Patent Publication Number: US-2022238138-A1

Title: Electronic device and control methods thereof

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an electronic device and control methods thereof, and particularly relates to an electronic device in which a recording medium is used, and control methods thereof. 
     Description of the Related Art 
     In electronic devices having an image capture function, such as digital cameras and smartphones, memory cards are widespread as recording media for image data obtained using the image capture function. Furthermore, some memory cards have a plurality of transfer modes with different data transfer speeds (Japanese Patent Laid-Open No. 2013-258469). 
     If the data rate of image data to be recorded or played back is higher than the memory card transfer speed, there are cases in which the image data cannot be recorded/played back properly or the operation of an electronic device slows down. Thus, for memory cards having a plurality of transfer modes with different transfer speeds, it is necessary to select the appropriate transfer mode. 
     For example, in a case in which a memory card has a first transfer mode in which a minimum transfer speed is guaranteed, and a second transfer mode in which a minimum transfer speed is not guaranteed and a maximum transfer speed is higher than the minimum transfer speed in the first mode is capable, it is important to switch appropriately between stable transfer and high-speed transfer. This problem applies not only to electronic devices that capture images but to electronic devices that generate and record data according to any appropriate method. 
     SUMMARY OF THE INVENTION 
     In one aspect thereof, the present invention provides an electronic device and control methods thereof that allow a recording medium having a plurality of transfer modes with different transfer speed characteristics to be appropriately used. 
     According to an aspect of the present invention, there is provided an electronic device that can perform communication with a recording medium that has a first transfer mode in which a minimum transfer speed is guaranteed, and a second transfer mode in which a minimum transfer speed is not guaranteed and a higher transfer speed than the minimum transfer speed in the first mode is capable, the electronic device comprising: a controller that communicates with a connected recording medium; and one or more processors that execute a program and thereby function as a determination unit that determines a transfer mode to be used by the controller for the communication, wherein: if the connected recording medium supports the second transfer mode, the determination unit determines the use of the first transfer mode as the transfer mode when the minimum transfer speed is higher than a necessary transfer speed for data that is to be recorded through the communication with the recording medium, and determines the use of the second transfer mode as the transfer mode when the minimum transfer speed is not higher than the necessary transfer speed; and if the connected recording medium does not support the second transfer mode, the determination unit determines the use of the first transfer mode as the transfer mode. 
     According to another aspect of the present invention, there is provided a control method for an electronic device that can perform communication with a recording medium that has a first transfer mode in which a minimum transfer speed is guaranteed, and a second transfer mode in which a minimum transfer speed is not guaranteed and a higher transfer speed than the minimum transfer speed in the first mode is capable, the control method comprising: determining a transfer mode to be used for the communication with a connected recording medium, wherein the determining includes: if the connected recording medium supports the second transfer mode, determining the use of the first transfer mode as the transfer mode when the minimum transfer speed is higher than a necessary transfer speed for data that is to be recorded through the communication with the recording medium, and determining the use of the second transfer mode as the transfer mode when the minimum transfer speed is not higher than the necessary transfer speed; and if the connected recording medium does not support the second transfer mode, determining the use of the first transfer mode as the transfer mode. 
     According to a further aspect of the present invention, there is provided a non-transitory computer-readable storage medium having stored therein a program for causing a computer to execute each step of a control method for an electronic device that can perform communication with a recording medium that has a first transfer mode in which a minimum transfer speed is guaranteed, and a second transfer mode in which a minimum transfer speed is not guaranteed and a higher transfer speed than the minimum transfer speed in the first mode is capable, the control method comprising: determining a transfer mode to be used for the communication with a connected recording medium, wherein the determining includes: if the connected recording medium supports the second transfer mode, determining the use of the first transfer mode as the transfer mode when the minimum transfer speed is higher than a necessary transfer speed for data that is to be recorded through the communication with the recording medium, and determining the use of the second transfer mode as the transfer mode when the minimum transfer speed is not higher than the necessary transfer speed; and if the connected recording medium does not support the second transfer mode, determining the use of the first transfer mode as the transfer mode. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an example of functional configurations of an electronic device and a recording medium according to embodiments. 
         FIG. 2  is a flowchart relating to a transfer mode-determining operation according to a first embodiment. 
         FIG. 3  is a flowchart relating to a transfer mode-determining operation according to a second embodiment. 
         FIG. 4  is a flowchart relating to a transfer mode-determining operation according to a third embodiment. 
         FIGS. 5A to 5C  are diagrams illustrating examples of display performed by the electronic device according to the embodiments. 
         FIG. 6  is a flowchart relating to a transfer mode-determining operation according to a fourth embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiments will be described in detail with reference to the attached drawings. Note, the following embodiments are not intended to limit the scope of the claimed invention. Multiple features are described in the embodiments, but limitation is not made to an invention that requires all such features, and multiple such features may be combined as appropriate. Furthermore, in the attached drawings, the same reference numerals are given to the same or similar configurations, and redundant description thereof is omitted. 
     Note that, in the following embodiments, a case in which the present invention is implemented using an electronic device having an image capture function, or more specifically, a digital camera, which is an image capture apparatus, will be described. However, the image capture function is not required in the present invention. The present invention can be implemented using various electronic devices, such as computer devices (personal computers, tablet computers, media players, PDAs, etc.), portable telephones, smartphones, game machines, robots, drones, and drive recorders. 
