JP3869110B2 - Disk unit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a disk apparatus that records and reproduces digital continuous data such as moving image data or audio data, and more particularly to a disk apparatus having a function of alternately recording and reproducing in a time division manner.
[0002]
[Prior art]
Development of a video disk device that records and reproduces digital moving images on a storage medium such as an optical disk using a digital moving image compression technique represented by MPEG is in progress.
[0003]
According to a conventional video disk device using an optical disk, digital moving image data compressed by an MPEG encoder, which is a digital moving image compressor, or digital moving image data delivered by broadcasting, CATV (cable television) or the like is stored in a buffer memory. In this buffer memory, the difference between the input digital video data bit rate (bit capacity sent per second) and the optical disc recording / playback speed (bit capacity that can be recorded / reproduced per second) is adjusted. Is done. Usually, the bit rate of the input digital moving image data is slower than the recording / reproducing speed of the optical disc.
[0004]
By the way, as one usage pattern of such a video disk device, if a moving image already recorded during recording can be reproduced, it is considered to be very effective in practice. For example, there is a case where the user wants to return home from the beginning while continuing the recording while returning home in the middle of the timer recording.
[0005]
However, in the conventional video disk device, the recorded moving image cannot be reproduced until the recording is finished. That is, during recording of a digital moving image, the moving image cannot be reproduced simultaneously. In order to solve this problem, a simultaneous recording / reproducing function has been realized by providing optical heads independent for recording and reproduction. However, this method increases the cost because a plurality of optical heads are used.
[0006]
[Problems to be solved by the invention]
As described above, the conventional disk device cannot basically reproduce a moving image already recorded during recording of a digital moving image or the like, and tries to realize such simultaneous recording and reproduction. As a result, there is a problem that the cost of the system becomes high because a plurality of recording / reproducing heads such as optical heads must be used.
[0007]
[Means for Solving the Problems]
The present invention provides a disk device capable of reproducing digital continuous data already recorded during recording of digital continuous data such as moving image data or audio data by using a single recording / reproducing head. Objective.
[0008]
According to the present invention, a digital continuous data input / output unit for inputting / outputting digital continuous data at a predetermined bit rate, a recording / reproducing unit for recording / reproducing digital continuous data on / from a disk-shaped recording medium, and a digital continuous recording unit Buffer memory for temporarily storing data and temporarily storing digital continuous data reproduced from the recording medium, recording digital continuous data in a predetermined recording area on the recording medium, and recording on the recording medium A control unit that performs control to alternately reproduce digital continuous data from a predetermined reproduction area in a time-division manner, and the control unit includes a recording and reproduction head during recording to and from the reproduction area, and a recording and reproduction head. Writes the continuous recording digital data to the buffer memory during access between the recording area and the reproduction area on the recording medium, When recording in the recording area, the recording digital continuous data stored in the buffer memory is read out at a recording speed more than twice the average bit rate of the recording digital continuous data, recorded in the recording area, and reproduced from the playback area. Sometimes, digital continuous data recorded in the reproduction area is reproduced at a reproduction speed more than twice the average bit rate and written to the buffer memory, and when recording into the recording area and reproduction from the reproduction area, When the recording / reproducing head accesses between the recording area and the reproducing area on the recording medium, the digital continuous data stored in the reproducing buffer memory is read out at a predetermined bit rate and output to the display device. A disk device is provided.
[0009]
In addition, when the recording to the recording area and the reproduction from the reproduction area are alternately performed in a time division manner, the average recording time per time is T1 seconds, the average reproduction time is T2 seconds, the maximum access time of the recording medium (recording / reproducing head) Is the seek time required to move from the innermost circumference to the outermost circumference of the recording medium plus the time required for one rotation of the recording medium), and the average bit rate of the input digital continuous data is A (bps). The recording speed is set to (T1 + T2 + 2S) * A / T1bps or higher, the playback speed is set to (T1 + T2 + 2S) * A / T2bps or higher, and the total storage capacity of the recording buffer memory and the playback buffer memory is set to (4 * S + T1 + T2) * Set to A bit or more.
[0010]
Further, the display screen of the display device as the continuous data output device is divided to simultaneously display the digital moving image as the digital continuous data being recorded in the recording area and the digital moving image being reproduced from the reproduction area.
[0011]
According to the disk device of the present invention configured as described above, the digital continuous data already recorded during the recording of the digital continuous data (for example, moving image data) is reproduced using a single recording / reproducing head. Can do. The reason for this will be described below.
[0012]
The average bit rate A (bps) of the digital continuous data is used, and the maximum access time of the disk-shaped recording medium (the time for which the recording medium makes one rotation is added to the time when the recording / reproducing head moves from the innermost circumference to the outermost circumference of the recording medium) Let time be S seconds. In order to simultaneously record digital continuous data and reproduce digital data already recorded on a recording medium with one recording / reproducing head, recording and reproduction on the recording medium are performed in a time-sharing manner, and two digital recording and reproduction are performed. It is necessary to perform at a speed not lower than the average bit rate of continuous data. That is, since digital continuous data is recorded on a recording medium for a certain time and digital continuous data is reproduced from the recording medium for a certain time, two digital continuous data for recording and reproduction are average bit rate A (bps). Therefore, the recording / reproducing speed of the recording medium needs to be at least 2 * A (bps) or more.
[0013]
Furthermore, since there is one recording / reproducing head and the positions of the recording area and the reproducing area on the recording medium are not always the same, an access time between the areas is required for switching between recording and reproducing. For example, a time division procedure consisting of “recording for T1 second” → “access for S seconds from the recording area to the playback area” → “playback for T2 seconds” → “access for S seconds from the playback area to the recording area” is repeated. When recording and reproduction are performed, access between two areas occurs in this one-cycle time division procedure.
[0014]
Accordingly, during recording, digital continuous data input for (T1 + T2 + 2S) seconds is recorded during T1 seconds, and the recording speed of the recording medium is (T1 + T2 + 2S) * A / T1 bps or more. Similarly, the reproduction speed of the recording medium is (T1 + T2 + 2S) * A / T2bps or more. When T1 = T2, the recording / reproducing speed of the recording medium is (2 + 2s / T1) * A (bps) or more. Here, 2S / T1 * A (bps) is an increase in recording / reproducing speed required for two accesses.
