Multimedia synchronization system

A method of synchronizing presentation of a time-based media sequence in response to a synchronization request specifying a new clock rate of presentation of the time-based media sequence on a computer having a storage and a display and a mechanism for providing a master time signal, the method comprising the steps of:

• (a) creating a clock object in the storage and including a mechanism for computing a current time value according to a clock function of the master time signal, an original clock rate value, and an original offset value
• (b) presenting the time-based media sequence in synchronism with the current-time value;
• (c) in response to the synchronization request, computing a new offset value according to a new clock function of the master time signal, the new clock rate, the original clock rate, and the original offset value;
• (d) replacing the original clock rate value and the original clock offset value of the clock object with the new clock rate and the new offset value respectively, so that the media sequence may be presented at the new clock rate while keeping the current time value unchanged at the instant of synchronization.

In a computer system having a storage and multimedia presentation object in the storage for presenting multimedia data in synchronism with a current time value provided to the presentation object, a synchronization framework residing in the storage for controlling time relationships in a multimedia application, which includes the multimedia presentation object and which operating on the computer system, the synchronization framework comprising:

• (a) in the storage, data defining a time source class having a master time value attribute for storing master time signal value and a get member function for retrieving the master time signal value and storing the master time signal value in the master time value attribute;
• (b) in the storage, data defining an application-subclassable clock class having
• a current time attribute,
• an offset value attribute,
• a rate value attribute,
• a member function for calculating the current time attribute of a clock object as a clock function of a master time signal value, the rate value attribute, end the offset value attribute of the clock object,
• a member function for providing the current time value to a multimedia presentation object to control presentation of multimedia data, and a member function, responsive to a synchronization request accompanied by a new clock rate, for computing a new offset value according to a new clock function of the master time signal, the rate value, the offset value, and the new clock rate, so that the presentation object may present the multimedia data at the new clock rate while keeping the current time value of the clock object unchanged at the instant of synchronization.