JP2005276316A - Data recording method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data recording method and device capable of recording moving picture data at a high bit rate close to a recordable maximum speed. <P>SOLUTION: A free area of a recording medium is retrieved before starting to record moving picture data (step S112), and test writing is respectively performed in one block of the first address of the free area and one block of the last address of the free area to measure recording speeds (step S114 and step S116). An initial bit rate is determined in accordance with the lower speed on the basis of measurement results (step S118). In addition, the free capacity of a recording buffer is monitored during recording the moving picture data, and a bit rate is controlled so as not to cause a buffer overflow. At this time, bit rates are changed in a unit equal to or greater than a minimum recording unit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a data recording method and apparatus, and more particularly to a data recording technique suitable for recording moving image data in an image recording apparatus such as a digital camera or a video camera.

  Patent Document 1 discloses an apparatus for recording or reproducing digital data obtained by compressing and encoding a moving image signal. In the case of moving image recording by variable-length coding, the apparatus shown in the same document groups a plurality of continuous image frames and adjusts them to have a certain size (information amount) for each certain group. Encoding is performed.

Patent Document 2 discloses a video signal recording apparatus that automatically selects a moving image or still image recording mode that is optimal for a recording medium in accordance with the transfer speed of the recording medium.
JP-A-6-284374 JP-A-10-233986

  Conventionally, when performing moving image recording, data compression processing is usually performed so as to suppress the bit rate within a predetermined bit rate. However, there is a difference in recording speed depending on the recording medium used and in the case of a disk-type medium such as a hard disk (HDD), depending on the physical recording position even within the same medium. When the bit rate is determined with a fixed value preset in the apparatus, the slowest state is set for safety, so that recording at a high bit rate close to the limit of the recording medium cannot be performed.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a data recording method and apparatus capable of recording at a high bit rate close to the maximum recordable speed.

  In order to achieve the above object, a data recording method according to the first aspect of the present invention includes an empty area detecting step for detecting an empty area of a recording medium, and a trial writing for performing trial writing of data in the detected empty area. A recording speed measuring step for measuring the recording speed of the test writing, and a bit rate determining step for determining a bit rate at the time of writing the recording data based on the measurement result of the recording speed by the test writing. It is characterized by.

  According to the first aspect of the present invention, before the recording data is written to the recording medium, a test writing process for detecting a free area of the recording medium and writing some data (for example, test data) in the free area is performed. Measure the recording speed. An optimum (highest possible) bit rate can be set from the actually measured information of the recording speed thus obtained. As a result, the bit rate can be optimized in accordance with the type of recording medium and the available status (in other words, the amount of stored information indicating the usage status), and the recording speed can be improved.

  A second aspect of the invention relates to the data recording method according to the first aspect, wherein each of the free areas detected in the free area detection step performs test writing in a plurality of recording blocks designated by different addresses. The bit rate is determined in accordance with the slowest recording speed from the measurement result of the recording speed of the trial writing performed in the plurality of recording blocks.

  When using a recording medium having a writing speed difference depending on a physical position where data is recorded, it is preferable to perform test writing for each of a plurality of recording blocks at different physical positions in the free space. For example, trial writing is performed on each block of the free space start address and final address, the recording speed is measured, and the bit rate is determined based on the slower one. Thereby, data can be continuously recorded over the entire empty area.

  According to a third aspect of the present invention, there is provided a data recording method comprising: a buffering step for temporarily storing recording data in a buffer memory; a writing step for recording the recording data read from the buffer memory on a recording medium; and the buffer A free space detecting step for detecting a free space in the memory, and a bit rate control step for controlling the bit rate of the recording data in accordance with the detection result of the free space so as not to cause an overflow of the buffer memory. It is characterized by that.

  While recording data is being recorded, the buffer memory is monitored to change the bit rate so that overflow does not occur. As a result, time-sequential data such as moving images and sounds can be recorded without interruption.

  According to a fourth aspect of the present invention, there is provided the data recording method according to the third aspect, wherein the bit rate control step sets a first compression rate of the recording data when the free space of the buffer memory exceeds a predetermined reference value. On the other hand, when the free space of the buffer memory is lower than a predetermined reference value, the compression rate of the recording data is set to a second compression rate that is higher than the first compression rate. Thus, the code amount is reduced.

