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android / platform / external / walt / c9bb045515820c78c4d7dc66739b95da573e5c7b
commitc9bb045515820c78c4d7dc66739b95da573e5c7b[log] [tgz]
authorTai Kuo <taikuo@google.com>Thu Jul 30 19:34:57 2020 +0000
committerAutomerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>Thu Jul 30 19:34:57 2020 +0000
tree27044bca824087616b2e2c3641c660d5ed082e9f
parenta31ab1793f9140452c1f24a8539ee074ae609028 [diff]
parent898a8083b67a5ecef26c9a6d825d0d6c6972b3ca [diff]
[automerger skipped] Remove redundant NOTICE copied from LICENSE. am: 5db98ebd4b am: 4db4fd9d94 am: 3fcbdd3647 am: 33053aca03 -s ours am: 0247368680 -s ours am: 898a8083b6 -s ours

am skip reason: Change-Id I9ca2f8c0713c2f11b014bf22b2f85c19437be2d6 with SHA-1 735624bc34 is in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/walt/+/11926621

Change-Id: I01ee73eaa31a091eb65cb1e07d0422428a19be65
tree: 27044bca824087616b2e2c3641c660d5ed082e9f
  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.