In a recent AVSforum post titled, "Audio Processing in Vista Explained", Amir Majidimehr, Corporate Vice President of Microsoft’s Consumer Media Technology Group, writes about the new audio capabilities planned for Vista. New audio features included in Vista are digital room correction (DRC), bass management, loudness equalization, headphone virtualization, and channel control tools.
When asked, if after you plug your PC into an A/V receiver and perform the room correction calibration on the PC and then disconnect the receiver from the PC, 'will the receiver retain the calibration settings?', Amir replied, "Unfortunatly not. All the processing is done inside the PC and only works if you use the PC as the source, driving your receiver. Take away the PC and there is nothing there anymore. For your receiver to have similar capabilities, it would have to have a ton more hardware in it." Anil then favorably compared Vista's room correction capabilities to a high end TacT processor by saying, "The TacT processors do what you say but the one I have cost me a cool $10K and it does less in some respects than Vista!"
For a quick explanation of what DRC is and how it can benefit you and your system, check out this DRC guide.
The bass management feature is very flexible and doesn't have some of the limitations you find with the bass management on most A/V receivers. For example, with Vista's bass management, you can have any combination of large or small speakers, with or without a subwoofer. The crossover point can be set to whatever your loudspeakers need. When sending a full range signal to any of your small speakers, the portion of the signal below the crossover point will be routed to the subwoofer, or in the case of a system without a subwoofer, the lower frequencies can be routed to the large speakers.
Most A/V receivers won't let you send a full range signal to the front speakers if the subwoofer is engaged. They force you to filter out the low frequencies from the fronts and send everything below the fixed crossover point to the subwoofer. This works okay with a sub/sat system, but isn't very appealing for anyone who has large or full-range loudspeakers in the front. There are also some A/V receivers and processors that will not send a signal to the subwoofer when it is set to stereo mode. Also, with most of the A/V receivers and processors, the subwoofer output jack is low-pass filtered so any signal above the frequency setting (usually in the 100Hz-150Hz range) is blocked. Most powered subwoofers also have a built-in low pass filter, and when the two filters combine you are increasing the steepness of the filter. Too steep of a filter slope makes for worse sound. Anyhow, it sounds like Vista's bass management feature will let you avoid these types of limitations.
Vista now has a new audio mixer that according to Amir works much better than Windows XP's Kmixer. Kmixer resampled all audio to 48KHz, unless the sample rate was already 48KHz. Audio originally from a CD source, which uses a sample rate of 44.1KHz, was always resampled to 48KHz and the method used by Kmixer degraded the sound quality. With the new mixer, maybe the algorithms for resampling are much better so the sound quality remains high. The new mixer also has a user mode audio engine where a user can set the default sample rate and includes an exclusive mode which provides access directly to the soundcard. With the user mode, the mixer will not apply resampling at all. However, its not clear if the mixer will just leave the source material alone so that if you are playing ripped CDs it will use 44.1KHz and when playing from a DVD, it will automatically switch to the native 48KHz.
Be sure to read Amir's posts in the thread linked above to learn about all of the other great audio processing features. Also, take a look at this post in the Windows Vista Team Blog about the new audio features in more detail. And here's an interview with Microsoft PM Hakon Strande who also talks about high definition audio in Windows Vista.
These features will only work if you send either a 2-channel PCM stream over S/PDIF to your A/V receiver, or analog signals directly to your receiver/amps. So for anything more than 2-channel stereo, including 2.1 (stereo plus subwoofer), you will need to use analog outputs. This might be a problem because most people prefer using their A/V receiver's processor and DACs especially when they perform better than the DACs included with inexpensive soundcards or the built-in audio chips on the motherboard. They also feel anytime an audio signal is present inside a computer, the signal will pick up noise generated by other internal components like the computer's power supply or hard drives, thus decreasing the sound quality even further.
However, using one of our future products, you'll be able to take full advantage of Vista's advanced audio capabilities and enjoy excellent sound quality because we use the same components found in high end dedicated DACs and the best pro soundcards. Since these DACs are located in our box, you don't have to worry about any possible noise generated inside the computer. In addition, our amp modules are very efficient, have lots of power, generate less heat and sound better than most amps inside your typical A/V receiver.