Method for seeking to a requested location within variable data rate

Abstract

A method for causing a computer controlled digital playback system to seek to a requested location within a selected playback file recorded in variable data rate encoding format (e.g., MPEG). The playback file is stored in a suitable recording media. The novel method receives a seek command to a requested playback time referenced by a time unit (e.g., seconds) or a frame number and also accesses an upper rate bound from a system header. The rate bound indicates the maximum data rate of the encoded data in the playback file. Using the rate bound and the requested playback time, an approximate location is determined in the playback file and the playback file is seeked to that approximate location. The method reads a first available time stamp near the approximate location and checks if the discovered time stamp matches with the requested playback time within a predetermined degree. If not, the novel method computes an adjusted data rate based on the discovered time stamp and the approximate location. This adjusted data rate is averaged with the prior data rate to obtain a current data rate used to compute a new approximate location. The above is repeated until a match occurs or until the new approximate location equals the old approximate location. Upon a match, an I frame or a sequence header is located, initialization information is pre-pended, the video processor unit is flushed, and the playback file data is downloaded for playback beginning at the requested playback time.