JPH11224464A - Information recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information recording device capable of preventing the overflowing of a memory even if accessing a recording position is not properly performed during the recording of data transferred in real time and thus the discontinuous state of recorded data. SOLUTION: Data from an MPEG encoder 12 is temporarily stored in a RAM 18, but a data rate control circuit 20 monitors a data quantity in the RAM 18 and controls a compression rate according to the data quantity in the RAM 18. That is, by setting a threshold value for comparison with the data quantity in the RAM 18 and increasing a compression rate as the data quantity is larger, a transfer rate is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus for recording video and audio data on a recording medium.

[0002]

2. Description of the Related Art Conventionally, a recording apparatus for recording data such as video data and audio data on a recording medium such as a disk has been known. In addition, there are various types of recording media for recording the data, but intermittent recording may be performed on a disk-type recording medium. In this intermittent recording, data is recorded by random access.

[0003]

However, when data transferred in real time is compressed at a fixed rate and recorded on a disk, the memory overflows when access to the disk fails for some reason. There is a possibility that. That is, when the predetermined recording position cannot be accessed, the data is transferred in real time, so that the capacity in the memory increases and there is a risk of overflow. As a situation in which the recording position cannot be accessed, impact, vibration, and the like on the recording apparatus can be considered. If the memory overflows, it is necessary to overwrite the data stored in the memory first, or to discard the data transferred after the capacity is full. Data such as video and audio is discontinuous.

Therefore, the present invention can prevent the memory from overflowing even when the recording position is not properly accessed when recording the data transferred in real time, and therefore, the recorded data can be recorded. It is an object of the present invention to provide an information recording device capable of preventing a state in which data is discontinuous.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and, first, is an information recording apparatus for recording predetermined data on a recording medium,
Compression means for compressing data to be recorded on the recording medium, storage means for temporarily storing data compressed by the compression means, and compression means for storing the data stored in the storage means. And control means for controlling a transfer rate of data output from the device. In the information recording apparatus having the first configuration, the compression unit compresses data to be recorded on a recording medium.
The data output from the compression means is temporarily stored in the storage means. The control means sets the transfer rate of the data output from the compression means in accordance with the data amount of the data stored in the storage means. Control. Therefore, by decreasing the transfer rate as the data amount of the data stored in the storage means increases, it is possible to prevent the storage means from overflowing.

Secondly, in the first configuration, the control means controls a data compression ratio in the compression means. The transfer rate can be controlled by controlling the data compression ratio in the compression means in this way. Third, in the second configuration, the control unit increases the compression ratio as the amount of data stored in the storage unit increases, so that the transfer rate of the data transferred from the compression unit is increased. It is characterized by lowering. Therefore, by increasing the compression ratio as the amount of data stored in the storage unit increases, the transfer rate can be reduced, and overflow of the storage unit can be prevented. Fourthly, in the second or third configuration, the control means compares the threshold value provided in advance with the data amount stored in the storage means; And selecting means for selecting a compression ratio according to the result of the comparison. This fourth
In the above configuration, the comparing means compares a predetermined threshold value with the amount of data stored in the storage means. Then, the selection means selects a compression ratio according to the comparison result of the comparison means. Then, the compression means performs compression according to the selected compression ratio. By performing the threshold determination in this manner, it is possible to adjust the data transfer rate and prevent the storage unit from overflowing.

Fifth, in the fourth configuration, a plurality of the thresholds are provided. Therefore, overflow can be further prevented by increasing the compression ratio as the threshold value increases. A sixth feature is that, in any one of the second to fifth configurations, data on a compression ratio is recorded on the recording medium together with data to be recorded on the recording medium. Therefore, the decoding process can be appropriately performed by reading the data on the compression ratio in the decoding.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, a recording / reproducing apparatus A as an information recording apparatus according to the present invention includes an A / D converter 10, an MPEG encoder 12,
A RAM 14, an encoder 16, a RAM 18, a data rate control circuit 20, an error correction symbol addition circuit 22, a modulation circuit 24, a magnetic head drive circuit 26,
A magnetic head 28, an optical head 30, a reproduced signal amplifying circuit 34, a low-pass circuit 36, a decoding circuit 38, an error correction processing circuit 40, a decoder 42, an MPEG decoder 44, a D / A converter 46, , The controller 48,
It has a servo circuit 50, a spindle motor 52, and a clock generation circuit 54.

