Disclosed are a transmitting method, a receiving method, a transmitting device, and a receiving device for audio and video data in a long-distance transmission. The receiving method comprises the follows. A first protocol data stream is obtained by the receiving device via a second transmission medium interface. The first protocol data stream is processed by the receiving device to obtain a second preset protocol data stream and second preset audio and video data. The second preset protocol data stream is outputted by the receiving device via a third transmission medium interface. The second preset audio and video data is outputted by the receiving device via a second high definition multimedia interface (HDMI). By adopting the disclosure, the extended transmission of audio and video data can be realized, which can reduce the transmission cost and construction time. This shall result in higher user experience.