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Compression for Great Video and Audio, 2nd Edition by Ben Waggoner

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CHAPTER 18 Windows Media Audio

WMA File Format

Windows Media Audio can refer to both a file format and a family of codecs. This chapter is mainly about the codecs. The .wma file format is just good old ASF, as described in Chapter 17; a WMA is just a WMV without video.

Rate Control in Windows Media Audio Codecs

One feature of the Windows Media Audio family rarely seen in other codecs is support for 2-pass encoding; most other audio codecs are 1-pass CBR or VBR. While 2-pass CBR rarely makes for a practical improvement over 1-pass CBR, 2-pass VBR can be a big improvement, particularly for soundtracks where audio complexity varies a lot. Progressive download content should use the VBR modes. However, VBR modes aren’t always available at every bitrate ...

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