Wireless auxiliary stream device, and screen projection method and system based on wireless auxiliary stream device

A wireless auxiliary stream device, wherein the wireless auxiliary stream device is connected to both a terminal device and an extended display device;

• and the wireless auxiliary stream device comprises:
• a first transmission module configured to establish a first connection between the wireless auxiliary stream device and the terminal device;
• an interaction interface generation module configured to display an interaction interface on a local display device of the terminal device when the terminal device is connected, wherein a plurality of triggerable function keys are provided on the interaction interface, the function keys comprise program display keys corresponding to a plurality of programs and a screen display key, and the programs are programs currently running on the terminal device;
• a to-be-projected data obtaining module configured to, when a command of a display key of a target program triggered by a user is received, obtain to-be-projected data of the target program generated on the terminal device, and receive, through the first transmission module, the to-be-projected data sent by the terminal device;
• a second encoding and decoding module configured to perform second encoding on the to-be-projected data after receiving the to-be-projected data sent by the terminal device;
• and
• a second transmission module configured to establish a second connection between the wireless auxiliary stream device and the extended display device, and transmit the encoded to-be-projected data to the extended display device, whereby the extended display device performs screen projection on the to-be-projected data after decoding.