To appropriately perform image forming processing in accordance with a communication velocity.

When an image data printing instruction is given by a host device connected through a wireless USB, image data reception is started (step S100), after waiting for the reception of one-pass image data (step S110), the communication velocity V1 is derived from the amount of one-pass image data and a time required to receive the one-pass image data (step S120). Whether or not the communication velocity is high enough to finish printing without a temporary stop even in the case reception and printing of the image data are performed in parallel is determined based on whether the communication velocity V1 is more than a threshold Vref or not (step S130). When the negative determination is given in the step S130, printing is performed after all the image data are received (steps S140 to S150), When the positive determination is given in the step S130, the reception and printing of the image data are performed in parallel (steps S160 to S180).

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