Patent ID: 6842485

Claim:
A compressively coded data reproduction method for starting transmission of reproduced data from a video frame and an audio frame corresponding to a reproduction start time specified from the outside, on a data stream in which the following data are multiplexed: compressively coded video data comprising I pictures obtained by subjecting a series of video frames to intra-frame compressive coding, P pictures each obtained by forward-direction predictive compressive coding utilizing the correlation with a video frame in the past, and B pictures each obtained by bi-directional predictive compressive coding utilizing the correlation with two video frames in the past or in the future, or two video frames one in the past and one in the future; compressively coded audio data obtained by subjecting a series of audio frames to compressive coding; and additional data relating to the compressively coded video data and the compressively coded audio data, said method comprising: separating the compressively coded video data, compressively coded audio data, and additional data from the data stream and outputting the separated data, and simultaneously performing head detection on the video frames and the audio frames; judging whether a detected head frame is a video frame or an audio frame corresponding to the reproduction start time, on the basis of reproduction time information that is one of additional data assigned to the detected frame; making a decoding request for decoding the detected video frame from the compressively coded vide data when the detected video frame is judged to be a video frame corresponding to the reproduction start time, and making a decoding request for decoding the detected audio frame from the compressively coded audio data when the detected audio frame is judged to be an audio frame corresponding to the reproduction start time; judging whether both of the video frame and the audio frame have been decoded or not; requesting synchronous output of the decoded video data and audio data when it is judged that both of the video frame and the audio frame have been decoded; wherein performing head detection on the video frames and the audio frames comprises: judging whether an effective reproduction time information is assigned to the detected head frame or not; and calculating reproduction time information of the video frame on the basis of display output order information that is one of the additional data of the video frame, and reproduction time information and display output order information of a video frame which has been decoded prior to the video frame, in the case where no effective reproduction time information is assigned to the detected frame, when the detected frame is a video frame, and alternatively calculating reproduction time information of the audio frame on the basis of reproduction time information of an audio frame which has been detected prior to the audio frame when the detected frame is an audio frame.