A DV (Digital Video) method is one of high-performance encoding methods for compressing the amount of information conveyed by an AV (Audio Visual) signal. The DV encoding method is disclosed in a document with a title of ‘Specification of Consumer-Use Digital VCRs using 6.3 mm magnetic tape’ disclosed in an HD DIGITAL VCR CONFERENCE. The DV method is adopted in applications such as a camcoder using a video cassette tape. A camcoder is a video tape recorder integrated with a camera to form a single apparatus.
A DV signal can be input and output by way of an IEEE (Institute of Electrical and Electronic Engineers) 1394 digital interface, which is referred to hereafter simply as an IEEE 1394 I/F. The format of a signal flowing through the IEEE 1394 I/F is shown in FIG. 1.
The IEEE 1394 I/F handles a DV signal in 80-byte block units each known as a DIF (Directory Interchange Format) block. 150 DIF blocks form 1 DIF sequence. A DIF sequence comprises a header section, a subcode section, a VAUX section and an audio & video section. In the case of an SD-DVCR, which is a standard compression mode of a standard TV (television) signal, one video frame comprises 10 DIF sequences in a 525-60 system such as the NTSC (National Television System Committee) or 12 DIF sequences in a 625-60 system such as the PAL (Phase Alternating Line). In the case of an SDL-DVCR, which is a high compression mode of a standard TV (television) signal, on the other hand, one video frame comprises 5 DIF sequences in a 525-60 system or 6 DIF sequences in a 625-50 system.
A DIF block comprises a 3-byte ID (Identifier) located at the beginning of the block and 77-byte data following the ID. The ID includes a DIF block type, a sequence number representing a color sequence, a DIF sequence number and a DIF block number. The DIF block type indicates the type of a section including the block. If a DIF block type indicates a header section, the DIF block with an ID including the DIF block is located at the beginning of a DIF sequence. A DIF block included in a header section has 3 most significant bits of 000 in the first byte thereof.
A DV signal having such a format flows through an IEEE 1394 I/F as isochronous packets. The payload of an isochronous packet conveying a DV signal is referred to as a source packet. A source packet has a fixed length of 6 DIF blocks or 480 bytes.
A relation between a source packet and DIF blocks in the 525-60 system is shown in FIG. 2. All frames of a DV stream are subjected to an intra-frame encoding process to generate frames each having a fixed bit rate (length) of 120,000 bytes. Thus, the number of source packets per video frame is also fixed. That is to say, the number of source packets per video frame in the SD-DVCR mode is 250 for the 525-60 system or 300 for the 625-50 system.
By the way, in recent years, there has been proposed a variety of optical discs as an information-recording medium implemented in the form of a disc that can be dismounted from a recording/reproducing apparatus. Such an optical disc usable for recording data is characterized in that the disc can be used as recording media having a large storage capacity of several gigabytes and allowing a high transfer bit rate of several tens of Mbps. Thus, the optical disc is very much expected to serve as storage media for recording an AV (Audio Visual) such as a video signal. It is anticipated that, in the future, there will be raised a demand for a DV recording/reproducing apparatus for recording a DV signal, which has been recorded on a tape by using a camcoder or the like, onto an optical disc by way of an IEEE 1394 I/F.
As described above, with the storage capacity of a recording medium increasing, the recording medium can be used for storing a large amount of data such as image and sound data of video materials. That is to say, the recording medium can be used for storing a large number of DV video materials. In consequence, there will be required an operation such as an editing work for producing a result, which allows the user to watch desired images selected from those numerous DV video materials recorded on the disc.
When an editing work is carried out, however, there will be raised a problem of a difficulty in speedily identifying an access position in the DV video materials recorded on the disc.