Image transmission device and control method thereof, image transmission system and display apparatus

An image transmission device, comprising:

• a frequency detector configured to receive an image frame, detect a frame rate of the image frame, and output a frequency switching mark signal when it is detected that the frame rate changes;
• a frequency configuration device coupled to the frequency detector, and configured to output a first configuration signal according to a safe frequency step value in response to the frequency switching mark signal from the frequency detector;
• a frequency processor coupled to the frequency configuration device, and configured to:
• output a reference clock signal;
• adjust a frequency of the output reference clock signal repeatedly according to the first configuration signal from the frequency configuration device, each adjustment value being less than or equal to the safe frequency step value;
• and until a frequency of an adjusted reference clock signal is substantially equal to a frequency of a reference clock signal corresponding to a changed frame rate of the image frame, end adjustment;
• and
• an image frame transmitter coupled to the frequency processor, and configured to receive the image frame and the adjusted reference clock signal that is from the frequency processor, convert a format of the image frame into a format corresponding to the image frame transmitter according to the adjusted reference clock signal, and output the format-converted image frame.