JP2014175954A - Data recording device, control method thereof, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique of selecting a data recording speed mode corresponding to a required data recording speed.SOLUTION: A data recording device, which records image data on a recording medium having a plurality of speed modes whose recording speeds are different from each other, includes: determination means for determining, on the basis of a kind of image data to be recorded on the recording medium, a recording speed for the recording of the image data on the recording medium; selection means for selecting one, out of the plurality of speed modes of the recording medium, whose recording unit is the smallest among each speed mode whose recording speed is higher than the determined recording speed; and recording means for recording the image data on the recording medium in accordance with the selected speed mode.

Description

  The present invention relates to a data recording apparatus, a control method therefor, and a computer program.

  There are various types of recording media for recording digital data such as music content, moving image content, and still image content, such as semiconductor recording media, magnetic disks, optical disks, and magneto-optical disks. In particular, since semiconductor recording media are characterized by being able to be reduced in size and weight, they are rapidly spreading mainly in portable devices such as digital still cameras and mobile phone terminals. A typical semiconductor recording medium includes an SD card (registered trademark).

  The capacity of SD cards has been increasing year by year, and application to moving picture recording applications is particularly expected as an application field that takes advantage of the large capacity. When moving image data is recorded in real time with a digital video camera or the like, it is important to guarantee a minimum recording processing speed in order to prevent recording stoppage due to insufficient recording speed on the recording medium.

  Data recorded on these SD cards is managed by a file system. In general, in a file system, a recording area of a medium is managed by being divided into sectors as minimum access units and clusters as a set of sectors. As a file system generally used in information equipment such as a PC (personal computer), a FAT (file allocation table) file system is an example. In FAT, a cluster is a minimum data writing unit.

  On the other hand, in the SD card, data is recorded / deleted for each unit of erase block. This erase block is generally composed of a plurality of clusters. Therefore, when one cluster data in the erase block is to be rewritten, the data in the entire erase block is once read into the RAM inside the SD card, the necessary data is rewritten in the RAM, and then written back into the entire erase block again. Operation is performed. This series of operations is called read modify write. Since the read modify write requires time for writing, it becomes a problem in a product such as a video camera that requires high-speed recording to some extent.

  Therefore, in order to prevent the occurrence of read-modify-write as much as possible, the standard defines a minimum writing unit called AU (Allocation Unit) that can guarantee the writing speed to the SD card. Each SD card host device manufacturer can avoid the occurrence of read-modify-write by satisfying the AU-aligned access and satisfy the required recording speed.

  However, since the AU size is larger than the cluster size and the erase block size, when writing a file with a small size or writing at the end of the file, it becomes impossible to satisfy access in units of AUs. In this case, the AU recorded only in a part cannot be used as a free area for speed guarantee recording. If data having a size not in units of AUs is repeatedly written, a waste area that cannot be handled for high-speed recording will occur on the recording medium.

  In Patent Document 1, when recording is completed, there is a method for preventing an increase in useless areas by moving a tail portion that is not an AU unit of recorded data to an AU that has already been partially recorded. It is stated.

JP 2009-64386 A

  However, since the digital video camera requires that the next recording can be started immediately after the recording is stopped, if the data is moved after the recording is completed as described above, the recording speed is not guaranteed and the recording is performed at the next recording. May collapse.

  On the other hand, with a digital video camera, a plurality of recording qualities can be set, and the image quality tends to be further improved. The recording speed required for the SD card has been increased as the image quality has been improved. In recent years, a plurality of AU sizes have been prepared according to the speed performance (speed mode) to be guaranteed. Some SD cards require AU size switching when the speed mode is switched. The AU size corresponding to such a high speed mode tends to be larger than that corresponding to the low speed mode. Therefore, if the fastest speed mode is simply selected in order to guarantee recording at all image quality settings, the AU size increases and is wasted when partial recording to the AU as described above occurs. There is a problem that the size of the area to be increased also increases.

  Therefore, an object of the present invention is to provide a technique for selecting a data recording speed mode corresponding to a required data recording speed so that the capacity of the recording medium can be used effectively.

The present invention for solving the above problems is a data recording apparatus for recording video data on a recording medium having a plurality of speed modes having different recording speeds,
Determining means for determining a recording speed for recording the video data on the recording medium based on a type of video data to be recorded on the recording medium;
A selection means for selecting a speed mode having the smallest recording unit among speed modes having a recording speed higher than the determined recording speed among a plurality of speed modes of the recording medium;
Recording means for recording the video data on the recording medium in accordance with the selected speed mode.

