JP4133877B2 - Data storage device and imaging device - Google Patents

Description

  The present invention relates to a memory for storing data, a data storage device for transferring data stored in the memory to a storage medium having a larger storage capacity than the memory, and an imaging for storing imaging data in the data storage device Relates to the device.

  2. Description of the Related Art Conventionally, there is a digital video camera that stores captured video data in a storage medium as a data storage device that stores data in a buffer memory and then transfers the data to a storage medium having a larger storage capacity than the buffer memory. In recent years, digital video cameras that digitally process video data and store the data in a storage medium such as a hard disk drive (hereinafter referred to as a hard disk) or a DVD have increased.

The power consumption of the hard disk or optical disk is higher in the writing state than in the state where data is not written (stored). Therefore, rather than always transferring the data stored in the buffer memory to the storage medium and writing it, it is better to accumulate a certain amount of data in the buffer memory and collect the data at a time interval and transfer it to the storage medium for writing. Power consumption can be reduced (see, for example, Patent Document 1). In this case, the more data capacity that can be stored in the buffer memory, the lower the frequency of writing to the storage medium and the lower the power consumption.
JP-A-9-270985

  In addition, since a digital video camera is carried around by a user, vibration or impact may be applied. When vibration or impact is applied, power supply to the buffer memory is temporarily stopped, and data stored in the buffer memory may be lost. To reduce the amount of data stored in the buffer memory when the power supply is stopped, transfer the data stored in the buffer memory to the storage medium at short time intervals to minimize the amount of data stored in the buffer memory. It is preferable to suppress to. However, when data is transferred to the storage medium at a time interval as short as possible so that the amount of data stored in the buffer memory is reduced, there arises a problem that power consumption increases as described above.

  The present invention has been made in view of such circumstances, and the time interval for intermittent data transfer from the memory to the storage medium, the data size for each transfer, or the data size to be stored in the memory is determined as the remaining amount of the battery. It is an object of the present invention to provide a data storage device and an imaging device capable of performing a good balance between the long-term use of a battery and the reduction of data loss when power supply is stopped.

  Further, the present invention sets the time interval or data size to increase as the remaining battery level decreases, thereby extending the battery usage time when the remaining battery level is low. Another object of the present invention is to provide a data storage device and an imaging device that can reduce the amount of data lost when power supply is stopped.

  In addition, the present invention reduces power consumption by continuously rotating the storage medium and retracting the head from the storage medium when data transfer from the memory to the storage medium is not performed, and by impact or the like. It is another object of the present invention to provide a data storage device and an imaging device that can prevent a head from colliding with a storage medium.

A data storage device according to the present invention includes a memory for storing data, and transfer control means for intermittently transferring the data stored in the memory to a storage medium having a storage capacity larger than that of the memory. In the data storage device that receives power from the detection means for detecting the remaining amount of the battery, and based on the remaining amount detected by the detection means, the time interval or intermittent transfer related to intermittent transfer of the transfer control means Setting means for setting a data size, and the setting means is configured to set such that the time interval or the data size increases as the remaining amount detected by the detection means decreases. It is characterized by.

In the data storage device according to the present invention, the setting unit is configured to set the time interval or the data size to be smaller than a predetermined value when the remaining amount detected by the detection unit is larger than a predetermined amount. characterized in that there.

  In the data storage device according to the present invention, the time interval related to the intermittent transfer is such that after the transfer to the storage medium of the data stored in the memory is started, the transfer is completed and then transferred. It is a time interval until resumption.

A data storage device according to the present invention includes a memory for storing data, and transfer control means for intermittently transferring the data stored in the memory to a storage medium having a storage capacity larger than that of the memory. In the data storage device that receives power from the detection unit, the detection unit that detects the remaining amount of the battery, and the data that is stored in the memory related to the intermittent transfer of the transfer control unit based on the remaining amount detected by the detection unit and a setting means for setting the size, the setting means, as the remaining amount of the detecting unit detects is decreased, and wherein the configuration tare Rukoto order to set such that the data size increases To do.

  A data storage device according to the present invention comprises a head for writing data to the storage medium, a position control means for controlling the position of the head, and a rotation means for holding and rotating the storage medium, from the memory When data transfer to the storage medium is not performed, the rotation unit continues to rotate the storage medium, and the position control unit is configured to retract the head from the storage medium. .

  An imaging apparatus according to the present invention includes a dividing unit that divides captured image data, a compression unit that performs compression processing on the image data divided by the dividing unit, and the data storage device according to the present invention. The data compressed by the means is stored in the memory.

