The invention provides a transmission method and a
system for video data. The
system comprises a
multicast gateway which is connected between a video source and a
client end, and the method comprises the following steps: the
multicast gateway receives a video source request message from the
client end, a video source protocol is adopted to connect with the video source, receives the video data and converts the video data into a protocol data packet of the
client end, the data packet is added with serial number, then the data packet is sent to the client end through a
multicast address which is corresponding to the video source, and the data packets sent in the
late period are stored in a buffer area; and then the client end judges whether
packet loss exists after receiving the data packet, if
packet loss exists, the client end sends a
packet loss feedback message. The multicast gateway searches the data packet corresponding to the serial number in the buffer area, if the search succeeds, then resends the data packet to the client end again. The transmission method of the invention stores the data packets sent lately in the buffer area, and the lost data packet is searched in the buffer area and is sent again when packet loss existing, thus ensuring the reliability of
data transmission.