     First Embodiment 
       FIG. 1  is a block diagram illustrating an example of functional configurations of an electronic device  100  and a recording medium  120  that can be attached to and detached from the electronic device  100 . The electronic device  100  records (writes) data to and plays back (reads) data from the recording medium  120  connected thereto by communicating with the recording medium  120  via a media control unit  106 . 
     In this embodiment, the electronic device  100  is a digital camera, and the data includes moving-image data and still-image data, for example. Furthermore, description is provided regarding that the recording medium  120  is a memory card (SD Express card) having a bus interface conforming to SD Express. Note that microSD Express cards are also regarded as being included among SD Express cards. Furthermore, the media control unit  106  has an SD Express host function for supporting both the SD and PCIe interfaces. 
     An SD Express card has a first transfer mode and a second transfer mode. The first transfer mode is a transfer mode in which a minimum transfer speed is guaranteed but having a low maximum transfer speed. Furthermore, the second transfer mode is a transfer mode in which a minimum transfer speed is not guaranteed but a higher transfer speed than the minimum transfer speed guaranteed in the first transfer mode is capable. In such a manner, an SD Express card is one example of a memory card having a plurality of transfer modes with different transfer-speed characteristics. 
     In the following description, the first transfer mode is a transfer mode (SD mode) in which a bus interface conforming to UHS-1 is used, and the second transfer mode is a transfer mode (PCIe mode) in which a bus interface conforming to SD Express is used. Note that the SD Express bus interface is based on PCI Express (PCIe). 
     The bus interfaces to be used in the plurality of transfer modes of the recording medium  120  may be those conforming to other specifications. For example, the bus interface for the first transfer mode may conform to UHS-II or UHS-III. 
     An image capture unit  101  includes an imaging optical system and an image sensor that is a CMOS image sensor, for example. A plurality of pixels are arrayed in the image sensor, and the image sensor generates a group of electric signals (image signal) corresponding to an optical image formed by the imaging optical system by photoelectrically converting the optical image using the plurality of pixels. The image capture unit  101  outputs the image signal to an image processing unit  102 . 
     The image processing unit  102  applies predetermined image processing to the image signal output from the image capture unit  101  to generate signals and image data, and to acquire and/or generate various types of information. Signals, image data, and information generated by the image processing unit  102  are output to a display control unit  105 , the media control unit  106 , a control unit  103 , etc. For example, the image processing unit  102  may be a dedicated hardware circuit such as an ASIC that is designed so as to realize one or more specific functions, or may have a configuration such that a programmable processor such as a DSP realizes one or more specific functions by executing software. 
     Here, the image processing applied by the image processing unit  102  includes preprocessing, color interpolation processing, correction processing, detection processing, data processing, evaluation value calculation processing, special effects processing, etc. 
     The preprocessing includes signal amplification, reference level adjustment, defective pixel correction, A/D conversion, etc. 
     The color interpolation processing is processing for interpolating values of color components that cannot be obtained during image shooting, and is also called demosaic processing or synchronization processing. 
     The correction processing includes white-balance adjustment, gradation correction (gamma processing), processing for correcting the influences of vignetting and the optical aberration of the image capture unit  101 , processing for correcting color, etc. 
     The detection processing includes the detection of feature regions (for example, face regions and human-body regions) and the movement thereof, human recognition processing, etc. 
     The data processing includes composition processing, scaling processing, encoding/decoding processing, header information generation processing, etc. Display data and recording data are generated as a result of the data processing. 
     The evaluation value calculation processing includes the generation of signals and evaluation values to be used for automatic focus detection (AF), processing for calculating evaluation values to be used for automatic exposure control (AE), etc. 
     The special effects processing includes the addition of blur, the changing of color tone, rewriting processing, etc. 
     Note that these are examples of image processing that can be applied by the image processing unit  102 , and these examples do not limit the image processing applied by the image processing unit  102 . 
     The term “operation unit  108 ” is used to collectively refer to input devices (one or more buttons, switches, dials, etc.) that are provided to allow a user to input various instructions to the electronic device  100 . The input devices constituting the operation unit  108  each have a name corresponding to the function allocated thereto. For example, the operation unit  108  includes a release switch, a moving-image recording switch, an image-shooting mode selection dial for selecting the image-shooting mode, a menu button, a direction key, an enter key, etc. The release switch is a switch for recording still images, and the control unit  103  recognizes a half-pressed state and a full-pressed state of the release switch as an image-shooting preparation instruction and an image-shooting start instruction, respectively. Furthermore, the control unit  103  recognizes the depression of the moving-image recording switch in an image-shooting standby state as a moving-image recording start instruction, and recognizes the depression of the moving-image recording switch during the recording of a moving image as a recording stop instruction. Note that the function allocated to an input device may be changed. Furthermore, the input devices may be software buttons or keys realized using a touchscreen. The operation unit  108  may also include input devices supporting contactless input methods, such as voice input and eye-controlled input. 
