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  1. eecd728 Add one Android.bp am: 3a08682315 by Yuntao Xu · 3 months ago master
  2. 3a08682 Add one Android.bp by Yuntao Xu · 3 months ago
  3. 925712a [automerger skipped] Mark ab/7061308 as merged in stage. am: ec33ddbdf6 -s ours am: e2537ad9e3 -s ours by Xin Li · 11 months ago android-s-v2-preview-1 android12--mainline-release android12-dev android12-qpr1-d-release android12-qpr1-d-s1-release android12-qpr1-d-s2-release android12-qpr1-d-s3-release android12-qpr1-release android-12.0.0_r16 android-12.0.0_r18 android-12.0.0_r19 android-12.0.0_r20 android-12.0.0_r21 android-12.0.0_r26 android-12.0.0_r27 android-mainline-12.0.0_r4 android-s-v2-beta-2 android-s-v2-preview-2
  4. e2537ad [automerger skipped] Mark ab/7061308 as merged in stage. am: ec33ddbdf6 -s ours by Xin Li · 11 months ago
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WALT Latency Timer

DISCLAIMER: This is not an official Google product.

WALT is designed to measure the latency of physical sensors and outputs on phones and computers. It can currently perform the following measurements:

  • Tap latency - time from the moment a finger-like probe touches down (or up) on the screen until the kernel timestamps an ACTION_DOWN (or ACTION_UP) event. This physical contact with the screen is timed using an accelerometer mounted on the probe.
  • Drag latency (scroll).
  • Screen draw latency - using a photodiode that detects whether the screen is black or white.
  • Audio output and microphone latencies.
  • MIDI input and output latencies

The WALT app for Android can be installed from Google Play or downloaded in the releases section; the iOS app must be built from source.

WALT photo

Notes

  • Hardware build instructions can be found in this repository under hardware/.
  • Clock synchronization details are described here.
  • The Android/iOS device and Teensy clocks have a tendency to diverge due to differing clock frequencies. This means they will go out of sync after several minutes. The workaround is to use the app to re-sync the clocks. Some, but not all tests in the app will sync the clocks when starting a measurement.
  • Python code used to communicate with WALT from Linux and ChromeOS can be found here.