The size of the foveal region, that is the region which the human eyes perceives with highest visual acuity, depends on the viewing distance. The effect of W on (normalized) offsets Q O applied to macroblocks of a frame with respect to distance from gaze location is illustrated in Figure (b)b. The parameters Q O m a x and W are tunable and allow us to investigate and evaluate the setup. We define foveal region as the region on the screen of the client machine where the game video quality should be high. In ( 1), Q O m a x is the maximum offset, i and j are indices of the matrix of macroblocks comprising the frame, x and y are the indices of the macroblock where the center of the gaze is, and W controls the width of the foveal region. Q O ( i, j ) = Q O m a x ( 1 − exp ( ( i − x ) 2 + ( j − y ) 2 2 ( W ) 2 ) ) F W is the width of the output frame in pixels Iii-C Encoder-Gaze Tracker Interfacing (a) Visual acuity of human eyeįig. The eye tracker is also capable of providing fixation information but we decided to use the periodically sampled gaze data because we do not know how Tobii computes fixations. The client transmits the gaze position data to the server as soon as it is available from the gaze tracker. The light filtering smoothes out sudden eye movements, such as saccadic movements that are very fast eye movements jumping around the target and happen during certain phases of fixation, and noise based on current and past data points as well as velocity of eye movements. We install the Eye Tracker on the client machine and configure it to output lightly filtered gaze data. It has an on board eye tracking ASIC and is capable of providing individual eye, gaze, gaze fixation and head location data. The Tobii 4C eye tracker is a consumer grade eye tracking device directed towards gaming and interactive applications.
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