  According to the present invention, it is possible to select a data recording speed mode according to the required data recording speed, and to effectively use the capacity of the recording medium.

The block diagram which shows an example of a structure of the data recording device corresponding to embodiment of invention. The flowchart which shows an example of the speed mode selection process corresponding to embodiment of invention.

  FIG. 1 is a block diagram illustrating a configuration example of a data recording apparatus according to an embodiment of the present invention. Hereinafter, a digital video camera will be described as an example of the data recording apparatus.

  The digital video camera 100 includes a recording medium control unit 110, a speed mode acquisition unit 120, a recording unit size acquisition unit 121, a recording rate determination unit 122, a speed mode selection unit 123, a control unit 130, a storage unit 140, a video acquisition unit 150, A recording unit 160 and an operation unit 170 are connected to each other via the internal bus 101, and recording / reproducing is performed on the recording medium 200.

  Although the present embodiment will be described focusing on recording video data on the recording medium 200, the data recording apparatus 100 is configured as an apparatus that enables playback of video data recorded on the recording medium 200. You can also. The data recording device 100 may be any device that can record video data on a connected recording medium, such as a digital camera, digital video camera, mobile phone, smartphone, PDA, notebook computer, tablet terminal. Etc. can be realized. In the digital video camera 100 of FIG. 1, each block may be configured by hardware using a dedicated logic circuit or a memory, except for a physical device such as an image sensor or a display element. Alternatively, the processing program stored in the memory may be configured by software by a computer such as a CPU executing the processing program.

  The recording medium control unit 110 delivers commands and data to the mounted recording medium 200. The speed mode acquisition unit 120 issues an instruction to the recording medium 200 via the recording medium control unit 110 and acquires information on all speed modes that can be selected by the recording medium 200. In the present embodiment, an SD card corresponding to a high-speed writing mode called an UHS (Ultra High Speed) mode will be described as the recording medium 200. In the UHS mode, a recording speed (writing speed) of 10 megabytes per second (MB / s) or more is guaranteed. Further, such an SD card also supports a non-UHS mode, and the speed mode is identified by class numbers such as Class2, Class4, Class6, and Class10 called "Speed Class". In each class, 2 MB / s, 4 MB / Recording speeds of s, 6 MB / s and 10 MB / s are guaranteed. The recording medium control unit 110 acquires information for identifying the UHS mode and the class from the recording medium 200. In the present embodiment, the recording medium 200 can be easily attached to and ejected from the video camera 100 by an unillustrated mounting / discharging mechanism.

  The recording unit size acquisition unit 121 issues an instruction to the recording medium 200 via the recording medium control unit 110, and acquires all AU (Allocation Unit) sizes that can be selected by the recording medium 200. In the non-UHS mode, the maximum value of the AU size is generally determined based on the capacity of the recording medium 200. For example, if the card size is 32 gigabytes (GB), the maximum AU size is 4 MB, which corresponds to the speed class. AU size is set. For example, 512 KB, 1 MB, 2 MB, and 4 MB can be set for each of Classes 2, 4, 6, and 10, respectively. Note that the AU size may be the same for each class. For the UHS mode, a larger AU size can be set, and for example, 32 MB is designated.

  The recording rate determination unit 122 determines a recording rate (recording speed) required when the recording unit 160 records video data on the recording medium 200 based on the type and image quality (quality) of the video data. More specifically, the digital video camera 100 has a plurality of operation modes for recording video data of different recording rates, such as a moving image shooting mode, a still image shooting mode, a continuous shooting image shooting mode, and the like. Images (including both single shots and continuous shooting) can be taken. Further, the user can set the image quality of the video data recorded in each mode from a plurality of image quality. The user can set the operation mode and the image quality via the operation unit 170, and the necessary recording rate is determined from the designated operation mode and the image quality setting or only one of them.

