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We developed a comprehensive set of techniques to address the visual echo problem in a full-duplex projectorcamera system. A calibration procedure records the geometric and photometric transfer between the projector and camera in a look-up table. With the calibration information, the predicted camera view of the projected image is compared against the captured camera image to find echo pixels. Only non-echo pixels are used for display, therefore achieving the goal of suppressing visual echo. Compared to previous techniques, our approachs main advantages are two-fold. First, it accurately handles full color images with no assumption about the surface reflectance or the photometric response of the projector or camera. Secondly, it is robust to geometric registration errors and quantization effect. It is particularly effective for high-frequency contents such as texts and hand drawings. We demonstrate the effectiveness of our approach with a variety of real images in a full-duplex projector-camera system.