Here, the A / D converter 10 performs A / D conversion processing on the input video / audio data. In addition, encoding processing relating to MPEG is performed. R
AM 14 is the WOR for MPEG encoder 12
A KRAM, which functions as a work RAM when the MPEG encoder 12 performs the encoding process.

The encoder 16 performs a process of multiplexing data encoded by the MPEG encoder 12, and as shown in FIG. 1, an input data address generation circuit 16a and an encode address generation circuit 16b. And a disk write address generating circuit 16c and an address switching circuit 16d. The input data address generation circuit 16a generates an address for writing the data sent from the MPEG encoder 12 into the RAM 18, and the encode address generation circuit 16b stores the data once recorded in the RAM 18. To generate an address when performing multiplexing processing. The disk write address generation circuit 16c
Generates an address when data is transferred from the RAM 18 to the error correction symbol adding circuit 22.

Also, a RAM 18 as the above-mentioned storage means
Is for temporarily storing data sent from the MPEG encoder 12. This RAM 18 is used as a circular buffer (ring buffer),
The data structure in 18 is configured as shown in FIG.

Further, the data rate control circuit 20 includes:
The amount of data in the RAM 18 is monitored, and a process of controlling the compression ratio in the MPEG encoder 12 according to the amount of data is performed. Note that the data capacity in the RAM 18 can be determined by monitoring the encoder 16. That is, since the encoder 16 knows the amount of data written in the RAM 18, the encoder 16 detects the amount of data in the RAM 18 from the data. Then, the data rate control circuit 20
Determines whether or not the data capacity in the RAM 18 exceeds a preset threshold value, and according to the determination result,
That is, the PEG encoder 12 controls the compression ratio when performing encoding.

Further, the error correction symbol adding circuit 2
2 adds an error correction symbol to the data encoded by the encoder 16. The modulation circuit 24
Performs a modulation process on data to which an error correction symbol has been added. Further, the magnetic head driving circuit 26 drives the magnetic head according to the data sent from the modulation circuit 24. The magnetic head 28 is used when recording data, and magnetizes the recording film of the disk 5 as the recording medium. The optical head 30 is used for recording and reproducing data. The optical head 30 has a semiconductor laser 30a and irradiates a laser beam, and receives a reflected light of the laser beam applied to the disk 5 from the semiconductor laser 30a. The head 32 is composed of the magnetic head 28 and the optical head 30.

The reproduction signal amplification circuit 34 amplifies data from the optical head 30. Further, the low-pass circuit 36 integrates the data amplified by the reproduction signal amplifying circuit 34. Further, the decoding circuit 38 demodulates data modulated at the time of recording and performs descrambling processing in synchronization with the clock sent from the clock generation circuit 54. Further, the error correction processing circuit 40 performs an error correction process according to an error correction symbol added to data such as video and audio data. Specifically, ECC (Error Co
rrecting Code) processing and EDC (Error Detecting Cod)
e) Perform the processing. Further, the decoder 42 performs a process of restoring the multiplexed data. The MPEG decoder 44 performs a decoding process on the MPEG encoded data. Further, the D / A converter 46 performs D / A conversion and performs video output. The controller 48
Controls the operation of each of the above units.

The operation of the recording / reproducing apparatus A having the above configuration will be described with reference to FIG. When the video / audio data is input to the A / D converter 10, the A / D converter 10 performs A / D conversion. The A / D-converted video / audio data is sent to the MPEG encoder 12 and
An encoding process for the EG is performed. That is, DCT transformation processing, quantization processing, and the like are performed. It is assumed here that the type of MPEG is MPEG1.

Next, the MPEG encoder 12 outputs the MPEG
The encoded video / audio data is transmitted to the encoder 16.
And the encoding process is performed. That is, when the video / audio data from the MPEG encoder 12 is sent to the encoder 16, the encoder 16 once writes into the RAM 18 according to the address generated by the input data address generation circuit 16 a. The written data is the input data in FIG. Then, according to the encode address generated by the encode address generation circuit 16b, the data once written is read and multiplexing processing is performed.
The data in the middle of the multiplexing is the data being encoded in FIG. Then, the multiplexed data is returned to R
It is written to AM18. The data subjected to the multiplexing processing is the encoded data in FIG. Then, the encoder 16 reads data according to the address generated by the disk write address generation circuit 16c, and outputs the data to the error correction symbol addition circuit 22. The switching of each address is performed by the address switching circuit 16d.

