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android / platform / external / walt / refs/tags/android-cts-9.0_r20
tagdf9574c3d3cccd42c45c1688324a4081a5fa0c8b
taggerThe Android Open Source Project <initial-contribution@android.com>Wed May 18 15:35:15 2022 -0700
object7e4f33307efd623f914665c0a1760efe65721936 
Android CTS 9.0 Release 20 (8503603)
commit7e4f33307efd623f914665c0a1760efe65721936[log] [tgz]
authorandroid-build-team Robot <android-build-team-robot@google.com>Thu Nov 16 08:23:07 2017 +0000
committerandroid-build-team Robot <android-build-team-robot@google.com>Thu Nov 16 08:23:07 2017 +0000
treeab4908b30d89402c2f18ffaacb8a95402ab286bf
parentb4c450a713278b98bca5c33979bef113dd21a506 [diff]
parent0fe49d4a5efe7c5bb6a932cc210371aa3a27596d [diff]
Snap for 4455093 from 0fe49d4a5efe7c5bb6a932cc210371aa3a27596d to pi-release

Change-Id: Icd87bc63ce8ca6f737a94c8a8235475f6fa7e6ca
tree: ab4908b30d89402c2f18ffaacb8a95402ab286bf
  1. android/
  2. arduino/
  3. docs/
  4. hardware/
  5. ios/
  6. pywalt/
  7. server/
  8. AUTHORS
  9. CONTRIBUTING.md
  10. CONTRIBUTORS
  11. LICENSE
  12. MODULE_LICENSE_APACHE2
  13. NOTICE
  14. README.google
  15. 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.