  In the present invention, the remaining amount of the battery is detected by the detecting means, and the time interval related to intermittent data transfer from the memory to the storage medium or the data size for each transfer is set by the setting means based on the detected remaining amount To do. Since the power consumption in the writing state in which writing (storing) to the storage medium is performed is higher than the power consumption in the standby state in which writing is not being performed, the time interval or data size is increased. The power consumption will be lower if the frequency of loading is reduced. However, when power supply is stopped, data stored in the memory is lost. Therefore, when the frequency of writing is reduced, the amount of data lost due to power supply stop increases. Conversely, when writing is performed at a high frequency by reducing the time interval or the data size, it is possible to reduce the amount of data lost due to power supply stop and prevent data loss due to power supply stop. However, when writing is performed with high frequency, the power consumption increases. The setting means sets the time interval or the data size according to the remaining battery level, and adjusts the power consumption and the amount of data lost when the power supply is stopped.

  In the present invention, the time interval related to intermittent data transfer from the memory to the storage medium is the time interval after the transfer ends after the transfer of the data stored in the memory to the storage medium is started. This is the time interval until transfer is resumed. Since the amount of data that can be transferred from the memory per unit time to the storage medium is larger than the amount of data stored in the memory per unit time, the time interval is increased (or decreased) to occupy the time interval. It is possible to increase (or decrease) the percentage of time during which no data is transferred. The setting means sets the time interval according to the remaining battery level, and adjusts the power consumption and the amount of data lost when the power supply is stopped.

  In the present invention, the remaining amount of the battery is detected by the detecting means, and the data size stored in the memory related to intermittent data transfer from the memory to the storage medium is set by the setting means based on the detected remaining amount. . Since the amount of data that can be transferred from the memory per unit time to the storage medium is larger than the amount of data stored in the memory per unit time, the data size stored in the memory can be increased (or decreased) to be stored. The frequency of data writing to the medium can be reduced (or increased). The setting means sets the data size to be stored in the memory according to the remaining battery level, and adjusts the power consumption and the amount of data lost when the power supply is stopped.

  In the present invention, the time interval or data size is set by the setting means so as to increase as the detected remaining amount decreases. As described above, since the power consumption is lower when the time interval or the data size is increased and the frequency of writing is decreased, the time interval or the data size is increased when the remaining amount of the battery is low. , Reduce power consumption and extend battery usage time. In addition, as described above, if the time interval or data size is reduced and writing is performed more frequently, the amount of data lost due to power supply stop is reduced. By reducing the data size, the amount of data lost when the power supply is stopped can be reduced.

  In the present invention, when data transfer from the memory to the storage medium is not performed, the rotation means continues to rotate the storage medium, and the position control means sets the head for writing data to the storage medium to the storage medium. Evacuate from above. Regarding the rotation of the storage medium, the power consumption is the lowest when the rotation is stopped, but the power consumption is higher in the starting state where the operation is started from the state where the rotation is stopped than in the rotation state. Therefore, when data is stored intermittently, power consumption is lower when rotation is stopped than when data writing is not being performed. Further, by retracting the head from the storage medium when data writing is not performed, it is possible to prevent the head from colliding with the storage medium due to impact or the like.

  In the present invention, the captured image data is divided by the dividing means, the compressed image data is subjected to compression processing by the compression means, and the compressed data is stored in the memory of the data storage device according to the present invention described above.

  According to the present invention, by setting the time interval for intermittent data transfer from the memory to the storage medium, the data size for each transfer, or the data size to be stored in the memory based on the remaining battery capacity, Since the power consumption and the amount of data lost when the power supply is stopped can be adjusted according to the remaining amount of the battery, it is possible to balance the use of the battery for a long time and the amount of data lost when the power supply is stopped.

  According to the present invention, the time interval or the data size is set so as to decrease as the remaining amount of the battery decreases. The battery usage time can be extended to reduce the amount of data lost when the power supply is stopped by increasing the frequency of writing when the remaining battery level is high.

  According to the present invention, when data transfer from the memory to the storage medium is not performed, the rotation of the storage medium is continued, and the power is reduced by retracting the head from the storage medium. It is possible to prevent the head from colliding with the storage medium due to an impact or the like.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
FIG. 1 is a block diagram showing a configuration example of a digital video camera (imaging device) including a data storage device according to the present invention. A digital video camera converts a captured analog video signal into a digital NTSC (National Television System Committee) or PAL (Phase Alternation Line) video signal, and further, MPEG (Moving Picture). Expert Group) -2 is compressed according to the format, and the compressed data is stored in a storage medium.

