Audio Fidelity Testing

Updated: July 2, 2012

The Windows Hardware Certification Program for Windows 7 and Windows 8 defines a minimum bar for audio fidelity quality. To validate fidelity quality, the test requires a specific piece of testing equipment: the Audio Precision (AP) SYS-2722 audio analyzer.

Given the expense of the equipment, alternative methods of creating test results provide some valid audio fidelity compliance options for system submissions.

Options for Submitting Audio Fidelity Tests

The audio fidelity tests validate a line output jack. Microsoft has developed tests that are designed to be used with an audio analyzer, which is described below. OEMs are expected to validate specific PC audio implementations by using the test kit (WLK 1.6 or Windows HCK) and this hardware. Options 1 and 2 are available to OEMs.

Option 1 - In-House Testing
OEM partners can complete the system submission test pass by using the audio analyzer hardware without assistance from third parties. To do this, follow these steps:

1. Purchase the AP machine.
2. Specific the machine requirements outlined below.
3. Run the audio fidelity tests.
4. Submit with the audio fidelity test results.

Option 2 - Leveraged Resource Testing
OEM partners can use DTM functionality to import audio fidelity test logs from an outside resource. To do this, import the logs from the following:

• The original device manufacturer/motherboard manufacturer
• Third-party test house
• IHV/codec vendor
• Any other test facility that has access to an AP machine and the DTM

Note: The imported log files must have identical audio 4-part PNPID and pin configuration.

Audio Quality

There are five keys advantages to successful audio solutions:

• Discoverability in hardware. Audio input and output devices and ports can be configurable as logical devices, and exposed and easily identified by the end user in Windows Vista.
• Extensibility in hardware. A standard design that lasts and is the basis for future audio solutions that enable new and exciting scenarios for the end user.
• Stability from software infrastructure. WaveRT and System Effects Infrastructure.
• Quality from hardware and software. Fidelity, latency, and glitch resilience.
• Connectivity opportunities. New ways to stream and capture audio content.

Audio fidelity affects the entire Windows experience because audio is an integrated part of it. Audio fidelity has migrated away from the levels that were achieved by Consumer Electronic (CE) devices. The decline of audio quality is apparent, and Windows users are taking notice.

Three different metrics are measured today that directly affect the end user:

• DYNAMIC RANGE - Perceived quality
• THD+N - Listener fatigue
• FREQUENCY RESPONSE - Legibility

Current Audio Fidelity Testing

The Fidelity Test verifies that the audio device meets the WLP requirements for a high-fidelity audio playback experience. The test plays a tone that is analyzed by an Audio Precision System Two device that is connected to the analog output jack of the system. The following test are evaluated:

• Output Level Test plays a digital full-scale signal and verifies that it meets the Full-Scale Output Voltage requirement in the Windows Logo Program (WLP) Device Fidelity Requirements.
• Dynamic Range Test takes a noise floor measurement in the presence of signal per AES-17 and verifies that the measurement meets the Dynamic Range requirement in the WLP Device Fidelity requirements.
• THD+N Test takes a THD+N measurement and verifies the measurement per the WLP Device Fidelity requirements document.
• Magnitude Response Test measures the frequency response of the device and verifies that it meets the Magnitude Response requirement in the WLP Device Fidelity requirements.
• Phase Delay Test measures phase differences between channels of multichannel streams on the device, and verifies that these meet the Phase Delay requirements in the WLP Device Fidelity requirements.

Audio Precision Machine Requirements

The Fidelity Test requires an Audio Precision 2700-series machine. This needs to include at least the following modules and filters:

• Analog generator for capture tests
• Analog analyzer for render tests
• AES-17 filter package
• A-weight filter

The following are not required for the audio fidelity test:

• Digital analyzer
• Digital generator
• Digital signal processor

AP models 2702, 2712, and 2722 with A-weight and AES-17 filter packages installed meet these requirements.

Importing Test Logs for Audio Fidelity Tests

OEM partners who want to import Audio Fidelity Test logs from an outside resource can use the following third-party test houses. These test houses are equipped with Audio Precision analyzers for audio and system testing.

Note: This information is provided for informational purposes only and Microsoft makes no warranties, either express or implied, therein. All URLs and other Web-site references are subject to change without notice. The entire risk for the use of this information remains with the user.

Company	Contact	Phone
Optimal Sound	Wayne Jones	800-380-0639 x803 (US + Canada) 512-879-4172 x803 (International) 512-879-4172 (Fax)
SEZZO Labs	Bill Alex	(925) 456-0677
Allion Test Labs, Inc.	Joseph Hu	+886-2-7722-8800
HCL-Lab GmbH	Michael Klein	+49 (0)30 254 593 600 +49 (0)30 254 593 699 (Fax)

More info

Windows Certification Program Requirements: http://msdn.microsoft.com/library/windows/hardware/hh833793

Setup Verification Details: To ensure that DCOM is working correctly, download DCOMTest.exe from http://support.microsoft.com/kb/259011/ and follow the instructions there.
Task error logs for failed tasks can be sent to the DTMsupp@microsoft.com.

WHDC Audio: http://msdn.microsoft.com/en-us/windows/hardware/gg454527.aspx

Additional fidelity test documentation is available in the Windows HCK help documentation at http://go.microsoft.com/fwlink/p/?LinkID=252774.