  That is, when the buffer memory space exceeds a predetermined reference value, recording data is generated at the first compression rate with a relatively low compression, and the data quality (image quality in the case of image data) is ensured. To do. On the other hand, when the free space in the buffer memory is lower than the predetermined reference value, the recording data is generated at the second compression rate of relatively high compression, and the code amount (data amount) is reduced. Continuous data recording is realized by avoiding buffer overflow.

  The inventions according to claims 5 to 9 provide an invention of an apparatus that embodies the method invention according to claims 1 to 4.

  That is, the data recording apparatus according to the invention described in claim 5 includes an empty area detecting means for detecting an empty area of a recording medium, a trial writing processing means for performing a trial writing of data in the detected empty area, and the trial A recording speed measuring means for measuring the recording speed of writing, a bit rate determining means for determining a bit rate at the time of writing recording data based on the measurement result of the recording speed by the trial writing, and the bit rate according to the determined bit rate. Media recording means for performing control of writing data to the recording medium.

  A sixth aspect of the present invention relates to the data recording apparatus according to the fifth aspect, wherein the test writing processing means records a plurality of locations designated by different addresses among the free areas detected by the free area detecting means. Each block performs test writing, and the bit rate determining means determines the bit rate according to the slowest recording speed from the measurement result of the recording speed of the test writing performed in the plurality of recording blocks. Features.

  According to a seventh aspect of the present invention, there is provided a data recording apparatus comprising: a buffer memory for temporarily storing recording data; a medium recording means for recording the recording data read from the buffer memory on a recording medium; Free space detecting means for detecting capacity, and bit rate control means for controlling the bit rate of the recording data in accordance with the detection result of the free capacity so as not to cause overflow of the buffer memory. Features.

  The invention according to claim 8 relates to the data recording apparatus according to claim 7, wherein the bit rate control means sets the compression rate of the recording data when the free space of the buffer memory exceeds a predetermined reference value. On the other hand, when the free space of the buffer memory is lower than a predetermined reference value, the compression rate of the recording data is set to a second compression rate that is higher than the first compression rate. The code amount is reduced by setting.

  The invention according to claim 9 provides an image recording apparatus using the data recording apparatus according to any one of claims 5 to 8, and the data recording according to any one of claims 5 to 8. And an image pickup means for converting an optical image into an electric signal, and a signal processing means for generating data for recording by encoding continuous image data acquired via the image pickup means. And

  According to the present invention, since the trial writing is performed on the free space of the recording medium and the bit rate is determined according to the recording speed, the bit rate is set according to the type of recording medium and the free space (usage status). It can be optimized and the recording speed can be improved.

  In addition, according to another aspect of the present invention, the bit rate is changed so as to prevent overflow from being monitored by monitoring the freeness of the buffer memory, so that continuous data such as moving images and sounds are not interrupted. You can keep recording.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram of a digital camera showing an embodiment of the present invention. The digital camera 10 is a digital camera having functions for recording and reproducing still images and moving images. As shown in the figure, the digital camera 10 has a photographing lens 12, an image sensor 14, an A / D converter 16, a signal processing unit 18, and a compression process. The unit 20 includes a media control unit 22, a memory 24, a central processing unit (CPU) 26, a display control unit 28, and a display unit 30.

  The taking lens 12 may be a single focus lens or a lens system such as a zoom lens with variable focal length (shooting magnification). The light that has passed through the photographing lens 12 enters the image sensor 14. A large number of photosensors (photoelectric conversion elements) are two-dimensionally arranged on the light receiving surface of the image sensor 14, and red (R), green (G), and blue (B) primary color filters corresponding to the photosensors. Are arranged in a predetermined arrangement structure. The imaging device 14 can also use various types of imaging devices such as a CCD image sensor and a CMOS image sensor. In implementing the present invention, not only a single plate type but also a configuration using a plurality of image sensors such as a 3CCD system is possible.

