Clone this repo:
  1. 0894351 DO NOT MERGE by Xin Li · 8 days ago master oreo-mr1-iot-release android-o-mr1-iot-release-1.0.7
  2. d4e5f84 Convert sync_clock_jni to Android.bp by Dan Willemsen · 4 weeks ago android-wear-8.0.0_r2
  3. 56b988d Merge Android Pie into master am: a096c61e90 am: 9cea0afe51 by Xin Li · 4 months ago android-o-mr1-iot-release-smart-display-r4
  4. 9cea0af Merge Android Pie into master am: a096c61e90 by Xin Li · 4 months ago
  5. a096c61 Merge Android Pie into master by Xin Li · 4 months ago master-cuttlefish-testing-release oreo-mr1-1.2-iot-release android-o-mr1-iot-release-1.0.3 android-o-mr1-iot-release-1.0.4 android-o-mr1-iot-release-1.0.5 android-o-mr1-iot-release-smart-display-r3

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.