JP3202283B2 - Image data reproducing method and reproducing circuit thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reproducing image data and a reproducing circuit therefor.

[0002]

2. Description of the Related Art As a large-capacity storage medium, there is a CD-ROM, which is used as an external storage medium in a game machine or a personal computer using a microcomputer.

FIG. 11 shows an example of a microcomputer which can use such a CD-ROM.

FIG. 11 shows an example in which such a microcomputer is applied to a game machine.
1 is the main body of the game machine, 3 is the sub-processing unit, 4 is the CD-RO
M and 5 are program cartridges.

[0005] The main body 1 of the game machine is constituted by a microcomputer.
U and 13 are RAMs for a work area and a buffer,
4 is a PPU (Picture Processing Unit), 1
5 is a video RAM. The circuits 11 to 14 are connected to the system bus 19, and the PPU 14 is connected to the video RAM 15 and the CRT display 6.

Further, in the main body 1, reference numeral 20 denotes a main processing unit for audio data, reference numeral 21 denotes its APU (audio processing unit), reference numeral 24 denotes a D / A converter, reference numeral 25
Is an audio output terminal. The APU 21 is connected to the bus 19 and to the D / A converter 24.

[0007] The sub-processing unit 3 is for enabling the use of the CD-ROM 4, and includes a CD player and a CD-ROM.
The image data and the program having a ROM decoder and the like read from the CD-ROM 4 are supplied to the bus 19 after necessary processing is performed in the processing unit 3.

Furthermore, the program cartridge 5
It has an OM 51 and a RAM 52, and programs and the like are written in the ROM 51. Also, RAM
52 is used to hold various data relating to the state at that time when the game is temporarily interrupted, for example, until the next game is resumed, and is backed up by the battery 53.

When the cartridge 5 is inserted into the slot 2 of the game machine main body 1, the ROM 51 and the RAM 52 are connected to the bus 19 through a connector (not shown).

If a game or the like can be executed only by the program cartridge 5, the cartridge 5
Is set in the slot 2 and the power of the game machine body 1 is turned on (or reset. The same applies hereinafter).

Then, the CPU 11 executes the program in the ROM 51 to form image data. The image data is written into the video RAM 15 by the PPU 14, and the image data in the video RAM 15 is read out in synchronization with horizontal and vertical scanning. Then, the read image data is supplied to the display 6 to display an image.

The CPU 11 loads audio data and a program for decoding the audio data into the APU 21.
The audio data is decoded into a digital audio signal, and the digital audio signal is D / A-converted into an analog audio signal by the converter 24 and then output to the terminal 25.

On the other hand, when a game or the like is executed using the CD-ROM 4, the CD-ROM 4 is
And the system cartridge 5 as the program cartridge 5 in the slot 2
Set to.

In this case, the system cartridge 5 is also RO
It has an M51 and a RAM 52, and an IPL is prepared in the ROM 51. As described above, the RAM 52 is used, for example, when temporarily suspending the game, to hold various data until the next game restart. CD-ROM
OS 4 and a game program for using the CD-ROM 4 are prepared in the CD-ROM 4.

When the power is turned on, the CPU 11
Executes the IPL of the ROM 51, and thereby the CD-RO
From M4, the OS and the game program are loaded into the RAM 13, and then the CPU 11 executes the program loaded into the RAM 13. Therefore, a game can be played.

[0016]

However, for example, FIG.
A, as shown in FIG.
Assuming that a frame (one screen) is composed of 256 pixels (horizontal) x 192 pixels (vertical), and the red, green, and blue of one pixel are each represented by 5 bits, the amount of image data of one frame Is Becomes

However, the capacity of one sector of the CD-ROM 4 is 2 Kbytes in mode 1, and the reproduction speed is
75 sectors / sec. That is, the data transmission rate of the CD-ROM 4 is 150 Kbytes / sec.

Therefore, if the above image data is
When recorded on CD-ROM 4 as it is, during playback,
The number of frames per second (number of frames) is 150K / 90K = less than 1.7 frames, and the number of frames is completely insufficient even when displaying moving images.

Therefore, when displaying a moving image, a CD-
By increasing the rotation speed of ROM 4, CD-ROM
4 may be increased to increase the number of frames per second.

However, when displaying the image data of the CD-ROM 4, the image data is reproduced from the CD-ROM 4.

Once the reproduced image data is RA
Write to M13.

The image data in the RAM 13 is sent to the PPU 14 during a vertical blanking period. Is performed.