  The optical image of the subject formed on the light receiving surface of the image sensor 14 via the photographing lens 12 is converted into a signal charge corresponding to the amount of incident light by each photosensor, and an electric signal (image signal) corresponding to the signal charge is converted. ) Sequentially. The image sensor 14 has an electronic shutter function for controlling the charge accumulation time (shutter speed) of each photosensor according to the timing of the shutter gate pulse.

  The image signal output from the image sensor 14 is subjected to correlated double sampling (CDS) processing, color separation processing, gain adjustment, and the like by an analog processing unit (not shown), and then converted into a digital signal by the A / D converter 16. Converted.

  The image data after A / D conversion is sent to the signal processing unit 18. The signal processing unit 18 includes a synchronization circuit (a processing circuit that calculates the color of each point by interpolating a spatial shift of the color signal associated with the color filter array of the single CCD), a luminance / color difference signal generation circuit, and a gamma correction. The image processing unit functions as an image processing unit including a circuit, a contour correction circuit, a white balance correction circuit, and the like and functions as an audio processing unit, and processes an image signal and an audio signal while utilizing the memory 24 in accordance with a command from the CPU 26.

  The image data input from the A / D converter 16 to the signal processing unit 18 is converted into a luminance signal (Y signal) and a color difference signal (Cr, Cb signal) and subjected to predetermined processing such as gamma correction. And stored in the memory 24.

  The memory 24 is used as a work area for the CPU 26 and is also used as a temporary storage area for image data and audio data. The memory 24 is also used as a buffer memory (recording buffer) for writing data to the recording medium 32 and a display memory for storing display data.

  When the image being captured is output to the monitor, the image data stored in the memory 24 is sent to the display control unit 28. The display control unit 28 converts the input image data into a predetermined display signal (for example, an NTSC color composite video signal) and outputs the converted signal to the display unit 30. The image data in the memory 24 is periodically rewritten by the image signal output from the image sensor 14, and the video signal generated from the image data is supplied to the display unit 30, so that the image being captured is real-time. Displayed as a video. The photographer can check the shooting angle of view from the moving image (through movie) displayed on the display unit 30.

  The display unit 30 displays not only the image being captured, but also the playback image of the image recorded on the recording medium 32, information on the currently set mode, image compression rate information, date / time information, frame number, etc. Information can also be displayed. The display unit 30 is also used as a display screen for a user interface when the user performs various setting operations, and displays menu information such as setting items as necessary. Note that various types of display means such as a liquid crystal display device and an organic EL display device can be applied to the display unit 30.

  Capture of a recording image is started based on a shooting execution instruction signal generated by an operation of an operation unit (not shown) (for example, a shooting button) or an automatic shooting program. The image data thus captured is subjected to necessary processing in the signal processing unit 18, and is then compression encoded by the compression processing unit 20 and converted into a bit rate that can be recorded on the recording medium 32.

  The media control unit 22 is means for controlling reading and writing of the recording medium 32 in accordance with instructions from the CPU 26, and the compressed image data is recorded on the recording medium 32 via the media control unit 22. In the case of video data, for example, it is recorded in a file format such as motion JPEG format or MPEG format.

  In the motion JPEG system, the image data acquired from the image sensor 14 is temporarily stored in the internal memory 24, and then converted into a luminance / color difference signal by the signal processing unit 18, and JPEG compression is performed within one image while recording media 32. The frame images are continuously stored at a constant frame rate (a preset frame rate). In the case of the MPEG system, recording is continuously performed on the recording medium 32 while performing intra-frame compression and inter-frame compression. Of course, the file format is not limited to the above example. The file format may be determined in advance or may be configured to be selectable by the user.

  Further, the media control unit 22 has a media detection terminal (not shown) for detecting whether or not the recording medium 32 is mounted, and a detection signal indicating whether the recording medium 32 is mounted / not mounted is a media control unit 22. To the CPU 26.

