JP3248366B2 - Data reproducing method and data reproducing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk data reproducing method and a disk data reproducing apparatus suitable for reproducing data such as video or audio recorded on an optical disk, a magneto-optical disk or the like. The present invention relates to a data reproducing method and a data reproducing apparatus capable of quickly performing special reproduction such as reverse reproduction.

[0002]

2. Description of the Related Art MPEG (Motion Pic) is used as a method for compressing and encoding digital image signals recorded on a conventional digital video disk (hereinafter referred to as DVD).
ture coding Experts Group) method has been proposed,
An example of an MPEG encoder will be described with reference to FIG. The MPEG encoder is an encoder configured to perform compression by predictive coding. A digitalized image input signal is converted into a block by the motion detecting circuit 101 for each block (MB) of a minimum unit of motion compensation prediction. Then, a motion vector for motion compensation prediction is detected for each block.

[0003] This block is predictively coded in the following predictive coder. (1) The image input signal is directly subjected to DCT.
(Discrete Cosine Transform: Intra block), (2) Forward block predicted only from the forward direction, (3) Backward block predicted only from the backward direction, and (4) Bipredictive block predicted from both directions. Are classified into two types.

That is, the DCT 103 performs DCT, which is a kind of Fourier transform, and the resulting DCT coefficient is quantized by the quantization circuit 104. Further, after the quantization is performed, the variable-length encoding means 109 performs variable-length encoding by assigning codes of different lengths according to the occurrence probability. Further, the quantized signal is subjected to inverse quantization in an inverse quantization circuit 105,
Furthermore, the original image signal is reproduced by performing the inverse DCT in the inverse DCT 106 and adding the output from the frame memory predictor 108. The reproduced image signal is supplied to the subtractor 102 as a prediction signal.

[0005] The prediction coded signal output from the variable length coding means 109 is multiplexed with prediction mode information and motion vector information in a multiplexing means 110, and these multiplexed data are transmitted at an irregular rate. , Is temporarily stored in the buffer 111 and output so that the coding rate becomes constant. In order to keep the average of the coding rates constant, the code amount control may be performed by changing the quantization scale factor q of the quantization means 104 according to the code amount stored in the buffer 111. .

FIG. 10A shows the structure of inter-frame prediction compressed and encoded by the MPEG method in this manner. In this figure, one GOP (Group Of Picture) is composed of, for example, nine frames, one frame of I picture, two frames of P picture, and six frames of B picture.
One GOP is composed of pictures. The GOP is a unit of encoding obtained by dividing one sequence of a moving image. The I picture is a coded image that has been predictively coded within a frame, and the P picture is an interframe predictive coding that predicts with reference to a previously coded temporally previous frame (I picture or P picture). B picture is an encoded image that has been subjected to inter-frame predictive encoding with reference to two temporally preceding and succeeding frames.

That is, as shown by the arrow, the I picture I ₀ is predictively encoded only within the frame, and the P picture P ₀ is inter-frame predictively encoded with reference to the I picture I _0. , P picture P ₁ are inter-frame predictive coded with reference to P picture P ₀ . Further, B pictures B ₀ and B ₁ are inter-frame predictive coded with reference to two I pictures I ₀ and P pictures P _0, and B pictures B ₂ and B ₃ are P pictures P ₀ and P pictures It is inter-frame predictive coded with reference to two pictures P ₁ . Thereafter, the subsequent pictures are created by predictive encoding in the same manner.

[0008] By the way, in order to decode the picture thus predictively coded, since the I picture is predicted and coded in the frame, it can be decoded only by the I picture. Are predicted and coded with reference to the temporally preceding I picture or P picture, the temporally preceding I or P picture is required at the time of decoding, and the B picture is temporally preceding or succeeding I picture. Alternatively, since the predictive coding is performed with reference to the P picture, the I picture or the P picture which is temporally preceding and succeeding is required at the time of decoding. Therefore,
The pictures are exchanged as shown in FIG. 10B so that the pictures required for decoding can be decoded first.

[0009] As shown in this replacement FIG, B-pictures B _-1, B _-2 since it requires the I-picture I ₀ is the time of decoding, B-pictures B _-1, I picture I ₀ from B _-2 prior Since the B pictures B ₀ and B ₁ require the I picture I ₀ and the P picture P ₀ at the time of decoding, the B pictures B ₀ and B ₁ are similarly set so that the P picture P ₀ precedes the B pictures B ₀ and B _{1. 2} and B ₃ are P pictures P
₀ and P picture P ₁ , so B picture B
_2, so that the P-picture P ₁ from B ₃ is preceded, for B-pictures B _4, B ₅ is in need of P-pictures P ₁ and I-picture I ₁ when decoding, the B picture B _4, B ₅ than I
Picture I ₁ is replaced as the preceding.