[0015]
On the other hand, regarding the required buffer memory capacity, the capacity of the recording buffer memory is the sum of twice the access time (reciprocation time of the recording / reproducing head between the recording area and the reproducing area) and the average reproducing time T2 from the recording medium. Multiplied by the average transfer rate of continuous data, and (2S + T2) * A bits or more are required. Similarly, the capacity of the reproduction buffer memory is the sum of the access time (the reciprocation time of the recording / reproducing head movement between the reproduction area and the recording area) and the average recording time T1 to the recording medium. Multiplied by (2S + T1) * A bits or more are required. Therefore, the capacity required for the buffer memory is (4S + T1 + T2) * A bits or more in total for recording and reproduction.
[0016]
The recording / reproducing speed of the recording medium and the buffer memory capacity are satisfied, and when recording digital continuous data, the recording / reproducing head is accessed from the recording area to the reproducing area in S seconds. The digital continuous data to be recorded is recorded in the recording buffer memory during the time of accessing the optical head in S seconds from the reproduction area to the radial position where the recording area is continuously recorded from the reproduction area, and the next average T1 is reproduced. The digital continuous data is read from the recording buffer memory per second and written to the recording medium.
[0017]
On the other hand, at the time of digital continuous data reproduction, reproduction is performed from the recording medium for an average of T2 seconds and stored in the reproduction buffer memory, and then the optical head is accessed from the reproduction area to the recording area in S seconds to obtain the digital continuous data. Recording is performed on the recording medium for an average of T1 seconds, and the recording / reproducing head is accessed in S seconds from the recording area to the radial position where the recording area is continuously recorded. The digital continuous data to be reproduced during the two access times and during recording on the recording medium is reproduced by reading out the digital continuous data stored in the reproduction buffer memory.
[0018]
By repeating such an operation, the digital continuous data input from the outside is continuously recorded on the recording medium without being lost, and the digital continuous data reproduced from the recording medium is continuously reproduced without being lost. Therefore, it is possible to simultaneously record and reproduce digital continuous data with one recording / reproducing head.
[0019]
Further, when a seek is retried when the seek fails, the average recording time per recording when recording in the recording area and the reproduction from the reproduction area are alternately performed in a time division manner is T1 seconds, and the average reproduction time is T2 seconds. , The maximum access time for the recording medium (the time required for the recording medium to rotate once to the seek time required for the recording / reproducing head to move from the innermost circumference to the outermost circumference of the recording medium) is input in S seconds When the average bit rate of continuous data is A (bps) and the maximum number of retries when seek fails is N, the recording speed of digital continuous data onto the recording medium is (T1 + T2 + 2 * S * (N + 1)) * A / T1 (bps) or higher, and the playback speed of digital continuous data from the recording medium is (T1 + T2 + 2 * S * (N + 1)) * A / T2 (bps) or higher, and the recording buffer memory and The total storage capacity of the reproduction buffer memory (4 * S * (N + 1) + T1 + T2) * may be set to A bit more.
[0020]
Further, by dividing the screen of the display device as the continuous data output means and displaying the digital moving image data as the digital continuous data being recorded and the digital moving image data being reproduced at the same time, the recorded image and the reproduced image are simultaneously displayed. I can confirm.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a configuration of a video disk device which is a disk device according to an embodiment of the present invention. This disk apparatus includes an analog image input unit 11, an MPEG encoder 12 which is a digital moving image data compressor, a digital image input unit 13, a recording buffer memory 14, a switching unit 15, a modem 16, an optical head 17, an optical disk 18, A reproduction buffer memory 19, an MPEG decoder 20 which is a digital moving image data decompressor for monitoring a reproduced image, a monitor 21 for displaying the reproduced image or both the reproduced image and the recorded image, and a monitor for the recorded image It comprises an MPEG decoder 22 which is a digital moving image data decompressor, a controller 23 for controlling each part, and a driver 24 for driving the optical head 17.
[0022]
In the following description, the bit rate of digital moving image data delivered from MPEG encoder 12, CATV, satellite broadcasting, etc. is 4 Mbps on average. The recording / reproducing speed (data transfer speed) of the digital moving image data on the optical disk 18 is 12 Mbps. Further, as shown in FIG. 2, the optical disk 18 is divided into an area 31 for recording digital moving image data and an area 32 for reproducing digital moving image data. The capacities of the recording buffer memory 14 and the reproducing buffer memory 19 are both 6M bits.
[0023]
Hereinafter, simultaneous recording and reproduction processing of digital moving image data in the present embodiment will be described.
[0024]
(Recording operation)
First, the recording operation will be described. When the input moving image data signal is an analog moving image signal such as an NTSC signal, the analog moving image signal is input from the analog image input unit 11, and after digital conversion and image compression are performed by the MPEG encoder 12. Are input to the digital image input unit 13. On the other hand, already compressed digital moving image data delivered from CATV, satellite broadcasting or the like is directly input to the digital image input unit 13.
[0025]
The digital moving image data input from the digital image input unit 13 is written into the recording buffer memory 14 at a bit rate of 4 Mbps, for example, by writing control by the controller 23. When an appropriate amount of digital moving image data is written in the recording buffer memory 14, the digital moving image data is read from the recording buffer memory 14 at a recording speed of 12 Mbps, which is the recording speed of the optical disc 18, by the reading control of the controller 23, and switched. Is input to the device 15. Here, the switching unit 15 inputs the digital moving image data from the recording buffer memory 14 to the modem 16 during recording, and the digital moving image data output from the modem 16 to the reproducing buffer memory 19 during reproduction. The controller 23 switches to input.
[0026]
The digital moving image data read from the recording buffer memory 14 is guided to a modem 16 by a switch 15 where it is modulated into a signal suitable for recording, and is not shown in the figure, a semiconductor laser, an objective lens, and a photodetector. Etc. are input to a known optical head 17 having the main components as a component and recorded on the optical disk 18 by the optical head 17. At this time, the laser drive for the seek operation and writing of the optical head 17 is performed by the controller 23 via the driver 24.
[0027]
The optical disk 18 is a recordable / reproducible medium, specifically a phase change recording medium, a magneto-optical recording medium, or the like.
[0028]
Since the recording speed of the optical disk 18 is faster than the bit rate of the digital moving image data input from the digital image input unit 13, the recording buffer memory 14 may become empty. In this case, recording on the optical disk 18 is interrupted. The processing is repeated from the operation of storing the digital moving image data in the recording buffer memory 14. Accordingly, the digital moving image data is continuously input to the recording buffer memory 14, but the digital moving image data is recorded on the optical disc 18 by intermittently reading the digital moving image data from the recording buffer memory 14. It is done intermittently. The read / write timing of moving image data to / from the buffer memory 14 is performed by the controller 23 while monitoring the data storage amount of the buffer memory 14 by monitoring the input address pointer.
