Abstract:
An image pickup apparatus operating in a moving picture photographing mode, wherein, before a start of moving picture photographing is indicated by a shutter button on a key input section, a clock frequency of a control section is made to be a normal frequency so that electricity consumption is reduced in a monitoring state to lengthen the life of a battery, and wherein, when the start of moving picture photographing is indicated, the clock frequency is increased to a large extent by a clock switching control section, so that an MPEG converter can access at a high speed an SDRAM storing YUV data such as reference data, search data, or the like at the time of encoding processing of moving picture data, and the moving picture compression can be achieved in real-time.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-324118, filed Sep. 17, 2003, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image pickup apparatus which can be used for, for example, a digital camera having a moving picture photographing function, and a moving picture photographing method thereof. 
   2. Description of the Related Art 
   Conventionally, as a recording system of moving picture having large information content, there is a system in accordance with MPEG (Motion Picture Experts Group) standard. In the MPEG system, an inter-frame predictive coding technique in which high encoding efficiency can be obtained in compression/extension of moving picture formed from a plurality of frames is used. Generally, in encoding processing of the MPEG system, because YUV data such as reference data, search data, or the like are stored in a memory such as an SDRAM or the like, and an MPEG encoder frequently accesses to the memory and repeats reading and writing the above-described data, extremely large memory transferring amounts are generated in the process. 
   On the other hand, there are many types of portable telephone with a camera and digital still camera (hereinafter, simply called a digital camera) which have a moving picture photographing function in addition to a normal still image photographing function. In recent years, there has been a trend in which the MPEG system is used for recording moving picture therein. 
   BRIEF SUMMARY OF THE INVENTION 
   According to an aspect of the present invention, there is provided an image pickup apparatus comprising: 
   an image pickup section which can carry out moving picture photographing; 
   a moving picture compressing section which compresses moving picture data obtained by moving picture photographing processing by the image pickup section using a working memory; 
   a recording control section which records the moving picture data compressed by the moving picture compressing section onto a recording medium; 
   a start indicating section which indicates a start of moving picture recording; 
   a processing control section which starts compression processing by the moving picture compressing section and recording processing by the recording control section when a start of moving picture recording is indicated by the start indicating section; and 
   a switching control section which switches a read/write speed of data in the working memory from a low speed to a high speed when a start of moving picture recording is indicated by the start indicating section. 
   According to another aspect, there is provided an image pickup apparatus comprising: 
   an image pickup section which can carry out moving picture photographing; 
   a moving picture compressing section which compresses moving picture data obtained by moving picture photographing processing by the image pickup section using a working memory; 
   a recording control section which records the moving picture data compressed by the moving picture compressing section onto a recording medium; 
   a transition indicating section which indicates a transition to a stand-by state of moving picture recording; 
   a start indicating section which indicates a start of moving picture recording; 
   a switching control section which switches a read/write speed of data in the working memory from a low speed to a high speed when a transition to a stand-by state of moving picture recording is indicated by the transition indicating section; and 
   a processing control section which starts compression processing by the moving picture compressing section and recording processing by the recording control section when a start of moving picture recording is indicated by the start indicating section. 
   According to another aspect, there is provided an image pickup apparatus comprising: 
   image pickup means for being able to photograph moving picture; 
   moving picture compressing means for compressing moving picture data obtained by moving picture photographing processing by the image pickup means using a working memory; 
   recording control means for recording the moving picture data compressed by the moving picture compressing means onto a recording medium; 
   start indicating means for indicating a start of moving picture recording; 
   processing control means for starting compression processing by the moving picture compressing means and recording processing by the recording control means when a start of moving picture recording is indicated by the start indicating means; and 
   switching control means for switching a read/write speed of data in the working memory from a low speed to a high speed when a start of moving picture recording is indicated by the start indicating means. 
   Further, according to another aspect, there is provided an image pickup apparatus comprising: 
   an image pickup means which can carry out moving picture photographing; 
   a moving picture compressing means which compresses moving picture data obtained by moving picture photographing processing by the image pickup means using a working memory; 
   a recording control means which records the moving picture data compressed by the moving picture compressing means onto a recording medium; 
   a transition indicating means which indicates a transition to a stand-by state of moving picture recording; 
   a start indicating means which indicates a start of moving picture recording; 
   a switching control means which switches a read/write speed of data in the working memory from a low speed to a high speed when a transition to a stand-by state of moving picture recording is indicated by the transition indicating means; and 
   a processing control means which starts compression processing by the moving picture compressing means and recording processing by the recording control means when a start of moving picture recording is indicated by the start indicating means. 
