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android / platform / external / walt / refs/heads/android12-mainline-ipsec-release
commite47d189efddac8f9fa38d8e9524b8b0df93e7fba[log] [tgz]
authorandroid-build-team Robot <android-build-team-robot@google.com>Mon Jun 21 15:08:16 2021 +0000
committerandroid-build-team Robot <android-build-team-robot@google.com>Mon Jun 21 15:08:16 2021 +0000
tree0e3b5815af1721855e158545a7b83536f826ba1f
parentd215878a4cc9c769ad0d1ad4f153ec1970c817b3 [diff]
parent436187edb12bc82f09b78c86f2c81484f71f1c3a [diff]
Snap for 7478067 from 436187edb12bc82f09b78c86f2c81484f71f1c3a to mainline-ipsec-release

Change-Id: I86207ae359ca73c0f16b4ad876a51e31722554a4
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.