JP2013017003A - Parameter determination device, imaging device, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly maintain an information amount while encoding data with few computational resources.SOLUTION: A parameter determination device comprises: an information acquisition unit that acquires information indicating a change in a code amount of first data; and a parameter determination unit that determines an encoding parameter for controlling, at each time, a code amount of second data obtained after the first data on the basis of the change in the code amount. A program causes a computer to execute: a step for acquiring information indicating a change in a code amount of first data; and a step for determining an encoding parameter for controlling, at each time, a code amount of second data obtained after the first data on the basis of the change in the code amount.

Description

  The present invention relates to a parameter determination device, an imaging device, and a program.

A technique is known that temporarily stores continuously input images, determines a GOP structure based on feature information extracted from the stored images, and predicts a bit amount necessary for encoding. (For example, refer to Patent Document 1).
[Prior art documents]
[Patent Literature]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-199398

  For example, when moving image data is encoded by a one-pass encoding method, the amount of code is adjusted so as to approach the target bit rate at each time, so that the image quality may be uneven. On the other hand, according to the multi-pass encoding method, enormous calculation resources may be required for encoding. As described above, there is a problem that data cannot be encoded with a small number of computing resources while keeping the amount of information uniform.

  In the first aspect of the present invention, the parameter determination device is obtained after the first data based on the information acquisition unit that acquires information indicating the change in the code amount of the first data and the change in the code amount. A parameter determination unit that determines an encoding parameter for controlling the code amount of the second data for each time.

  In the second aspect of the present invention, the program acquires the information indicating the change in the code amount of the first data, and the second data obtained after the first data based on the change in the code amount. And determining a coding parameter for controlling the amount of code for each time.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

An example of the usage form of the imaging system 50 according to the embodiment is shown. 2 shows an example of a block configuration of the imaging apparatus 10. An example of a functional block configuration of the compression unit 270 is shown. An example of the compression strength in moving image shooting of one sequence is shown. The change of the code amount by a quantization step is typically shown. An example of a quantization table applied to DCT coefficients is shown in a table format. An example of an operation flow in the imaging system 50 is shown. An example of the process which determines a quantization step is shown. An example of processing in actual photographing will be shown.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 shows an example of a usage pattern of an imaging system 50 according to an embodiment. In the present embodiment, the shooting system 50 is used for shooting in the studio 60. The imaging system 50 includes an imaging device 10, a carriage device 20, a control device 30, and a lighting device 40. The photographing system 50 provides a system that provides moving image data with uniform image quality by encoding a moving image in real time.

  Prior to the main shooting, the shooting system 50 performs trial shooting in the same shooting environment as the main shooting. Then, the imaging apparatus 10 determines in advance encoding parameters to be applied when encoding moving image data obtained by actual shooting in consideration of encoding information of moving image data obtained by trial shooting. For example, the imaging apparatus 10 determines the quantization step for each time so that the image quality becomes substantially constant over one shooting sequence in consideration of the change in the code amount of moving image data obtained by trial shooting. Then, the imaging apparatus 10 performs quantization by applying a predetermined quantization step during the main photographing. According to the imaging apparatus 10, an optimal quantization step as a whole of one sequence can be determined in advance from one sequence of moving image data obtained by trial shooting. In addition, at the time of actual photographing, it is not necessary to perform enormous calculations in order to allocate an appropriate code amount. For this reason, the imaging device 10 can provide moving image data with more uniform image quality while encoding a moving image in real time.

  The control device 30 includes an operation input unit 32, a controller 34, and a control data storage unit 36. The control device 30 is, for example, a computer that controls the shooting environment of the imaging device 10.

  Specifically, the control data storage unit 36 reads out control data defining control contents of the imaging device 10, the carriage device 20, and the lighting device 40 from the recording medium 38 and stores the control data. For example, the control data defines the light emission conditions of the illumination device 40, the imaging conditions of the imaging device 10, the position and orientation of the imaging device 10, etc. for each time. The controller 34 transmits a control signal for controlling the imaging device 10, the carriage device 20, and the lighting device 40 based on the control data stored in the control data storage unit 36. The operation input unit 32 acquires user instructions such as a trial shooting start instruction and a main shooting start instruction. In response to an instruction from the operation input unit 32, the controller 34 starts control of each device of the imaging device 10, the carriage device 20, and the lighting device 40. Further, the controller 34 transmits a control signal to each device at each timing in accordance with information defined by the control data.

