The present invention relates to a data structure suitable for recording/playing back video data sent in digital broadcast or the like or stream data sent with a packet structure, a method of recording stream data using this data structure, and a method of playing back stream data recorded with this data structure.
In recent years, TV broadcast has come into the era of digital broadcast. Accordingly, an apparatus for saving digital data of digital TV broadcast as they are irrespective of their contents, i.e., a so-called streamer, has been demanded.
The current digital TV broadcast uses an MPEG transport stream. In the future, an MPEG transport stream is projected to be used as a standard one in the field of digital broadcast using moving picture.
In such digital broadcast, the contents (mainly, video information) to be broadcasted are time-divided into groups of data each having a predetermined size (e.g., 188 bytes) called transport packets, and broadcast data is sent in units of transport packets.
As a streamer for recording digital broadcast data, a home digital VCR such as D-VHS (digital VHS) or the like is currently commercially available. A streamer using D-VHS directly records a broadcasted bitstream on a tape. For this reason, a plurality of programs are multiplexed and recorded on a video tape.
Upon playback, all data are output from the VCR to a set-top box (digital TV reception apparatus; to be abbreviated as an STB hereinafter) when they are played back either from the beginning or the middle of the tape. In this STB, a desired program is selected from the output data by user operation or the like. The selected program information is transferred from the STB to a digital TV receiver, and is played back (playback of video+audio and the like).
Since this D-VHS streamer uses a tape as a recording medium, it cannot attain quick random access, and it is difficult to quickly jump to a desired position of a required program so as to play it back.
As a promising candidate that can combat such shortcoming (difficulty of random access) of the tape, a streamer that uses a large-size disc medium such as a DVD-RAM or the like has been proposed. In this case, management data must be inevitably recorded together with broadcast data in consideration of random access, special playback, and the like.
Problem
Digital TV broadcast adopts an MPEG transport stream as a transmission method of stream data containing video information, and video information is sent while being combined in units of application packets each having, e.g., 188 bytes. By contrast, when a recording medium such as a DVD-RAM disc or the like that belongs to a DVD family is used, recording must be done in units of sectors, the minimum recording unit of which is 2,048 bytes. However, the following problems remain unsolved.
(1) A method of efficiently recording information of 188-byte application packets in units of 2,048-byte sectors is not settled yet.
(2) A method of playing back stream data recorded on an information storage medium while holding the reception timing of digital TV broadcast is not settled yet.
Furthermore, there is also a need for recording digital data which is transferred with a packet structure in a local area network (LAN) or a digital telephone line such as ISDN or the like using a streamer.
However, the following problem also remains unsolved.
(3) No versatile recording method that can record digital data other than digital TV is available.
Object
It is an object of the present invention to provide a data structure (recording format) on an information storage medium, which can efficiently record stream data on an information storage medium, and can play back stream data from an information storage medium while holding transfer timings between application packets received in digital TV broadcast.
It is another object of the present invention to provide a method of recording stream data using the data structure.
It is still another object of the present invention to provide a method of playing back stream data recorded with the data structure.
In order to achieve the above object, in a data structure according to the present invention, a set of one or more stream objects (SOB) that represent playback data for a recorded bitstream constitutes stream data, the stream object (SOB) is formed of one or more stream packs (S_PCK), and the stream pack (S_PCK) is formed of a pack header and stream packet (S_PKT). The pack header includes predetermined time information (SCR), and the stream packet (S_PKT) includes one or more application packets (AP_PKT) assigned with predetermined time stamps (ATS). The application packet (AP_PKT) is incoming (to a streamer) during recording of the stream object (SOB) is time-stamped (modified time stamp in FIG. 14; ATS in FIG. 15) by a local reference clock (440 in FIG. 9) (in the streamer) corresponding to the predetermined time information (SCR).
In order to achieve the other object, in a recording method according to the present invention, a set of one or more stream objects (SOB) that represent playback data for a recorded bitstream constitutes stream data, the stream object (SOB) is formed of one or more stream packs (S_PCK), and the stream pack (S_PCK) is formed of a pack header and stream packet (S_PKT). The pack header includes predetermined time information (SCR), and the stream packet (S_PKT) includes one or more application packets (AP_PKT) assigned with predetermined time stamps (ATS). The application packet (AP_PKT) is incoming (to a streamer) upon recording the stream object (SOB) on an information medium (201) is time-stamped (modified time stamp in S4 in FIG. 10; time stamp in ST106, ST212, and ST312 in FIGS. 21 to 23) by a local reference clock (440 in FIG. 9) (in the streamer) corresponding to the predetermined time information (SCR).
In order to achieve the still other object, a playback method according to the present invention uses an information medium (201) on which stream objects (SOB) are recorded in a format in which a set of one or more stream objects (SOB) that represent playback data for a recorded bitstream constitutes stream data, the stream object (SOB) is formed of one or more stream packs (S_PCK), the stream pack (S_PCK) is formed of a pack header and stream packet (S_PKT), the pack header includes predetermined time information (SCR), the stream packet (S_PKT) includes one or more application packets (AP_PKT) assigned with predetermined time stamps (ATS), the incoming application packet (AP_PKT) (to a streamer) is time-stamped by a local reference clock (440 in FIG. 9) (in the streamer) corresponding to the predetermined time information (SCR). When recorded information is played back from this medium, a playback reference clock is set (S37 in FIG. 11) on the basis of the local reference clock (SCR 303 in FIG. 5, SCR base in FIG. 15) played back from the information medium (201), and contents of the bitstream are played back from the information medium (201) on the basis of the set playback reference clock (SCR).
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.