The error correction symbol addition circuit 22 adds an error correction symbol and sends it to the modulation circuit 24. The modulation circuit 24 performs a predetermined modulation process. After that, the modulated audio / video data is sent to the magnetic head drive circuit 26. When writing data to the disk 5, the recording position is accessed by moving the head 32 to the recording position, and the recording film that has been magnetized by the magnetic head 28 is irradiated with laser light from the semiconductor laser 30a. To record data.

Here, the data rate control circuit 20
Detects the data capacity (memory capacity) of the RAM 18 and controls the data compression ratio in the MPEG encoder 12. That is, the data rate control circuit 20 detects the data amount of the video and audio data stored in the RAM 18 by monitoring the encoder 16. Specifically, since the data structure in the RAM 18 is as shown in FIG. 3, the capacity between the pointer indicating the input position and the pointer indicating the output position is the data amount in the RAM 18. Here, the pointer indicating the input position corresponds to an address generated by the input data address generation circuit 16a, and the pointer indicating the output position corresponds to an address generated by the disk write address generation circuit 16c. Therefore, the data rate control circuit 20 can detect the amount of data in the RAM 18 from the information. That is, the thick line portion in FIG. 3B indicates the data amount.

Then, the data compression ratio is determined by comparing a predetermined threshold value with the detected data amount. The compression rate of the data is set to increase as the amount of data in the RAM 18 increases. For example, as shown in FIG. 2, a first threshold (= P) and a second threshold (= P)
When the two threshold values of Q) are provided, the following is performed. That is, the detected data amount in the RAM 18 is represented by S, and when S ≦ P, the compression rate a1 is represented by:
When <S ≦ Q, the compression ratio is a2, and when Q <S, a3 is satisfied, and when a3 is satisfied, a1 <a2 <a3. That is, the compression ratio is increased as the amount of data in the RAM 18 exceeds the higher threshold.

As a specific method for increasing the compression ratio, there is a method for removing high-frequency components in quantization processing in MPEG coding. This gives M
The amount of data output from the PEG encoder 12 can be reduced. For example, what is 10 MB per GOP can be reduced to 2 MB per GOP by increasing the compression ratio.

FIG. 2 shows the transition of the data amount in the RAM 18. That is, in the steady state, the recording on the disk 5 is performed by repeating the processing including the access and the recording processing following the access. That is, since the video / audio signals are sequentially input to the A / D conversion unit 10, the data amount in the RAM 18 increases at the time of access. Then, at the time of recording, since the video and audio signals are written on the disk 5, the data amount in the RAM 18 decreases. At the time of this recording, the A / D converter 10
Will continue to be entered. The above record,
The access is performed when the amount of data in the RAM 18 reaches the disk write start position in FIG. 2, while the access is performed when the amount of data in the RAM 18 reaches the access start position in FIG. As described above, when operating normally, that is, at the time of steady operation, the compression rate in the MPEG encoder 12 is a1. Note that, in FIG.
This indicates that an access error has occurred between the time point, the time point e and the time point g, and between the time point h and the time point i.

Then, at the time point a, data cannot be written to the disk 5, so that the amount of data in the RAM 18 increases, and exceeds the first threshold after the time point b. Therefore, the data rate control circuit 20
It outputs a first low-rate setting signal for instructing the encoder 12 to perform encoding at a higher compression rate (that is, a compression rate a2). Then, the MPEG encoder 12 performs compression encoding at the compression rate a2, and
Since the amount of data per unit time output from the G encoder 12 decreases, the degree of increase in the amount of data in the RAM 18 decreases from the time point b. That is, the slope of the graph becomes smaller. However, assuming that the state of the access error still continues, the data amount in the RAM 18 exceeds the second threshold value at the time point c. Then, the data rate control circuit 20
Outputs a second low-rate setting signal for instructing the MPEG encoder 12 to perform encoding at an even higher compression rate (that is, the compression rate a3). Then
The MPEG encoder 12 performs compression encoding at the compression ratio a3, and the amount of data output from the MPEG encoder 12 per unit time further decreases. Therefore, the degree of increase in the amount of data in the RAM 18 from point c is further reduced. . Then, if the access is successful at the time point d, the writing to the disk 5 is performed, so that the data amount in the RAM 18 decreases.