  The control device 30 controls the light emission conditions of the lighting device 40. Examples of the light emission conditions include the light emission timing of the illumination light, the light emission amount, and the color. For example, the control device 30 controls the light emission conditions by supplying a control signal indicating the light emission conditions to the illumination device 40.

  The carriage device 20 controls the position and orientation of the imaging device 10. For example, the carriage device 20 controls the position, pan, tilt angle, and the like of the imaging device 10. Specifically, the control device 30 supplies a control signal for driving the gantry device 20 to the gantry device 20. The gantry device 20 operates according to the control signal to control the position and orientation of the imaging device 10.

  Further, the control device 30 controls the imaging conditions of the imaging device 10. Examples of the imaging condition include a zoom value, an aperture value, an exposure amount, and a focal position. Further, the control device 30 controls the light emission conditions of the flash device 12 included in the imaging device 10. The control device 30 controls the imaging condition and the light emission condition by supplying a control signal indicating the imaging condition and the light emission condition to the imaging device 10.

  In the photographing system 50, prior to the main photographing, the trial photographing is performed under the same conditions as the main photographing. For example, the control device 30 performs trial shooting by controlling the carriage 20, the imaging device 10, and the illumination device 40 under the same operating conditions as the main shooting. For example, the control device 30 supplies the same control signal as that for the main photographing to the carriage 20, the imaging device 10, and the lighting device 40, and performs the trial photographing under the same operation conditions as the main photographing. Thereby, the imaging device 10 can perform trial shooting under the same shooting environment as the main shooting. The imaging device 10 compresses and records moving image data obtained by trial shooting. The compressed and encoded moving image data obtained by trial shooting may be referred to as preliminary shooting data. In addition, a moving image obtained by actual shooting may be referred to as actual shooting data.

  The imaging device 10 determines a coding parameter for main shooting based on the code amount of the trial moving image data. For example, the imaging device 10 determines a quantization step for each time in one sequence in the main photographing. Note that one sequence indicates a period from the start of shooting a moving image to be encoded to the end of shooting. The imaging device 10 calculates the total code amount of the trial moving image data and calculates an average value of the code amount from the target code amount. The imaging apparatus 10 determines the quantization step for each time so that the image quality is made more uniform and the average code amount of one sequence approaches the average value. The imaging device 10 stores the determined quantization step and applies it in real time to the encoding at the time of actual photographing.

  According to the imaging system 50, it is possible to determine the quantization step so that the code amount is uniform by looking at the change in the code amount predicted for the entire sequence in the main imaging. For this reason, it is possible to perform encoding with an optimal quantization step without applying a multi-pass encoding method at the time of actual photographing. Therefore, the imaging device 10 can generate moving image data with more uniform image quality while encoding in real time without requiring a huge amount of computing resources.

  FIG. 2 shows an example of a block configuration of the imaging apparatus 10. The imaging apparatus 10 includes a lens system 221 that includes a zoom lens, a focus lens, and the like. The light flux from the subject enters the lens system 221 along the optical axis 219 and forms an image of the subject on the imaging surface of the image sensor 231. The functional blocks of the lens system 221 and the image sensor 231 mainly function as an imaging unit.

  The image pickup device 231 picks up a subject by photoelectrically converting a subject image as an optical image that is transmitted through the lens system 221 and formed on the image pickup device 231. As the image sensor 231, for example, a CCD or CMOS sensor can be used. The subject image photoelectrically converted by the image sensor 231 is converted from an analog signal to a digital signal by the A / D converter 232. The charge readout control of the image sensor 231 and the conversion control of the A / D converter 232 are synchronized by a clock signal supplied from the timing generation unit 234 that receives the synchronization control of the memory control unit 233.

  The subject image converted into the digital signal is sequentially processed as image data. The image data converted into a digital signal by the A / D converter 232 is temporarily stored in the internal memory 235 under the control of the memory control unit 233. The internal memory 235 is a random access memory that can be read and written at high speed, and for example, a DRAM, an SRAM, or the like is used. The internal memory 235 serves as a buffer memory that waits for the order of image processing when image data is continuously generated at high speed in continuous shooting and moving image shooting.