[0029]
For example, when 4 Mbit or more of digital moving image data stored in the recording buffer memory 14 is stored, recording on the optical disk 18 is performed. When 4 Mbits are stored in the recording buffer memory 14, the digital moving image data from the digital image input unit 13 is read at a speed of 4 Mbps while the digital moving image data is read from the recording buffer memory 14 at a speed of 12 Mbps. Since the data is written in the memory 14, the recording buffer memory 14 becomes empty in about 4M bits / (12Mbps-4Mbps) = 0.5 seconds, and recording on the optical disk 18 is interrupted. In the next 1 second, the recording buffer memory 14 becomes 4 Mbits, and recording is performed again on the optical disk 18.
[0030]
Thus, the optical disk 18 has a time during which recording is interrupted during recording, and reproduction is performed using this time. At the time of reproduction, the digital moving image data input from the digital moving image data input unit 13 during access from the recording area 31 of the optical head 17 to the reproducing area 32 and access from the reproducing area 32 to the recording area 31 is 4 Mbps. Are written into the recording buffer memory 14 at a speed of
[0031]
(Playback operation)
Next, the reproduction operation will be described. A reproduction signal reproduced from the optical disk 18 by the optical head 17 is demodulated into digital moving image data by the modem 16. The demodulated digital moving image data is written to the reproduction buffer memory 19 through the switch 15 at a speed of 12 Mbps. At the same time, digital moving image data is read from the buffer memory 19 at a speed of 4 Mbps, decompressed by the MPEG decoder 20 and output to the monitor 21.
[0032]
Since the playback speed of the optical disk 18 is faster than the bit rate of the digital moving image data, the playback buffer memory 19 may become full. At this time, the controller 23 controls the driver 24 to store the digital data stored in the buffer memory 19. Playback is interrupted until the moving image data is reduced to an appropriate amount. At this time, the controller 23 records the address information of the recording area where the reproduction is interrupted, and seeks according to the address information recorded in the recording area when reproducing again. As a result, reading of the digital moving image data from the reproduction buffer memory 19 is performed continuously, but reproduction of the digital moving image data from the optical disc 18 is performed intermittently.
[0033]
For example, when the digital moving image data stored in the reproduction buffer memory 19 is 2 Mbit or less, reproduction from the optical disk 18 is performed. In this case, the digital moving image data is read from the reproduction buffer memory 19 at a speed of 4 Mbps while being input to the MPEG decoder 20 while the digital moving image data is written to the reproduction buffer memory 19 at a speed of 12 Mbps. The reproduction buffer memory 19 is filled with 2 Mbits + (12 Mbps-4 Mbps) * 0.5 seconds = 6 Mbits in about 0.5 seconds, and the reproduction is interrupted. In the next 1 second, the playback buffer memory 19 becomes 2M bits, so that the digital moving image data is played back from the optical disc 18 again.
[0034]
As described above, the optical disk 18 has a time during which playback is interrupted, and recording is performed using this time. At the time of recording, the digital moving image data stored in the reproduction buffer memory 19 during the access from the reproduction area 32 to the recording area 31 and the access from the recording area 31 to the reproduction area 32 of the optical head 17 is read at a speed of 4 Mbps. And input to the MPEG decoder 20.
[0035]
FIG. 3 is a flowchart showing a processing procedure for simultaneous recording and reproduction of digital moving image data in the present embodiment.
As shown in the figure, first, the controller 23 checks whether or not digital moving image data remains in the recording buffer memory 14 (buffer memory A) (step S1). If the recording buffer memory 14 is empty, the optical disk 18 stops recording, and the driver 24 moves the optical head 17 to the reproduction area 32 to reproduce from the optical disk 18 (step S2). The optical head 17 reproduces the digital moving image data recorded in the reproduction area 32, transfers it to the reproduction buffer memory 19 (buffer memory B) via the modem 16 and the switch 15, and stores it there (step). S3).
[0036]
Next, it is checked whether or not 6 Mbits of digital moving image data is stored in the reproduction buffer memory 19, that is, whether or not it is full (step S4). Here, if the reproduction buffer memory 19 is full, the optical disk 18 stops reproduction, so that the optical head 17 is moved to the recording area 31 to perform recording on the optical disk 18 (step S5). The digital moving image data in the recording buffer memory 14 is recorded in the recording area 31 on the optical disk 18 until the buffer memory 14 becomes empty (steps S6 to S7).
Thereafter, the process returns to step S2, and the above-described recording and reproduction of the optical disk 18 are repeated alternately.
[0037]
4A and 4B are diagrams showing temporal changes in the amount of digital moving image data in the recording buffer memory 14 and the reproducing buffer memory 19 during simultaneous recording and reproduction of digital moving image data in the present embodiment. In this example, the average access time between the recording area 31 and the reproduction area 32 is 0.25 seconds. Further, it is assumed that the optical head 18 is located in the reproduction area 32. With reference to the figure, the operation at the time of simultaneous recording and reproduction in the present embodiment will be described in detail step by step.
[0038]
(1) First, since the digital moving image data in the reproduction buffer memory 19 is 0, the digital moving image data is reproduced from the optical disc 18 at a speed of 12 Mbps for 0.75 seconds and written to the buffer memory 19.
[0039]
Also, during this 0.75 seconds, the digital moving image data reproduced from the optical disk 18 is written to the reproducing buffer memory 19, while the digital moving image data is read from the reproducing buffer memory 19 at a speed of 4 Mbps. Since it is output to the MPEG decoder 20, the digital moving image data remaining in the buffer memory 19 is (12 Mbps-4 Mbps) * 0.75 seconds = 6 Mbits.
[0040]
Further, since recording on the optical disk 18 is not performed for 0.75 seconds, 4 Mbps * 0.75 seconds = 3 Mbits of digital moving image data is written into the recording buffer memory 14 from the digital image input unit 13.
[0041]
(2) Access is performed by moving the optical head 17 from the reproduction area 32 to the recording area 31 in the next 0.25 seconds. During this access, neither recording nor reproduction is performed on the optical disk 18, so the digital moving image data in the recording buffer memory 14 is 3 Mbit + 4 Mbps * 0.25 seconds = 4 Mbit, and the digital moving image in the reproduction buffer memory 19 is obtained. The image data is 6M bits-4 Mbps * 0.25 seconds = 5M bits.
