JPH06124451A - Optical disk device - Google Patents

Abstract

PURPOSE:To obtain an optical disk device such as video data with a high recording density. CONSTITUTION:A recognition code is marked with a format with a different transfer rate depending on a part where the amount of needed information needs to be large and one where it needs not be large and a recorded disk is reproduced at a refresh speed corresponding to the maximum rate using a reproduction drive 4. A memory 7 is overflown at a part where the transfer rate is slow and the overflow is detected, the drive 4 is paused, and data are read at a virtually variable rate and are decoded, thus reproducing data with a high performance using a disk with the same amount of information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an apparatus capable of recording and reproducing voice and moving picture data at high density on an optical disk such as a compact disk.

[0002]

2. Description of the Related Art A compact video (CD) disc, which records digital data on a CD-ROM disc, etc., can be used to record and reproduce compressed movie data, etc. to reproduce a compact and long-term movie. Has been realized.

[0003]

However, a CD-ROM
In such cases, since there is a limited amount of information (reproduction bit rate) per unit time, the resolution is low and there is a drawback that it becomes unnatural in a scene where the image movement is intense.

Further, if the reproduction rotation speed is increased in order to improve these, the reproduction time is shortened, and it has been a problem that long reproduction cannot be realized with a small disc.

An object of the present invention is to obtain a device capable of reproducing a high resolution natural reproduction for a long time by using a small disc, and there are various methods for compressing moving image data. Rate cosine conversion (DC
T) etc., divide into frequency domain, and change the allocation of bits for each spectrum to reduce the required number of bits,
The required bits are reduced by predicting the correlation between the frames of the image and using the difference as information data.

In any of the methods, a thin image having many high frequency components and a signal having a large amount of movement require a large amount of information. However, most moving images include when there is little movement or when there is no high frequency component, and in this case a small amount of information is sufficient. In an apparatus that records and reproduces these data as data such as a CD-ROM, there is a drawback that the grade such as the resolution of the apparatus is determined by a bit rate with an upper limit of a portion that requires the most information.

[0007]

In the present invention, attention is paid to the change in the required amount of information, and even if the information amount of the entire disc is the same as the conventional one, the information is recorded on the disc and reproduced in correspondence with the image. This is intended to be improved by making the bit rate to be variable.

That is, a large amount of data on the disk is used per unit time in a portion that requires a large bit rate of information data, and conversely, the amount of data per unit is reduced when the bit rate is small. These identification data are recorded in the area (1) and are decoded according to the identification data at the time of reproduction to obtain a video signal. This is achieved by performing spindle servo and reading control so as to support variable rate reproduction during this reproduction.

[0009]

FIG. 2 shows an embodiment of the data structure on the disc. Similar to the data format of a CD-ROM, data is recorded as a stream of data bytes, synchronization words 1 are provided at regular intervals, and a data frame is determined so that data can be extracted during reproduction.

Further, a header portion 2 is provided after this sync word to indicate the type of data contained in this data frame and the compression mode, and this serves as an identifier for switching the decoding mode of the data 3 of this frame. In this figure, for example, data 3 has three modes, that is, mode A having the highest compression rate, intermediate B, and modest C. In A, data corresponding to one field of a video signal is stored in one data frame. , B two data frames,
In the case of C, four data frames form one field of data.

Now, assuming that B has a standard bit rate, assuming that all frames store data in A, the reproduction time is twice as long as in the case of standard B alone.

On the contrary, in the case of only C, it becomes 1/2. A part requiring high-density data according to the flow of images at the time of recording and a part requiring only high density are distributed to A, B, and C, and a magnetic disk, a magnetic tape, etc. can be used to easily integrate data. Can be

Further, in the production of optical discs, since it is allowed to perform the disc production in one hour in a longer time than the production time, it is easy to store data in these formats. An example of a block diagram for reproduction of data in these formats is shown in FIG.

Disk drive unit 4 for reproducing a disc
In the same manner as in a general CD-ROM drive, reproduction can be performed from a predetermined portion, and a pause operation such as a pause can be performed, and reproduction can be performed from the same address by a play command for restart. Here, the rotation speed of the disc to be reproduced corresponds to the required bit rate of the reproduced data. That is, in the present embodiment, when the C mode is continuously reproduced, the reproduction can be performed at a predetermined bit rate, that is, at a rotation speed twice as high as the standard B mode.

In this state, the data reproduced from the disc drive unit 4 detects the sync pattern by the data separator 5, separates the header 2 and the data, and the data frame and the like are separated from these data by the subsequent decoder 8. It is added to the data so that it can be recognized and output in parallel. On the other hand, the SYNC header 1 is sent to the CPU 6.

The header information includes the address information of the disc other than the MODE, and the CPU 6 can recognize the address of the reproduction data on the disc. These data are stored in the memory 7, buffered, and output in the order of input,
This is a so-called FIFO memory. This output is the decoder 8
The compressed data is decoded by and output as the original expanded data.