     The control unit  103  includes a programmable processor (CPU), a ROM, and a RAM. The CPU controls the operations of the functional blocks of the electronic device  100  and realizes the functions of the electronic device  100  by loading one or more programs stored in the ROM to the RAM and executing the programs. For example, the ROM is rewritable, and stores programs that can be executed by the CPU, setting values of the electronic device  100 , GUI data, etc. The RAM is used to load programs to be executed by the CPU, and to store values that are necessary during the execution of programs. Note that, while not shown in the drawing, the control unit  103  is connected to each of the functional blocks illustrated in the drawing. 
     Furthermore, the control unit  103  executes processing in accordance with user instructions provided via the operation unit  108 . For example, if an instruction to switch the operation mode of the electronic device  100  is input, the control unit  103  switches the operation mode of the electronic device  100 . The electronic device  100  has a plurality of operation modes including a moving-image recording mode, a still-image recording mode, and a playback mode, for example. The control unit  103  notifies the media control unit  106  and a speed designation unit  107  of the operation mode to which switching was performed. 
     A display unit  104  is a touchscreen, for example. The display unit  104  displays the display data input thereto from the display control unit  105 . For example, the display data is moving-image data, still-image data, or GUI data. GUIs include GUIs, such as a menu screen, that can be operated, and GUIs indicating information regarding the electronic device  100 . 
     The display control unit  105  converts data input thereto from the image processing unit  102  and the media control unit  106  into a format suitable for the display unit  104 , and outputs the converted data to the display unit  104 . 
     For example, the media control unit  106  is an SD host controller, and based on control by the control unit  103 , supplies control signals such a clock to the recording medium  120  and executes operations relating to the transfer of data to and from the recording medium  120 . Furthermore, the media control unit  106  determines the transfer mode to be used for the transfer of data to and from the recording medium  120  in accordance with: the operation mode of the electronic device  100 ; necessary speed information from the speed designation unit  107 ; and card information acquired from a holding unit  110  via a communication control unit  109 . The operation of the media control unit  106  for determining the transfer mode will described in detail later. 
     The media control unit  106  writes and reads data to and from the recording medium  120  using the determined transfer mode. The media control unit  106  outputs the read data to the control unit  103 , the image processing unit  102 , or the display control unit  105 . 
     For example, the card information that the media control unit  106  acquires from the holding unit  110  of the recording medium  120  is information (supported transfer mode information) of transfer modes supported by the recording medium  120 , and transfer speed information for each transfer mode. The transfer speed information includes at least one of a maximum transfer speed and a guaranteed minimum transfer speed. Note that the card information can be acquired only by means of a command that is transmitted to the recording medium  120  using the first transfer mode. 
     In accordance with the operation mode of the electronic device  100  that the speed designation unit  107  is notified of by the control unit  103 , the speed designation unit  107  notifies the media control unit  106  of the necessary minimum transfer speed. For example, if the operation mode of the electronic device  100  is the moving-image recording mode, the speed designation unit  107  outputs, to the media control unit  106 , information (necessary speed information) of the minimum transfer speed that is necessary to continue recording a moving image. The necessary minimum transfer speed may be stored in advance for each operation mode. Note that there may be one or more operation modes for which the minimum transfer speed is not set. 
     Next, the recording medium  120  will be described. 
     The holding unit  110  is a non-volatile memory that holds information (card information) regarding the recording medium  120 , such as the supported transfer mode information, the transfer speed information, and storage capacity information. 
     A recording area  111  is a non-volatile memory for recording data. 
     The communication control unit  109  communicates with the media control unit  106  of the electronic device  100  to which the recording medium  120  is connected. By communicating with the media control unit  106 , the communication control unit  109  outputs, to the electronic device  100 , information held by the holding unit  110  and data recorded in the recording area  111 . Furthermore, by communicating with the media control unit  106 , the communication control unit  109  writes data input from the electronic device  100  to the recording area  111  using a designated transfer mode. Also, by communicating with the media control unit  106 , the communication control unit  109  outputs data recorded in the recording area  111  to the electronic device  100  using a designated transfer mode. 
       FIG. 2  is a flowchart relating to the operation of the media control unit  106  for determining the transfer mode to be used for the communication between the electronic device  100  and the recording medium  120 . While this operation may be performed at any appropriate timing, here, the operation is executed by the media control unit  106  being notified of the operation mode of the electronic device  100  by the control unit  103 . 
     In step S 202 , the media control unit  106  determines whether or not the operation mode that the media control unit  106  is notified of by the control unit  103  is the moving-image recording mode. This determination corresponds to a determination of whether or not the present operation mode of the electronic device  100  is an operation mode having a necessary minimum transfer speed. The media control unit  106  executes step S 203  if the operation mode is the moving-image recording mode, and executes step S 210  if the operation mode is not the moving-image recording mode. 
     Note that, after executing step S 202 , the media control unit  106  may execute step S 205  without executing steps S 203  and S 204  if the present transfer mode is the second transfer mode. 
     In step S 203 , after changing the transfer mode to the first transfer mode as necessary, the media control unit  106  acquires the supported transfer mode information from the holding unit  110  of the recording medium  120  by issuing a command requesting the supported transfer mode information to the recording medium  120 . Then, the media control unit  106  executes step S 204 . Note that, in step S 203 , the media control unit  106  may acquire not only the supported transfer mode information but also the transfer speed information. 