  An optical subject video captured by a CCD (Charge Coupled Device) 1 is converted into an electrical analog video signal and sent to the CDS / AGC circuit 2. The CDS / AGC circuit 2 suppresses the low frequency noise peculiar to the CCD 1 included in the video signal read from the CCD 1 by CDS (Correlated Double Sampling), and the signal level of the output signal of the CCD 1 is AGC (Automatic Gain Control). In addition, the amplitude of the video signal level is limited in the vicinity of the input upper limit value of the ADC 3 in order to compensate for the lack of dynamic range of the subsequent ADC (Analog Digital Converter) 3.

  A video signal output from the CDS / AGC circuit 2 and converted into a digital form by the ADC 3 is input to a DSP (Digital Signal Processor) 4. Although not shown in the figure, the DSP 4 converts a digital video signal input from the ADC 3 into a luminance signal Y and color difference signals U and V, a function of adding a synchronization signal, a function of adjusting white balance, a digital A function to zoom in and out is provided. The DSP 4 outputs a horizontal / vertical drive signal pulse to the CCD 1 and reads out a video signal from the CCD 1 while taking a timing with the synchronization signal. Also, the DSP (dividing means) 4 divides the video signal and sends the divided video signal to the MPEG encoder 5.

  An MPEG encoder (compression unit) 5 receives a digital video signal (luminance signal Y and color difference signals U and V) generated by the DSP 4 and compresses (encodes) the input data into an MPEG-2 format. Reduce the amount of data to tens of ones. The compressed data is sent to a data storage device and stored in a storage medium.

  The data storage device includes an HDD 6, a buffer RAM (Random Access Memory) 7, and a microcomputer 8, and an MPEG encoder 5, HDD 6, buffer RAM 7, and microcomputer 8 are connected to the bus 11. As the buffer RAM 7, for example, a synchronous DRAM is used.

  The HDD 6 includes a magnetic disk (storage medium), a motor (rotating means) for rotating the magnetic disk, a magnetic head, a servo circuit (position control means) for controlling the position of the magnetic head, a digital signal storage processing circuit, and an input / output Interface buffer memory is provided.

  The microcomputer (transfer control means) 8 includes a ROM for storing a control program and control data, and a RAM for storing temporary data, and a buffer RAM 7 for data compressed by the MPEG encoder 5. And control of each component in the data storage device such as data transfer from the buffer RAM 7 to the HDD 6. The microcomputer 8 controls each component in the digital video camera.

  The digital video camera is equipped with a battery (battery) 9, and power is supplied from the battery 9 to each component in the digital video camera. As the battery 9, a rechargeable secondary battery, a dry battery, or the like can be used.

  The bus 11 is connected to a remaining amount detection unit 10 that detects the remaining amount of the battery 9. The microcomputer 10 acquires the remaining amount of the battery 9 detected by the remaining amount detection unit 10.

  The amount of data that can be stored in the HDD 6 per unit time is several tens of times larger than the amount of compressed data generated per unit time, and the compressed data can be stored together in the HDD 6. The microcomputer 8 transfers the data stored in the buffer RAM 7 to the HDD 6 in a set data size unit. The storage capacity of the buffer RAM 7 is larger than the set data size. In addition, when MPEG compression is performed at a fixed bit rate, it is possible to start transfer of data stored in the buffer RAM 7 to the HDD 6 at time intervals corresponding to the set data size.

  FIG. 2 is a diagram illustrating an example of transfer of compressed data stored in the buffer RAM 7 to the HDD 6. In FIG. 2, T0 is a time during which compressed data corresponding to the set data size to be transferred to the HDD 6 is accumulated in the buffer RAM 7. Data transfer from the buffer RAM 7 to the HDD 6 is started at time T0 intervals. T1 is a time during which writing processing to the HDD 6 is performed, and T2 is a time during which writing processing to the HDD 6 is not performed. However, at time T2, the magnetic disk continues to rotate.

  The writing process (time T1) includes a process of loading the magnetic head onto the magnetic disk (time T11), a process of seeking the magnetic head to the track to be written (time T12), and data on the magnetic disk. A process of writing (storing) (time T13) and a process of unloading (saving) the magnetic head from the magnetic disk (time T14) are included. Although the time T13 increases or decreases according to the set data size, the times T11, T12, and T14 can be regarded as substantially constant. These writing processes are performed under the control of the microcomputer 8.

