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android / platform / external / walt / 41e2472a820433c0b656897ffba290dadcbd8af1
commit41e2472a820433c0b656897ffba290dadcbd8af1[log] [tgz]
authorXin Li <[email protected]>Thu Sep 05 17:02:50 2024 -0700
committerXin Li <[email protected]>Thu Sep 05 17:02:50 2024 -0700
tree2d2abb3883e3d49daa405ba6ca7315492e41c0d8
parent9d0c17a0d166de904b47fab93b7c3e7f7dd38fa7 [diff]
parent01d392b914fde9e220d60a958430d55181ade402 [diff]
Merge 24Q3 to AOSP main

Bug: 357762254
Merged-In: Id55979b34f94b9d6819a9e3054aa3a37ac8b44e4
Change-Id: If5ed43038e47bfcb4c1040fb1cf4d01ff724a067
tree: 2d2abb3883e3d49daa405ba6ca7315492e41c0d8
  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.