  The internal memory 235 also serves as a work memory in image processing and compression processing performed by the image processing unit 237. In particular, in the present embodiment, the internal memory 235 stores frame data of a plurality of frames constituting a moving image when the moving image is encoded. The internal memory 235 has a sufficient memory capacity corresponding to these roles.

  The system memory 236 is an electrically erasable / recordable nonvolatile memory, and is configured by, for example, an EEPROM (registered trademark). The system memory 236 records constants, variables, programs, and the like necessary for the operation of the imaging apparatus 10 so that they are not lost even when the imaging apparatus 10 is not operating. The system control unit 250 that directly or indirectly controls the entire imaging apparatus 10 expands constants, variables, programs, and the like in the internal memory 235 as appropriate, and uses them for controlling the imaging apparatus 10.

  The image processing unit 237 converts the image data into a predetermined image format in accordance with the set shooting mode and instructions from the user. For example, when generating a JPEG file as a still image, the preprocessing unit 260 performs image processing such as color interpolation processing, gamma correction processing, and contour compensation on image data as a still image, and then the compression unit 270 performs discrete processing. A compression encoding process is performed by performing cosine transform, quantization, and the like. In addition, when generating an MPEG file as a moving image, the compression unit 270 performs intra-frame encoding and inter-frame encoding on a frame image as a continuous still image generated by being reduced to a predetermined number of pixels. To compress.

  The compression unit 270 encodes the frame image according to the encoding parameter determined by the encoding parameter determination unit 280. At the time of actual shooting, the encoding parameter determination unit 280 supplies the quantization step determined based on the preliminary shooting data to the compression unit 270 and controls the quantization in the compression unit 270. Still image data and moving image data processed by the image processing unit 237 are transferred from the internal memory 235 to the recording medium 209 via the recording medium IF 240 and recorded.

  The image processing unit 237 generates image data for display in parallel with the image data processed for recording. The generated image data for display is converted into an analog signal by the D / A converter 239 under the control of the display control unit 238 and displayed on the display unit 201. The system control unit 250 can also display various menu items related to various settings of the imaging apparatus 10 on the display unit 201.

  The external IF 241 receives a control signal from the controller 34. For example, the external IF 241 receives a control signal for changing the imaging condition and supplies the control signal to the system control unit 250. When receiving a control signal, the system control unit 250 controls the imaging conditions by controlling each unit according to the received control signal. For example, the system control unit 250 controls the lens system 221 by controlling the lens drive control unit 243 according to the control signal.

  The imaging apparatus 10 includes a plurality of operation members 202 that receive operations from the user. The system control unit 250 detects that the operation member 202 has been operated, and executes an operation corresponding to the operation.

  The lens system 221 is controlled by the lens drive control unit 243 under the overall control of the system control unit 250. The lens drive control unit 243 mainly drives the zoom lens among the lenses included in the lens system 221 to change the angle of view of the subject image. Further, the lens drive control unit 243 mainly drives the focus lens among the lenses included in the lens system 221 to change the focal position. In addition, the lens drive control unit 243 controls the aperture device included in the lens system 221 to control the exposure amount. When receiving a control signal for changing zooming, focusing, or aperture, the system control unit 250 controls the lens drive control unit 243 so that the lens system 221 is driven according to the control signal.

  The power supply unit 208 supplies power to each unit of the imaging device 10. The recording medium 209 is a nonvolatile recording medium, and can hold recorded data even when there is no power supply from the power supply unit 208.

  FIG. 3 shows an example of a functional block configuration of the compression unit 270. The compression unit 270 is an example of an encoding unit that encodes moving image data in accordance with the encoding parameter determined by the encoding parameter determination unit 280. The compression unit 270 includes an encoding control unit 300, a subtraction unit 310, a conversion unit 320, a quantization unit 330, a variable length encoding unit 340, an inverse quantization unit 332, an inverse conversion unit 322, an addition unit 312, and a deblocking unit 360. , An inter-frame prediction unit 370, an intra-frame prediction unit 350, and a prediction control unit 380. Here, the operation of each unit in the case of compressing and encoding a frame that is an image constituting a moving image will be described.

