Method and apparatus for reproducing compressively coded data

A compressively coded data reproduction apparatus 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 subjected 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 apparatus comprising:
• a system decoder for separating the compressively coded video data, the compressively coded audio data, and the additional data from the data stream and outputting these data and, at this time, performing head detection on the video frames and the audio frames;
• a video decoder for decoding the video frames from the compressively coded video data to output video data;
• an audio decoder for decoding the audio frames from the compressively coded audio data to output audio data;
• and
• a synchronous controller for judging whether a head frame detected by the system decoder 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 the additional data assigned to the detected frame;
• outputting a decoding request to the video decoder when the detected frame is judged as a video frame corresponding to the reproduction start time;
• outputting a decoding request to the audio decoder when the detected frame is judged as an audio frame corresponding to the reproduction start time;
• and outputting an output request to the video decoder and to the audio decoder at the point of time when both of the video frame and the audio frame have been decoded.

A compressively coded data reproduction method for starting transmission of reproduced data from a picture and an audio frame corresponding to a reproduction start time specified from the outside, on a data stream in which coded video data arranged in non-chronological order, coded audio data relating to the coded video data, and additional data attendant on these data are multiplexed, said method comprising the steps of:

• separating the coded video data, the coded audio data, and the additional data from the data stream and outputting these data and, at this time, performing head detection on reproduced pictures and reproduced audio data;
• judging whether the detected head picture per screen or head audio data is a picture per screen or audio data corresponding to the reproduction start time specified from the outside, on the basis of reproduction time information that is one of the additional data assigned to the detected picture or audio data;
• making a decoding request for decoding the picture per screen and the audio data corresponding to the reproduction start time;
• judging whether both of the picture per screen and the audio data have been decoded or not;
• and
• making a request for synchronous output of the decoded picture per screen and the decoded audio data, when both of the picture and the audio data have already been decoded.

A compressively coded data reproduction apparatus for starting transmission of reproduced data from a picture and an audio frame corresponding to a reproduction start time specified from the outside, on a data stream in which coded video data arranged in non-chronological order, coded audio data relating to the coded video data, and additional data attendant on these data are multiplexed, said apparatus comprising:

• a system decoder for separating the coded video data, the coded audio data, and the additional data from the data stream and outputting these data and, at this time, performing head detection on reproduced pictures and reproduced audio data;
• a video decoder for decoding pictures per screen from the coded video data;
• an audio decoder for decoding audio data from the coded audio data;
• and
• a synchronous controller for judging whether the detected head picture per screen or head audio data is a picture per screen or audio data corresponding to the reproduction start time specified from the outside, on the basis of reproduction time information that is one of the additional data assigned to the picture per screen or the audio data detected by the system decoder;
• outputting a decoding request for decoding the picture per screen and the audio data corresponding to the reproduction start time, to the video decoder and the audio decoder;
• and outputting an output request to the video decoder and the audio decoder at the point of time when both of the picture per screen and the audio data have been decoded.