     In step S 204 , the media control unit  106  refers to the supported transfer mode information acquired in step S 203 , and determines whether or not the recording medium  120  supports the second transfer mode (SD Express). The media control unit  106  executes step S 205  if it is determined that the recording medium  120  supports the second transfer mode. On the other hand, the media control unit  106  executes step S 208  if it is not determined that the recording medium  120  supports the second transfer mode. 
     In step S 205 , the media control unit  106  changes the transfer mode to the first transfer mode as necessary, and then issues a command requesting the transfer speed information to the recording medium  120 . Note that the media control unit  106  need not execute step S 205  if the media control unit  106  has already acquired the transfer speed information in step S 203 . Furthermore, before issuing the command requesting the transfer speed information, the media control unit  106  may increase the frequency of the clock supplied to the recording medium  120 . By increasing the clock frequency, the operation speed of the recording medium  120  increases, and the time required to acquire the transfer speed information can be reduced. The media control unit  106  executes step S 206  once the transfer speed information is acquired. 
     Note that, in step S 205 , the media control unit  106  may acquire only the information of the guaranteed minimum transfer speed out of the transfer speed information. Furthermore, the media control unit  106  may execute step S 209  without executing steps S 206  and S 207  if it is determined that the present transfer mode does not have a guaranteed minimum transfer speed. 
     In step S 206 , the media control unit  106  compares the necessary minimum transfer speed when the electronic device  100  is in the moving-image recording mode and the minimum transfer speed guaranteed by the recording medium  120 . In accordance with the present operation mode, a notification of the necessary minimum transfer speed in the operation mode is provided by the speed designation unit  107  to the media control unit  106 . The necessary minimum transfer speed in the operation mode, in the case of the moving-image recording mode, differs depending on moving image recording settings such as the recording size (number of pixels), the bit rate, the frame rate, the compression rate, and the image-quality mode of moving images, for example. 
     In step S 207 , the media control unit  106  determines whether or not the minimum transfer speed guaranteed in the present transfer mode of the recording medium  120  is higher than the necessary minimum transfer speed in the present operation mode of the electronic device  100 . Then, the media control unit  106  executes step S 208  if it is determined that the guaranteed minimum transfer speed is higher than the necessary minimum transfer speed, and otherwise executes step S 209 . 
     In step S 208 , the media control unit  106  determines to perform the communication with the recording medium  120  using the first transfer mode. 
     In step S 209 , the media control unit  106  determines to perform the communication with the recording medium  120  using the second transfer mode. 
     On the other hand, if it is determined that the operation mode of the electronic device  100  is not the moving-image recording mode, the media control unit  106  determines, in step S 210 , whether or not the present operation mode of the electronic device  100  is the still-image recording mode. This determination corresponds to a determination of whether or not the present operation mode of the electronic device  100  is an operation mode not having a necessary minimum transfer speed. The media control unit  106  executes step S 211  if it is determined that the present operation mode is the still-image recording mode, and otherwise executes step S 214 . 
     Note that, after executing step S 202  or S 210 , the media control unit  106  may execute step S 213  without executing steps S 211  and S 212  if the present transfer mode is the second transfer mode. 
     In step S 211 , the media control unit  106  acquires the supported transfer mode information from the holding unit  110  of the recording medium  120  by issuing a command requesting the supported transfer mode information to the recording medium  120 . The media control unit  106  either outputs the acquired supported transfer mode information to the control unit  103  or stores the acquired supported transfer mode information to a memory included in the media control unit  106 . Then, the media control unit  106  executes step S 212 . 
     In step S 212 , the media control unit  106  refers to the supported transfer mode information acquired in step S 211 , and determines whether or not the recording medium  120  supports the second transfer mode (SD Express). The media control unit  106  executes step S 213  if it is determined that the recording medium  120  supports the second transfer mode. On the other hand, the media control unit  106  executes step S 214  if it is not determined that the recording medium  120  supports the second transfer mode. 
     In step S 213 , the media control unit  106  determines to perform the communication with the recording medium  120  using the second transfer mode. 
     In step S 214 , the media control unit  106  determines to perform the communication with the recording medium  120  using the first transfer mode. 
     In such a manner, the media control unit  106  determines whether or not the operation mode of the electronic device  100  is an operation mode, such as the moving-image recording mode, for which there is a necessary minimum transfer speed. Furthermore, if the minimum transfer speed guaranteed by the recording medium  120  is higher than the necessary minimum transfer speed in the operation mode, the media control unit  106  determines to use the transfer mode guaranteeing the minimum transfer speed for the communication with the recording medium  120 . Thus, interruption of recording and playback attributable to transfer speed can be suppressed. 
     On the other hand, the media control unit  106  determines to use the transfer mode having the highest transfer speed among the transfer modes supported by the recording medium  120  for the communication with the recording medium  120  if: 
     the minimum transfer speed guaranteed by the recording medium  120  is not higher than the necessary minimum transfer speed in the operation mode; 
     there is no minimum transfer speed guaranteed by the recording medium  120 ; or 
     the operation mode of the electronic device  100  is an operation mode, such as the still-image recording mode, for which there is no necessary minimum transfer speed. 
     Thus, full use can be made of the ability of the recording medium  120 . 
