencies, and can often encode more efficiently using standard WMV 9.
For efficiency, WMV Screen needs access to the uncompressed RGB source video of the screen shots, and it doesn’t work well when compressing from screen shots that have had any lossy encoding already applied to them. It’s typically used in conjunction with lossless screen recording products like TechSmith’s Camtasia. On a fast computer, it’s possible to use Windows Media Encoder to record, or even broadcast, live screen activity with the Screen codec.
Compared to other screen capture codecs, WMV 9 Screen is unique in providing full support for 2-pass VBR and CBR encoding, making it possible to use it for real-time streaming.
Windows Media Video 9.1 Image
The WMV 9.1 Image codec is designed for video sequences made out of individual still images, including transitions. For this special class of content, Image can be quite a bit more efficient than WMV 9, but it is much less efficient for typical motion video sources.
Windows Media Audio 9.2
Windows Media Audio (WMA) 9.2 is a fully backwards-compatible upgrade to the venerable WMA standard. It’s compatible back to WMP from the mid-'90s (predating ".WMA" files!), and can be played back virtually anywhere. The 9.2 version includes some minor (but welcome) performance and quality enhancements compared to the previous version.
WMA is the general, safe codec choice for any Windows Media file. It’s flexible, offers high quality with sufficient bit rate, and is playable by anything that can play a .WMV file. However, there are some scenarios where Voice or WMA 10 Pro can offer better performance.
Windows Media Audio Voice 9
WMA 9 Voice is designed for low bit rate applications below 32Kbps, where WMA and WMA Pro don’t perform as well. Despite its name, it does a credible job with music and other non-voice content. You’re not going to dance to WMA Voice at low bit rates, but it can intelligibly compress music interludes and sound effects in otherwise voice-centric content.
WMA Voice 9 is supported in WMP 9 and higher. Note that Voice is not currently supported in all non-Windows players. Most notably, it isn’t supported in the current versions of Flip4Mac or the Kinoma player for PalmOS.
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