1 ## WALT Latency Timer ## 2 3 **DISCLAIMER:** This is not an official Google product. 4 5 * [Post about WALT on Android Developers Blog](http://android-developers.blogspot.ca/2016/04/a-new-method-to-measure-touch-and-audio.html) 6 * [Instructional videos showing how to use WALT](https://www.youtube.com/playlist?list=PLd6Fi7WgXfcCEJg1FDqNCoQfpWo7W3J5a) 7 * [Detailed usage instructions](docs/usage/WALT_usage.md) 8 * Mailing list - [walt-discuss](https://groups.google.com/forum/#!forum/walt-discuss) 9 * Low-traffic mailing list for major announcements [walt-announce](https://groups.google.com/forum/#!forum/walt-announce) 10 11 WALT is designed to measure the latency of physical sensors and outputs on phones and computers. It can currently perform the following measurements: 12 13 * [Tap latency](docs/TapLatency.md) - time from the moment a finger-like probe touches down (or up) on the screen 14 until the kernel timestamps an ACTION_DOWN (or ACTION_UP) event. This physical contact with 15 the screen is timed using an accelerometer mounted on the probe. 16 * [Drag latency](docs/DragLatency.md) (scroll). 17 * [Screen draw latency](docs/ScreenLatency.md) - using a photodiode that detects whether the screen is black or white. 18 * [Audio output and microphone latencies](docs/AudioLatency.md). 19 * MIDI input and output latencies 20 21 The WALT app for Android can be 22 [installed from Google Play](https://play.google.com/store/apps/details?id=org.kamrik.latency.walt) 23 or downloaded in the [releases section](https://github.com/google/walt/releases); the iOS app must be built from source. 24 25  26 27 28 ## Notes 29 * Hardware build instructions can be found in this repository under `hardware/`. 30 * Clock synchronization details are described [here](android/WALT/app/src/main/jni/README.md). 31 * The Android/iOS device and Teensy clocks have a tendency to diverge due to 32 differing clock frequencies. This means they will go out of sync after 33 several minutes. The workaround is to use the app to re-sync the 34 clocks. Some, but not all tests in the app will sync the clocks when starting a measurement. 35 * Python code used to communicate with WALT from Linux and ChromeOS can be found 36 [here](https://chromium.googlesource.com/chromiumos/platform/touchbot/+/master/quickstep/). 37 38