   Further, according to another aspect, there is provided a moving picture photographing method of an image pickup apparatus comprising an image pickup section which can carry out moving picture photographing, a moving picture compressing section which compresses moving picture data obtained by moving picture photographing processing by the image pickup section using a working memory, and a recording control section which records the moving picture data compressed by the moving picture compressing section onto a recording medium, 
   the moving picture photographing method comprising: 
   indicating a start of moving picture recording; 
   switching a read/write speed of data in the working memory from a low speed to a high speed when a start of moving picture recording is indicated; and 
   starting compression processing by the moving picture compressing section and recording processing by the recording control section after the read/write speed of data in the working memory is switched from the low speed to the high speed. 
   Further, according to another aspect, there is provided a moving picture photographing method of an image pickup apparatus comprising an image pickup section which can carry out moving picture photographing, a moving picture compressing section which compresses moving picture data obtained by moving picture photographing processing by the image pickup section using a working memory, and a recording control section which records the moving picture data compressed by the moving picture compressing section onto a recording medium, 
   the moving picture photographing method comprising: 
   indicating a transition to a stand-by state of moving picture recording; 
   switching a read/write speed of data in the working memory from a low speed to a high speed when a transition to a stand-by state of moving picture recording is indicated; 
   indicating a start of moving picture recording; and 
   starting compression processing by the moving picture compressing section and recording processing by the recording control section when a start of moving picture recording is indicated. 
   Further, according to another aspect, there is provided a moving picture photographing program for causing a computer, which is provided in an image pickup apparatus comprising an image pickup section which can carry out moving picture photographing, a moving picture compressing section which compresses moving picture data obtained by moving picture photographing processing by the image pickup section using a working memory, and a recording control section which records the moving picture data compressed by the moving picture compressing section onto a recording medium, to execute: 
   a process of indicating a start of moving picture recording; 
   a process of switching a read/write speed of data in the working memory from a low speed to a high speed when a start of moving picture recording is indicated; and 
   a process of starting compression processing by the moving picture compressing section and recording processing by the recording control section after the read/write speed of data in the working memory is switched from the low speed to the high speed. 
   Further, according to another aspect, there is provided a moving picture photographing program for causing a computer, which is provided in an image pickup apparatus comprising an image pickup section which can carry out moving picture photographing, a moving picture compressing section which compresses moving picture data obtained by moving picture photographing processing by the image pickup section using a working memory, and a recording control section which records the moving picture data compressed by the moving picture compressing section onto a recording medium, to execute: 
   a process of indicating a transition to a stand-by state of moving picture recording; 
   a process of switching a read/write speed of data in the working memory from a low speed to a high speed when a transition to a stand-by state of moving picture recording is indicated; 
   a process of indicating a start of moving picture recording; and 
   a process of starting compression processing by the moving picture compressing section and recording processing by the recording control section when a start of moving picture recording is indicated. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIG. 1  is a block diagram showing an electrical configuration of a digital camera common to respective embodiments of the present invention. 
       FIG. 2  is a flowchart showing operations in a moving picture photographing mode in a first embodiment. 
       FIG. 3  is a flowchart showing operations in a moving picture photographing mode in a second embodiment. 
       FIG. 4  is a flowchart showing operations in a moving picture photographing mode in a third embodiment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, embodiments of the present invention will be described with reference to the drawings. 
   First Embodiment 
     FIG. 1  is a block diagram showing an electrical configuration of a digital camera common to respective embodiments of the invention. This digital camera has a moving picture photographing function in addition to a normal still image photographing function, and has a CCD  1 , an A/D converter  2 , a timing generator (TG)  3 , a driving circuit  4 , an image signal processing section  5 , a JPEG converter  6 , an MPEG converter  7 , an SDRAM  8 , and a display section  9 . 
   Due to the CCD  1  being driven by the driving circuit  4  on the basis of a timing signal transmitted from the timing generator  3 , the CCD  1  photo-electrically converts an optical image of an object which has been incident via an optical system (not shown), and outputs analog image pickup signals of one screen at given intervals. The A/D converter  2  converts the analog image pickup signals outputted by the CCD  1  into digital image signals. The converted image pickup signals are transmitted to the image signal processing section  5  via the timing generator  3 . 
