28 February 2014 Automatic exposure for panoramic systems in uncontrolled lighting conditions: a football stadium case study
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Abstract
One of the most common ways of capturing wide eld-of-view scenes is by recording panoramic videos. Using an array of cameras with limited overlapping in the corresponding images, one can generate good panorama images. Using the panorama, several immersive display options can be explored. There is a two fold synchronization problem associated to such a system. One is the temporal synchronization, but this challenge can easily be handled by using a common triggering solution to control the shutters of the cameras. The other synchronization challenge is the automatic exposure synchronization which does not have a straight forward solution, especially in a wide area scenario where the light conditions are uncontrolled like in the case of an open, outdoor football stadium. In this paper, we present the challenges and approaches for creating a completely automatic real-time panoramic capture system with a particular focus on the camera settings. One of the main challenges in building such a system is that there is not one common area of the pitch that is visible to all the cameras that can be used for metering the light in order to nd appropriate camera parameters. One approach we tested is to use the green color of the eld grass. Such an approach provided us with acceptable results only in limited light conditions.A second approach was devised where the overlapping areas between adjacent cameras are exploited, thus creating pairs of perfectly matched video streams. However, there still existed some disparity between di erent pairs. We nally developed an approach where the time between two temporal frames is exploited to communicate the exposures among the cameras where we achieve a perfectly synchronized array. An analysis of the system and some experimental results are presented in this paper. In summary, a pilot-camera approach running in auto-exposure mode and then distributing the used exposure values to the other cameras seems to give best visual results.
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Vamsidhar Reddy Gaddam, Vamsidhar Reddy Gaddam, Carsten Griwodz, Carsten Griwodz, Pål Halvorsen, Pål Halvorsen, } "Automatic exposure for panoramic systems in uncontrolled lighting conditions: a football stadium case study", Proc. SPIE 9012, The Engineering Reality of Virtual Reality 2014, 90120C (28 February 2014); doi: 10.1117/12.2040145; https://doi.org/10.1117/12.2040145
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