However, when such processing is performed, C
When the data transfer rate of the D-ROM 4 is increased, the reproduction speed of the item becomes faster than the transfer speed of the image data of the item, and the RAM 13 of the item may overflow.

In this case, the capacity of the RAM 13 is changed to a CD-RO
If the capacity is increased to about the capacity of M4, the overflow of the RAM 13 does not occur, but it is impossible to increase the capacity of the RAM 13 in terms of cost.

The present invention aims to solve the above problems.

[0026]

Therefore, in the present invention, if the reference numerals of the respective parts correspond to the embodiments described later, the image data RECD reproduced from the recording medium 4 is written into the buffer memory BUFM, When converting the image data RECD written in the BUFM into image data for display, the buffer memory BUFM is configured by a buffer memory having a capacity larger than one frame of the image data RECD reproduced from the recording medium 4, and Before writing the image data RECD reproduced from the buffer memory BUFM to the buffer memory BUFM, the circuit 11 checks whether or not the buffer memory BUFM has an empty space for one frame. Writes the image data RECD reproduced from to the buffer memory BUFM. Providing a circuit 11 to discard the image data RECD reproduced from the recording medium 4.

[0027]

[Function] The reproduced image data RECD is stored in the buffer memory BUFM.
When there is room for one frame, the image data RECD is written to the buffer memory BUFM.
When there is no space for one frame, the image data RE
The CD is discarded.

[0028]

Embodiment << Recording process of image data >> First, a CD-RO
FIG. 3 shows an example of image data recorded in M4.
This will be described with reference to FIG.

FIGS. 3 and 4 are flowcharts showing the process of recording the image data. FIG. 5A
Is one frame (one screen) of the screen to be recorded
This one frame consists of 256 pixels (horizontal) x 19
It is composed of two pixels (vertical), and red, green and blue of one pixel are represented by 5 bits each. Actually, one dummy bit is added to the highest order for the sake of processing, and one pixel is one bit (dummy) +5 bits × 3.
Color, that is, 16 bits. The original image data is recorded on a frame basis.

That is, in step 81 (FIG. 3), the original image data of one frame shown in FIG.
As shown in the figure, each is 8 pixels (horizontal) x 8 pixels (vertical)
(Hereinafter, this block is called a “character”). Therefore, as shown in FIG. 5B, an image of one frame is divided into 32 × 24 = 768 characters C0 to C767, and the original image data is divided into character data CHR (0) to CHR (767). . Note that one character data CHR (i) (i = 0 to 767) is 8 bytes × 8 pixels × 16 bits = 128 bytes.

Then, in step 82, first-order vector quantization is performed on the character data CHR (i). In this vector quantization, quantization is performed such that the number of colors of pixels in one character Ci is four or less. As a method of this vector quantization, a method already proposed can be adopted, but in this example, red,
Considering a three-dimensional color space in which the green and blue color components are taken on three coordinate axes orthogonal to each other, the distance between pixels in this color space is determined, and pixels having the short distance are put together to obtain 1 The pixel data is rounded so that the number of pixels in one character Ci falls within the "representative color" of four or less.

Further, at the time of this quantization, the maximum value of the quantization error (corresponding to the distance between the representative color in the color space and each pixel) of each character Ci in each frame is Emax.
, Vector quantization is performed until immediately before the quantization error exceeds the maximum value Emax in each character Ci, and the S / N of all the characters C0 to C767 is made uniform for each frame.

When the quantization is performed in this manner, the number of colors decreases in a character having a flat color change.
This is because the quantization error does not increase so much even if the number of colors decreases.

In this way, the character data CHR (i) is quantized to have four or less colors in each character Ci.

In step 83, the quantized character data CHR (i) is classified into eight groups by grouping characters having similar colors. "). That is, each character data CHR (i) is classified so as to belong to one of the eight pallets P0 to P7.
In this case, each character Ci is only classified,
The order is not interchanged. Therefore, the pallet Pj (j = 0 to 7) does not need to be an area of continuous characters,
One pallet may be configured. For example, as shown in FIG. 5C, when regions A to E having similar color tones are generated, a pallet Pj may be formed for each of the regions A to E.

In step 84, the second-order vector quantization is performed on the character data CHR (i) classified into the pallet Pj for each pallet Pj.

