Communication devices and systems with correct regeneration of an audio signal are disclosed. In one example, a communication device measures a number of predetermined reference clocks included in one cycle of a frequency divided signal, on the basis of an audio master clock having a frequency obtained by multiplying a frequency of a sampling clock to sample an audio signal, a frequency division ratio of a frequency divided signal of the audio master clock, and a predetermined reference clock. A packet generator generates a packet including information including the measured number, a bit width of serial data (SD) conforming to an Inter-IC Sound (I2S) standard, the frequency of the sampling clock, a frequency division ratio of the frequency divided signal to the audio master clock, a frequency ratio of the frequency of the audio master clock to the frequency of the sampling clock, and the SD.