Google has released Walt, a toolset for measuring touch and audio latency on mobile devices, as open source. Previous solutions to measure device latency have mostly focused on providing a single, round-trip number that shows overall latency by either detecting how long audio took to go from the microphone to the speaker, or how long it took for the screen to change after a button was pressed. However, there are multiple steps involved in these processes, so it would be helpful to measure each one independently.
This is where Walt comes in; it uses a Teensy LC microcontroller, photodiodes, a laser, accelerometer board, and a few other pieces of hardware, and it synchronizes this hardware with the hardware clock on the mobile device to provide latency readings that are accurate to within 1ms. It’s capable of measuring four separate sources of latency: tap latency, drag latency, screen draw latency, and audio input / output latency, and the parts cost less than $50.
