Google Open Sources Tool for Gauging Touch and Voice Latency
Google has gone on an open source tear recently, opening up several projects for community development and advancement. It has announced VR View, an open source tool that lets developers tembed 360-degree photo and video content into sites and native apps. I also covered Google's decistion to open source TensorFlow. It’s based on the same internal toolset that Google has spent years developing to support its AI software and other predictive and analytics programs.
Now, Google is open sourcing Walt, software that can be used to measure how long it takes for a device to respond to touch or voice input. Google uses Walt to do performance tests on both Android devices and Chromebooks.
Walt is available under an open source Apache license on GitHub.
"When you use a mobile device, you expect it to respond instantly to your touch or voice: the more immediate the response, the more you feel directly connected to the device. Over the past few years, we have been trying to measure, understand, and reduce latency in our Chromebook and Android products."
"Before we can reduce latency, we must first understand where it comes from. In the case of tapping a touchscreen, the time for a response includes the touch-sensing hardware and driver, the application, and the display and graphics output. For a voice command, there is time spent in sampling input audio, the application, and in audio output. Sometimes we have a mixture of these (for example, a piano app would include touch input and audio output)."
"Most previous work to study latency has focused on measuring a single round-trip latency number. For example, to measure audio latency, an app would measure time from app to speaker/mic and back to the app using the Dr. Rick O'Rang loopback audio dongle together with an appropriate app such as the Dr Rick O’Rang Loopback app or Superpowered Mobile Audio Latency Test App. Similarly, the TouchBot uses a fast camera to measure the round-trip delay from physical touch until a change on the screen is visible. While valuable, the problem with such a setup is that it’s very difficult to break down the latency into input vs output components."
"An important innovation in WALT (a descendant of QuickStep) is that it synchronizes an external hardware clock with the Android device or Chromebook to within a millisecond. This allows it to measure input and output latencies separately as opposed to measuring a round-trip latency."
"WALT is simple. The parts cost less than $50 and with some basic hobby electronics skills, you can build it yourself."
Google has used Walt for Nexus and Chromebook development, but is opening this tool to app developers in the hope "that having readily accessible tools will help the industry as a whole improve and make all our devices more responsive to touch and voice."