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android / platform / external / walt / refs/heads/main
commit2cb5a7281a8e71b7b7d21294ee2dbd523ba91533[log] [tgz]
authorXin Li <delphij@google.com>Wed Mar 06 09:29:57 2024 -0800
committerXin Li <delphij@google.com>Wed Mar 06 09:29:57 2024 -0800
tree972b56335b352dc4793abb6e97c22f8278aefe8e
parent24f527b4e971249eef0fcd97c1f0a0d15bd99d63 [diff]
parentdc02379d3d9d9ebf64b1f7a0a1171f0e25cf6d19 [diff]
Merge Android 14 QPR2 to AOSP main

Bug: 319669529
Merged-In: I4b2711b4392ca6ddd1609bb765b9c3ca0773da35
Change-Id: If2fbd5179ab679a94935ffbc8cd24c6b26b48d57
tree: 972b56335b352dc4793abb6e97c22f8278aefe8e
  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.