An introduction to computer audio
At the time I wrote this page, Vista was rather new.
Today you probably won’t go the Vista way as there is Windows 7.
However there isn’t much difference between Vista and Windows 7 as far as audio is concerned. Windows 7 offers some minor improvements but the core audio remains the same.
Most of the configuration options described here, apply to Windows 7 as well
There are claims that minimizing system activities improves sound quality. Besides the obvious, a system so overloaded that the audio stream is interrupted, the explanation is that minimizing system activity reduces the electrical ‘noise’ and therefore offers a better environment for the sound card.
A claim that WAV sounds better than FLAC while both are lossless formats was explained this way. Uncompressing FLAC requires more system resources than WAV (uncompressed).
One might argue that if the sound quality of a sound cards fluctuates with system load, it is a badly designed sound card or if DA conversion is such a delicate process, the DAC should be an outboard one.
Often forum users ask ‘how many processes have you running’ and less is more of course.
Most server processes just sit there and wait, one might wonder if removing them really helps.
Despite all the above, so many musicians seem keen to delve into the intricacies of the Service list that I decided to carry out a practical experiment by disabling all the Services I possibly could on my own music PC and then measuring any improvements I could find. Initially, the Windows Task Manager told me that as soon as I reached the desktop Windows was using 205.6MB of my system RAM, and that the only CPU overhead was the two percent taken by Task Manager itself.
After very carefully disabling every possible Service that a non-networked music-only PC wouldn't need (on my PC, some 46 Services in all), I rebooted. The total CPU overhead was still exactly the same, at two percent, but the system RAM consumption was now down to 197.6MB: a negligible improvement of just 8MB. To double-check for any audio improvement, I ran a song that had previously been struggling at the limits of both my CPU and RAM, even with an audio interface latency of 20ms, and found no improvement at all. I rest my case!
Source: Sound on Sound
it's not as simple as "less services/threads = better sound quality", unless of course we are talking about the signal path itself, in which case i do believe that the simpler the signal path, the less chance for problems.
what can happen though is that background activities may impact generated EMI and logic induced modulation (LIM) affecting sound quality.
but simply turning on and off services does not necessarily reduce EMI or LIM
A more moderate one can be found on Audio Forums
WASAPI in exclusive mode (also called DMA mode), sends unmixed audio streams directly to the audio driver. This the trick to bypass the Vista mixer.
In exclusive mode (also called DMA mode), unmixed audio streams are rendered directly to the audio adapter and no other application's audio will play and signal processing has no effect. Exclusive mode is useful for applications that demand the least amount of intermediate processing of the audio data or those that want to output compressed audio data such as Dolby Digital, DTS or WMA Pro over S/PDIF.
If an application opens a stream in exclusive mode, the application has exclusive use of the audio endpoint device that plays or records the stream. In contrast, several applications can share an audio endpoint device by opening shared-mode streams on the device.
Exclusive-mode access to an audio device can block crucial system sounds, prevent interoperability with other applications, and otherwise degrade the user experience.
To improve the performance of exclusive-mode applications that connect to audio devices that rely on the system for data transport, WASAPI automatically increases the priority of the system threads that transfer data between the applications and the hardware.
So no system sound when playing my music? That's the kind of degraded user experience I'm looking for!
Exclusive mode can be set in the advanced tab of the device.
Setting exclusive mode here won't do anything at all. It allows applications to take exclusive control, not to be mistaken for forcing them to do so.
The media player must be explicitly configured to use WASAPI.
You can't do that using WMP11 or iTunes.
Foobar can be easily configured to play over Direct Sound or WASAPI
A simple test is to play 2 audio streams. If you hear them both, you are not using WASAPI or exclusive mode is not enabled.
Play an audio file with a sample rate not supported by your sound device, it should fail. If not, SRC is still applied, not by Vista this time but by the player software!
In the sound panel you can configure a device.
You can test the channels
You can select the type of speakers
If you use your PC to drive a stereo, check if full range is on.
More detailed information about the 'enhancements' can be found here.
Microsoft offers a couple of them.
The manufacturer of the onboard audio might add a couple of its own.
My Realtek driver offers Voice cancellation. One day I will try this on a Schubert Lied.
Vista has the following default options:
In systems that have speakers with limited bass capability—such as laptops—it is sometimes beneficial to boost the bass in the frequency range that the speaker can support, in order to increase the perceived quality of the audio. Bass boost essentially provides this functionality by providing a gain in the mid-bass range, thereby making the audio sound better on mobile devices with very small speakers.
The bass management mode that is used depends on the availability of a subwoofer and the bass-handling capability of the main speakers. In Windows Vista, the user provides this information via the Sound applet in Control Panel.
The loudness equalization DSP ensures that the volume level across different sources of audio signal stays constant.
Low frequency protection is a form of forward bass management. It is used when there is no subwoofer and all the speakers are small and lack bass capability.
The user places the microphone where the user intends to sit and then activates a wizard that measures the room response. The wizard plays a set of specially designed tones from each loudspeaker in turn, and measures the distance, frequency response, and overall gain of each loudspeaker from the microphone's location.
More about how it is done can be found here
Speaker fill simulates a multichannel loudspeaker setup. It allows music that would otherwise be heard on only two speakers to be played on all of the loudspeakers in the room.
Usually, all the loudspeakers in a multichannel system, including the center and satellite loudspeakers, are always present. However, users might not have all the expected loudspeakers or they might choose to turn one or more of them off. A common example is a multichannel system that lacks a center loudspeaker. Speaker phantoming reproduces the sound from the missing loudspeaker, typically by splitting it between the adjacent loudspeakers. However, phantoming can also use other combinations such as the rear-left and rear-right or side-left and side-right speakers.
Virtual surround uses simple digital methods to combine a multichannel signal into two channels. This is done in a way that allows the transformed signal to be restored to the original multichannel signal, using the Pro Logic decoders that are available in most modern audio receivers. Virtual surround is ideal for a system with a two-channel sound card and a receiver that has a surround sound enhancement mechanism.
Virtualized surround sound allows users who are wearing headphones to distinguish sound from front to back as well as from side to side. This is done by transmitting spatial cues that help the brain localize the sounds and integrate them into a sound field. This has the effect of making the sound feel like it transcends the headphones, creating an "outside-the-head" listening experience. This effect is achieved by using an advanced technology called Head Related Transfer Functions (HRTF). HRTF generates acoustic cues that are based on the shape of the human head. These cues not only help listeners to locate the direction and source of sound but it also enhances the type of acoustic environment that is surrounding the listener.
A very good enhancement is to disable all digital signal processing.
Often a third party driver comes with your sound card.
It might be that this driver is not an improvement as far as sound quality is concerned, compared with the default Vista HD audio driver.
A simple way to try:
If your PC supports digital out you might check these settings.
Try various sample rates. If the outboard DAC does upsampling you can use these options to find out what sounds better, upsampling by Vista or by your DAC.
You can put it off in case you don't like a full blast e-mail notification over your stereo.
Often you have more than one playback device.
If your media player has the option to select an output device other than system default you can do the following:
Set the system default to the onboard speakers.
Mute them if needed.
Set your media player to use a different device.
Now all sounds go to the onboard speakers except the output of the media player.