  The power consumption of the HDD 6 is the standby state in which the motor that rotates the magnetic disk is stopped, the start-up state in which the motor starts rotating, the motor is rotating but the magnetic head is retracted from the magnetic disk and the storage process is suspended. The idle state (time T2), and the read / write state (time T1) in which the magnetic head reads / writes data facing the magnetic disk. The power consumption in each of these states is “startup state”> “read / write state”> “idle state”> “standby state”.

  The power consumption during the time T2 when the HDD 6 is in the idle state and the writing process is paused is less than the power consumption during the time T1 (= T11 + T12 + T13 + T14) during which the writing process is performed. As the time T2 becomes longer, the power consumption of the HDD 6 can be reduced. In order to lengthen the time T2, the set data size as a data unit to be transferred from the buffer RAM 7 to the HDD 6 is increased (the storage capacity of the buffer RAM 7 is also increased if necessary), and data transfer from the buffer RAM 7 to the HDD 6 is started. What is necessary is just to lengthen time interval (T0). FIG. 3 is a diagram showing the relationship between the set data size and the power consumption of the HDD 6. The power consumption of the HDD 6 decreases in inverse proportion to the set data size. When the remaining battery level is low, it is preferable to increase the setting data size to reduce power consumption.

  On the other hand, when the set data size is increased, the power consumption of the HDD 6 is reduced. However, when vibration or impact is applied to the digital video camera, power supply from the battery 9 to the buffer RAM 7 is temporarily stopped. The data stored in the buffer RAM 7 may be lost. In order to reduce the loss of data stored in the buffer RAM 7 when power supply is stopped, the set data size should be reduced and the time interval (T0) for starting data transfer from the buffer RAM 7 to the HDD 6 should be shortened. . When the remaining amount of battery is large, it is preferable to reduce the set data size, increase the frequency of data transfer from the buffer RAM 7 to the HDD 6, and reduce the amount of loss when power supply is stopped.

  The microcomputer 8 operates as means for setting the setting data size based on the remaining amount of the battery 9 detected by the remaining amount detection unit 10. The macro computer 8 sets the setting data size so as to increase as the remaining amount of the battery 9 decreases. The set setting data size and the detected remaining amount of the battery 9 are stored in the RAM of the microcomputer 8.

  For example, when the remaining amount of the battery 9 detected by the remaining amount detection unit 10 is equal to or larger than Vmax / 2, the microcomputer 8 sets the set data size to SM. When the remaining amount is less than Vmax / 2, the set data size is set to SL (SL> SM). The reference values of Vmax / 2 and SL and SM used for the set data size are stored in the ROM of the microcomputer.

  The correspondence between the remaining amount of the battery 9 and the value used for the setting data size is, for example, the setting data size S when the remaining amount is less than 0.25 Vmax, and the remaining amount is 0.25 Vmax to 0.5 Vmax. Setting data size is 0.75S, setting data size is 0.5S when the remaining amount is 0.5Vmax to 0.75Vmax, and setting data size is 0.25S when the remaining amount is 0.75Vmax to Vmax. Etc. are arbitrary. Further, the correspondence between the remaining amount of the battery 9 and the value used for the setting data size is arbitrary, and a map, a mathematical expression, a table, and the like representing the correspondence can be stored in the ROM.

  FIG. 4 is a flowchart illustrating an example of compressed data storage processing. When shooting is started, each part in the digital video camera is controlled by the microcomputer 8, MPEG encoding of the video signal by the MPEG encoder 5 is started (S10), and the encoded data is controlled by the microcomputer 8. Is stored in the buffer RAM 7.

  The microcomputer 8 acquires the battery remaining amount detected by the remaining amount detection unit 10 (S12), and determines the setting data size according to the battery remaining amount (S14). Based on the value stored in the ROM, the setting data size is set to be small when the remaining amount of battery is large, and is set to be large when the remaining amount of battery is small. The microcomputer 8 monitors the accumulated data size accumulated in the buffer RAM 7, and when the accumulated data size reaches the set data size (S16: YES), the HDD 6 is controlled to load the magnetic head of the HDD 6 onto the magnetic disk. Then, seek to the track to be stored (S18), write the compressed data of the set data size unit read from the buffer RAM 7 to the magnetic disk of the HDD 6 (S20), and save the magnetic head from the magnetic disk after writing (unloading) (S22).