  The moving image shooting mode is a mode for shooting a moving image, in which the video signal input from the image sensor of the video acquisition unit 150 is encoded by the recording unit 160 (MPEG2, H.264, etc.), and the recording medium is recorded. Recording is performed on the recording medium 200 via the control unit 110. The recording unit 160 controls the bit rate (data rate) of moving image data to be encoded according to the set image quality. In the present embodiment, for example, control is performed so that the bit rate of moving image data to be encoded increases as the setting of high image quality is achieved. The still image shooting mode is a mode for shooting a still image. The recording unit 160 encodes a still image (JPEG) to generate and record a still image such as a JPEG image. The recording unit 160 changes the compression rate, for example, according to the image quality setting. The continuous shooting image shooting mode is a mode for continuously shooting a predetermined number of still images per unit time, and the generation of the still image is repeated for the predetermined number of images. A plurality of speeds may be set as the continuous shooting speed. In the present embodiment, it is assumed that the recording rate is set in advance in accordance with the set image quality in each shooting mode. For example, in the moving image shooting mode, it is assumed that the image quality of the moving image data to be recorded can be set to any one of three levels (Q1, Q2, Q3 may be in the order of Q1> Q2> Q3). The corresponding recording rates R1, R2, and R3 increase in the order of R1> R2> R3. Since the recording rate is compared with the recording speed in each speed mode of the recording medium, it is determined as a value in units of MB / s, for example, 3 MB / s.

  The speed mode selection unit 123 exceeds the recording rate determined by the recording rate determination unit 122 among the selectable speed modes obtained by the speed mode acquisition unit 120 when the recording medium 200 is mounted, and acquires the recording unit size. The speed mode with the smallest AU size obtained by the unit 121 can be selected. Further, since the required recording rate may change even when the operation mode of the digital video camera 100 is switched and the type of video data to be acquired is changed, the speed mode is selected again. Further, the speed mode may be selected at the timing of starting recording on the recording medium 200, for example, at the start of recording.

  The control unit 130 is responsible for the central processing of the digital video camera 100, and includes a recording medium control unit 110, a recording unit size acquisition unit 121, a recording rate determination unit 122, a speed mode selection unit 123, a storage unit 140, a video acquisition unit 150, The recording unit 160 and the operation unit 170 are controlled. Control unit 130 includes a CPU that operates according to a program stored in storage unit 140. The storage unit 140 is configured by a storage element such as a RAM and a ROM, for example, and is used as a work area or a program storage area. For example, the storage unit 140 stores information on the speed mode and AU size acquired by the speed mode acquisition unit 120 and the recording unit size acquisition unit 121. Further, setting information regarding the operation mode and image quality setting of the digital video camera 100 set by the user by operating the operation unit 170, and information on the speed mode determined by the processing according to the embodiment of the invention are stored. Furthermore, a program for controlling the operation of the digital video camera 100 is stored. The video acquisition unit 150 inputs a video signal input from an image sensor such as a CCD or CMOS, and inputs the video signal to the recording unit 160.

  The recording unit 160 encodes the video signal input by the video acquisition unit 150 as a moving image or a still image, and records the encoded video signal on the recording medium 200 via the recording medium control unit 110. At this time, the bit rate corresponds to the image quality instructed by the user via the operation unit 170. The operation unit 170 is a button, a switch, or the like, and inputs an operation from the user.

  The recording medium 200 is an SD card and has a plurality of speed modes. In accordance with a command from the recording medium control unit 110, input / output of recording data, AU size notification, and speed mode switching are performed.

  Next, the procedure for selecting the speed mode of the recording medium 200 in the present embodiment will be described. FIG. 2 is a flowchart showing a procedure of speed mode selection processing in the present embodiment. The processing corresponding to the flowchart can be realized, for example, by executing a corresponding program (stored in the storage unit 140) by a CPU functioning as each block.

  In S <b> 201, the speed mode acquisition unit 120 acquires information on speed modes that can be selected by the recording medium 200 from the recording medium 200 via the recording medium control unit 110. If there are a plurality of selectable speed modes, all of them are acquired and stored in the storage unit 140. For example, if the storage medium is compatible with the UHS mode, information indicating that is acquired and stored. For the non-UHS mode, information indicating each class is acquired and stored. In step S <b> 202, the recording unit size acquisition unit 121 acquires the AU size corresponding to each speed mode acquired in step S <b> 201 via the recording medium control unit 110, and stores it in the storage unit 140. As described above, the AU size is provided as information indicating the size of a recording unit such as 512 KB, 1 MB, 2 MB, and 4 MB.