However, if an access error occurs during writing, the amount of data in the RAM 18 increases again. The point e in FIG. 2 indicates this state. At this point e, an access error occurs again, and thereafter the data amount of the RAM 18 increases. If no access error occurs at this point e, the RAM 1
The data amount in 8 will further decrease.

Thereafter, as described above, at time f, RA
Since the amount of data in M18 exceeds the first threshold, f
From the time point, encoding is performed at the compression rate a2. And g
If the access succeeds at this point, the writing to the disk 5 is performed, so that the amount of data in the RAM 18 decreases.

However, if an access error occurs during writing, the amount of data in the RAM 18 increases again. The time point h in FIG. 2 indicates this state, and at this time point h, an access error occurs again, and thereafter the data amount of the RAM 18 increases. If no access error occurs at the time point h, the RAM 1
The data amount in 8 will further decrease.

If the access succeeds at the time point i, the writing to the disk 5 is performed, so that the amount of data in the RAM 18 decreases. Note that even if the access was successful between the time point h and the time point i, the data amount in the RAM 18 did not reach the disk write start position, so no recording was performed, and the disk write start position was reached. At this point, recording is performed, and the amount of data in the RAM 18 decreases. From the time point a to the time point i,
It can be said that it is abnormal when the normal operation as shown in the steady state in FIG. 2 is not performed. In the above processing, the compression ratio is changed for each GOP. That is, when an instruction to change the compression ratio is input from the data rate control circuit 20 during the encoding of a certain GOP, the MPEG encoder 12 performs the encoding based on the changed compression ratio from the next GOP. Do.

When performing the above processing,
Since the compression ratio is not constant, it is necessary to write the data of the compression ratio to the disk for each predetermined data amount. Specifically, in MPEG1, BR (a full spelling name is “Bi
t Rate ") is provided in the sequence layer, so that this BR will be written. That is, this BR
In advance, information on the bit rate for each GOP is stored,
At the time of reproduction, decoding is performed according to this bit rate information.

As described above, the compression ratio at the time of encoding is changed according to the amount of data in the RAM 18 and the RAM 18
As the amount of data in the RAM 18 increases, the compression ratio increases. Therefore, when the amount of data in the RAM 18 increases, the transfer rate of data to the RAM 18 is reduced to reduce the amount of data.
Can be prevented from overflowing. Therefore, the inconvenience of discontinuous images and sounds due to overflow does not occur.

In the above description, the case where the number of thresholds is two has been described. However, the number of thresholds may be one, or three or more thresholds may be provided. At this time, the number of types of compression ratios is the number of thresholds + 1.

Although the above description has been made on the assumption that the MPEG encoder 12 performs encoding of MPEG1, MPEG2 may be used. In that case, the information on the bit rate is the BRV provided in the sequence layer.
(The full spelling name is "BitRate Value")
Will be stored. Also, in the above description, MPEG has been described as an example of a data compression method, but the present invention is not limited to this, and other compression methods may be used.

[0031]

According to the information recording apparatus of the present invention,
By reducing the transfer rate as the data amount of the data stored in the storage means increases, it is possible to prevent the storage means from overflowing.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an operation of the recording / reproducing apparatus according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a data structure in a RAM 18.

[Explanation of symbols]

 A recording / reproducing apparatus 5 disk 12 MPEG encoder 14, 18 RAM 16 encoder 20 data rate control circuit

Claims (6)

[Claims] 1. An information recording apparatus for recording predetermined data on a recording medium, comprising: compression means for compressing data to be recorded on the recording medium; and storage for temporarily storing data compressed by the compression means. An information recording apparatus comprising: means for controlling a transfer rate of data output from the compression means in accordance with a data amount of data stored in the storage means. 2. The information recording apparatus according to claim 1, wherein said control means controls a data compression ratio in said compression means. 3. The apparatus according to claim 2, wherein said control means reduces a transfer rate of data transferred from said compression means by increasing a compression rate as an amount of data stored in said storage means increases. 3. The information recording device according to 2. 4. A comparison means for comparing the threshold value provided in advance with the data amount stored in the storage means, and a selection means for selecting a compression rate according to a comparison result of the comparison means. 4. The method according to claim 2, wherein
An information recording device according to claim 1. 5. The information recording apparatus according to claim 4, wherein a plurality of the thresholds are provided. 6. The information recording apparatus according to claim 2, wherein data on a compression ratio is recorded on the recording medium together with data to be recorded on the recording medium.