[0010] The I picture, the P picture and the B picture are recorded on the DVD in the order shown in FIG. 10 (b). The amount is not constant for each picture, but becomes a different code amount depending on the complexity and flatness of the image. Therefore, in order to easily handle data, when these pictures are recorded on a DVD, data is recorded using sectors defined by a fixed code amount. FIG. 11 shows an aspect of recording by this sector.
For example, the I picture I ₀ is recorded in the sector m, the sector (m + 1), and a part of the sector (m + 2), and the B picture B ₋₂ is recorded in the remaining area of the sector (m + 2) and the sector (m + 3).
Will be recorded. Hereinafter, each picture is sequentially recorded in a sector. In this example, one GOP is composed of a sector m to a sector (m + 1).
It is recorded in sector 3). However, a GOP is not always recorded with such a number of sectors, and the code amount varies depending on the complexity and flatness of an image. Therefore, the number of sectors for recording one GOP is generally different.

The data read out from the DVD in units of sectors is temporarily stored in a storage means (ring buffer), which is virtually represented as a ring buffer and is called a ring buffer. The operation of the write pointer will be described with reference to FIG.
In FIG. 12A, the read pointer RP is located at the address position a1 of the ring buffer,
The write pointer WP is located at the address position of b1 slightly before a1. The ring buffer reads data in sector units while moving the read pointer in the clockwise direction shown in the figure, and supplies the data to the decoder.

Further, by controlling the write pointer WP to be located slightly before a1 in time, the unread area (URD) is made as large as possible so that there is no shortage of data to be reproduced. Therefore, the read area (ARD) is a small area between a1 and b1, but the area may be controlled to be zero. Then, the state where the read pointer RP is advanced and data is read from the ring buffer is the state shown in FIG.
It proceeds from 1 to a2. Therefore, the area of the URD becomes smaller as the address position advances, while the area of the ARD becomes larger accordingly.

Therefore, as shown in FIG. 1C, data is written to the ring buffer while the write pointer WP is advanced clockwise so as to enlarge the unread area URD. In this case, the data is data newly read from the disk. As a result, the address position of the write pointer advances from b1 to b2, and the ARD area is reduced accordingly, while the URD area is increased accordingly. By performing such control, a large URD area is always secured in the ring buffer.

[0014]

SUMMARY OF THE INVENTION However, DVD
When playing back video data by reading data in units of sectors recorded in the ring buffer from the ring buffer and trying to perform special playback such as reverse playback, for example, at the moment of switching to reverse playback, Has almost no data in the reverse direction to be reproduced (that is, ARD data), so it is necessary to access the DVD and wait for the supply of data to be read, and it is not possible to smoothly switch between forward and reverse reproduction. was there. That is,
In order to decode the video signal displayed on the display unit during the reverse reproduction, the current GOP is followed by the one-time GO
It is necessary to read the data of P by accessing the DVD using a pickup, but this readout is mechanical and time-consuming, and it takes time to decode the pictures constituting the read-out GOP to obtain a video signal. This is necessary.

Here, the reason why decoding takes time will be described. The GOP immediately before the current GOP is shown in FIG.
Assuming that the picture is composed of I picture I ₀ to B picture B ₅ shown in (a), in order to perform reverse playback, a picture obtained by decoding the I picture I ₁ of the current GOP is added to the B picture.
Displaying video obtained by decoding the picture B _5, followed by B-picture B _4, P picture P _1, B picture B _3, B picture B _2, P picture P _0, B-pictures B _1, B-pictures B _0, I picture so as to display an image obtained by decoding the I _0, it is necessary to perform reverse playback.

However, B picture B ₅ , B picture B
₄ is necessary data from those predicted by referring to the I-picture I ₁ and P picture P _1, and I-picture I ₁ and P picture P ₁ when decoding Nevertheless, P picture P ₁ has been predicted with reference to P picture P _0, further P-picture P ₀ is I-picture I
₀ reference from those predicted by a decode the P-picture P ₀ by referring to decode after all I-picture I _0, the P-picture P ₁ further reference to P picture P ₀ Must be decoded. Since the B picture B ₅ and the B picture B ₄ must be decoded with reference to the I picture I ₁ and the P picture P ₁ decoded in this way, time is consumed for decoding. is there.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a data reproducing method and a data reproducing apparatus in which special reproduction is performed quickly even during special reproduction such as reverse reproduction.

