A light-emitting device has a base, a light-emitting chip and a light emitter. In the present method, when receiving video data encoded by a 4:4:4 sampling format, color components of each set of neighboring pixels in the video data is down-sampled and a first difference of the color components between the video data before and after down-sampling in a down-sampling mode is calculated. If not, then the wireless switch transmits an instruction to the wireless computing device to associate with a particular access point that wireless computing device is to be associated with.