     Note that, while the moving-image recording mode and the still-image recording mode have been respectively used here as an operation mode having a necessary minimum transfer speed and an operation mode not having a necessary minimum transfer speed, these are mere example. It may be determined, as appropriate, for each electronic device  100  whether or not a necessary minimum transfer speed is to be associated with an operation mode. For example, a necessary minimum transfer speed may be associated with the playback mode in order to prevent interruption of playback. Furthermore, even for the still-image recording mode, a configuration may be adopted such that a necessary minimum transfer speed is associated with a consecutive shooting mode, and a necessary minimum transfer speed is not associated with a single shooting mode. 
     Furthermore, in this embodiment, an operation mode of the electronic device  100  and a necessary minimum transfer speed are associated with one another, and a transfer mode is determined in accordance an operation mode. However, a configuration may be adopted in which a necessary minimum transfer speed is associated with the purpose of use, characteristic, etc., of data recorded (written) to or played back (read) from the recording medium  120 , and a transfer mode is determined in accordance with the purpose of use and characteristic of data. Examples of the purpose of use and characteristic of data played back (read) include the playback frame rate, data format (whether or not encoding is performed), encoding method, resolution, etc., of moving-image data, but there is no limitation to these examples. 
     Furthermore, the card information of the recording medium  120 , which includes the supported transfer mode information and the transfer speed information, may be acquired upon connection of the recording medium  120 . Accordingly, if the supported transfer mode information and the transfer speed information of the recording medium  120  have already been acquired when the operation described with reference to the flowchart in  FIG. 2  is started, the steps for acquiring such information may be omitted. Specifically, steps S 203 , S 205 , and S 211  may be omitted. 
     According to this embodiment, the transfer mode to be used for communication with a recording medium having a plurality of transfer modes with different transfer-speed characteristics is determined in accordance with the operation mode of the electronic device and the minimum transfer speed guaranteed by the recording medium. Thus, both stable recording/playback of data and utilization of the transfer capability of the recording medium can be achieved. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described. This embodiment can be implemented using the electronic device  100  and the recording medium  120  described in the first embodiment. Accordingly, description will be provided focusing on the differences from the first embodiment. 
     In the first embodiment, an operation in which the media control unit  106  determines a transfer mode in response to being notified of the operation mode of the electronic device  100  from the control unit  103  was described. In this embodiment, the operation is executed upon activation of the electronic device  100  in a state in which the recording medium  120  is connected thereto, or upon connection of the recording medium  120  to the already-activated electronic device  100 . 
       FIG. 3  is a flowchart relating to the operation of the media control unit  106  for determining the transfer mode to be used for the communication between the electronic device  100  and the recording medium  120  in this embodiment. The same reference numerals as those in  FIG. 2  are appended to steps in which the same operation as that performed in the first embodiment is performed, and description thereof is omitted. As discussed above, this operation is executed upon activation of the electronic device  100  having the recording medium  120  connected thereto, or upon connection of the recording medium  120  to the already-activated electronic device  100 . 
     In step S 302 , the media control unit  106  executes initialization of the operation of the recording medium  120 . The initialization of the operation of the recording medium  120  may be performed by issuing an initialization command from the media control unit  106 , for example. Furthermore, the media control unit  106  sets the transfer mode of the recording medium  120  to the first transfer mode (SD mode) upon initializing the operation of the recording medium  120 . 
     Note that the initialization of the operation of the recording medium  120  differs from the initialization (formatting) of the recording area  111 . For example, the initialization of the operation of the recording medium  120  is executed for the purpose of checking the operation of the recording medium  120 , etc. 
     In step S 202 , the media control unit  106  determines whether or not the operation mode of the electronic device  100  is the moving-image recording mode. The media control unit  106  executes step S 203  if the operation mode is the moving-image recording mode, and executes step S 210  if the operation mode is not the moving-image recording mode. 
     The operation following step S 203  in a case in which the operation mode of the electronic device  100  was the moving-image recording mode is the same as that in the first embodiment, and thus description thereof is omitted. 
     In this embodiment, the media control unit  106  acquires the supported transfer mode information and the transfer speed information from the recording medium  120  even if the operation mode of the electronic device  100  is not the moving-image recording mode. 
     If it is determined in step S 212  that the recording medium  120  supports the second transfer mode, the media control unit  106  executes step S 303  before determining the transfer mode in step S 214 , and acquires the transfer speed information in a similar manner as in step S 205 . The media control unit  106  either outputs the acquired transfer speed information to the control unit  103  or stores the acquired transfer speed information to the memory included in the media control unit  106 . 
     Furthermore, if it is determined in step S 210  that the operation mode of the electronic device  100  is not the still-image recording mode, the media control unit  106  executes steps S 304  and S 305  before executing step S 214 . In step S 304 , the media control unit  106  acquires the supported transfer mode information from the recording medium  120  in a similar manner as in step S 203 . In step S 305 , the media control unit  106  acquires the transfer speed information from the recording medium  120  in a similar manner as in step S 205 . 
     By acquiring the supported transfer mode information and the transfer speed information in advance while the first transfer mode is used even if the operation mode is not the moving-image recording mode in such a manner, such information can be used if necessary while the second transfer mode is being used. As discussed above, the card information can be acquired only using the first transfer mode. Accordingly, if the card information becomes necessary while the second transfer mode is being used, it is necessary to switch to the first transfer mode to acquire the card information and then switch back to the second transfer mode. The operation of the recording medium needs to be initialized to switch the transfer mode of the recording medium, and the initialization of operation is not negligible because the initialization takes several hundred microseconds each time. 
