Fitt´s Law is a model of human movement and ' predicts that the time to acquire a target is logarithmically related to the distance over the target size(MacKenzie, 1991, page 161)'. Vitus and another student of the class - Ariane Demleitner - wrote their literature reviews about latency and Fitt´s Law. In this way, latency can be measured (Casiez et al, 2015).įor our research it is interesting, how much latency is too much latency. A standard computer mouse gets positioned at a fixed on a horizontally oriented monitor where ‘ a given texture is displayed on the screen and moved of a controlled distance while a timestamp is recorded (Casiez et al., 2015, page 631).’ This movement gets recognized as a normal event by the mouse sensor and the timestamps get recorded. The second one is a simple method for measuring end-to-end latency using an optical mouse. After that, the experimenter has to go through the video frame by frame and ‘ then count the number of frames between the two events to get one measure latency (Casiez et al., 2017, page 30).’ This method is time consuming but the most commonly used. The first one is ‘ a low cost method to measure and characterize the end-to-end-latency when using a touch system or an input device equipped with a physical button (Casiez et al., 2017, page 29).’ They describe the approach of measuring the end-to-end latency by using an external camera, in the best case a high frame rate one, for recording the physical action of the user and the on-screen response. provide two methods for measuring end-to-end latency. They tested several input devices (gamepads, keyboards, mice) and collected 5000 samples for each device.Ĭasiez et al. not only write about latency itself, but as well about latency variance. This system can measure latency with sub-millisecond accuracy and can help identify the sources of input lag in order to reduce end-to-end latency. provide a Raspberry-Pi-based tool before measuring the latency of USB-connected input devices: ‘LagBox’. Now we know what latency is, we need to understand how it gets measured.īockes et al. Other aspects of latency play an important role in online games, for example the latency of the other players and the bandwidth of the internet connection. define the processing time of the computer running an application, ‘system latency’ (Martens et al., 2018). Wilson (2009) says that this ‘ is an unavoidable reality that can only be minimized and never eliminated (Wilson, 2009).’ He defines it as the time between the user action and the corresponding event arriving at an application (Wilson, 2009).Īnother aspect of latency is the network latency or, how Martens et al. The first regarded aspect of latency is the input lag. As Andrea stated in her literature review, ‘ latency seems to be an easy to grasp topic, whereas upon further investigation it turns out to be complex: Several different aspects in the signal influence overall latency (Fischer, 2018). ‘ ‘Depending on its amount and variation over time (jitter), the end-to-end latency can degrade the action-perception loop, impact user performance and make the system feel less responsive and interactive (Casiez et al., 2017, page 29)’. cursor movement, object displacement) (Casiez et al., 2015, page 629). movement of an input device or human limb) and the corresponding on-screen visual feedback (e.g. With the term ‘latency’ we usually mean the so called end-to-end latency, which is commonly defined as the duration between a user action (e.g. The shortest definition is probably: latency is delay. Before investigating about latency, it is important to know what exactly latency is and how it gets defined.
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