[0018]

In order to achieve the above object, according to a data reproducing method of the present invention, data read by a pickup from a disk is demodulated and written to a storage means, and the data read from the storage means is read. In a data reproducing method for reproducing an original video signal by decoding data, the storage means may be configured such that an unread data area and a read data area in the storage means are each about half of the total storage capacity. It is intended to be controlled.

Further, in the data reproducing method, control is performed such that the data is written in the storage means in units of a sector having a fixed data amount .

According to another aspect of the present invention, there is provided a data reproducing apparatus for demodulating data read by a pickup from a digital video disk, a memory for temporarily writing the demodulated data,
In a data reproducing apparatus provided with a decoder for decoding data read from the storage means into an original video signal, the unread data area and the read data area in the storage means each have about half of the total storage capacity. Thus, a control circuit for controlling the storage means is provided.

Further, the control circuit in the data reproducing apparatus writes the data in the storage means in units of a sector having a fixed data amount.
is there.

[0022]

According to the present invention, the storage means is controlled so that the unread data area and the read data area in the storage means are each about half of the total storage capacity. Since necessary data remains in the storage means, trick play can be performed quickly.
Further, for the same reason, switching from special reproduction to normal reproduction can be performed quickly. As described above, according to the present invention, by storing past data in the buffer at all times, the number of disk accesses can be reduced, and special reproduction can be performed only by controlling the buffer even during normal reproduction.

[0023]

FIG. 1 is a conceptual diagram of a data reproducing apparatus (DVD player) according to an embodiment of the present invention. In this figure, 1
Is a disk (D) as a storage medium in which digital video data, digital audio data, and the like are compression-encoded by the MPEG system and recorded in units of sectors.
VD), 2 is a pickup as reproducing means for accessing the disk 1 and reading recorded digital data, 3 is a sector detection circuit for detecting a sector sync and a sector address from the digital data read from the disk 1, and 4 A ring buffer (storage means) for writing data read from the disk 1 in units of sectors under the control of the control circuit 8 and supplying the read data to the decoder 5 as necessary; Reference numeral 5 denotes a decoder for decoding the supplied data in units of sectors into a video signal to be displayed on a display device.

Further, reference numeral 6 denotes a frame memory for storing three frames decoded by the decoder 5, 7 a display for displaying a video signal supplied from the frame memory 6, 8 a tracking servo circuit 9 as access means, and the like. And a control circuit (control means) for performing tracking control, thread control, focus control, etc., and controlling writing / reading of the ring buffer 4. This is a tracking servo circuit that performs tracking control of the pickup 2 in order to access 1.

The operation of the data reproducing apparatus thus constructed will be described below. The rotation of the disk 1 is controlled by a spindle motor (not shown) so as to rotate at a predetermined number of revolutions. When a laser beam is irradiated from the pickup 2 to the track of the disk 1, the compression encoded data recorded on the track is compressed. The read digital data is read. This digital data is recorded in units of the fixed-length sector shown in FIG. 11 described above, and a sector sync and a sector header are added to the head of each sector.

The digital data read from the pickup 2 is input to a sector detection circuit 3, where a sector sync is detected to detect a sector break and a sector address and the like from a sector header. It is supplied to the control circuit 8. Pickup 2
The focus control and the tracking control are performed by the tracking servo circuit 9 and the like under the control of a system control (not shown) based on a focus error signal and a tracking error signal obtained from information read from the pickup 2.

Then, based on the detected sector address, the control circuit 8 controls the writing of data in units of the sector to the ring buffer 4. The write address in this case is indicated by a write pointer (WP) 8-1 in the control circuit 8. The buffer 5 has a storage capacity capable of storing at least 2 GOPs of digital data. GOPs composed of pictures in the order shown in FIG. 10B are read out from the ring buffer 4 in units of sectors, and supplied to the decoder 5 to form GOPs. The I picture, the P picture, and the B picture are decoded and sequentially written to the frame memory 6.