     For example, if the operation mode switches to the moving-image recording mode from a state in which the second transfer mode is being used in the still-image recording mode, the first transfer mode needs to be used to execute steps S 203  and S 205 . By acquiring the card information in advance using the first transfer mode upon activation of the electronic device  100  or upon connection of the recording medium  120  as in this embodiment, there is no need to switch to the first transfer mode to acquire the card information even if the second transfer mode is subsequently used. 
     Furthermore, in a case in which the second transfer mode is used in the moving-image recording mode, it becomes unnecessary to switch back to the second transfer mode in step S 209  from a state in which switching to the first transfer mode has been performed to execute step S 205 . 
     Accordingly, even in a case in which the operation mode switches to the moving-image recording mode from a state in which the second transfer mode is being used in the still-image recording mode, the transfer mode to be used can be quickly determined and the time until a moving image can be recorded can be reduced. 
     In this embodiment, the supported transfer mode information and the transfer speed information are first acquired from the recording medium using the first transfer mode upon activation of the electronic device or upon connection of the recording medium. Thus, in addition to the effects of the first embodiment being achieved, the switching of transfer mode for acquiring the supported transfer mode information and the transfer speed information can be omitted, and the operation speed of the electronic device can be increased. 
     Third Embodiment 
     Next, a third embodiment of the present invention will be described. While an operation for determining the transfer mode during recording was mainly described in the first and second embodiments, this embodiment relates to an operation for determining the transfer mode during playback. This embodiment can be implemented using the electronic device  100  and the recording medium  120  described in the first embodiment. Accordingly, description will be provided focusing on the differences from the first embodiment. 
       FIG. 4  is a flowchart relating to the operation of the media control unit  106  for determining the transfer mode to be used in the communication between the electronic device  100  and the recording medium  120  in this embodiment. For example, this operation may be executed when the operation mode of the electronic device  100  is switched to the playback mode via the operation unit  108 . The control unit  103  switches the operation mode of the electronic device  100  to the playback mode upon detecting an operation for switching the operation mode to the playback mode. Furthermore, the control unit  103  notifies the media control unit  106  and the speed designation unit  107  of the switch to the playback mode. 
     In step S 502 , upon being notified by the control unit  103  of the switch to the playback mode, the media control unit  106  sets the transfer mode to be used for the communication with the recording medium  120  to the first transfer mode. The media control unit  106  executes an operation for switching to the first transfer mode if the second transfer mode was being used upon receiving the notification from the control unit  103 , and keeps using the same transfer mode if the first transfer mode was being used. Next, the media control unit  106  executes step S 503 . 
     In step S 503 , the media control unit  106  reads, from the recording medium  120 , thumbnail-view image data of moving-image files recorded on the recording medium  120 , and outputs the thumbnail-view image data to the image processing unit  102 . For example, moving-image files can be determined from file extensions. Furthermore, the media control unit  106  reads, from the recording medium  120  along with the thumbnail-view image data, information of the transfer mode used to record the moving-image files. Information of the transfer mode used during recording is recorded as information accompanying moving-image data. 
     The information of the transfer mode used during recording is associated with the moving-image file names or the file names of the thumbnail-view image data and is stored to the internal memory of the media control unit  106 . Alternatively, the media control unit  106  may output such information to the control unit  103 . The control unit  103  stores the information received from the media control unit  106  to the internal RAM. 
     The image processing unit  102  generates data of a GUI screen in which the thumbnail-view image data is displayed as a list in a predetermined layout, and outputs the data to the display control unit  105 . The display control unit  105  displays a list display screen of thumbnails in a selectable state on the display unit  104 . The list display screen is a screen for selecting data to be read from among data recorded on the recording medium  120 . 
       FIGS. 5A and 5B  are each an example of a thumbnail list display screen  500 . The list display screen  500  may be displayed over the entire display unit  104  or in a partial area of the display unit  104 . While examples in which six thumbnails are displayed in a listed state in one screen are illustrated here, the number of thumbnail images per one screen may be set as appropriate. Furthermore, in a case in which all of the thumbnail images to be displayed cannot be displayed in one screen, the thumbnail images can be displayed using well-known methods such as forming the list display screen  500  from multiple pages or using scrolling display. 
       FIG. 5A  illustrates a case in which thumbnails  601  to  606  are all thumbnails of moving-image files recorded using the first transfer mode. Furthermore,  FIG. 5B  illustrates a case in which thumbnails  609  and  610  are thumbnails of moving-image files recorded using the first transfer mode, and thumbnails  607 ,  608 ,  611 , and  612  are thumbnails of moving-image files recorded using the second transfer mode. 
     For the thumbnails displayed on the list display screen  500 , in step S 504 , the media control unit  106  performs a comparison between the number of thumbnails of moving-image files recorded using the first transfer mode and the number of thumbnails of moving-image files recorded using the second transfer mode. This comparison corresponds to an operation for determining the transfer mode likely to be used during playback of moving-image files whose thumbnails are displayed on the list display screen  500 . Note that, even if only some of the read thumbnails are displayed on the list display screen  500 , the comparison is performed with respect to the thumbnails displayed on the list display screen  500 . 
