9/13/02 - Windows Media 9 Series Beta: Technical Review

The long awaited release from Microsoft’s Windows Media Group, code named Corona, has finally appeared in a beta version. Now dubbed Windows Media 9 Series, it is the first comprehensive platform review in four years. It includes new audio and video codecs, enhanced encoding software and tools, a new server, a new look for the player, and a new SDK for developers.

As expected, this release is much more than a streaming media release. Many of the new features are more broadly targeted at consumer media consumption. These features enable consumers to watch DVDs, listen to downloaded or ripped music tracks, and even include personal video recorder functions built in to the upcoming Windows XP Media Center release. This preliminary review concentrates on the features of most interest to today's streaming media professionals.

New Codecs
Perhaps most eagerly anticipated have been the new codecs. Traditionally each release from the major streaming media platforms raises the bar on codec quality. The Windows Media Group claims a 20% improvement in audio quality, and anywhere from 15-50% improvement in video quality. While these measurements are highly subjective, there is no doubt that the new codecs are a definite improvement over the previous Windows Media codecs, and strengthen Microsoft's position in the codec wars.

On the audio side, the most exciting news is a new low bit rate mixed-mode codec. This codec is designed to encode content that has both voice and music content. Previously, content creators had to decide whether to optimize their low bit rate streams for either voice or music. This codec does justice to both. Even more impressive is that WMA 9 is backwards compatible - no need to upgrade older players or devices.

The WMA 9 hybrid codec is apparently two separate codecs, with intelligence to dynamically switch between them based on the source content. It is definitely a huge improvement over WMA 8. For those of you working on the Windows Media platform, you have a great new option for low bit rate mixed-mode content. When compared to the other platforms, however, the competition gets a little tougher.

Codec designers have to trade off audio fidelity with frequency range, and the subtle differences between the platforms reflect this. Some codecs sound a bit brighter but perhaps with more artifacts; others a bit less bright but less audible artifacts. Personally, I prefer fidelity to extended frequency range, but have been astounded repeatedly at consumer preference for extended frequency ranges. Then again, consumers prefer "loud" speakers to accurate speakers – ask any stereo salesperson.

Bearing this in mind, both the WMA9 hybrid voice and RealAudio 8 music codecs do a good job, with the QuickTime and MPEG-4 codecs bringing up the rear (The MPEG-4 codec available in the QuickTime encoder does not offer any bit rates below 16kbps). The new Windows Media hybrid voice codec does an outstanding job on the voice, but the strings in this example have an annoying ring. RealAudio 8 music sounds a bit hollow on the voice, but the strings sound more natural. Between Windows Media and RealAudio, there is no clear winner – it comes down to individual preference.

In addition to this low bit rate hybrid codec, Windows Media 9 Series adds a host of other audio codecs, targeted to higher-end non-streaming applications. These are called Windows Media 9 Professional codecs, and include a new lossless codec for audiophiles, a surround codec that can handle up to 8 channels, and support for 96KHz/24 bit audio. Additionally, the WMA 9 codecs now support 2-pass and variable bit rate encoding for higher fidelity.

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