[0042]
(3) For the next 0.5 seconds, digital moving image data is written from the digital image input unit 13 to the recording buffer memory 14 at a speed of 4 Mbps, while the digital moving image is written from the recording buffer memory 14 at a speed of 12 Mbps. Data is read and recorded on the optical disc 18. After the elapse of 0.5 seconds, the digital moving image data in the recording buffer memory 14 is 4 Mbit- (12 Mbps-4 Mbps) * 0.5 seconds = 0.
[0043]
Since reproduction from the optical disk 18 is not performed for 0.5 seconds, the digital moving image data stored in the reproduction buffer memory 19 is sent to the MPEG decoder 20 at a speed of 4 Mbps, and the digital video data in the buffer memory 19 is transmitted. The moving image data is 5M bits-4 Mbps * 0.5 seconds = 3M bits.
[0044]
(4) In the subsequent 0.25 seconds, the optical head 17 is moved from the recording area 31 to the reproduction area 32 for access. During this access, neither recording nor reproduction is performed on the optical disk 18, so the digital moving image data in the recording buffer memory 14 is 4 Mbps * 0.25 seconds = 1 Mbit, and the digital moving image data in the reproduction buffer memory 19 is obtained. Is 3 Mbps -2 Mbps * 0.25 seconds = 2M bits.
[0045]
(5) For the next 0.5 seconds, the digital moving image data is reproduced from the optical disk 18 following the previous reproduction, and written into the reproduction buffer memory 19 at a speed of 12 Mbps.
[0046]
Further, since the digital moving image data is read from the reproduction buffer memory 19 at a speed of 4 Mbps for 0.5 seconds and output to the MPEG decoder 20, the digital moving image data remaining in the buffer memory 19 is 2M bits. + (12 Mbps-4 Mbps) * 0.5 seconds = 6 Mbits.
[0047]
On the other hand, since recording on the optical disk 18 is not performed for 0.5 seconds, digital moving image data of 1 Mbit + 4 Mbps * 0.5 seconds = 3 Mbit is written from the digital image input unit 13 to the recording buffer memory 19. It is.
[0048]
(6) For the next 0.25 seconds, access is performed by moving the optical head 17 from the reproduction area 32 to the recording area 31 again. During this access, neither recording nor reproduction is performed on the optical disk 18, so the digital moving image data in the recording buffer memory 14 is 3 Mbit + 4 Mbps * 0.25 seconds = 4 Mbit, and the digital moving image in the reproduction buffer memory 19 is obtained. The image data is 6M bits-4 Mbps * 0.25 seconds = 5M bits.
[0049]
(7) For the next 0.5 seconds, digital moving image data is written from the digital image input unit 13 to the recording buffer memory 14 at a speed of 4 Mbps, while the digital moving image is written from the recording buffer memory 14 at a speed of 12 Mbps. Data is read and recorded on the optical disc 18. After the elapse of 0.5 seconds, the digital moving image data in the recording buffer memory is 4 Mbit- (12 Mbps-4 Mbps) * 0.5 seconds = 0.
[0050]
Further, since the reproduction from the optical disk 18 is not performed for 0.5 seconds, the digital moving image data stored in the reproduction buffer memory 19 is read out at a speed of 4 Mbps and sent to the MPEG decoder 20, and the buffer memory The digital moving image data in 19 is 5 M bits-4 Mbps * 0.5 seconds = 3 M bits.
[0051]
Thereafter, access of the optical head 17 from the recording area 31 to the reproduction area 32 (0.25 seconds) → reproduction of digital moving image data from the optical disk 18 (0.5 seconds) → light from the reproduction area 32 to the recording area 31 Access of the head 17 (0.25 seconds) → recording of digital moving image data on the optical disk 38 (0.5 seconds) is repeated.
[0052]
As can be seen from FIG. 4, the digital moving image data in the recording buffer memory 14 does not exceed the buffer memory capacity, and the digital moving image data in the reproduction buffer memory 19 is also 0 except when reproduction is started. Don't be. This indicates that recording and reproduction of digital moving image data are performed simultaneously.
[0053]
(Recording / playback speed of optical disc)
Next, the recording / reproducing speed of the optical disk 18 necessary for the present invention will be described.
The average bit rate of the digital moving image data in the present embodiment is A = 4 bps, and the optical disk 18 is 1 in the maximum access time of the optical disk 18 (the seek time required for the optical head 17 to move from the innermost circumference to the outermost circumference). The time obtained by adding the rotation time) is S = 0.25 seconds.
[0054]
In order to simultaneously record digital moving image data on the optical disc 18 and reproduce digital moving image data already recorded on the optical disc 18 with one optical head 17, recording and reproduction are performed alternately in a time-sharing manner. In addition, it is necessary to perform at a speed not lower than the average bit rate of the digital moving image data to be reproduced. That is, since digital moving image data is recorded on the optical disk 18 for a certain time and digital moving image data is reproduced from the optical disk 18 for a certain time, the digital moving image data recorded and reproduced is processed at an average bit rate of 4 Mbps. In order to do this, the recording / reproducing speed of the optical disk 18 must be at least 2 * 4 Mbps = 8 Mbps or more.
[0055]
Further, since the number of the optical head 17 is one and the positions of the recording area 31 and the reproduction area 32 on the optical disk 18 are not always the same, an access time between the areas 31 and 32 is required for switching between recording and reproduction. For example, when recording and playback are repeated by repeating the time-sharing procedure consisting of “recording” → “access” → “playback” → “access”, two accesses occur in one time-sharing procedure. Therefore, at the time of recording, the digital moving image data input between the reproduction time and the two accesses must be recorded within an average recording time of 0.5 seconds on the optical disk 18 of the digital moving image data.
[0056]
From FIG. 4, the average recording time per time is 0.5 seconds, and the reproduction time is 0.75 seconds only at the beginning and 0.5 seconds from the next time. Is 0.5 seconds and the access time is 0.25 seconds. Therefore, the recording speed of the optical disk 18 may be (0.5 + 0.5 + 2 * 0.25) * 4 / 0.5 bps = 12 Mbps or more. Similarly, the playback speed of the optical disk 18 may be (0.5 + 0.5 + 2 * 0.25) * 4/4 Mbps = 12 Mbps or more. Here, 4 Mbps is an increase in recording / reproducing speed required for two accesses. The recording / reproducing speed of the optical disk 18 in this embodiment is 12 Mbps, which satisfies this condition.