Here, for example, when mode C continues, the bit rate (byte rate) required by the decoder and the reproduction bit rate (byte rate) are equal, so the written data is successively taken out in the memory 7. Therefore, it can be reproduced without any problem. Here, when the reproduction data of the B mode or the A mode is input to the memory 7 and read by the decoder 8, first, the read clock of the data to the decoder 8 is set to 1 / th of that of the C mode by the bit of each mode.
2 or 1/4. As a result, predetermined decoding is performed, and the same is output from the decoder 8. The output rate from the decoder 8 is a predetermined bit rate regardless of the mode. This is because the bit rate of the information amount of each input mode is different, and the target decoded decompressed data is always the same.

Here, the input data of the memory 7 has the same bit rate (byte rate) as that of the mode C, and the reading becomes 1/2, so that the data stored and accumulated in the memory 7 increases. Here, the CPU 6 determines the difference between the address written in the memory 7 and the address read out to determine whether the memory 7 is saturated. (Of course, the state of the memory 7 can be judged from the memory control counter or the like.) When the memory 7 approaches saturation, the CPU
A pause command is issued from 6 to the disc drive 4 to pause the reproduction.

The amount of this memory 7 cannot return to the place where the next address is reproduced until the disc is paused and the play is resumed until the disc rotates at least one revolution. Therefore, it is sufficient that the memory capacity is one rotation or more.

However, in order to reproduce the address by the read command, it may be necessary to wait a maximum of one rotation. If this is included, a capacity for storing data of two or more rotations is required. Therefore, when the data is reduced to half the memory capacity, the CPU 6 issues a play command to the disk drive 4 so that the data can be reproduced from the previous address, and the data separator 5 reproduces the previously reproduced address. The memory is restored by controlling the data to be sent to the memory 7 from the next frame.

By repeating these steps, in the case of only the B mode, the reproduction time is 1 and the pause time is 1, A
In the case of the mode, the ratio is 1 to 3 as well. However, since the disks are randomly generated and the average rate of the entire disk is the same as that of the standard B, the disk is paused for half the time.

These data are decompressed by the decoder 8 and D
The data converted by the A converter 9 is used as the original video data, and the data is put into a memory such as a frame memory, and the output is put into a video signal generating unit 10 which forms a video signal having an oscillating unit such as a synchronizing signal. It is output to the output 11 as a video signal.

In the present embodiment, the disk rotation of the disk drive 4 is reproduced twice as a predetermined value and the variable bit rate is set by pausing. However, as shown in FIG. 3, this can be kept constant by the address difference of the memory. The same can be achieved by changing the rotation of the spindle motor. However, in this case, if the response of the spindle servo or the like is slow, it is necessary to increase the capacity of the memory 7.

In general, moving images also require audio data such as audio. Bits can be reduced by compressing these as well. Since this data amount is smaller than the video data, it can be added to the video data and stored. However, in this case, the disc does not play at a constant transfer rate. An example of realizing these problems is shown in FIG. That is, a constant transfer rate can be obtained by using the inverse number of bits of the reproduction transfer rate.

Therefore, a constant audio data 12 is always set in the A data frame, and the audio data 12 is set only in the first data frame in the B and C modes, and the second and subsequent ones are not provided. By using all video data, audio data can be constantly obtained regardless of the reproduction bit rate.

FIG. 3 shows a reproduction block. Only the audio part is separated by the data separator and put in the FIFO memory 13. The buffered output is restored to the original data compressed by the decoder 14 and output as an audio signal 11 '.
Output to. Here, the data read from the memory has a constant rate, and the average input rate also becomes a constant rate.

However, since data of repeated pauses and plays is input, a buffer having a capacity of time corresponding to this pause is required. As a result, audio data can be recorded and reproduced only as necessary regardless of the video data having a variable bit rate.

Another embodiment of the present invention will be described with reference to FIG. The disk drive 4 enables reproduction in synchronization with an input clock signal that controls the reproduction speed. That is, CD
In the player, generally, as the system clock, an integer multiple of n times such as 192 times the sample frequency of the data is used to reproduce at a predetermined sample rate. When the system clock is changed, all signals including the rotation of the spindle are changed correspondingly, and as a result, 1 / n of the system clock can be taken out as sample data.

In order to lock and reproduce the variable range of the system clock in a wide range, it is possible to correspond to the data extraction portion including the phase locked loop inside the player corresponding to the input frequency. Although necessary, these techniques are omitted because they are well known in the art.
The input clock input to this disk drive 4 is VCO
It is oscillated by 15 and given. This VCO15 is VC
It is convenient to set the speed just to the average transfer rate when there is no input to O. The data reproduced by the disc drive 4 in this state is stored in the memory 7. This memory buffer is output in the order of input data in a FIFO manner, the output is read by the clock from the decoder 8 and the input is written by the reproduction clock from the disk drive 4.

