Voice Clarity Loopback Bandwidth Test
Test description
For Voice Clarity echo control to operate properly, the rendered frequencies through the built-in loudspeaker must be present in the loudspeaker signal. This test is to verify that the loopback signal contains all the frequency information necessary to reconstruct the signal reproduced by the loudspeaker. If there is signal coming from the speakers that is not well represented in the captured loopback signal, the speaker, and thus the acoustic echo signals, cannot be reconstructed using the loopback signal, which would result in deficient echo cancellation performance.
Test details
| Specifications |
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| Expected run time (in minutes) | 1 |
| Category | Development |
| Timeout (in minutes) | 5 |
| Requires reboot | false |
| Requires special configuration | false |
| Type | automatic |
Test steps
- Render (default mode) and capture (raw mode) a logarithmic sine sweep signal. Note: the recording captures all microphone channels simultaneously, but only the first channel is used in calculation.
- Capture QPC (Query Performance Counter) timestamps. The interval between two consecutive time stamps corresponds to the system’s capture and render period, respectively.
- Align the stimulus and speaker signals by maximizing cross-correlation. Align the recorded microphone and speaker signals using QPC (Query Performance Counter) timestamps as described above and enforce a look-ahead between the microphone and speaker/stimulus signals.
- Take one of the recorded microphone signals and apply a high-pass filter for robustness against DC-blocking filters.
- Downmix all recorded speaker signals to obtain a mono speaker signal.
- Calculate the transfer function between the stimulus and the speaker signal, and the transfer function between the stimulus and microphone signal.
- Normalize the transfer functions to ensure that they transfer the same amount of energy.
- Compute the point-wise ratio between the transfer functions.
Pass/Fail criteria
The point-wise ratio between the transfer functions must not exceed the threshold.
Troubleshooting
- Verify microphone and render have matched sampling rates. We strongly recommend setting an OOBE (Out of Box Experience) default of 48 kHz.
- Verify speaker processing does not include filters with aggressive stop-band attenuation.
- Verify loopback processing does not include filters with aggressive stop-band attenuation.
- Verify device is not in a configuration that produces frequency selective resonances.
If your failure mode is not included on this list, search the error code in MSDN.
For generic troubleshooting of HLK test failures, see Troubleshooting Windows HLK Test Failures and Troubleshooting System Fundamentals Testing.
More Information
Parameters
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Additional Documentation
Tests in this feature area might have additional documentation, including prerequisites, setup, and troubleshooting information, that can be found in the following topic(s): - Device.Audio additional documentation and System.Fundamentals additional documentation.