Google Git
Sign in
android / platform / external / walt / a7906d21cc11d98131e8be228bb68835158d4927
commita7906d21cc11d98131e8be228bb68835158d4927[log] [tgz]
authorBob Badour <bbadour@google.com>Fri Feb 12 15:14:47 2021 -0800
committerBob Badour <bbadour@google.com>Fri Feb 12 15:14:47 2021 -0800
tree0e3b5815af1721855e158545a7b83536f826ba1f
parenta7ea31985d6b06a3f2208ab99f320dbfbde3ce9e [diff]
[LSC] Add LOCAL_LICENSE_KINDS to external/walt

Added SPDX-license-identifier-Apache-2.0 to:
  android/WALT/app/src/main/jni/Android.mk

Bug: 68860345
Bug: 151177513
Bug: 151953481

Test: m all

Exempt-From-Owner-Approval: janitorial work
Change-Id: Ic4bd96c96a68accaa7af94c81d0dfe0e5abe1bb2
1 file changed
tree: 0e3b5815af1721855e158545a7b83536f826ba1f
  1. android/
  2. arduino/
  3. docs/
  4. hardware/
  5. ios/
  6. pywalt/
  7. server/
  8. AUTHORS
  9. CONTRIBUTING.md
  10. CONTRIBUTORS
  11. LICENSE
  12. METADATA
  13. MODULE_LICENSE_APACHE2
  14. OWNERS
  15. README.google
  16. README.md
README.md

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.