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android / platform / external / walt / 24f527b4e971249eef0fcd97c1f0a0d15bd99d63
commit24f527b4e971249eef0fcd97c1f0a0d15bd99d63[log] [tgz]
authorYuntao Xu <yuntaoxu@google.com>Fri Nov 12 20:44:48 2021 +0000
committerAutomerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>Fri Nov 12 20:44:48 2021 +0000
treeee43c6b47d9f36bdabb1b33437d56e46091c22de
parent2ca4697b4d7a64c17444a5e6ce17246b394db640 [diff]
parent0a4748634ce44e1980d3d719df45c03b96f0acc5 [diff]
Add one Android.bp am: 3a08682315 am: eecd7280ee am: d65535a89e am: 0a4748634c

Original change: https://android-review.googlesource.com/c/platform/external/walt/+/1870875

Change-Id: I96e22005b1164943035bdbf24fcbc0a6fb583068
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.