In an earlier article, we discussed that sensors and sensor subsystem architecture can be a major source of fragmentation that would continue to frustrate app developers for smart phone and mobile devices. As the industry embarks on creating a new class of situation aware mobile devices, it is key to establish and improve sensor system standards.
For example, the Khronos Group through its StreamInput working group has identified “system-wide sensor synchronization for advanced multi-sensor applications” as an area in which standards is lacking. Indeed, for an application to, say, use inertial sensors to track camera angles it is necessary for the accelerometer, magnetometer, and image sensors to share the same timing reference.
Each sensor, today, runs on its own free-running clock and relative timing among samples are not defined. Synching up sensor data with video would mean that every set of sensor data is tagged with a corresponding video frame number. At 60 frames per second, this would be a relatively simple task that can be handled using only software. However, if the application requires synchronization to occur at a scan line, or about 64kHz, it will require some hardware support to generate a time stamp for each set of sensor data.
Establishing a timing standard is but one fundamental area an open standards group like Khronos can contribute. A minimum guaranteed sensor performance is another aspect that needs to be established. Performance characteristics such as sensor bandwidth, accuracy and repeatability and latency are different among smartphone models running the same operating system. We are hopeful that new operating systems like Android and Windows 8 will start to establish some of these requirements.
Going beyond minimum performance, an open standard is necessary to allow innovators access to richer sensor content. For example, a smart algorithm might be able to use inertial sensors to detect when a smartphone is inside an elevator. Such a new function would be released in a sensor library and an open standard will have to establish a method by which a mall map application can see that the capability exists and use it to serve up different maps to the mobile user.