   In a photographing stand-by state in a still image photographing mode and a moving picture photographing mode, the image signal processing section  5  generates a digital image signal for each of R, G, and B from an image pickup signal which has been outputted from the CCD  1  and converted into a digital signal, and applies various picture processing such as pixel interpolation processing, white-balance processing, luminance/chromatic-difference signal conversion processing, or the like to the image signal, and generates a video signal on the basis of the processed image data and transmits the video signal to the display section  9 . 
   The display section  9  includes a liquid-crystal display on which color display is possible and a driving circuit thereof, and displays an image based on the above-described video signal which is transmitted from the image signal processing section  5  and is sequentially varied, i.e., a through image. Further, the display section  9  carries out, as is for an operational assistance, a display of processing menu at the time of selecting functions and a display of diagrams, icons or the like for setting. 
   The JPEG converter  6  is formed from a circuit dedicated to carrying out compression and expansion of still image data in accordance with a JPEG (Joint Photographic Experts Group) standard, and at the time of photographing in a still image photographing mode, the JPEG converter  6  compresses image data onto which image processing is applied by the image signal processing section  5 . Here, the compressed data is transferred to a flash memory  11  or a recording media interface circuit  13  which will be described later. Further, in a reproduction mode, the JPEG converter  6  expands still image data which has been recorded in a state of being compressed. Here, the expanded still image data is displayed as a still image on the display section  9  by being transmitted to the image signal processing section  5  and converted into a video signal. 
   The MPEG converter  7  is formed from a circuit dedicated to carrying out compression and expansion of moving picture data in accordance with the MPEG standard, and at the time of photographing in a moving picture photographing mode, the MPEG converter  7  successively compresses moving picture data onto which picture processing are applied by the image signal processing section  5 , i.e., the image data for each frame which has been sequentially picked-up by the CCD  1 . Here, the compressed data is transferred to the flash memory  11  or the recording media interface circuit  13  which will be described later. Further, in a reproduction mode, the MPEG converter  7  expands moving picture data which has been recorded in the compressed state. Here, the expanded moving picture data are successively transmitted to the image signal processing section  5  and converted into video signals, and thereafter, are displayed as a moving picture on the display section  9 . 
   The SDRAM  8  is a working memory in the embodiments, and YUV data such as reference data, search data, or the like, i.e., image data is temporarily stored therein at the time of compression and expansion of moving picture data by the MPEG converter  7 . Further, image data generated in the process at the time of compressing and expanding a still image by the JPEG converter  6  is temporarily stored in the SDRAM  8 . 
   Further, the digital camera has a control section  10 , the flash memory  11 , a key input section  12 , the recording media interface circuit  13 , and an I/O port  14 . 
   The control section  10  is composed of peripheral circuits including a processor (CPU) and a program ROM and RAM which are not illustrated, and a clock switching control section  101  and a timer control section  102  which are illustrated. In the control section  10 , the above-described processor functions as control means of the embodiments by controlling the above-described respective sections of the digital camera on the basis of various control programs stored in the program ROM and key operation signals transmitted from the key input section  12 . 
   Further, the clock switching control section  101  is switching means of the embodiments, and receives a clock switching signal from the above-described processor, and switches an access speed (a read or write speed of data) of the aforementioned SDRAM  8  by switching the clock signal frequency. The timer control section  102  starts various time-counting operations by receiving a count start signal from the above-described processor, and outputs an ending signal to the processor at a point in time when the time-counting operations are completed. 
   The flash memory  11  is a nonvolatile memory storing the data required to be maintained even when the power source is turned off as well, for example, various setting data set by a user. Note that some or all of the control programs stored in the program ROM of the control section  10  described above may be recorded in the flash memory  11 . 
   The key input section  12  has a shutter button, a power source on/off key, a mode switching key used for switching an operation mode, a cursor key used for selecting a function and selecting a screen, a set key, or the like, and outputs an operation signal corresponding to the key operation to the control section  10 . The above-described mode switching key is used for switching a still image photographing mode and a moving picture photographing mode, and a reproduction mode for reproducing a still image or a moving picture. Further, the above-described shutter button has a configuration in which it is possible to operate at two-stages of a half-pressed state for indicating AF locking in a still image photographing mode and a moving picture photographing mode, and a fully-pressed state for indicating photographing, and functions as indicating means of the embodiments in a moving picture photographing mode. 