The frame memory 6 outputs the pictures from the decoder 5 in the order of the pictures shown in FIG.
Each frame memory M constituting the frame memory 6
1, M2, M3. Here, FIG. 2 shows an example of decoded frames written to the frame memories M1, M2, M3 during normal reproduction. 2 will be described with reference to FIG. 10. In state 1, an I ₀ frame obtained by decoding I picture I ₀ is written in the frame memory M1, and a P picture preceding the I picture I ₀ Are decoded and the B pictures B _-2 and B _-1 decoded with reference to the decoded _I0 frame in the frame memory M1 are written in the frame memories M2 and M3, respectively. This state 1
In, from the frame memory M1, M2, M3, B _-2 as shown in FIG. 10 (a), B _-1, is rearranged to the original image sequence of I ₀ frame is sent to the display 7, the image is displayed Is done.

Next, the state 2 is entered, and the sector of the P picture P ₀ is read from the ring buffer 4, decoded by referring to the I ₀ frame in the frame memory M 1, and written into the frame memory M 2. further,
Proceeding to state 3, the sector of the B picture B ₀ is read from the ring buffer 4, and is decoded by referring to the I ₀ frame in the frame memory M1 and the P ₀ frame in the frame memory M2, and the frame memory M3
Is written to. Then, the _B0 frame is read from the frame memory M3 and sent to the display 7, and the image is displayed and the state 4 is set.

[0030] In this state, B-pictures B ₁ sector is read from the ring buffer 4, B-pictures B ₁ by referring to the I ₀ frame and P ₀ frame within the frame memory M2, in the frame memory M1 is The decoded data is written to the frame memory M3. Then, the frame memories M are arranged in the order of B ₁ and I ₀ frames.
3, M1 is sent to the display 7 and the video is displayed.

[0031] In the subsequent state 5, the sector P-picture P ₁ is read from the ring buffer 4, is decoded by referring to P ₀ frame within the frame memory M1, it is written in the frame memory M1. further,
Advances to state 6, the sector B picture B ₂ is read from the ring buffer 4, is decoded by referring to the P ₁ frame and P ₀ frame within the frame memory M2, in the frame memory M1, the decoded B pictures B ₂ are written to the frame memory M3. Then, it sent to B ₂ frame is read display 7 which is decoded from the frame memory M3, the video is displayed. Thereafter, decoding is performed in the same manner, and B ₃ , P ₁ ,
Are sent to the display 7 in the frame order of B ₄ , B _5, ... And their images are sequentially displayed.

During normal reproduction, an image is displayed in this manner. The movement of the write pointer WP and the read pointer RP on the ring buffer 4 during normal reproduction will be described with reference to FIG. FIG. 4A shows a case where the read pointer RP8-2 is at the address position R1 and the write pointer WP8-1 is at the address position W1, and the clock direction shown in the ring buffer 4 is the normal reproduction direction. Writing / reading is performed in this direction. Since the address position R1 and the address position W1 are substantially opposed to each other on the ring buffer 4, the unread data area URD and the read data area ARD have substantially the same size.

The state in which the read pointer RP8-2 advances to the address position R2 and data is read from the ring buffer 4 is the state shown in FIG. 4B, and the unread data area URD decreases, and the read data Area AR
D is increasing. The control circuit 8 detects this, controls the pickup 2 to access the disk 1 to read out new data, and advances the write pointer WP8-1 to the address position W2 shown in FIG. The read data of one sector is stored in the ring buffer 4.
It is controlled to be written to. As a result, the unread data area URD and the read data area ARD have the same size again. The control circuit 8 performs such control at any time.
Unread data area URD and read data area A
The RD is controlled so that the area is always almost the same size. In this case, when new data is not read from the disk 1, the pickup 2 is controlled to jump one track and read data on the same track.

By the way, when the operation button is operated from the normal reproduction mode, for example, the reverse reproduction mode is set, the past video already reproduced during the normal reproduction is decoded in the reverse order of the time, and the decoded video is decoded. Although it is necessary to send the data from the frame memory 6 to the display 7 for display, in the case of the present invention, when the reverse reproduction mode is set, the already read data is stored in the ring buffer 4 as shown in FIG. Since the data is stored in the area ARD, the read / write of the ring buffer 4 is simply controlled by the control circuit 8 so as to perform reverse reproduction, and the pickup 2 is controlled backward to quickly perform reverse reproduction without reading new data. Can be displayed on the display 7.