That is, the representative color of each character Ci is 4
Even if it is a color, the number of colors in the palette Pj, which is a group of the characters Ci, may exceed 16 colors. Therefore, if the number of colors in one palette Pj is more than 16 colors, the first-order vector quantization is performed. In the same manner as in the case (2), the second-order vector quantization is performed, and the colors in the palette Pj are rounded up to a maximum of 16 colors, and the resulting 16 colors are used as new representative colors.

Therefore, for each pallet Pj, the character data C of the character Ci belonging to that pallet Pj
HR (i) is quantized into color data (15-bit color data) of any one of the 16 representative colors of the palette Pj.

Subsequently, at step 85, a color number conversion table COL (j) is created for each pallet Pj. As shown in FIG. 6, the table COL (j) includes, for each palette Pj, color data (15-bit color data) of 16 representative colors and a 4-bit color number (15-bit color number) specifying the color data. 0 to 15). Therefore, at this point, the character data CHR (i) is stored in the table COL (j) of the palette to which the character data belongs.
Equal to one of the color data.

Then, in step 86, as shown in FIG. 7, the second-order quantized character data
Each color data of CHR (i) is converted to a color number of the color number conversion table with reference to the color number conversion table COL (j) of the pallet Pj to which the character data CHR (i) belongs. Therefore, at this time, the pixel of each character Ci indicates the color number of the 4-bit color and the table of the color number conversion table COL (j) corresponding to the color number (for each character Ci). ) Data.

Therefore, in step 87, a screen table SCR is formed. This screen table
As shown in FIG. 8, the SCR has an address of 24 characters × 32 characters corresponding to one frame of the original image data, that is, a total of 768 addresses. Each address has a size of 2 bytes, as shown in FIG. 9. The lower 10 bits of the 2 bytes are the number Ci of the character Ci, and the upper 3 bits are the character data of the character number Ci. The pallet number Pj of the pallet Pj to which CHR (i) belongs is set.

Further, in this example, step 88
Gives the character number Ci of the screen table SCR.
Is shifted by 16 to the larger, and the character number Ci
Are assigned to the color numbers of the single-color characters Ci. That is, depending on the character Ci,
In some cases, the colors of all the pixels are equal, and thus the character Ci is a single color. In the case of such a character Ci, if the pallet number Pj and the color number are given to the character Ci, the colors of all the pixels of the character Ci can be specified.

Therefore, for a single-color character Ci, the pallet number Pj is the original pallet number Pj of the character Ci, but the character number Ci is a color number. At this time, the monochrome character C
The address of i in the table SCR indicates the character number Ci. Even in this case, the maximum value of the character number Ci before the shift is 767.
Even if the character is shifted to the larger one by 16, the character number Ci
Can also be represented by 10 bits.

As described above, the image data is converted into a color number conversion table COL (j), a screen table SCR, and a 4-bit color number for each pixel for each frame. In the following description, the color number conversion table COL (j) is called a color number conversion table COL,
The 4-bit color number for each pixel is called color number data DAT.

The data DAT, SCR, COL
Is assembled into recording data RECD having a format as shown in FIG. 10, for example.
Recorded in OM4. In this case, the recording data RECD
Is recorded on the CD-ROM 4 after encoding processing for recording in mode 1 such as addition of an error correction code is performed. The CD-ROM 4 is provided with a program for displaying or using image data (recording data) RECD recorded on the CD-ROM 4 as necessary.

Here, the data amount per frame of the recorded image data RECD is obtained as follows. That is, since there are eight pallets Pj per frame and one pallet has 16 colors and one color has 16 bits (1 bit is dummy), the color number conversion table COL has a total of 8 pallets × 16 colors × 16 bits = This is 256 bytes.

The screen table SCR has 768 characters and 2 bytes per character, so that 2 bytes × 768 = 1536 bytes.

Further, since the color number data DAT is 4 bits per pixel, the data amount of the data DAT per character is 4 bits × 64 pixels = 32 bytes.

Since the data of the single-color character Ci is transmitted as a part of the screen table SCR, there is no need to separately transmit the data.

Therefore, for example, if 1/4 of 768 characters in one frame are monochromatic characters, the color number conversion table COL = 256 bytes, the screen table SCR = 1536 bytes, the color number data DAT = 32 bytes × 768 pieces x 3/4 = 18432 bytes-------------------------------Total = 20224 bytes. That is, it is slightly less than 20 Kbytes.

Then, the CD-ROM 4 is stored in, for example, a normal
If the rotation speed is doubled, the data transmission rate is 300
K bytes / sec.

Therefore, in the case of the data amount of the image data described above, a moving image can be recorded or reproduced at a rate of 300 Kbytes / 20224 bytes = 15.2 frames or less.

