Monday, August 21, 2006

Vista Audio - Digital Room Correction, Bass Management, etc.

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.

8 comments:

  1. Sounds like a receiver with a USB input, like the JVC line-up, would obviate the need for your amplithingamobber. You get a pure digital path to the DACs on the receiver for the full 7.1 channels, allowing vista, or whatever Free alternative, to do its thing without the D/A A/D degradation. Bonus on the JVCs for using digital amps too.

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  2. I hope to provide a better solution than the JVC receivers, but I don't ever expect to compete at the same sales level as these large electronics giants. Hopefully, we can provide a competitive option or alternative by including higher quality DACs and analog circuitry, along with better sounding, more powerful amplifier modules. I checked the JVC website for information on these new receivers (www.jvc.com/press/index.jsp?item=437), and couldn't determine if the PC will recognize the receiver as a soundcard or if it just streams the audio data to the receiver like it would to a digital media server (like those from Roku, Linksys, DLink, Buffalo, etc.).
    JVC also refers to their digital amps as a Hybrid Feedback digital amplifier. My guess is their marketing department is attempting to ride the "digital" wave, but they are not real PCM-PWM amplifiers (which is probably a good thing). Please read Bruno Putzey's "The Truth About Digital (Class D) Amplifiers" article in the blogs article section to learn more about the issues related to direct digital amplification.

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  3. This comment has been removed by the author.

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  4. There's another article on this topic at the Arstechnica website. Here's the website address:

    http://arstechnica.com/news.ars/post/20060907-7682.html

    I don't think you can create links in a comment. I wish you could... Anyhow, I put the link in our 'Articles' section.

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  5. It looks like the address from ars technica was truncated. If your interested, just click the link labeled: Vista Audio Enhancements Revealed, by Jeremy Reimer, which you can find in our 'Articles' section in the right column of Ampliozone.

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  6. A product like you are designing that can take advantage of Vista's audio capabilities would be perfect for people like me designing a dedicated theater around an HTPC. Just be sure to fully support Vista's features such as room correction rather than replace it with watered down versions like Realtek has done with their drivers for their HD audio codecs.

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  7. Just to make things clear, you will get MUCH better sound quality using Vista's audio setting adjustments and an audiophile grade sound card such as the Auzentech X-Meridian using analog outs to your receiver/amp then you will by using the USB input on a JVC or even something higher up like a Pioneer Elite (like I have). Vista's audio processing with analog outs will completely blow away anything that JVC or even Pioneer have to offer over USB.

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  8. Just to make things clear, you will get MUCH better sound quality using Vista's audio setting adjustments and an audiophile grade sound card such as the Auzentech X-Meridian

    - nice... the analog outs are pretty much useless to me

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