What's New for Audio in Windows Vista?
Completely new User Mode Audio (UMA) mix engine
The core audio engine of Windows Vista has been completely rewritten from the bottom up. All audio processing is performed in User Mode rather than in Kernel Mode, which will avoid blue screens caused by poorly designed audio drivers. New multimedia timing services provide resilience to glitches by prioritizing audio threads above other system tasks. 'Shims' are used to re-connect older functionality such as DirectSound and Wave to the new engine.
High-performance audio applications can write directly to the new Windows Audio Session API (WASAPI), while most applications will choose to use Media Foundation or the new DirectX Media Object (DMO) to interface with audio streams coming and going from various system audio endpoints. Optimal Sound provides training and technical documentation
Completely new Unified Audio Architecture (UAA)
UAA is Microsoft's solution to a host of issues prevalent in earlier versions of Windows, mostly having to do with proprietary audio systems requiring customized drivers for each and every implementation. UAA is based on the ability for a generalized audio class driver to discover the audio capabilities directly from the hardware, without the need for custom audio drivers. Much like VGA, this effort is focused on making audio work after a clean install of the OS, without the need to install custom audio drivers or go online to download the correct drivers.
Both USB and Intel High Definition Audio buses are supported by their respective class drivers, and support for IEEE-1394 is slated for the future. Only UAA-compliant solutions can qualify for the Windows Vista logo, older PCI sound cards or integrated AC97 solutions will not qualify. PCI or PCIe cards which incorporate the HD Audio bus can qualify, but no commercially available models exist at the time this is written.
Completely new WaveRT driver model
Older WDM audio driver architectures such as WavePCI and WaveCyclic suffer from the operating system requirement that any data passed from an application to a driver must be copied across the boundary between User Mode and Kernel mode, using up extra CPU cycles and introducing latency in many cases. The new WaveRT architecture connects the User Mode Audio mixer's output buffer directly to the HD Audio controller's cyclic DMA buffer, which runs constantly with no interrupts whenever the associated endpoint is inputting or outputting audio.Intel* High Definition Audio or USB required for Vista logo
A USB or Intel High Definition Audio device is required for the Vista logo program. Only UAA-compliant solutions can qualify for the Windows Vista logo, older PCI sound cards or integrated AC97 solutions will not qualify. PCI or PCIe cards which incorporate the HD Audio bus can qualify, but no commercially available models exist at the time this is written.New Logo and Audio Fidelity Requirements
The Windows Logo Program 3.0 requirements documentation, now at version 3.07, describes the new requirements for audio in Vista. A number of new requirements have been put in place for correct audio configuration, correct jack color coding, and for audio fidelity testing. Click here to see the Audio Fidelity Requirements Comparison Chart created by Optimal Sound.
System vendors must run the audio fidelity tests on all logo submissions for Windows Vista, even though for system submissions these tests are not required to pass until June 1, 2007. The audio fidelity test logs must be included in the submission package for both audio device and overall system logo submissions.
Built-in and extensible Audio System Effects
Microsoft has developed a number of new audio processing modules which integrate at the system level. These include room correction, bass management, headphone virtualization, and more. System vendors can also choose to include system Audio Processing Objects (sAPO) to augment or even replace the built-in processing. Click here for more info.
Built-in Acoustic Echo Canceller and Microphone Array Processing
Microsoft has included a new High Quality Voice Capture DirectX Media Object (DMO) in Vista that allows applications such as Skype or Instant Messenger to apply acoustic echo cancellation and microphone array processing to speech signals. This is an important technology for moving speech processing forward on the PC platform. Click here for more info.By deploying the Driver Test Manager, Microsoft has completed the lengthy process of fully automating their WHQL submissions system. The WHQL organization is now a policy-making organization, and does not usually get involved in the case of test failures. Instead, support has transitioned to the CSS group inside Microsoft.
Microsoft has put a whole new support and tracking infrastructure in place to quantify and track DTM support issues, and to ensure that the issues are reflected back to the proper development and documentation teams within Microsoft. Up until Vista RTM, issues process by the dtmsupp@microsoft.com alias will not be charged. After Vista RTM, Microsoft is likely to start charging its normal support incident rates for issues submitted to dtmsupp@microsoft.com, though the charges may be reversed for incidents which involve actual Microsoft bugs or lack of documentation. This is all new for Vista.
New Audio Development Workflow
Because of the new audio logo requirements for Windows Vista, a number of new development steps are required. The BIOS developer now must insert properly configured pin configuration verb tables into the BIOS to comply with UAA requirements, and the audio design and layout engineers must employ best practices for audio subsystem design on the motherboard to avoid costly motherboard re-spins that may be necessary if any of the audio fidelity logo tests fail. Click here for more info.
Software vendors developing custom Audio System Effects or sAPOs no longer need to rely on a technical relationship with the audio codec chip vendor. Much of the value add will move to the APO. White-box and channel motherboards will be driven to use the class driver because of the reduced support costs, which will further commoditize the audio codec market. New types of HD audio devices will also come into play, including HDMI, integrated speaker amplifiers, integrated VoIP SLIC, and separate front panel codec.Use Optimal Sound services to add an audio expert to your team, and ensure that your systems sound great, are easy to understand, and function properly with Windows Vista. Contact us for more info.
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