If a moving image can be reproduced at such a frame speed, a satisfactory moving image can be obtained. Moreover, when the image data is recorded as described above, the color number data DAT can be converted into the original color image data only by referring to the color number conversion table COL at the time of reproduction. It's easy.

Further, since no special IC is required,
CD can be provided as a recording medium while providing low cost.
-Since a ROM can be used, it is effective when applied to software of a computer game machine.

<< Reproduction Circuit >> Next, the above-described image data RECD
The basic configuration and operation of a microcomputer capable of reproducing moving image data by reproducing the original image data from the CD-ROM 4 on which the data is recorded will be described with reference to FIG. Note that some of the circuits are the same as those in FIG.

FIG. 1 shows an example in which such a microcomputer is applied to a game machine, 1 is the game machine main body, 3 is a sub-processing section, 4 is a CD-ROM, and 5 is a program cartridge.

The game machine body 1 is constituted by a microcomputer, and 11 is its CP.
U and 12 are DMACs (DMA controllers), 13 is a main RAM serving as a work area, 14 is a PPU, and 15 is a video RAM.

In this case, the video RAM 15 has a screen area of two frames or more (two screens or more), and the image data of one screen area is converted by the PPU 14 into a CRT.
The image is read out in synchronization with the vertical and horizontal scanning of the display 6 and displayed as an image on the display 6, and while this display is being performed, image data of an image to be displayed next on another screen area is displayed. Written. In addition,
A part of the area of the video RAM 15 is also a work area of the PPU 14, and is used as an area of the color number conversion table COL (a pallet area).

The sub-processing unit 3 has a CD player to enable the use of the CD-ROM 4.
1 is the CD player, 32 is the DSP, 33 is the CD-R
OM decoder, 34 is RAM for the work area, 3
5 is a controller. As described above, the CD-ROM 4 stores audio data, image data RECD, a program for playing back the image data RECD, a game program, and an OS. CD
-The ROM 4 reproduces the sector of the image data RECD at twice the normal rotation speed.

Further, the DSP 32 corrects errors in the reproduction signal of the player 31 and separates user data such as image data RECD and control data such as track numbers from the reproduction signal. Reference numeral 35 is for controlling the player 31 based on the control data from the DSP 32 and the instruction data from the CPU 11 to reproduce target data. Further, when the reproduction signal of the player 31 is a reproduction signal of the mode 1 of the CD-ROM 4, the decoder 33 performs a process such as an error correction of the mode 1.

Further, in this example, a general-purpose DSP 44 is provided in the processing unit 3, and when necessary, this DS 44
Part of the processing of the CPU 11 can be borne by P44. Although the processing unit 3 is integrated with the game machine main body 1 in this example, it may be in the form of an adapter with respect to the game machine main body 1.

Then, the image data RECD on the CD-ROM 4 is read.
Is displayed as a moving image, the procedure of the reproduction process for the image data RECD is as follows.

(1) One frame of the image data RECD is reproduced from the CD-ROM 4 by the CD player 31, and this image data
RECD transmits the DSP 32 and the decoder 33 from the player 31.
Are sequentially supplied to the image data RECD to perform processing such as error correction.
Is transferred from the decoder 33 to the buffer area of the RAM 13 by DMA.

(2) DM in the buffer area of the RAM 13
Color number data DAT of the transferred image data RECD
During the vertical blanking period of the CRT display 6,
Video RAM 1 through PPU 14 by DMAC 12
5 is DMA-transferred.

(3) When the processing of (2) is completed, during the vertical blanking period of the CRT display 6, the screen table SCR of the image data RECD DMA-transferred to the buffer area of the RAM 13 is read by the DMAC 12.
DMA transfer is performed to the video RAM 15 through the PU 14.

(4) During the horizontal blanking period of the CRT display 6, the color number conversion table CO of the image data RECD DMA-transferred to the buffer area of the RAM 13
L is the video R through the PPU 14 by the DMAC 12.
DMA transfer is performed to the AM 15.

(5) When the above processing is performed, the PPU 14
Refers to the color number conversion table COL (j) in real time, and obtains the color number data DAT transferred by (2).
Is converted into pixel data of an actual color, and the pixel data is written to an address corresponding to the original character position in the video RAM 15 by referring to the screen table SCR.

(6) When one frame of pixel data is written into the video RAM 15 as described above,
The 15 display areas are switched, the area in which the pixel data is written becomes active, and an image of the activated area is displayed on the display 6.