  Thereafter, the same processing is repeated until the photographing is finished and the MPEG encoding is finished (S24: NO). When the MPEG encoding is completed (S24: YES), the compressed data remaining in the buffer RAM 7 is transferred to the HDD 6 under the control of the microcomputer 8, and the storage of the captured video data in the HDD 6 is completed. Processing is performed.

  In the above-described embodiment, the case where the setting data size, which is a data unit to be transferred from the buffer RAM 7 to the HDD 6, is changed according to the remaining battery capacity is described as an example. However, data transfer from the buffer RAM 7 to the HDD 6 is performed. It is also possible to change the time interval for execution (start).

  In the above-described embodiment, the data size or time interval transferred from the buffer RAM 7 to the HDD 7 is changed according to the remaining amount of the battery 9, but the data size or the time interval corresponding to the remaining amount of the battery 9 is changed. It is also possible for the user to switch on / off the change of the time interval. Further, when the change is switched off, the user can switch the data size or the time interval large or small (for example, SL or SM in the above-described embodiment). These switching operations are received by an operation unit (not shown) connected to the microcomputer 8, and the microcomputer 8 performs control processing according to the received operation.

  In the above-described embodiment, the case where the data stored in the buffer RAM 7 is stored in the HDD 6 has been described as an example. However, the present invention is not limited to the HDD, and for example, DVD-RAM, DVD-RW, DVD-R, and the like. It is also possible to use this storage medium. It is also possible to use a storage medium such as a flash memory.

  The data storage device of the present invention is not limited to a digital video camera. For example, the data storage device is used for a portable MD recorder that stores audio data on an MD (Mini Disc), or stores video data on a DVD-RAM or the like. It can be used for a portable DVD recorder. In the case of a portable MD recorder or portable DVD recorder, the CCD 1, CDS / AGC circuit 2, ADC 3, DSP 4, and MPEG encoder 5 shown in FIG. 1 correspond to the portable MD recorder or portable DVD recorder. To be changed.

It is a block diagram which shows the structural example of a digital video camera provided with the data storage device which concerns on this invention. It is a figure which shows the example of transfer to the HDD of the compression data accumulate | stored in buffer RAM. It is a figure which shows the relationship between setting data size and the power consumption of HDD. It is a flowchart which shows the example of the memory | storage process of compressed data.

Explanation of symbols

1 CCD
2 CDS / AGC circuit 3 ADC
4 DSP
5 MPEG encoder 6 HDD
7 Buffer RAM
8 Microcomputer 9 Battery 10 Remaining amount detection unit 11 Bus

Claims (6)

In a data storage device comprising a memory for storing data, and transfer control means for intermittently transferring data stored in the memory to a storage medium having a larger storage capacity than the memory, and receiving power from a battery,
Detecting means for detecting the remaining amount of the battery;
Setting means for setting a time interval related to intermittent transfer of the transfer control means or a data size for each transfer based on the remaining amount detected by the detection means ;
The data storage device according to claim 1, wherein the setting means is configured to set the time interval or the data size so that the remaining amount detected by the detection means decreases . 2. The configuration according to claim 1, wherein the setting unit is configured to set the time interval or the data size to be smaller than a predetermined value when the remaining amount detected by the detection unit is larger than a predetermined amount. The data storage device described .   The time interval related to the intermittent transfer is a time interval from the start of the transfer of the data stored in the memory to the storage medium until the transfer is completed and then the transfer is restarted. The data storage device according to claim 1 or 2. In a data storage device comprising a memory for storing data, and transfer control means for intermittently transferring the data stored in the memory to a storage medium having a larger storage capacity than the memory, and receiving power from a battery,
Detecting means for detecting the remaining amount of the battery;
Based on the remaining amount detecting means detects, provided with setting means for setting a data size to be stored in the memory according to the intermittent transfer of said transfer control means,
The data storage device according to claim 1, wherein the setting means is configured to set the data size to increase as the remaining amount detected by the detection means decreases . A head for writing data to the storage medium;
Position control means for controlling the position of the head;
Rotating means for holding and rotating the storage medium,
When data transfer from the memory to the storage medium is not performed, the rotation means continues to rotate the storage medium, and the position control means is configured to retract the head from the storage medium. the data storage device according to any one of claims 1 to 4, characterized. A dividing unit for dividing the captured image data;
Compression means for compressing the image data divided by the dividing means;
A data storage device according to any one of claims 1 to 5 ,
An image pickup apparatus, wherein data compressed by the compression means is stored in the memory.

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