   Various recoding media  15  mounted on a camera body (not shown) are connected to the aforementioned recording media interface circuit  13 . When the shutter button is operated so as to be fully pressed in a still image photographing mode, the recording media interface circuit  13  records the compressed still image data which has been transferred from the aforementioned JPEG converter  6  onto the recording medium  15 , and when the shutter button is operated so as to be fully pressed in a moving picture photographing mode, the recording media interface circuit  13  records the compressed moving picture data which are successively transferred from the MPEG converter  7  onto the recording medium  15 . Note that, for example, when the recording medium  15  is not mounted thereon, the compressed still image data or moving picture data is recorded on an image recording area which has been ensured in advance in the flash memory  11 . 
   The I/O port  14  is used for inputting/outputting various data including image data between the digital camera and an external device, for example, for transferring the still image data or the moving picture data which has been already recorded onto the recording medium  15 . 
   Next, operations in accordance with the control of the control section  10  when a moving picture photographing mode is selected by a user in the digital camera formed from the above-described configuration will be described in accordance with a flowchart of  FIG. 2 . 
   When a moving picture photographing mode is selected, the digital camera is made to be in a monitoring state, i.e., a photographing stand-by state, and starts to drive the CCD  1 , and continues the processing of displaying a picked-up through image of an object on the display section  9  (step SA 1 ). In this state, when the shutter button is fully pressed by the user (YES at step SA 2 ), a clock signal is switched to a clock signal having a frequency higher than a normal frequency by the clock switching control section  101 , and in accordance therewith, an access speed of the SDRAM  8  is made to be a high speed (step SA 3 ). Thereafter, the time when the operation of switching the frequency is completed is waited for, and at the point in time when it is completed (YES at step SA 4 ), the digital camera proceeds to a moving picture photographing/recording state, and starts MPEG encoding processing in which image data of each frame which has been sequentially picked-up by the CCD  1  is successively compressed by the MPEG converter  7  and the SDRAM  8 , and records moving picture data onto the recording medium  15  by continuing the processing (step SA 5 ). 
   Then, when the shutter button is fully pressed again by the user, or when a photographing-forced-terminating period has come in which the storage capacity of the recording medium  15  reaches the upper limit, or it has reached a maximum moving picture photographing time determined in advance (YES at step SA 6 ), the moving picture photographing is completed at that point in time, and the MPEG encoding processing by the MPEG converter  7  and the SDRAM  8  is completed (step SA 7 ). Continuously, the clock signal is switched to a clock signal having a normal frequency by the clock switching control section  101 , and the access speed of the SDRAM  8  is made to return to a normal speed (low speed) (step SA 8 ). Thereafter, the time when the operation of switching the frequency is completed is waited for, and at the point in time when it is completed (YES at step SA 9 ), the digital camera proceeds to a monitoring state again (step SA 1 ), and the above-described operations are repeated. 
   Note that, in the present embodiment, the access speed of the SDRAM  8  is switched from a normal speed to a high speed at the time of starting moving picture photographing at the point in time when the fully-pressed state of the shutter button for the first time is carried out, and is made to return to the normal speed at the time of ending the moving picture photographing started by the fully-pressing operation of the shutter button for the second time. However, it may be carried out as follows. 
   For example, the access speed of the SDRAM  8  may be switched from a normal speed to a high speed at the point in time when a moving picture photographing mode is set by the user, and may be made to return to the normal speed at the point in time when a moving picture photographing mode is completed (is switched to another operating mode) by the user. Further, additionally, the access speed of the SDRAM  8  may be switched from a normal speed to a high speed at the point in time when the fully-pressing operation of the shutter button for the first time is carried out after a moving picture photographing mode is set, and the access speed may be made to return to the normal speed at the point in time when a moving picture photographing mode is completed by the user. 
   Second Embodiment 
   Next, a second embodiment of the present invention will be described. The present embodiment has the configuration shown in  FIG. 1 , and relates to a digital camera in which a control program for causing the shutter button on the aforementioned key input section  12  to function as first indicating means and second indicating means is stored in the program ROM of the control section  10 . 
     FIG. 3  is a flowchart showing operations in accordance with the control of the control section  10  when a moving picture photographing mode is selected by the user in the digital camera of the present embodiment. 
   In the present embodiment, when a moving picture photographing mode is selected, the digital camera is immediately made to be in a monitoring state (a photographing stand-by state) (step SB 1 ). In this state, when the shutter button is pressed by half by the user (YES at step SB 2 ), a clock signal is switched to a clock signal having a frequency higher than a normal frequency by the clock switching control section  101 , and in accordance therewith, an access speed of the SDRAM  8  is made to be a high speed (step SB 3 ), and at the point in time when it is completed (YES at step SB 4 ), the digital camera once proceeds to a photographing stand-by state (step SB 5 ). Note that the content of the operation in this state is the same as in the monitoring state at step SB 1 . 