[0057]
(About buffer memory capacity)
Next, the buffer memory capacity required in the present invention will be described.
First, the capacity required for the recording buffer memory 14 is the sum of the access time (the reciprocation time of the optical head 17 between the recording area 31 and the reproduction area 32) and the average reproduction time T2 from the optical disk 18. Multiplyed by the average transfer rate of the image data, (2S + T2) * A bit = more. In the case of the present embodiment, the reproduction time is 0.75 seconds only from the beginning in FIG. 4 and is 0.5 seconds from the next. The capacity is (2 * 0.25 + 0.5) * 4 = 4 Mbits or more.
[0058]
Similarly, the capacity required for the reproduction buffer memory 19 is digitally equal to the sum of twice the access time (the reciprocation time of the optical head 17 between the reproduction area 32 and the recording area 31) and the average recording time T1 on the optical disk 18. Multiplying the average transfer rate of moving image data, it is (2S + T1) * A bits or more. In this embodiment, since the average recording time is 0.5 seconds as shown in FIG. 4, the capacity required for the reproduction buffer memory 19 is (2 * 0.25 + 0.5) * 4 = 4 Mbits or more.
[0059]
Therefore, the necessary buffer memory capacity is 8 Mbits or more in total for the recording buffer memory 14 and the reproduction buffer memory 19. In the present embodiment, both the recording buffer memory 14 and the reproduction buffer memory 19 are 6 Mbits, and the total is 12 Mbits, so this condition is satisfied.
[0060]
However, it can be seen from FIG. 4 that the recording buffer memory 14 uses only 4 Mbits at the maximum, so that its capacity may be 4 Mbits. The reproduction buffer memory 19 also has a change of 6M bits only at the time of the first reproduction, but after that, there is only a maximum change of 4M bits. Therefore, the capacities of the buffer memories 14 and 19 can be 4 Mbits depending on the memory control.
[0061]
When recording the digital moving image data while satisfying the recording / reproducing speed and buffer memory capacity conditions of the optical disc 18, the optical head 17 is accessed from the recording region 31 to the reproducing region 32, and the digital moving image data is recorded. Is recorded on the recording buffer memory 14 while the optical head 17 is accessed from the reproduction area 32 to the radial position where the recording area 31 continues to be recorded. The digital moving image data is read from the recording buffer memory 14 and written to the optical disk 18 for the next average of 0.5 seconds.
[0062]
On the other hand, at the time of reproduction of digital moving image data, reproduction is performed from the optical disk 18 for an average of 0.5 seconds and stored in the reproduction buffer memory 19, and then the optical head 17 is accessed from the reproduction area 32 to the recording area 31, Digital moving image data is recorded on the optical disk 18 for an average of 0.5 seconds, and the optical head 17 is accessed from the recording area 31 to the radial position where recording is continued in the reproduction area 32. The digital moving image data to be reproduced during the access time of two times and during recording on the optical disk 18 is reproduced by reading out the digital moving image data stored in the reproduction buffer memory 14.
[0063]
In the above recording and reproduction, recording and reproduction are performed in units of sectors in order to ensure the recording position on the optical disk, and data is read and written together with the sector address at the time of recording and reproduction.
[0064]
By repeating such an operation, the digital moving image data input from the outside is continuously recorded on the optical disc 18 without being lost, and the digital moving image data reproduced from the optical disc 18 is continuously lost without being lost. Since it is reproduced, digital moving image data can be recorded and reproduced simultaneously by one optical head 17.
[0065]
(Retry when seek fails)
Next, the retry when seek fails will be described. The movement from one recording area on the optical disk 18 to another recording area, that is, seek, may fail because the address information recorded on the optical disk 18 can be read. In such a case, the video disk apparatus according to the present embodiment performs seek again with the number of retrials included in advance as a limit. Considering the retry at the time of seek failure, the bit rate of the digital moving image data is set to A (bps), and the maximum access time for the optical disc 18 (the optical head 17 seeks from the innermost circumference to the outermost circumference of the optical disc 18). The time obtained by adding the time required for one rotation of the optical disk 18 to the time) is S seconds, and the maximum number of retries at the time of seek failure is N. The seek time is the maximum (N + 1) * S seconds. The reproduction speed and the capacity of the buffer memories 14 and 19 may be estimated.
[0066]
Accordingly, the recording speed of the digital moving image data on the optical disk 18 is (T1 + T2 + 2 * S * (N + 1)) * A / T1 (bps) or more, and the reproduction speed of the digital moving image data from the optical disk 18 is (T1 + T2 + 2 * S). * (N + 1)) * A / T2 (bps) or more, and if the total storage capacity of the buffer memories 14 and 19 is (4 * S * (N + 1) + T1 + T2) * A bits or more, the seek of the optical head 17 Even if there is a retry, the digital moving image data to be recorded can be stored in the recording buffer memory 14, and the digital moving image data for the re-seek time can be stored in the reproduction buffer memory 19 in advance. It is obvious that digital video can be reproduced without interruption.
[0067]
(Display example)
FIG. 5 shows a display example on the monitor 21 in the present embodiment. The screen 40 of the monitor 21 is divided into two, and the recorded image 41 and the reproduced image 42 are divided and displayed simultaneously. By doing this, it is possible to check the recorded image 41 and confirm that the recording is normally performed, or confirm what image is currently recorded, and reproduce the already recorded image. The image 42 can be reproduced.
[0068]
In the present embodiment, the recording image data is input from the digital image input unit 13 to the monitor 21 via the MPEG decoder 22, but when the input moving image data is analog, the MPEG encoder 12, digital The image may be input directly to the monitor 21 without going through the image input unit 13 and the MPEG decoder 22.
[0069]
(Change bit rate during playback)
In the above-described embodiment, for example, when a digital moving image is recorded by reserved recording or the like, the already recorded digital moving image is reproduced while continuing recording from the recording start position (recording start time). It is possible. Therefore, for example, program A from 7 pm to 8 pm is reserved for recording, and even when the user returns home at 7:10 pm, the user can reproduce and watch from the beginning of program A ( Time shift function).
[0070]
In this case, since the average bit rate of moving image data is the same for both recording and reproduction, the time axis between the recording position and the reproduction position always has a difference of 10 minutes in the above example. Therefore, the user finishes watching program A at 8:10 pm.