Here, the picture decoded by the decoder 5 in the reverse reproduction mode and the frame memories M1, M2,
The relationship with the frame stored in M3 will be described with reference to FIG. State 0 of FIG. 3, after the decoding of up to the frame B ₃ is completed, a state where the I-picture I ₁ is stored in the frame memory M1 are decoded. In the reverse playback mode, in the arrangement shown in FIG. 10A, the decoded frames must be sent to the display 7 and displayed in the order from right to left.
First, the P ₁ and B ₃ frames are sent from the frame memories M 2 and M 3 to the display 7 in the order of P ₁ and B ₃ , and the images are displayed on the display 7. Then, since it is necessary to send the B ₂ frame, first, I picture I ₀ is decoded is read from the ring buffer 4, it is stored in the frame memory M1 (State 1). Subsequently, the P picture P ₀ is read from the ring buffer, and is decoded with reference to the I ₀ frame, and the frame memory M 3
(State 2). Then, the B picture B ₂ is read from the ring buffer 4 and the P ₁ frame and the P
₀ frame is referenced decoded, stored in the frame memory M1, is sent to the display 7 B ₂ frame of image is displayed (state 3).

Next, the I picture I ₀ is read from the ring buffer 4 again, decoded, and
2 (state 4). Next, the B picture B ₁ is read from the ring buffer 4, decoded with reference to the P ₁ frame and the P ₀ frame, stored in the frame memory M _1, and sent to the display 7 to display the image of the B ₁ frame. It is displayed (state 5). continue,
The B picture B ₀ is read from the ring buffer 4, similarly decoded with reference to the P ₁ frame and the P ₀ frame, stored in the frame memory M 1, and sent to the display 7 to display the image of the B ₀ frame. It is displayed (state 6).

Next, the movements of the write pointer WP and the read pointer RP during such reverse reproduction will be described with reference to FIG. FIG. 6A shows that the GOP stored in the area from the address position R3 to the address position R4 of the ring buffer 4 is being decoded, and the read pointer RP is located in this area. Then, the address position R3 in which the unread data area URD includes the area being decoded.
To the address position W3, and the remaining area is the read data area ARD. Note that the write pointer WP is located substantially opposite to the address position R3. However, since the reverse reproduction is being performed, the counterclockwise direction is the reproduction direction in the ring buffer 4.

The state in which decoding has proceeded to the next GOP is the state shown in FIG. 4B, and the GOP stored in the area from the address position R4 to the address position R5 is:
It is read from the ring buffer 4 and decoded. In such a state, the area of the unread area URD is reduced, and the control circuit 8 controls the pickup 2 to move backward so as to read past new data from the disk 1. At the same time, the write pointer WP is jumped from the address position W3 to the address position W4, and the disk 1 is moved while moving the write pointer WP clockwise.
Is written into the ring buffer 4. In this case, the write pointer WP8-1 for the area in which the sum of the number of sectors written previously and the number of sectors written this time can be written is controlled to jump.

By the way, in the compression by MPEG, as described above, it is not possible to code an I-picture because another picture in the GOP must be read first. Therefore, even if the GOP is read in order from the succeeding picture at the time of reverse reproduction, it cannot be decoded. Therefore, in the TOC or the like recorded at the head of the disc 1,
Write which sector each GOP is composed of. The control circuit 8 stores this, and controls the read pointer RP to jump to the beginning of the GOP at the time of reverse reproduction, to return while decoding in order from the I picture, and to decode the picture to be output next. I have.

The read pointer RP at the time of such reverse reproduction
FIG. 7 shows the detailed movement of the write pointer WP and FIG. 8 shows the detailed movement of the write pointer WP. The movement of the read pointer RP and the write pointer WP as shown in FIGS. The decoded frames can be stored in the memories M1, M2, and M3. FIG. 7A is the same as FIG. 6A,
In the figure, the part surrounded by a broken line is enlarged and shown in FIG.
Is shown in As shown in FIG.
When decoding a GOP, first, address position R3
Jumps to address position R4 in the playback direction from
The I-picture at the head of is read.

Subsequently, the read pointer RP is jumped one by one in the opposite direction to the reproduction direction to read out a P picture, and then one jump is made in the same direction to read out the next P picture. A B picture adjacent to R3 is read. The decoded pictures are sequentially decoded by the decoder 5, so that the decoded frames are stored in the frame memories M1, M2 and M3 as shown in FIG. As described above, in the reverse playback mode, the decoding is performed toward the past as a GOP unit.
As described above, since it is necessary to decode each picture referenced at the time of encoding as described above, the picture is read out and decoded in the direction opposite to the reproduction direction.

FIG. 8A is a view showing the same state as FIG. 6C, and the portion shown by the broken line is enlarged and shown in FIG. In this figure, the address position W
3, the read pointer WP jumps from the address position W4 to the address position W4 at the time of data writing, as described above. Data of the number of sectors, which is the sum of the number of sectors to be written, is set as a writable address position. Then, while returning from the address position W4, the sectors S0, S1, S2, S3, S4, S
... Are written.