Further, the data stored in the memory 7 is separated and decoded by the decoder section in synchronization with the data. Here, the original data is expanded and output according to the data mode. At this time, when the data mode is A, the required data bit rate is low, and conversely, when the data mode is C, the highest data rate is required, and the bit rate read from the memory is variable and taken out. Therefore, the amount of data in the memory 7 decreases in the mode C and increases in the mode A.

Data addresses are separated from the data stored in the memory and the output data by the header separators 16 and 17, and the difference is extracted by the data comparator 18. Here, in the comparison output, it is good that the data of the above difference takes a predetermined value, generally a value of 1/2 of the memory capacity, etc., but this reference value (REF) 19 is further subtracted and this data is converted into a DA converter. Put it in 20 and make it an analog signal.

When this analog signal is 0, it means that the predetermined data has just been stored in the memory, and when it is +, it increases and when it is-, it decreases. This is made an inverse output and is input to the VCO 15 via the low pass filter 21.

That is, when the data in the memory decreases, VC
The oscillation frequency of O is increased, the reproduction speed of the drive is increased, the data in the memory is returned to a predetermined value, and the servo loop is formed so as to always have this value. Here, the low-pass filter is necessary because the change in the frequency given to the drive falls within the range in which the spindle servo of the drive can respond to the increase / decrease in the amount of data. The faster the response, the higher the cutoff frequency. it can.

The capacity of the memory corresponds to the delay in the response of these drives, and is set so that it will not overflow. As a result, when the image data is small or the screen continues slowly, the drive speed is slow, and conversely, when a scene with drastic changes continues, fast reproduction is performed.

If the low-pass filter 21 is set to a low frequency and the memory 7 having a large memory capacity is used, the speed close to the average speed increases with a small change rate of the reproduction speed of the drive. A fast drive with a wide variable range is required, but the memory capacity can be reduced.

The data decompressed by the decoder 8 is converted into an analog RGB signal or the like by the DA converter 9, a video signal of NTSC or the like by the video signal forming circuit 10, and the output 11
It will be realized by Since the same applies to the audio signal, description thereof will be omitted. As described above, the total amount of data stored on the disk is the same as the conventional one, but it is possible to reproduce a high-resolution natural moving image equivalent to twice the bit rate of the conventional one, which is useless in a place with little movement. By omitting such data, the total playback time can be made the same.

Also, if the resolution is the same as the conventional one, the reproduction time can be extended. Here, in the embodiment, three modes of A, B, and C are shown for easy understanding, but the number of modes can be further increased, and conversely, two modes can be used. Of course, it can also be applied to audio data. Regarding the ratio, in the embodiment, the description has been made with the ratio of 4 times, but generally about 2 times is sufficient and it can be widely applied.

[0038]

As described above, the data stored in the disk can reproduce a high-resolution natural moving image corresponding to a bit rate that is twice or more the bit rate of the conventional one, and wasteful data is generated in a place where there is little motion. By omitting it, the total reproduction time can be made the same, and if the resolution is the same as the conventional one, the reproduction time can be extended.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a format example of a signal recorded on the disc of the present invention.

FIG. 3 is a block diagram for reproducing an audio signal of the present invention.

FIG. 4 is a diagram showing an example of a format of a signal recorded on the disc of the present invention.

FIG. 5 is a block diagram of another embodiment of the present invention.

[Explanation of symbols]

 1 sync header 2 header 3 data 4 disk drive unit 5 data separator 6 CPU 7 memory 8 decoder 9, 20 DA converter 10 video signal generation unit 11, 11 'output 12 audio data 13 memory 14 decoder 15 VCO 16, 17 header separator 18 comparison Device 19 Reference value 21 Low-pass filter

Claims (3)

[Claims] 1. An optical disk device for reproducing an optical disk in which video data is compressed and recorded, corresponding to a part requiring a large amount of data per unit time and a part requiring a small amount of data, and each part is provided with respective identification data. A disc recorded so as to have a corresponding data length, and at the time of reproduction, the reproduction data amount is changed from the disc according to the identification data in accordance with the recording information to read and reproduce, and the data is demodulated and expanded corresponding to the identification data. An optical disk device characterized by being video data. 2. A reproduction is performed at a reproduction rate higher than that corresponding to the maximum data recording unit per unit time, buffer memory means is provided, and disk reproduction is temporarily stopped when more than a predetermined amount of data is stored in the buffer means. 2. The optical disk device according to claim 1, further comprising a reproducing device adapted to change the reproduced data per unit time and reproduce the reproduced data by continuing the reproduction when it becomes less than a predetermined value. 3. An optical disk apparatus according to claim 1, wherein a disk having audio data recorded therein is provided by providing a data portion of an amount that is the reciprocal of the number of pieces of video data per unit time.