[0071]
FIG. 7A illustrates this. That is, assuming that the bit rate is 4 Mbps for both recording and reproduction, the recording side has already recorded a moving image for 10 minutes on the moving image time axis when the reproduction starts with a delay of 10 minutes from the recording. It can be seen from the figure that the difference between the time axis of recording and playback is always 10 minutes. For example, at 60 minutes after the start of recording, the playback side plays back a 50 minute moving image on the moving image time axis, and it can be seen that there is a time difference of 10 minutes between the reproduced moving image and the recorded moving image.
[0072]
By the way, the case where the user plays the program A with a delay of 10 minutes, and when the playback ends, the case where the recording and the playback end simultaneously, that is, the case where the playback catches up with the recording will be described.
[0073]
In this case, the average bit rate of the digital moving image to be reproduced is set higher than the recording. For example, if the average bit rate of digital moving images to be recorded is 4 Mbps, moving image data to be recorded in 60 minutes can be reproduced in 50 minutes, so the required bit rate during reproduction is 60 seconds * 10 * 4 Mbps / 50 seconds. * 10 = 4.8 Mbps.
[0074]
Therefore, when the average bit rate of the digital moving image to be recorded is 4 Mbps, the average bit rate at the time of reproducing the digital moving image is set to 4.8 Mbps. Re If it is played, the playback position on the disc coincides with the recording position at 8 pm. That is, the position (time axis) of the currently recorded moving image and the currently reproduced digital moving image coincide. In other words, playback catches up with recording. FIG. 7B shows this state. That is, it is assumed that the average bit rate of recording is 4 Mbps and the average bit rate of reproduction is 4.8 Mbps. Under this condition, when the reproduction starts 10 minutes later than the recording, the recording side has already recorded the moving image of 10 minutes on the moving image time axis. Since the playback bit rate is higher than that of recording, the playback side becomes 60 minutes on the moving image time axis, and it can be seen that both times coincide.
[0075]
After the coincidence, if the average bit rate of the digital moving image to be reproduced remains at 4.8 Mbps, the non-recorded portion is reproduced. Therefore, the reproduction is stopped and the transmitted digital image is viewed in real time or recorded. The recorded digital moving image is reproduced at the bit rate of the digital moving image.
[0076]
The recording / reproducing speed on the disk for simultaneous recording / reproducing and the buffer capacity can be easily obtained by calculating the bit rate of the digital moving image of the previous embodiment as different between recording and reproducing. The configuration of this apparatus is the same as in FIG.
[0077]
The average bit rate Abit / s of the digital moving image to be recorded and the average bit rate Bbit / s of the digital moving image to be played back, and the maximum access time of the video disk (the disk at the time when the recording / reproducing head seeks from the inner circumference to the outermost circumference) S) is defined as the time obtained by adding the time required for one rotation. In order to simultaneously record a digital digital moving image and reproduce a digital moving image that has already been recorded on a disc with one recording / reproducing head, recording and reproduction on the disc are performed in a time-division manner. It must be done at a speed that does not fall below the average bit rate. Since a moving image is recorded on a disc for a certain time and a moving image is reproduced from the disc for a certain time, a recording / reproducing speed of (A + B) bit / s or more is required to process two moving images. Become. Furthermore, since there is one recording / reproducing head and the positions of the recording area and the reproducing area on the disc are not always the same, an access time between the areas occurs in switching between recording and reproducing. For example, a time division procedure consisting of “T1 second recording” → “S second access from recording area to reproduction area” → “T2 second reproduction” → “S second access from reproduction area to recording area” is repeated. When recording and playback are performed, two accesses occur in one time division procedure.
[0078]
Accordingly, during recording, since the digital moving image data input for (T1 + T2 + 2S) seconds is recorded during T1 seconds, the recording speed of the recording medium is (T1 + T2 + 2S) * A / T1 (bps) or more. Become. Similarly, the reproduction speed of the recording medium is (T1 + T2 + 2s) * B / T2 (bps) or more.
[0079]
On the other hand, regarding the required buffer memory capacity, the capacity of the recording buffer memory is the sum of twice the access time (the reciprocation time of the optical head movement between the recording area and the reproduction area) and the average reproduction time T2 from the disk. Multiplying the average transfer speed of moving images, (2S + T2) * Abit or more is required. Similarly, the buffer size on the playback side is the sum of the access time (reciprocation time of the optical head movement in the playback area and recording area) and the average recording time T1 from the disk multiplied by the average moving image transfer rate. (2S + T1) * Bbit or more is required. Therefore, the total is (2S + T2) * Abit + (2S + T1) * Bbit or more.
[0080]
If the recording / playback speed and buffer capacity of these discs are satisfied, on the digital moving image recording side, the optical head accesses the playback region from the recording region in S seconds, and the moving image is reproduced from the disc for an average of T2 seconds, Subsequently, the digital moving image to be recorded while the optical head accesses the radial position from the reproduction area to the recording area in S seconds is stored in the buffer memory, and the digital moving image is read out from the buffer memory in the next average T1 seconds. Written to optical disc. On the digital video playback side, the optical head plays an average T2 second video from the disk, and this playback video is recorded in the buffer memory. Next, the optical head accesses the recording area from the playback area in S seconds. An image is recorded on the disk for an average of T1 seconds, and then the shining head accesses the radial position from the recording area to the reproduction area in S seconds. The digital moving image to be reproduced during the two access times and recording on the disc is reproduced from the buffer memory. The digital moving images distributed by repeating these operations are continuously recorded on the optical disc without being lost, and the digital moving images reproduced from the disc are also continuously reproduced without being lost. Furthermore, the conditions for recording, reproducing speed, and buffer capacity of the recording medium in the case of retrying at the maximum N times when seek fails can be calculated by converting the maximum access time S as (N + 1) S seconds. T1 + T2 + 2 * S * (N + 1)) * A / T1 bps or higher, the medium playback speed is (T1 + T2 + 2 * S * (N + 1)) * B / T2 bps or higher, and the total recording capacity of the recording buffer memory and the playback buffer memory is ( 2 * S * (N + 1) 10 2) * A hit ten (2 * S * (N + 1) ten T1) * B bits or more.