     The media control unit  106  executes step S 505  if the number of thumbnails of moving-image files recorded using the first transfer mode is more than or equal to the number of thumbnails of moving-image files recorded using the second transfer mode. Furthermore, the media control unit  106  executes step S 506  if the number of thumbnails of moving-image files recorded using the first transfer mode is less than the number of thumbnails of moving-image files recorded using the second transfer mode. Accordingly, the media control unit  106  executes step S 505  in the example illustrated in  FIG. 5A , and executes step S 506  in the example illustrated in  FIG. 5B . 
     In step S 505 , the media control unit  106  determines the first transfer mode as the transfer mode to be used for the communication with the recording medium  120 . If the second transfer mode is being used at this time point, the media control unit  106  executes an operation for switching to the first transfer mode. The display of the list of thumbnails on the display unit  104  is continued even if the transfer mode is switched. Next, the media control unit  106  executes step S 507 . 
     In step S 506 , the media control unit  106  determines the second transfer mode as the transfer mode to be used for the communication with the recording medium  120 . If the first transfer mode is being used at this time point, the media control unit  106  executes an operation for switching to the second transfer mode. The display of the list of thumbnails on the display unit  104  is continued even if the transfer mode is switched. 
     While the switching of transfer mode requires several hundred milliseconds for processing by the recording medium  120 , the user would not recognize the switching of transfer mode because the switching of transfer mode is performed simultaneously with the display of the list of thumbnails on the display unit  104 . 
     In step S 507 , the control unit  103  determines whether or not an instruction to switch the list display screen  500  has been detected via the operation unit  108  (includes the touchpanel of the display unit  104 ). The switching instruction may vary depending on the form in which the list display screen  500  is displayed, and may be a page skipping or page returning instruction, a scroll instruction, etc. If it is determined that an instruction to switch the list display screen  500  has been detected, the control unit  103  instructs the image processing unit  102  to generate data of a list display screen  500  that is in accordance with the switching instruction. Thus, step S 503  is executed again, and the image processing unit  102  generates data of a list display screen  500  for the next or previous page or a scrolled list display screen  500 , and outputs the data to the display control unit  105 . 
     On the other hand, the control unit  103  executes step S 508  if it is not determined that an instruction for switching the list display screen  500  has been detected. 
     In step S 508 , the control unit  103  determines whether or not a playback instruction for a thumbnail displayed on the list display screen  500  has been detected via the operation unit  108  (includes the touchpanel of the display unit  104 ). For example, the playback instruction may be an operation of selecting a thumbnail. The selection operation may be a touch operation on the display unit  104 , or may be a combination of a key operation and a button operation performed on the operation unit  108 . 
     If it is determined that a playback instruction for a displayed thumbnail has been detected, the control unit  103  notifies the media control unit  106  of the thumbnail for which a playback instruction has been issued or identification information of the moving-image file for which a playback instruction has been issued. Furthermore, the control unit  103  executes step S 507  if it is not determined that a playback instruction for a displayed thumbnail has been detected. 
     In step S 509 , the media control unit  106  determines whether or not the transfer mode used to record the moving-image file for which a playback instruction has been issued and the presently used transfer mode differ. The media control unit  106  executes step S 510  if it is determined that the transfer modes differ, and executes step S 511  if it is determined that the transfer modes are the same. 
     In step S 510 , the media control unit  106  switches the transfer mode to be used for the communication between the electronic device  100  and the recording medium  120  so as to match the transfer mode used to record the moving-image file for which a playback instruction has been issued. Then, the media control unit  106  executes step S 511 . 
     In step S 511 , the media control unit  106  reads, from the recording medium  120 , the moving-image file for which a playback instruction was issued by the user in step S 508 , and outputs the moving-image file to the image processing unit  102 . The image processing unit  102  decodes the moving-image data stored in the image file to generate display moving-image data, and outputs the display moving-image data to the display control unit  105 . The display control unit  105  displays the moving image on the display unit  104 . 
     For example, if the second transfer mode is used to play back a moving image that was recorded using the first transfer mode, the playback of the moving image may be interrupted because no minimum transfer speed is guaranteed in the second transfer mode. Furthermore, there is a possibility that a moving image that was recorded using the second transfer mode cannot be played back smoothly using the first transfer mode because the moving image might have been recorded at a speed higher than the maximum transfer speed of the first transfer mode. The possibility of such problems occurring can be reduced in this embodiment because the transfer mode used during recording is used in a case in which a moving-image file recorded on the recording medium  120  is played back. 
     Furthermore, switching to a transfer mode likely to be used during playback is performed in advance before a playback instruction for a moving-image file whose thumbnail is displayed in a list is provided. Thus, a delay in the start of playback that would otherwise occur as a result of the switching of transfer mode being performed after a playback instruction is accepted can be suppressed. Furthermore, by performing the switching of transfer mode simultaneously with the display of thumbnails, the switching of transfer mode can be executed without being recognized by the user. 
     Note that the transfer mode to be used during playback can be determined based on information other than the transfer modes used during recording. For example, bit-rate information of moving-image files may be acquired, and the transfer mode to be used during playback may be determined based on the transfer speed necessary to play back moving-image files smoothly. 