(7) The process returns to (1), and thereafter, the processes of (1) to (6) are repeated for each frame.

The image data reproduced from the CD-ROM 4 is sent from the RAM 13 to the video RAM 15 through the PPU 14 one after another.
Is reproduced. Accordingly, an image based on the image data RECD of the CD-ROM 4 is displayed on the display 6 as a moving image.

<< Prevention of Overflow of Buffer Area of RAM 13 >> RAM
13 is the image data RECD reproduced from the CD-ROM 4.
However, in order to prevent the overflow, the image data RECD from the CD-ROM 4 is used.
Writes to the buffer area as follows:

That is, as described above, the image data RECD for one frame is about 20 Kbytes, which corresponds to the CD-R.
This corresponds to 10 sectors of OM4.

Therefore, as shown in FIG. 2, when the buffer area of the RAM 13 is a memory BUFM,
The FM has a size of, for example, 32 sectors of the CD-ROM 4, that is, 64 Kbytes (= 2 Kbytes × 32 sectors). In FIG. 2, # 0 to # 31 indicate that the memory BUFM is 1
Indicates the area number when the area is divided into sectors (2 Kbytes).

Further, the memory BUFM is a ring buffer, and when image data RECD for one frame is written in this memory BUFM, the image data RECD is written in the address order (area order), and the highest-order address is written. Is written to the lowest address.

For example, when the image data RECD of the Q-th frame from the CD-ROM 4 is written from the area # 25 of the memory BUFM, as shown in FIG.
5 → # 26 → ‥‥‥ → # 31 → # 0 → # 1 → # 2

Then, the next (Q +
1) When the image data RECD of the frame is written to the memory BUFM, it is checked whether or not an area # 12 10 sectors behind the last area # 2 in which the image data RECD of the Qth frame has been written is free. Then, the image data RECD of the (Q + 1) th frame is sequentially written from area # 3 following area # 2.

However, as a result of checking whether or not the area # 12 is empty, if the area # 12 is not empty, the (Q +
1) The frame image data RECD is discarded without being written to the memory BUFM (is skipped).

That is, when the image data RECD of the Qth frame from the CD-ROM 4 is written into the memory BUFM, the last data of the image data RECD (the last byte of the data COL) is stored in the area # of the buffer memory BUFM. 0 to # 3
It is assumed that data has been written to the R-th area #R of 1 (R is any one of 0 to 31). Then, 1. When the image data RECD of the next (Q + 1) th frame is written to the buffer memory BUFM, the buffer memory BUM
It is checked whether or not unprocessed image data RECD remains in the area one frame behind the FM area #R, that is, the area # (R + 10), which is, on average, ten sectors behind (R + When 10 ≧ 32, R + 10 is a value obtained by subtracting 32. The same applies hereinafter.

2. As a result of the check in item 1, area # (R + 1
(0), when there is no unprocessed image data RECD, the image data RE of the (Q + 1) th frame from area # (R + 1)
Write CDs in order.

3. As a result of the check in item 1, area # (R + 1
0), when unprocessed image data RECD remains,
The image data RECD of the (Q + 1) th frame is skipped, and is not written to the memory BUFM.

4. Thereafter, the same processing is repeated. And

It should be noted that the check of the free area in the item 1
The writing or skipping of the image data RECD of the items 2 and 3 is performed by the DMAC 12 based on the instruction of the CPU 11.

The check in item 1 can be realized by preparing a flag. That is, areas # 0 to # 3
In each area, a flag is prepared. When a new image data RECD (for one sector) is written in a certain area, a corresponding flag is set. When the image data RECD is sent to the PPU 14, the corresponding flag is set. Reset. If the flag is set, the corresponding area is not empty, but if the flag is reset,
It is sufficient that the corresponding area is vacant.

In this way, even if the processing speed of the image data RECD in the PPU 14 is lower than the reproduction speed of the image data RECD from the CD-ROM 4,
The BUFM does not overflow, and the image data RECD can be correctly converted to the original image data.

Further, in this case, as is apparent from the above description, the size of the buffer memory BUFM may be several frames of the image data RECD, which is low cost.

Further, when checking whether there is a space for writing new image data RECD in the buffer memory BUFM, since it is checked whether there is a space for one frame, the processing is simplified.

That is, when it is checked whether there is a space in the buffer memory BUFM for writing new image data RECD, it is checked whether there is a space for each area, and if there is a space, the new image data is stored in that area.
If one sector of the RECD is written, it is necessary to instruct the PPU 14 to invalidate the previously written data when there is no free area in the middle of one frame, which makes the processing complicated. Become.