[0081]
In the above embodiment, the present invention has been described by taking a video disk device as an example. However, the present invention can be applied to an audio device. In this case, as shown in FIG. 6, at the time of recording, an audio signal is output. For example, the audio signal from the receiver 51 is converted into a digital signal by the A / D converter 52 and stored in the buffer memory 53. The digital audio signal read from the buffer memory 53 is input to the modem 55 via the switch 54. The modulation / demodulation device 55 modulates the signal into a signal suitable for recording, and inputs the signal to the recording / reproducing device 56. The recording / reproducing device records the signal on a recording medium.
[0082]
At the time of reproduction, the reproduced audio signal reproduced by the recording / reproducing device 56 is stored in the buffer memory 57 via the modem 55 and the switch 54. The reproduced audio signal read from the buffer memory 57 is converted into an analog audio signal by the D / A converter 58 and output to the speaker 59.
[0083]
Even while the audio signal from the buffer memory 53 is recorded by the recording / playback device 56, the audio signal read from the playback-side buffer memory 57 is played back by the speaker 59 even in the above-described audio device. I can listen to music.
[0084]
In the present embodiment, the case where the recording medium is an optical disk has been described. However, the present invention can be used in principle as long as data can be recorded / reproduced by a recording / reproducing head using a disk-shaped recording medium. (Hard disk device) or floppy disk device may be used. Further, the recording buffer A and the reproduction buffer B can be constituted by a one-chip semiconductor memory.
[0085]
【The invention's effect】
As described above, according to the present invention, a single recording / reproducing head is used to repeatedly record digital moving image data on a disk-shaped recording medium and to reproduce digital moving image data from the disk alternately. It is possible to reproduce a digital moving image already recorded during recording of moving image data.
[0086]
Specifically, in the present invention, the bit obtained by adding the access time for the recording / reproducing head to reciprocate between the recording area and the reproducing area to the sum of the bit rate of the digital moving image data for recording / reproducing speed of the recording medium and the reproducing bit rate. The recording rate is higher than the rate and the recording side stores the digital moving image data that is input during the reproduction of the digital moving image data from the recording medium and the time when the recording / reproducing head reciprocally accesses the recording area and the reproducing area. Reproduction buffer that can store digital moving image data having a capacity to be sent to the digital moving image data expander during recording of the digital moving image data and during a reciprocating access time between the reproduction area and the recording area. By providing a memory, recording media can be recorded without losing input digital video data. It can be continuously recorded and also continuously reproduced without missing digital video data reproduced from the recording medium.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a video disk device according to an embodiment of the present invention.
FIG. 2 is a view showing a recording area and a reproduction area on the optical disc in the embodiment.
FIG. 3 is a flowchart showing a processing procedure for recording / reproducing digital moving image data in the embodiment;
FIG. 4 is a view showing a change in the amount of digital moving image data in the buffer memory in the embodiment.
FIG. 5 is a view showing a display example in the embodiment.
FIG. 6 is a block diagram of a disk device according to another embodiment.
FIG. 7 is a diagram for explaining a time relationship between moving image recording and reproduction.
[Explanation of symbols]
11. Analog image input unit
12. MPEG encoder
13. Digital image input unit
14 ... Buffer memory for recording
15 ... Switching unit
16 Modem / Demodulator
17: Optical head
18 ... Optical head
19 ... Playback buffer memory
20 ... MPEG decoder
21 ... Monitor
22. MPEG decoder
23 ... Controller
24 ... Driver

Claims (9)

In a disk apparatus for recording and reproducing digital continuous data by a recording / reproducing head using a disk-shaped recording medium,
A buffer memory for recording to temporarily store the input digital continuous data;
A buffer memory for reproduction for temporarily storing digital continuous data reproduced from the recording medium;
Control means for performing control to alternately perform time-division recording of digital continuous data in a predetermined recording area on the recording medium and reproduction of digital continuous data from the predetermined reproduction area on the recording medium,
The control means includes
When recording to the recording area and during reproduction from the reproduction area, and while the recording / reproducing head is accessing between the recording area and the reproducing area on the recording medium, the input digital continuous data is used for the recording. Write to buffer memory,
When recording in the recording area, the digital continuous data stored in the recording buffer memory is read out at a recording speed of at least twice the average bit rate of the input digital continuous data and recorded in the recording area,
At the time of reproduction from the reproduction area, the digital continuous data recorded in the reproduction area is reproduced at a reproduction speed at least twice the average bit rate and written to the reproduction buffer memory,
When recording in the recording area and reproduction from the reproduction area are alternately performed in a time division manner, the average recording time per time is T1 seconds, the average reproduction time is T2 seconds, and the maximum access time of the recording medium (the recording medium) The average bit of the input digital moving image data is S seconds obtained by adding the time required for one rotation of the recording medium to the seek time required for the reproducing head to move from the innermost circumference to the outermost circumference of the recording medium. When the rate is A (bps), the recording speed is set to (T1 + T2 + 2S) * A / T1 bps or higher, the playback speed is set to (T1 + T2 + 2S) * A / T2 bps or higher,
Digital recording stored in the reproduction buffer memory during recording in the recording area and during reproduction from the reproduction area and when the recording / reproduction head is accessing between the recording area and the reproduction area on the recording medium A disk device that performs control to read out data at a predetermined bit rate and output the data to a display device. When recording in the recording area and reproduction from the reproduction area are alternately performed in a time division manner, the average recording time per time is T1 seconds, the average reproduction time is T2 seconds, and the maximum access time of the recording medium (the recording medium) The seek time required for the reproducing head to move from the innermost circumference to the outermost circumference of the recording medium plus the time for which the recording medium makes one revolution) is S seconds, and the average bit rate of the input digital continuous data Is A (bps),
2. The disk device according to claim 1, wherein the total storage capacity of the recording buffer memory and the reproducing buffer memory is set to (4 * S + T1 + T2) * A bits or more. In a disk apparatus for recording and reproducing digital continuous data by a recording / reproducing head using a disk-shaped recording medium,
A buffer memory for recording to temporarily store the input digital continuous data;
A buffer memory for reproduction for temporarily storing digital continuous data reproduced from the recording medium;
Control means for performing control to alternately perform time-division recording of digital continuous data in a predetermined recording area on the recording medium and reproduction of digital continuous data from the predetermined reproduction area on the recording medium,
The control means includes
When recording to the recording area and during reproduction from the reproduction area, and while the recording / reproducing head is accessing between the recording area and the reproducing area on the recording medium, the input digital continuous data is used for the recording. Write to buffer memory,