   Continuously, when the shutter button in the half-pressed state is fully pressed by the user during the time of being in this photographing stand-by state (YES at step SB 6 ), the digital camera proceeds to a moving picture photographing/recording state, and starts MPEG encoding processing by the MPEG converter  7  and the SDRAM  8 , and records moving picture data onto the recording medium  15  by continuing the processing (step SB 8 ). 
   Then, when the shutter button is fully pressed again by the user, or when the photographing-forced-terminating period described above has come (YES at step SB 9 ), at that point in time, the moving picture photographing (MPEG encoding processing) is completed (step SB 10 ). Thereafter, a clock signal is switched to a clock signal having a normal frequency, and the access speed of the SDRAM  8  is made to return to a normal speed (low speed) (step SB 11 ), and at the point in time when it is completed (YES at step SB 12 ), the digital camera proceeds to a monitoring state again (step SB 1 ), and the above-described operations are repeated. 
   On the other hand, when the shutter button in the half-pressed state is cancelled without being fully pressed by the user after the digital camera has been made to be in a photographing stand-by state at step SB 5 , (NO at both steps SB 6 , SB 7 ), the digital camera immediately proceeds to step SB 11  described above without executing moving picture photographing, and the access speed of the SDRAM  8  is made to return to a normal speed (low speed), and at the point in time when it is completed (YES at step SB 12 ), the digital camera proceeds to a monitoring state again (step SB 1 ), and the above-described operations are repeated. 
   Third Embodiment 
   Next, a third embodiment of the present invention will be described. The present embodiment relates to a digital camera in which, although a state of a half-pressing operation is not provided to the shutter button on the aforementioned key input section  12  in the configuration shown in  FIG. 1 , a control program for causing the shutter button to function as first indicating means and second indicating means of the invention is stored in the program ROM of the control section  10 . 
     FIG. 4  is a flowchart showing operations in accordance with the control of the control section  10  when a moving picture photographing mode is selected by the user in the digital camera of the present embodiment. 
   Namely, in the present embodiment, after the digital camera is made to be in a monitoring state by selecting a moving picture photographing mode (step SC 1 ), when the shutter button is pressed (YES at step SC 2 ), an access speed of the SDRAM  8  is made to be a high speed due to a clock signal being switched to a clock signal having a frequency higher than a normal frequency (step SC 3 ), and at the point in time when it is completed (YES at step SC 4 ), and the digital camera once proceeds to a photographing stand-by state (step SC 5 ). 
   Then, when a second operation of the shutter button is carried out in the photographing stand-by state (YES at step SC 6 ), the digital camera proceeds to a moving picture photographing/recording state, and starts to record moving picture data onto the recording medium  15  (step SC 8 ). Then, when an operation of the shutter button for the third time is carried out by the user, or when a photographing-forced-terminating period described above has come (YES at step SC 9 ), the moving picture photographing (MPEG encoding processing) is completed at that point in time (step SC 10 ). Thereafter, a clock signal is switched to a clock signal having a normal frequency, and the access speed of the SDRAM  8  is made to return to a normal speed (low speed) (step SC 11 ), and at the point in time when it is completed (YES at step SC 12 ), the digital camera proceeds to a monitoring state again (step SC 1 ), and the above-described operations are repeated. 
   On the other hand, after the digital camera is made to be in a photographing stand-by state at step SC 5 , when a given time has passed from the time when the digital camera is made to be in a photographing stand-by state without the shutter button being pressed by the user (NO at step SC 6  and YES at step SC 7 ), the digital camera immediately proceeds to step SC 11  described above without executing moving picture photographing, and the access speed of the SDRAM  8  is made to return to a normal speed (low speed), and at the point in time when it is completed (YES at step SC 12 ), the digital camera proceeds to a monitoring state again (step SC 1 ), and the above-described operations are repeated. 
   Further, in the first to third embodiments described above, the moving picture photographing processing may be made to be different in a monitoring state (photographing stand-by state) and in a moving picture photographing/recording state. For example, a frame rate may be changed, or an image size (resolution) may be changed. 
   Further, in the first to third embodiments described above, the case in which the invention is used for a digital camera was described. However, the invention is not limited thereto, the invention can be used for cameras which are built-in into a portable telephone and other portable information terminals.