Network switching method, device and system for mobile multimedia services

1. A network switching method for mobile multimedia services, the method comprising:

sending a Real Time Streaming Protocol (RTSP) DESCRIBE request to an acquiring point that provides media stream data in a second network, and acquiring a Session Description Protocol (SDP) description file;

sending an RTSP session SETUP request according to the description file to the acquiring point; and

sending an RTSP session PAUSE request to the acquiring point after receiving an RTSP session SETUP response message;

setting a first preset value, wherein time for which the signal strength of media stream data of a first network attenuates from the first preset value to such a value that the first network is unavailable is equal to or longer than a sum of time required for establishing a unicast connection with a Streaming Media (SM) server plus time required for buffering the media stream data of the second network until the media stream data of the second network is capable of being decoded and played;

detecting signal strength of media stream data of the first network, and when the signal strength of the media stream data of the first network is smaller than the first preset value, sending an RTSP session PLAY request and receiving the media stream data of the second network in parallel with the media stream data of the first network, wherein the first network is a terrestrial digital broadcast network, and the second network is a mobile communication network; and

buffering the media stream data of the second network, when the media stream data of the second network is buffered to such an extent that the media stream data of the second network is capable of being decoded, terminating receiving and playing of the media stream data of the first network, and decoding the buffered media stream data of the second network, and playing the decoded media stream data of the second network.

2. The network switching method for mobile multimedia services according to claim 1 , wherein after the playing the decoded media stream data of the second network, the method further comprises:

detecting the signal strength of the media stream data of the first network, and when the signal strength of the media stream data of the first network is greater than the first preset value, sending the RTSP session PAUSE request carrying RTSP session reservation time.

3. The network switching method for mobile multimedia services according to claim 1 , wherein the media stream data of the second network is a Multimedia Broadcast/Multicast Service (MBMS) Real-time Transport Protocol (RTP) media stream data packet or a Broadcast Multicast Service (BCMCS) RTP media stream data packet; wherein after the playing the decoded media stream data of the second network, the method further comprises:

buffering the MBMS RTP media stream data packet or the BCMCS RTP media stream data packet of the second network in a first buffer area;

when it is detected that signal strength of the MBMS RTP media stream data packet or the BCMCS RTP media stream data packet of the second network is smaller than a second preset value, receiving a unicast RTP media stream data packet of the second network in parallel with the MBMS RTP media stream data packet or the BCMCS RTP media stream data packet, and buffering the unicast RTP media stream data packet of the second network in a second buffer area; and

when time stamp information carried in the RTP media stream data packet in the first buffer area is consistent with that carried in the RTP media stream data packet in the second buffer area, decoding the RTP media stream data packet in the second buffer area, and playing the decoded RTP media stream data packet in the second buffer area.

4. The network switching method for mobile multimedia services according to claim 3 , further comprising: setting the second preset value, wherein time for which the signal strength of the MBMS RTP media stream data packet or the BCMCS RTP media stream data packet of the second network attenuates from the second preset value to such a value that the network is totally unavailable is equal to or longer than a sum of time required for establishing a unicast connection with the SM server plus time required for buffering the unicast RTP media stream data packet of the second network until the unicast RTP media stream data packet of the second network is capable of being decoded and played.

5. A network switching device for mobile multimedia services, the device comprising a processor and a non-transitory computer readable storage medium, wherein the non-transitory computer readable storage medium comprises computer program code which when executed by the processor causes the processor to:

receive media stream data of a first network;

detect signal strength of the media stream data of the first network;

enable pre-switching when detecting that the signal strength of the media stream data of the first network is smaller than a first preset value, wherein time for which the signal strength of the media stream data of the first network attenuates from the first preset value to such a value that the first network is unavailable is equal to or longer than a sum of time required for establishing a unicast connection with a Streaming Media (SM) server plus time required for buffering media stream data of a second network until the media stream data of the second network is capable of being decoded and played;

receive the media stream data of the second network in parallel with the media stream data of the first network when enabling the pre-switching, wherein the first network is a terrestrial digital broadcast network, and the second network is a mobile communication network;

buffer the media stream data of the second network; and

terminate receiving and playing of the media stream data of the first network when the media stream data of second network is buffered to such an extent that the media stream data of the second network is capable of being decoded, and decoding the buffered media stream data of the second network, and playing the decoded media stream data of the second network;

establish a Real Time Streaming Protocol (RTSP) session connection with an acquiring point that providing the media stream data in the second network and send an RTSP session PAUSE request to the acquiring point before detecting the signal strength of the media stream data of the first network, and send an RTSP session PLAY request when enabling the pre-switching.

6. The network switching device for mobile multimedia services according to claim 5 , wherein further comprising computer program code which when executed by the processor causes the processor to:

buffer a Multimedia Broadcast/Multicast Service (MBMS) Real-time Transport Protocol (RTP) media stream data packet or a Broadcast Multicast Service (BCMCS) RTP media stream data packet of the second network in a first buffer area;

detect signal strength of the MBMS RTP media stream data packet or the BCMCS RTP media stream data packet of the second network in the first buffer area;

receive a unicast RTP media stream data packet of the second network in parallel with the MBMS RTP media stream data packet or the BCMCS RTP media stream data packet and buffer the unicast RTP media stream data packet of the second network in a second buffer area when detecting that the signal strength is smaller than a second preset value;

determine whether time stamp information carried in the RTP media stream data packet in the first buffer area is consistent with that carried in the RTP media stream data packet in the second buffer area; and

decode the RTP media stream data packet in the second buffer area and playing the decoded RTP media stream data packet in the second buffer area, when determining that the time stamp information carried in the RTP media stream data packet in the first buffer area is consistent with that carried in the RTP media stream data packet in the second buffer area.