When recording in the recording area, the digital continuous data stored in the recording buffer memory is read out at a recording speed of at least twice the average bit rate of the input digital continuous data and recorded in the recording area,
At the time of reproduction from the reproduction area, the digital continuous data recorded in the reproduction area is reproduced at a reproduction speed at least twice the average bit rate and written to the reproduction buffer memory,
When recording in the recording area and reproduction from the reproduction area are alternately performed in a time division manner, the average recording time per time is T1 seconds, the average reproduction time is T2 seconds, and the maximum access time to the recording medium (the recording The seek time required for the reproducing head to move from the innermost circumference to the outermost circumference of the recording medium plus the time for which the recording medium makes one revolution) is S seconds, and the average bit rate of the input digital continuous data Is A (bps), and the maximum number of retries when seek fails is N,
The recording speed of digital continuous data on the recording medium is set to (T1 + T2 + 2 * S * (N + 1)) * A / T1 (bps) or higher, and the playback speed of digital continuous data from the recording medium is set to (T1 + T2 + 2 * S * (N + 1)) * A / T2 (bps) or higher ,
Digital recording stored in the reproduction buffer memory during recording in the recording area and during reproduction from the reproduction area and when the recording / reproduction head is accessing between the recording area and the reproduction area on the recording medium A disk device that performs control to read out data at a predetermined bit rate and output the data to a display device. When recording in the recording area and reproduction from the reproduction area are alternately performed in a time division manner, the average recording time per time is T1 seconds, the average reproduction time is T2 seconds, and the maximum access time to the recording medium (the recording The seek time required for the reproducing head to move from the innermost circumference to the outermost circumference of the recording medium plus the time for which the recording medium makes one revolution) is S seconds, and the average bit rate of the input digital continuous data Is A (bps), and the maximum number of retries when seek fails is N,
4. The video disk device according to claim 3 , wherein the total storage capacity of the recording buffer memory and the reproduction buffer memory is set to (4 * S * (N + 1) + T1 + T2) * A bits or more. In a disk apparatus for recording and reproducing digital continuous data by a recording / reproducing head using a disk-shaped recording medium,
A buffer memory for recording to temporarily store the input digital continuous data;
A buffer memory for reproduction for temporarily storing digital continuous data reproduced from the recording medium;
Control means for performing control to alternately perform time-division recording of digital continuous data in a predetermined recording area on the recording medium and reproduction of digital continuous data from the predetermined reproduction area on the recording medium,
The control means includes
When recording to the recording area and during reproduction from the reproduction area, and while the recording / reproducing head is accessing between the recording area and the reproducing area on the recording medium, the input digital continuous data is used for the recording. Write to buffer memory,
When recording in the recording area, the digital continuous data stored in the recording buffer memory is read out at a recording speed of at least twice the average bit rate of the input digital continuous data and recorded in the recording area,
Wherein during reproduction from the reproduction region, writes the digital continuous data recorded in the reproduction region in the reproducing buffer memory and reproduced twice or more the playback speed of the average bit rate,
When the recording of the digital moving image data as the continuous data is started before the reproduction, the control means reproduces at an average bit rate higher than the average bit rate of the input moving image data, and reproduces the reproduction position on the disc. Is the same as the recording position on the disc, or when the input moving image and the position (time axis) of the reproduced moving image are the same, the average bit rate of the moving image data to be reproduced is the average of the inputted moving image data Set to the same bit rate or stop playback,
Digital recording stored in the reproduction buffer memory during recording in the recording area and during reproduction from the reproduction area and when the recording / reproduction head is accessing between the recording area and the reproduction area on the recording medium A disk device that performs control to read out data at a predetermined bit rate and output the data to a display device.   The control means has an average recording time of T1 second, an average recording time of T2 seconds, and an average recording time of T2 seconds when recording in the recording area and reproduction from the reproduction area are alternately performed in a time division manner. The access time (seek time required for the recording / reproducing head to move from the innermost periphery to the outermost periphery of the recording medium plus the time for one rotation of the recording medium) is S seconds, and the input digital moving image When the average bit rate of data is A (bps) and the average bit rate of moving image data to be reproduced is B (bps), the recording speed is set to (T1 + T2 + 2 * S) * A / T1 bps or more, 6. The disk device according to claim 5, wherein the reproduction speed is set to (T1 + T2 + 2 * S) * B / T2 bps or more.   The control means has an average recording time of T1 seconds, an average recording time of T2 seconds, and a critical access time of the recording medium when alternately performing time-division recording to the recording area and reproduction from the reproduction area. (The time obtained by adding the time for which the recording / reproducing head makes one rotation of the recording medium to the seek time required for the recording / reproducing head to move from the innermost circumference to the outermost circumference of the recording medium) is input for S seconds. When the average bit rate of digital moving image data is A (bps) and the bit rate of moving image data to be reproduced is B (bps), the total recording / reproducing capacity of the buffer memory is (2 * S + T2) * A 7. The disk device according to claim 5, wherein the bit device is set to bit + (2 * S + T1) * B bits or more.   The control means has an average recording time of T1 seconds, an average recording time of T2 seconds, and a maximum access of the recording medium when recording in the recording area and reproduction from the reproduction area are alternately performed in a time division manner. The time (the time required for the recording / reproducing head to make one rotation of the recording medium to the seek time required for the recording / reproducing head to move from the innermost circumference to the outermost circumference of the recording medium) is input for S seconds. When the average bit rate of digital moving image data is A (bps), the bit rate of moving image data to be reproduced is B (bps), and the maximum number of retries upon seek failure is N, the recording speed is 6. The data processor according to claim 5, wherein (T1 + T2 + 2 * S * (N + 1)) * A / T1 bps or higher is set, and the playback speed is set to (T1 + T2 + 2 * S * (N + 1)) * B / T2 bps or higher. Disk apparatus. The control means has an average recording time of T1 seconds, an average recording time of T2 seconds, and a maximum access of the recording medium when recording in the recording area and reproduction from the reproduction area are alternately performed in a time division manner. The time (the time required for the recording / reproducing head to make one rotation of the recording medium to the seek time required for the recording / reproducing head to move from the innermost circumference to the outermost circumference of the recording medium) is input for S seconds. When the average bit rate of digital moving image data is A (bps) and the bit rate of reproduced moving image data is B (bps), the total recording / reproducing capacity of the buffer memory is (2 * S * ( 7. The disk device according to claim 5, wherein the N + 1) + T2) * A bit + (2 * S * (N + 1) + T1) * B bit or more is set.

Images