     For example, in step S 504 , the media control unit  106  determines whether or not the number of moving-image files for which the transfer speed necessary for playback is lower than the minimum transfer speed guaranteed in the first transfer mode is more than or equal to half the number of moving-image files whose thumbnails are displayed. Furthermore, the media control unit  106  determines to use the first transfer mode in step S 505  if it is determined that the number of moving-image files for which the transfer speed necessary for playback is lower than the minimum transfer speed guaranteed in the first transfer mode is more than or equal to half the number of moving-image files whose thumbnails are displayed. On the other hand, the media control unit  106  determines to use the second transfer mode in step S 506  if it is not determined that the number of moving-image files for which the transfer speed necessary for playback is lower than the minimum transfer speed guaranteed in the first transfer mode is more than or equal to half the number of moving-image files whose thumbnails are displayed. The above-described effects can be realized by such an operation as well. 
     Fourth Embodiment 
     Next, a fourth embodiment of the present invention will be described. Similar to the third embodiment, this embodiment also relates to an operation for determining the transfer mode during playback. Furthermore, this embodiment can be implemented using the electronic device  100  and the recording medium  120  described in the first embodiment. Accordingly, description will be provided focusing on the differences from the third embodiment. 
     In this embodiment, the time required to switch between the two transfer modes differs depending on the direction in which the switching is performed. 
       FIG. 6  is a flowchart relating to the operation of the media control unit  106  for determining the transfer mode to be used in the communication between the electronic device  100  and the recording medium  120  in this embodiment. The same reference numerals are appended to steps in which the same operation as that performed in the third embodiment is performed. As is the case with the third embodiment, this operation may be executed when the operation mode of the electronic device  100  is switched to the playback mode via the operation unit  108 , for example. 
     In step S 502 , upon being notified by the control unit  103  of the switch to the playback mode, the media control unit  106  sets the transfer mode to be used for the communication with the recording medium  120  to the first transfer mode. The media control unit  106  executes an operation for switching to the first transfer mode if the second transfer mode was being used upon receiving the notification from the control unit  103 , and keeps using the same transfer mode if the first transfer mode was being used. Next, the media control unit  106  executes step S 703 . 
     Here, the time required to switch from the first transfer mode to the second transfer mode is shorter than the time required to switch from the second transfer mode to the first transfer mode. Thus, the first transfer mode is used in step S 502 . If the time required to switch from the second transfer mode to the first transfer mode is shorter, the second transfer mode is used in step S 502 . 
     In step S 703 , the media control unit  106  reads, from the recording medium  120 , thumbnail-view image data of moving-image files recorded on the recording medium  120 , and outputs the thumbnail-view image data to the image processing unit  102 . Furthermore, the media control unit  106  reads, from the recording medium  120  along with the thumbnail-view image data, information of the transfer mode used to record the moving-image files. 
     Furthermore, the information of the transfer mode used during recording is associated with the moving-image file names or the file names of the thumbnail-view image data and is stored to the internal memory of the media control unit  106 . Alternatively, the media control unit  106  may output such information to the control unit  103 . The control unit  103  stores the information received from the media control unit  106  to the internal RAM. 
     The image processing unit  102  generates data of a thumbnail-view screen in a similar manner as in step S 503 . However, in this embodiment, the image processing unit  102  generates data of a screen for displaying one thumbnail  613  in one screen as illustrated in  FIG. 5C . 
     Subsequently, the control unit  103  executes steps S 507  and S 508  in a similar manner as in the third embodiment. 
     In step S 706 , the media control unit  106  determines whether or not the transfer mode used to record the moving-image file whose thumbnail is displayed was the first transfer mode, and executes step S 511  if it is determined that the first transfer mode was used and executes step S 707  if it is not determined that the first transfer mode was used. Note that, if a configuration is adopted such that the second transfer mode is used in step S 502 , the media control unit  106  determines in step S 706  whether or not the transfer mode used to record the moving-image file whose thumbnail is displayed was the second transfer mode. The branching in accordance with the result of the determination does not change. 
     In step S 707 , the media control unit  106  switches the transfer mode to be used for the communication between the electronic device  100  and the recording medium  120  to the second transfer mode. The switching of transfer mode is executed simultaneously with the display of a thumbnail. Then, the media control unit  106  executes step S 511 . Note that, if a configuration is adopted such that the second transfer mode is used in step S 502 , the transfer mode is switched to the first transfer mode in step S 707 . 
     In step S 511 , the media control unit  106  reads, from the recording medium  120 , the moving-image file for which a playback instruction was issued by the user in step S 508 , and outputs the moving-image file to the image processing unit  102 . The image processing unit  102  decodes the moving-image data stored in the image file to generate display moving-image data, and outputs the display moving-image data to the display control unit  105 . The display control unit  105  displays the moving image on the display unit  104 . 
     In this embodiment, the initially used transfer mode is determined taking the time required to switch the transfer mode to be used for the communication between the media control unit  106  and the recording medium  120  into consideration. Specifically, the transfer mode is determined so that the transfer mode requiring a longer time to switch to and use the transfer mode is initially used. This embodiment differs from the third embodiment in that the switching of transfer mode may occur after a playback instruction is accepted because the switching of transfer mode is not performed before a playback instruction is accepted; however, the delay occurring in such a case can be reduced according to this embodiment. 
     Other Embodiments 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2021-008939, filed on Jan. 22, 2021, which is hereby incorporated by reference herein in its entirety.