However, in the present invention, when checking whether there is a space for writing new image data RECD in the buffer memory BUFM, it is checked whether there is a space for one frame. Very simple to handle when not.

[0089]

According to the present invention, when writing the image data RECD reproduced from the CD-ROM 4 to the buffer memory BUFM, it is determined whether or not the buffer memory BUFM has an empty area for writing one frame of the image data RECD. If there is a vacancy, the writing is performed, but if there is no vacancy, the image data RECD is skipped. Therefore, even if the processing speed after the PPU 14 is lower than the reproduction speed of the image data RECD from the CD-ROM 4, the buffer memory BUFM does not overflow, and the image data RECD can be correctly displayed on the original image.

Further, in this case, the size of the buffer memory BUFM may be the size of several frames of the image data RECD, and the cost is low.

Further, when checking whether there is a space for writing new image data RECD in the buffer memory BUFM, it is checked whether there is a space for one frame. Very simple.

The image data RECD has a variable length, and the time required for the display processing of the image data RECD varies depending on the content of the image. However, the programmer must consider the time required for the display processing. Therefore, there is no need to build a program, and the burden on the programmer can be reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram of an example of the present invention.

FIG. 2 is a diagram for explaining a use state of a memory according to the present invention.

FIG. 3 is a flowchart illustrating an example of a part of a process of recording image data.

FIG. 4 is a view showing a continuation of FIG. 3;

FIG. 5 is a diagram for explaining terms in image data.

FIG. 6 is a diagram for explaining a color number conversion table.

FIG. 7 is a diagram for explaining data to be recorded.

FIG. 8 is a diagram illustrating a screen table.

FIG. 9 is a diagram for explaining a data structure of a screen table.

FIG. 10 is a diagram illustrating an example of a format of recording data.

FIG. 11 is a system diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Game machine main body 2 Slot 3 Sub-processing part 4 CD-ROM 5 Program cartridge 6 CRT display 11 CPU 12 DMA controller 13 RAM 14 PPU 15 Video RAM 19 System bus 20 Main processing part 21 APU 24 D / A converter 31 CD player 32 DSP 33 CD-ROM decoder 35 Controller 51 ROM 52 RAM

Claims (4)

(57) [Claims] When writing image data reproduced from a recording medium into a buffer memory and converting the image data written into the buffer memory into image data for display, the image reproduced from the recording medium is used as the buffer memory. A buffer memory having a capacity larger than one frame of data is provided. Before writing image data reproduced from the recording medium to the buffer memory, it is checked whether or not the buffer memory has a space for the one frame. As a result of this check, if the space is available, the image data reproduced from the recording medium is written into the buffer memory. If the result of the check is not available, the image data reproduced from the recording medium is discarded. How to play back image data. 2. When writing image data reproduced from a CD-ROM into a buffer memory and converting the image data written into the buffer memory into image data for display, reproducing the image data from the CD-ROM as the buffer memory. A buffer memory having a capacity larger than one frame of the reproduced image data is provided, and before writing the image data reproduced from the CD-ROM to the buffer memory, whether or not the buffer memory has a space for the one frame. Is checked, and as a result of this check, if there is the above vacancy, the above C
The image data reproduced from the D-ROM is written into the buffer memory.
A method of reproducing image data in which image data reproduced from a D-ROM is discarded. 3. A circuit for writing image data reproduced from a recording medium into a buffer memory and converting the image data written into the buffer memory into image data for display, wherein the buffer memory stores the image reproduced from the recording medium. Before writing the image data reproduced from the recording medium to the buffer memory, it is checked whether or not the buffer memory has a space for the one frame. When the check shows that there is free space, the image data reproduced from the recording medium is written into the buffer memory. When the check shows that there is no free space, the image data reproduced from the recording medium is written. And a circuit for regenerating image data. 4. A circuit for writing image data reproduced from a CD-ROM to a buffer memory and converting the image data written in the buffer memory into image data for display, wherein the buffer memory is reproduced from the CD-ROM. Before writing the image data reproduced from the CD-ROM into the buffer memory, the buffer memory has a space for the one frame before the image data reproduced from the CD-ROM is stored. A circuit for checking whether or not there is a vacancy as a result of this check;
The image data reproduced from the D-ROM is written in the buffer memory.
A circuit for discarding image data reproduced from the D-ROM.