Method and device for stream synchronization of real-time multimedia transport over packet network

A device for synchronizing real-time multimedia streams transported over a packet network, the multimedia streams comprising a first stream and a second stream, and the device comprising:

• a first stream buffering device,
• a second stream buffering device,
• a delay detection module, and
• a synchronization module,
• wherein:
• the first and second stream buffering devices are adapted to buffer the first and a second streams, respectively, and to provide the synchronization module with calculated transport delay jitters of the first and second streams, respectively;
• the delay detection module is adapted to calculate average transport delays of the first and second streams, and to provide the synchronization module with calculated average transport delays;
• and
• the synchronization module is adapted to calculate a delay difference between the first and second stream according to the average transport delays and the transport delay jitters of the first and second streams, and to set buffer durations in the first and second stream buffering devices according to the calculated delay difference;
• wherein in the event that a difference between the average transport delays of the first and second streams is within a tolerable synchronization offset range, and the average transport delays of the first and second streams are both smaller than maximum buffer durations in the corresponding buffering devices, the buffer durations in the buffering devices are set to the average transport delays;
• wherein in the event that the difference between the average transport delays of the first and second streams is larger than the tolerable synchronization offset range, either of the buffer durations is set so that the difference there between is within the synchronization offset range;
• and
• wherein in the event that both the average transport delays of the first and second streams are larger than the maximum buffer durations, the buffer durations in the buffering devices are set to be the maximum buffer duration.

A method for synchronizing real-time multimedia streams transported over a packet network, the multimedia streams comprising a first stream and a second stream, the first and second stream being buffered and played through their respective buffering devices at receivers, comprising:

• measuring a first average transport delay (L1) of the first stream and a second average transport delay (L2) of the second stream, respectively;
• measuring a first transport delay jitter (J1) of the first stream and a second transport delay jitter (J2) of second stream, respectively;
• calculating a delay difference between the first stream and the second stream according to the values of L1, L2, J1 and J2, and
• setting a first buffer durations (A1) in the first stream buffering device and a second buffer durations (A2) in the second stream buffering device according to the calculated delay difference;
• wherein the first buffer duration A1 and the second buffer duration A2 are determined by the following conditions:
• a) if L1≧L2, a first common average delay (S1) of the first stream and a second common average delay (S2) of the second stream are determined by:
• S1=L1−L2+J1;
• and S2=J2;
• wherein if S1≧S2, the first and second buffer durations are A1=J1 and A2=S1;
• otherwise, the first and second buffer durations are A1=J1+S2−S1 and A2=J2;
• b) if L1<L2, the first common average delay (S1) of the first stream and the second common average delay (S2) are determined by:
• S1=J1;
• and S2=L2−L1+J2;
• wherein if S2≧S1, the first and second buffer durations are A1=S2 and A2=J2;
• otherwise, the first and second buffer durations are A1=J and A2=J2+S1−S2.