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android / platform / external / walt / refs/heads/android14-mainline-resolv-release
commitb1385778b49804c4edc3c419d216f31313847182[log] [tgz]
authorAndroid Build Coastguard Worker <android-build-coastguard-worker@google.com>Tue May 10 07:04:23 2022 +0000
committerAndroid Build Coastguard Worker <android-build-coastguard-worker@google.com>Tue May 10 07:04:23 2022 +0000
treeee43c6b47d9f36bdabb1b33437d56e46091c22de
parent1a3829be3cb2d255e60adfce42b0d184f5b35846 [diff]
parent24f527b4e971249eef0fcd97c1f0a0d15bd99d63 [diff]
Snap for 8564071 from 24f527b4e971249eef0fcd97c1f0a0d15bd99d63 to mainline-resolv-release

Change-Id: I3f1acf73b7e8ac2da8b9b7c918877c93ac52e163
tree: ee43c6b47d9f36bdabb1b33437d56e46091c22de
  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.