As described above, the data in the GOP is written while being arranged in the same direction as that during the normal reproduction, but when the reverse reproduction mode is set, the data before the next sector to be overwritten during the normal reproduction is written. The control circuit 8 controls the write pointer WP so as to start writing from. That is, FIG.
As shown in (3), when writing over three sectors from sector 22 to sector 24 during the normal reproduction, the write pointer WP is jumped to the position of the sector 106 and the sector 22 is overwritten. And
Subsequently, the sectors 23 and 24 are overwritten on the sectors 107 and 108.

The unread data area URD (or read data area ARD) during normal reproduction
However, it goes without saying that during reverse reproduction, the read data area ARD (or the unread data area URD) is reversed. As described above, the ring buffer 4
The control circuit 8 controls the storage area of the control circuit 8 such that the storage area of
By controlling the writing / reading of the ring buffer 4, it is possible to quickly cope with not only frame-by-frame playback in the reverse playback mode but also slow playback and variable-speed playback such as double-speed playback.

Further, it is possible to cope with not only the reverse reproduction but also the variable speed reproduction during the normal reproduction. When the mode is set to the variable speed reproduction mode, for example, only the I picture or only the I picture and the P picture may be reproduced to cope with the variable speed reproduction such as double speed. The disk 1 can be an optical disk or a magneto-optical disk.

[0046]

As described above, according to the present invention, the writing / reading of the storage means is controlled such that the unread data area and the read data area in the storage means are each about half of the total storage capacity. So that trick play can be quickly displayed. Further, for the same reason, the display can be quickly performed even when switching from the special reproduction to the normal reproduction. As described above, according to the present invention, by storing past data in the buffer at all times, the number of times of disk access is reduced, and special reproduction can be performed only by controlling the storage means even during normal reproduction.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a configuration of an embodiment of a data reproducing apparatus of the present invention.

FIG. 2 is a diagram showing decoded frames stored in a frame memory during normal reproduction in the data reproducing apparatus of the present invention.

FIG. 3 is a diagram showing decoded frames stored in a frame memory during reverse playback in the data playback apparatus of the present invention.

FIG. 4 is a diagram illustrating the movement of a write pointer and a read pointer during normal reproduction in the data reproduction device of the present invention.

FIG. 5 is a diagram illustrating the movement of a write pointer during reverse playback in the data playback device of the present invention.

FIG. 6 is a diagram illustrating the movement of a write pointer and a read pointer during reverse playback in the data playback device of the present invention.

FIG. 7 is a diagram illustrating in detail the movement of a read pointer during reverse playback in the data playback apparatus of the present invention.

FIG. 8 is a diagram illustrating in detail the movement of a write pointer during reverse playback in the data playback apparatus of the present invention.

FIG. 9 is a diagram illustrating a configuration example of an encoder that performs MPEG encoding of a digital moving image signal.

FIG. 10 is a diagram showing a structure of inter-frame prediction in a GOP and a structure of a recording frame.

FIG. 11 is a diagram showing a relationship between a sector recorded on a disk and pictures forming a GOP.

FIG. 12 is a diagram illustrating movement of a read pointer and a write pointer in a ring buffer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disc 2 Pickup 3 Sector detection circuit 4 Ring buffer 5 Decoder 6 Frame memory 7 Display 8 Control circuit 9 Tracking servo circuit

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-161115 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/76-5/956 G11B 20 / 10-20/12

Claims (4)

(57) [Claims] 1. A data reproducing method for demodulating data read from a disk by a pickup and writing the data in a storage means, and reproducing the original video signal by decoding the data read from the storage means. A data reproducing method, wherein the storage means is controlled such that the unread data area and the read data area of the means are each about half of the total storage capacity. 2. The data reproducing method according to claim 1, wherein the data is controlled to be written in the storage unit in units of a sector having a fixed data amount. 3. A demodulating means for demodulating data read by a pickup from a digital video disk, a storage means for temporarily writing the demodulated data, and a data read from the storage means as an original image. In a data reproducing apparatus comprising a decoder for decoding into a signal, a control circuit for controlling the storage means so that an unread data area in the storage means and a read data area in the storage means are each about half of the total storage capacity. A data reproducing device, comprising: 4. The data reproducing apparatus according to claim 3 , wherein the control circuit writes the data to the storage unit in units of a sector having a fixed data amount.