1. A communication apparatus for decoding and displaying image data received by wireless communication, comprising: a display unit to display image data; a communication establishing unit configured to establish wireless communication with each of a first device which transmits first image data, and a second device which transmits second image data; a reception unit configured to receive the first image data and the second image data from the first device and the second device respectively, after wireless communication has been established by the communication establishing unit; a generating unit configured to generate display image data to be displayed on the display unit by decoding the received first image data and the received second image data in correspondence with compression schemes of the respective data; and a control unit configured to switch decoding schemes in the generating unit in correspondence with the compression schemes of the first image data and the second image data, wherein types of the first image data and the second image data are different from each other and each of the first image data and the second image data has been coded by using a compression scheme including orthogonal transformation processing of transforming two-dimensional image data into image data in a spatial frequency domain and quantization processing for the image data having undergone the orthogonal transformation processing, and the generating unit implements inverse orthogonal transformation processing and dequantization processing for decoding the first image data and the second image data by a single processing circuit.