ClockDrift

This app lets you measure the sample clock drift of multimedia devices. Ever wondered how much the sample clock in your audio interface is off its nominal rate? Why audio or video files recorded in parallel with different devices do not play back at the same speed when synchronized afterwards?

Usage: an extensive user guide can be found at http://protyposis.net/clockdrift/user-guide/

To measure, run the app, set it to a measurement frequency (the default setting is fine, but the Ultrasonic mode preferred by your ears), play back the test tone on a device you want to measure, and hit analyze. The test tone can either also come from this app if you measure an Android device, you can generate a file within the app and copy it to other devices, use a frequency generator app (sine wave) on other platforms, or generate a file yourself in an audio editor. The measurement result is the relative time drift between the two devices.

Android Beam support: To measure a device with the app installed, simply launch the app and beam it to another device which will then automatically start measuring (the app will be installed automatically on the other device if missing).

Note: The results are relative drifts by default. The app can be calibrated for absolute drift measurement, for which you need very precise lab equipment.

Permissions:

• NFC for Android Beam

• Audio to analyze incoming signal

• Storage for the optional storage of the analyzed signal, and for test tone generation

• Internet for measurement upload and exception/error reporting