Display device and display method

A display apparatus, comprising:

• a display, configured to display an image and/or a user interface;
• an external device interface, configured to connect an external device;
• at least one processor, configured to execute instructions to cause the display apparatus to:
• obtain a first command input from a user for switching a viewing angle ratio;
• obtain audio and video meta information of the external device, and parse a flag field in the audio and video meta information;
• send declaration information to the external device according to the first command in response to the flag field being identical to a determination field, wherein the determination field is an identification value set by a graphic processor of the external device at a fixed position in a frame of the audio and video meta information, the declaration information comprises identification data that conforms to a protocol version of the external device interface and a switched viewing angle ratio;
• receive video data returned from the external device for the declaration information, wherein an image ratio of the video data is equivalent with the switched viewing angle ratio;
• and
• control the display to display the video data.