  In step S <b> 203, the recording rate determination unit 122 determines a recording rate for the recording unit 160 to record a moving image or a still image on the card and stores the recording rate in the storage unit 140. The recording rate is determined based on the operation mode and the image quality setting set by the user of the digital camera 100 by operating the operation unit 170. Since the setting information is stored in the storage unit 140, it can be referred to. The storage unit stores recording rate information according to each operation mode and image quality setting, for example, in a look-up table format, and the recording rate determination unit 122 can determine the recording rate with reference to the LUT. it can.

  In subsequent steps S204 to S208, the speed mode selection unit 123 selects a speed mode. First, in S204, the recording speed and recording rate of each speed mode acquired in S201 are compared to determine whether there is a speed mode having a recording speed higher than the recording rate. If there is a speed mode exceeding the recording rate (“YES” in S204), the process proceeds to S205, the AU size stored in the storage unit 140 is referred to in S202, and the speed mode corresponding to the minimum AU size is selected. Thereafter, the process proceeds to S207. On the other hand, when the recording medium 200 does not have any speed mode that satisfies the recording rate (“NO” in S204), the process proceeds to S206, and the speed mode closest to the recording rate, that is, the speed mode with the highest speed is selected. At this time, the control unit 130 may warn the user that the optimum speed mode is not available.

  In step S207, it is determined whether only one speed mode is selected in step S205. Depending on the recording medium 200, there may be a plurality of minimum AU speed modes. If there is only one minimum AU speed mode (“YES” in S207), the speed mode selection by the speed mode selection unit 123 is terminated as it is. On the other hand, when there are a plurality of minimum AU speed modes (“NO” in S207), the process proceeds to S208, and the slowest speed mode is selected from among the plurality of speed modes. This is because the recording rate necessary for recording a moving image or a still image is already satisfied in S204, and it is advantageous from the viewpoint of power consumption to select a low speed mode.

  As described above, in this embodiment, the digital video camera 100 can select a speed mode that satisfies the recording speed required by the system and has the smallest AU size. If the AU size to be used is reduced, it is possible to effectively prevent the occurrence of “partially recorded AU” that cannot be used as a free area for speed-guaranteed recording, thereby preventing the generation of a waste area on the recording medium. It can be avoided. Therefore, it is possible to effectively use the capacity of the recording medium 200 without breaking the moving image recording operation.

  In the description of the present embodiment, the recording medium 200 has been described as an SD card. However, the type of the recording medium 200 is not limited to this, and can be applied to all information recording media having a plurality of speed modes. .

(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

Claims (8)

A data recording apparatus for recording video data on a recording medium having a plurality of speed modes with different recording speeds,
Determining means for determining a recording speed for recording the video data on the recording medium based on a type of video data to be recorded on the recording medium;
A selection means for selecting a speed mode having the smallest recording unit among speed modes having a recording speed higher than the determined recording speed among a plurality of speed modes of the recording medium;
A data recording apparatus comprising: recording means for recording the video data on the recording medium in accordance with the selected speed mode.   The data recording apparatus according to claim 1, further comprising an acquisition unit configured to acquire information on the plurality of speed modes included in the recording medium and information on the recording unit in each speed mode from the recording medium.   The data recording apparatus according to claim 1, wherein the determining unit determines the recording speed further based on the quality of the video data.   The selection means selects a speed mode having a slower recording speed when there are a plurality of speed modes having the smallest recording unit among speed modes having a recording speed faster than the determined recording speed. The data recording device according to any one of claims 1 to 3.   The selection means, when there is no speed mode having a recording speed faster than the determined recording speed, selects a speed mode having the fastest recording speed from among the plurality of speed modes. 5. The data recording apparatus according to any one of 1 to 4. The selection means selects the speed mode,
When the recording medium is mounted on the data recording device,
When the type of video data to be recorded on the recording medium is changed,
6. The data recording apparatus according to claim 1, wherein the recording is performed in at least one of cases where recording of the video data on the recording medium is started. A control method of a data recording apparatus for recording video data on a recording medium having a plurality of speed modes with different recording speeds,
A determining step for determining a recording speed for recording the video data on the recording medium based on a type of video data to be recorded on the recording medium;
A selection step of selecting a speed mode with the smallest recording unit among speed modes having a recording speed faster than the determined recording speed among a plurality of speed modes of the recording medium;
A control method for a data recording apparatus, comprising: a recording unit that records the video data on the recording medium according to the selected speed mode.   The program which makes a computer function as each means of the data recording device of any one of Claims 1 thru | or 6.

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