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android / platform / external / walt / android-9.0.0_r22
tag1a4a8d0f41fcee01157f5866191b5bbd0316f6c0
taggerThe Android Open Source Project <initial-contribution@android.com>Tue Dec 11 15:40:42 2018 -0800
object0fe49d4a5efe7c5bb6a932cc210371aa3a27596d 
Android 9.0.0 release 22
commit0fe49d4a5efe7c5bb6a932cc210371aa3a27596d[log] [tgz]
authorAndrew Lehmer <alehmer@google.com>Wed Nov 15 09:52:30 2017 -0800
committerAndrew Lehmer <alehmer@google.com>Wed Nov 15 09:52:30 2017 -0800
treeab4908b30d89402c2f18ffaacb8a95402ab286bf
parenta15eed89fef8ef771026d8cdfc21d2992b01dd36 [diff]
Add NOTICE and MODULE_LICENSE_APACHE2

Bug: 69316634
Test: N/A
Change-Id: Id6cebc72a370a4f0aca4ad56ef3984c2d394f18b
2 files changed
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.