The present invention relates generally to devices for recording data onto recordable optical discs, such as a CD-R (Compact Disc-Recordable) or DVD (Digital Video Disc-Recordable) where data are recorded on a packet-by-packet basis, and it relates more particularly to a packet-write-type optical disc recording device which records data in packets each having a predetermined data length.
Examples of the conventionally-known methods for recording data on a CD-R include the "disc-at-once" method in which data for a whole optical disc are recorded in succession by single recording operation and the "track-at-once" method in which a plurality of sessions are allowed to be written onto a disc in an additive fashion (additive writing). All of these recording methods, however, involve recording of a great quantity of data per recording operation, consuming a managing memory area of 10 to 20 megabytes per recording operation. Thus, the known recording methods are not suited to applications where a relatively small quantity of data are written a plurality of times in an additive fashion.
In contrast, the so-called "packet-write" recording method, in which a small quantity of data are written onto an optical disc on a packet-by-packet basis, has the advantage that any necessary file can be additively written in much the same way as normally done on conventional hard discs, and hence it has been becoming increasingly popular in applications where a CD-R is used as an external storage device for a computer.
FIG. 5 is a diagram illustrating a packet-write recording format. Each track is composed of a pre-gap, which is a managing area provided at the head of the track, and a plurality of packets following the pre-gap. In this format, data are written on the packet-by-packet basis; that is, each packet is written onto a disc, following an already-written packet. For this purpose, the pre-gap contains track descriptors, and a specific position to record a new packet is determined by reference to position information of a last packet written on the optical disc. In additively writing a new packet, it is impossible to physically link the new packet with the preceding already-written packet in a continuous manner, so that a pratically unreadable block called a "link block" is provided between every adjoining packets. Link information called a "splice" is stored in a data link period between the packets. The splice comprises information stored in a total of seven blocks: run-out information (Run-out) stored in two blocks at the end of a preceding packet; link information (Link) stored in one block at the head of a succeeding packet; and run-in information (Run-in) in four blocks of the succeeding packet.
The packet length is set by an external host computer. Because each packet comprises a plurality of blocks (sectors) each having a length of about 2K bytes, the packet length may be determined using 2K-byte units in principle However, due to the splice consuming a total of 14K bytes, the recording areas can not be used efficiently if the packet length is too short. For this reason, the packet length is normally set to 64K bytes, 128 bytes or the like so that the effective use rate of the recording areas exceeds 80 per cent.
Because of the nature of the packet-by-packet additive writing, the conventional optical disc recording devices conduct data recording onto an optical disc on the packet-by-packet basis. When one packet of data is to be recorded, a series of operations is generally required to store data for one packet from the host computer into an internal data buffer of a disc drive device, move a recording head to a particular writing position facing the disc (seek operation) and then initiate recording of the stored one-packet data by means of the recording head. The reason why the recording is initiated after storage of the one-packet data is that if there ocurs a break or interruption of data during recording, all data having so far been recorded would become errors.
If the size of a file is short enough to fit within a single packet, the above-mentioned recording method would present no significant problem; however, if the file is longer, a problem would arise that the seek operation frequently takes place, making recording of the file time-consuming. In addition, laser power of the recording head is frequently calibrated, which would result in shortage of a calibrating area. Such a problem may be lessened if the packet size is increased, but the increased packet size would considerably deteriorate the advantageous function of the packet-write recording method which allows a small quantity of data to be recorded in an additive fashion.