  The CPU 26 performs control so that each process in the digital camera 10 is performed without delay. That is, the CPU 26 functions as a control unit that performs overall control of the camera system according to a predetermined program, and also functions as a calculation unit that performs various calculations such as automatic exposure (AE) calculation and automatic focus adjustment (AF) calculation. The CPU 26 controls each circuit in the digital camera 10 based on a signal (operation signal) received from an operation unit (not shown) and detection signals from various sensors, for example, file management of the recording medium 32 and management of free space. , Operation mode switching control, lens drive control, imaging control, image processing control, compression rate control of the compression processing unit 20, image / audio data recording / playback control, power supply control, display control of the display unit 30, and the like. The CPU 26 also functions as a means for measuring the writing speed (recording speed) of the recording medium 32.

  When a moving image shooting mode is selected by a mode selection unit (not shown) and moving image recording is performed, if the compression rate in the compression processing unit 20 is low, the amount of data increases and the recording process on the recording medium 32 cannot catch up. In order to avoid the situation, the digital camera 10 of this example is configured to adaptively vary the compression rate in the compression processing unit 20.

  The form of the recording medium 32 is not particularly limited, and a semiconductor memory card represented by SmartMedia (trademark) or xD Picture Card (trademark), a portable small hard disk represented by Microdrive (trademark), or a magnetic disk. Various media such as optical disks and magneto-optical disks can be used.

  In FIG. 1, only one recording medium 32 is shown. However, in implementing the present invention, a configuration in which a plurality of recording media of the same type or different types can be used is also possible. The means for storing image data is not limited to a removable medium (a portable recording medium having a structure that is detachable from the digital camera 10), and is a non-removable recording medium (internal memory) built in the digital camera 10. May be.

  Next, the operation of the digital camera 10 configured as described above will be described.

  FIG. 2 is a flowchart showing a sequence before the start of recording. When the recording medium 32 is inserted into the digital camera 10 (step S110), the CPU 26 grasps the type of the recording medium 32 related to the mounting through the media control unit 22 and searches for an empty area of the recording medium 32 (step S110). S112).

  If it is determined by the free space search that there is a free space in the recording medium 32, trial writing is performed with one block at the head address of the free space, and the recording speed is measured (step S114). Next, trial writing is performed with one block at the final address of the free area, and the recording speed is measured (step S116).

  From these measurement results, the maximum recordable bit rate is determined in accordance with the slower speed (lower speed side) (step S118). Thus, the (initial) bit rate at the start of recording is set, the compression rate of the compression processing unit 20 is set according to this bit rate, and is reflected in the recording mode display on the display unit 30 (step S120). For example, there is an aspect in which information on the determined bit rate is displayed, or an aspect in which selection items in the bit rate selection menu are limited.

  In this way, recording at the maximum writable bit rate is realized by measuring the recording speed by trial writing and optimizing the processing (weight function control) according to the actual writing speed to the recording medium 32. .

  If there is no free space in step S112 or if a recording start instruction is input before the free space search is completed, if trial writing cannot be performed, a preset is made for each media type. Use the value that is present. Also in this case, the information of the bit rate determined by the preset value is reflected in the recording mode display on the display unit 30 (step S120).

  Note that if a non-recordable medium such as a medium with no free space (media full) or a write-protected (write-protected) medium is inserted, an error message or the like is displayed on the display unit 30 in step S120. And media exchange is prompted.

  In the flowchart shown in FIG. 2, trial writing was performed for each of the first address block and the last address block in the empty area. However, as in the case of a semiconductor memory card, the recording speed depends on the physical position where data is recorded. In the case of using a recording medium with almost no difference, it is only necessary to perform test writing in any one block.

  FIG. 3 is a flowchart showing a sequence during data recording. When data recording to the recording medium 32 such as moving image shooting is started (step S210), the CPU 26 determines the free capacity of the recording buffer (a buffer memory using a partial area of the memory 24) (S210). If the free space in the recording buffer exceeds a predetermined reference value, the compression rate in the compression processing unit 20 is lowered to ensure high image quality (step S212).

  On the other hand, if the buffer capacity of the recording buffer is below a predetermined reference value (there is little space), the compression rate is increased to reduce the code amount (step S214), thereby avoiding buffer overflow.

