Early media handling
A communication device sends a Session Initiation Protocol (SIP) INVITE message to establish a call. In response, the call is forked. For example, in parallel forking, the SIP INVITE may be sent to two different communication devices. The forking causes each communication device to send at least one provisional response message. In this case, first and second SIP provisional response messages are received that include Session Description Protocol (SDP) information for a media stream. A first media stream associated with one of the first or second SIP provisional response messages is received and played. A second media stream associated with the other one of the first or second SIP provisional response messages is received within a first time period. In response to receiving the second media stream within the first time period, the first media stream is discarded and the second media stream is played.
1. A method comprising:
sending a Session Initiation Protocol (SIP) INVITE message to establish a call;
in response to sending the SIP INVITE message, receiving first and second SIP provisional response messages;
receiving a first media stream associated with one of the first or the second SIP provisional response messages;
playing the first media stream;
receiving a second media stream associated with the other one of the first or the second SIP provisional response messages;
determining that the first and second media streams are received within a first time period; and
in response to receiving the second media stream, discarding the first media stream in favor of playing the second media stream.
2. The method of claim 1 , further comprising:
in response to receiving the first and second SIP provisional response messages, determining if either of the first or second media streams have been received within a second time period, wherein the second time period is shorter than the first time period; and
in response to determining that neither of the first or second media streams have been received within the second time period, playing a local progress tone.
3. The method of claim 1 , further comprising:
after receiving the first and second SIP provisional response messages, receiving a SIP 180 RINGING message;
determining that the first time period has expired before receiving the SIP 180 RINGING message; and
in response to determining that the first time period has expired before receiving the SIP 180 RINGING message, discarding the second media stream and begin playing a local ring back signal.
4. The method of claim 1 , wherein the second SIP provisional response message is a SIP 181 call is being forwarded message and further comprising: deleting any information associated with the first SIP provisional response message in response to receiving the SIP 181 call being forwarded message.
5. The method of claim 1 , further comprising:
detecting that the second media stream has ended;
in response to detecting that the second media stream has ended, determining if the first media stream is still active;
in response to determining that the first media stream is still active, playing the first media stream; and
in response to determining that the first media stream is not active, playing a local progress tone.
6. The method of claim 5 , wherein detecting that the second media stream has ended is based on receiving a SIP UPDATE message that indicates the second media stream is inactive or identifies a 0 port number.
7. The method of claim 1 , further comprising:
receiving a SIP 200 OK message in response to the SIP INVITE;
in response to receiving the SIP 200 OK message, determining if the SIP 200 OK message includes Session Description Protocol (SDP) information; and
if the SIP 200 OK message includes the SDP information:
determining if the SDP information is associated with the first media stream; and
in response to determining that the SDP information is associated with the first media stream, playing the first media stream.
8. The method of claim 1 , wherein the first and second media streams use Real-Time Protocol.
9. The method of claim 1 , wherein the first and second SIP provisional response messages comprise at least one of the following: a SIP 180 RINGING message, a SIP 181 Call is Being Forwarded message, a SIP 182 Queued message, and a SIP 183 Session in Progress message.
10. The method of claim 1 , further comprising:
time stamping receipt of the first and second SIP provisional response messages;
time stamping receipt of the first and second media streams; and
tracking SIP Synchronization Source Identifiers for the first and second media streams.
11. A communication device comprising:
a call processing module that sends a Session Initiation Protocol (SIP) INVITE message to establish a call and receives first and second SIP provisional response messages in response to sending the SIP INVITE message;
a media module that receives a first media stream associated with one of the first or the second SIP provisional response messages, plays the first media stream, receives a second media stream associated with the other one of the first or the second SIP provisional response messages, discards the first media stream and plays the second media stream in response to receiving the second media stream; and
a timer module that determines that the first and second media streams are received within a first time period.
12. The communication device of claim 11 , wherein:
the timer module determines if either of the first or second media streams have been received within a second time period, which is shorter than the first time period, in response to receiving the first and second SIP provisional response messages; and
the media module plays a local progress tone in response to determining that neither of the first or second media streams have been received within the second time period.
13. The communication device of claim 11 , wherein:
after receiving the first and second provisional response messages, the call processing module receives a SIP 180 RINGING message;
the timer module determines that the first time period has expired before receiving the SIP 180 RINGING message; and
the media module discards the second media stream and begins playing a local ring back signal in response to determining that the first time period has expired before receiving the SIP 180 RINGING message.
14. The communication device of claim 11 , wherein the second SIP provisional response message is a SIP 181call is being forwarded message and wherein the call processing module deletes any information associated with the first SIP provisional response message in response to receiving the SIP 181 call being forwarded message.
15. The communication device of claim 11 , wherein:
the media module detects that the second media stream has ended, determines if the first media stream is still active in response to detecting that the second media stream has ended, plays, the first media stream in response to determining that the first media stream is still active, and plays a local progress tone in response to determining that the first media stream is not active.
16. The communication device of claim 15 , wherein detecting that the second media stream has ended is based on receiving a SIP UPDATE message that indicates the second media stream is inactive or identifies a 0 port number.
17. The communication device of claim 11 , wherein:
the call processing module receives a SIP 200 OK message in response to the SIP INVITE, determines if the SIP 200 OK message includes Session Description Protocol (SDP) information in response to receiving the SIP 200 OK message, and if the SIP 200 OK message includes the SDP information: determines if the SDP information is associated with the first media stream and plays the first media stream in response to determining that the SDP information is associated with the first media stream.
18. The communication device of claim 11 , wherein:
the call processing module receives a SIP 200 OK message in response to the SIP INVITE, determines if the SIP 200 OK message includes Session Description Protocol (SDP) information in response to receiving the SIP 200 OK message, and uses an identifier in one of the first or second SIP provisional response message to identify which of the first or second media streams needs to be played if the SIP 200 OK message does not include the SDP information.
19. The communication device of claim 11 , wherein:
the call processing module time stamps receipt of the first and second SIP provisional response messages; and
the media module time stamps receipt of the first and second media streams, and track SIP Synchronization Source Identifiers for the first and second media streams.
20. A method comprising:
sending a Session Initiation Protocol (SIP) INVITE message to establish a call;
starting a timer to detect sequential forking;
in response to sending the SIP INVITE message, receiving a first provisional response message;
receiving a first media stream associated with the first provisional response message;
playing the first media stream;
receiving a second provisional response message after the timer to detect sequential forking has expired; and
in response to receiving the second provisional response message after the timer to detect sequential forking has expired, doing at least one of:
playing a local progress tone; and
playing an early media stream associated with the second provisional response message.