  The compression rate set in step S212 or step S214 is reflected in the recording mode (step S216), and data recording to the next block of the recording medium 32 is performed (step S218). After step S218, the process returns to step S212, and the above processing steps are repeated.

  In this way, the bit rate is controlled by monitoring the free space in the recording buffer during moving image recording. At this time, it is preferable to change the bit rate in units equal to or greater than the minimum recording unit.

  Movie capture is performed based on a shooting stop instruction signal generated by operating an operation unit (not shown) (for example, a shooting stop button also used as a shooting button), by an automatic shooting program, or when the media is full. finish.

  The scope of application of the present invention is not limited to the digital camera according to the embodiment described above, and the present invention can also be applied to various information devices such as a video camera, a DVD camera, a camera-equipped mobile phone, a PDA, and a mobile personal computer. The data to be recorded is not limited to moving image data, and may be other data such as audio data.

1 is a block diagram of a digital camera showing an embodiment of the present invention. The flowchart which shows the control procedure before the recording start in the digital camera of this example Flowchart showing the control procedure during recording in the digital camera of this example

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Digital camera, 14 ... Imaging device, 18 ... Signal processing part, 20 ... Compression processing part, 22 ... Media control part, 24 ... Memory, 26 ... CPU, 32 ... Recording medium

Claims (9)

A free space detection step for detecting a free space on the recording medium;
A trial writing step of performing trial writing of data in the detected free space;
A recording speed measuring step for measuring the recording speed of the test writing;
A bit rate determining step for determining a bit rate at the time of writing data for recording based on the measurement result of the recording speed by the test writing;
A data recording method comprising: Perform test writing in each of the plurality of recording blocks specified by different addresses among the free areas detected in the free area detection step,
2. The data recording method according to claim 1, wherein the bit rate is determined in accordance with the slowest recording speed from the measurement result of the recording speed of trial writing performed in the plurality of recording blocks. A buffering step for temporarily storing recording data in a buffer memory;
A writing step of recording the recording data read from the buffer memory on a recording medium;
A free space detecting step for detecting free space in the buffer memory;
A bit rate control step of controlling the bit rate of the recording data according to the detection result of the free capacity so as not to cause an overflow of the buffer memory;
A data recording method comprising: The bit rate control step includes
When the free space of the buffer memory exceeds a predetermined reference value, the compression rate of the recording data is set to the first compression rate, while when the free space of the buffer memory falls below a predetermined reference value, 4. The data recording method according to claim 3, wherein the code amount is reduced by setting the compression rate of the recording data to a second compression rate higher than the first compression rate. Free space detecting means for detecting free space on the recording medium;
Trial writing processing means for performing trial writing of data in the detected free space;
A recording speed measuring means for measuring the recording speed of the test writing;
A bit rate determining means for determining a bit rate at the time of recording data writing based on the measurement result of the recording speed by the test writing;
Media recording means for performing control to write data to the recording medium according to the determined bit rate;
A data recording apparatus comprising: The test writing processing means performs test writing in each of a plurality of recording blocks specified by different addresses among the free areas detected by the free area detection means,
6. The bit rate determination unit according to claim 5, wherein the bit rate is determined in accordance with a slowest recording speed from a measurement result of a recording speed of trial writing performed in the plurality of recording blocks. Data recording device. A buffer memory for temporarily storing recording data;
Media recording means for recording the recording data read from the buffer memory on a recording medium;
Free space detecting means for detecting free space in the buffer memory;
Bit rate control means for controlling the bit rate of the recording data in accordance with the detection result of the free space so as not to cause an overflow of the buffer memory;
A data recording apparatus comprising:   The bit rate control means sets the compression rate of the recording data to a first compression rate when the free space of the buffer memory exceeds a predetermined reference value, while the free space of the buffer memory is set to a predetermined reference value. 8. The data according to claim 7, wherein when the value is lower than the value, the code amount is reduced by setting the compression rate of the recording data to a second compression rate higher than the first compression rate. Recording device. A data recording device according to any one of claims 5 to 8,
Imaging means for converting an optical image into an electrical signal;
Signal processing means for generating data for recording by encoding data of a continuous image acquired via the imaging means;
An image recording apparatus comprising:

Images