  The subtraction unit 310 subtracts the prediction image supplied from the prediction control unit 380 from the compression target frame. The predicted image is a motion-compensated image generated in the intra-frame prediction unit 350 or the inter-frame prediction unit.

  The transform unit 320 performs discrete cosine transform (DCT transform) on the residual signal output from the subtractor 310. In this DCT transform, a DCT coefficient is calculated for each block.

  The quantization unit 330 quantizes the DCT coefficient. Specifically, the quantization unit 330 divides each DCT coefficient in one block by the quantization step value at the corresponding position in the quantization table. Therefore, lossy compression is performed by the quantization unit 330. The encoding control unit 300 controls the amount of generated code by controlling the quantization step in the quantization unit 330. For example, when the predicted generated code amount or the generated code amount is larger than a predetermined value, the value of the quantization step is set to be large. The variable length coding unit 340 performs variable length coding on the data quantized by the quantization unit 330. One frame of encoded data output from the variable length encoding unit 340 is stored in the internal memory 235.

  Among the functional blocks of the compression unit 270, from the functional blocks of the inverse quantization unit 332, the inverse transformation unit 322, the addition unit 312, the deblocking unit 360, the inter-frame prediction unit 370, the intra-frame prediction unit 350, and the prediction control unit 380 Motion compensation is realized. The inverse quantization unit 332 performs inverse quantization by applying the quantization step used for quantization by the quantization unit 330. The inverse transform unit 322 performs the inverse transform of the DCT transform applied by the transform unit 320 on the DCT coefficient obtained by the inverse quantization. The adder 312 adds the residual signal obtained by the inverse transformation to the difference target frame. The deblocking unit 360 applies a deblocking filter that reduces block noise to the image data obtained by the addition process. The inter-frame prediction unit 370 performs inter-frame prediction on the input frame, and provides a motion-compensated predicted image to the prediction control unit 380. The intra-frame prediction unit 350 generates a prediction image from the input frame and provides the prediction image to the prediction control unit 380. The prediction control unit 380 provides the prediction image to the subtraction unit 310.

  The moving image data generated by the trial shooting is compressed by the compression unit 270, temporarily stored as preliminary shooting data in the internal memory 235, and transferred to the recording medium 209. The encoding parameter determination unit 280 acquires the preliminary shooting data from the recording medium 209 and analyzes it. Then, the encoding parameter determination unit 280 determines the value of the quantization step for main photographing every time and stores it in the internal memory 235. When the compression unit 270 compresses and encodes the moving image data obtained in the actual shooting, the encoding control unit 300 performs quantization by applying the quantization step value stored in the internal memory 235 to each time. .

  As described above, the encoding parameter determination unit 280 acquires information indicating a change in the code amount of the pre-shooting data that is the moving image data shot in advance. Specifically, the encoding parameter determination unit 280 acquires preliminary shooting data that has been subjected to encoding processing including quantization. Then, the encoding parameter determination unit 280 determines an encoding parameter for controlling the code amount of the moving image data captured after the preliminary capturing data for each time. Specifically, the parameter determination unit 280 determines a parameter for controlling the compression strength for irreversibly compressing the main shooting data as the encoding parameter. More specifically, the parameter determination unit 280 determines a value of a quantization step for quantizing the main photographing data as an encoding parameter.

  For example, the encoding parameter determination unit 280 determines a quantization step having a small value during a period in which the generated code amount is large in the preliminary shooting data and is quantized by a quantization step having a large value. On the other hand, a quantization step having a large value is determined in a period in which the generated code amount is small and quantization is performed by a quantization step having a small value. As a result, when the moving image data obtained by the actual photographing is compression-encoded, it is possible to prevent the image quality during the period in which the generated code amount is large from decreasing without significantly increasing the entire code amount. In addition, since the quantization step determined in advance based on the preliminary shooting data is applied, the amount of calculation required to control the generated code amount can be significantly reduced. Therefore, the one-pass encoding method can be applied at the time of actual photographing, and one sequence of frame data need not be stored in the internal memory 235. Therefore, it is possible to compress and encode the moving image data obtained by the actual photographing in real time without requiring a huge amount of computing resources.

  FIG. 4 shows an example of the compression strength in one sequence of moving image shooting. In this figure, the time evolution of the high frequency component contained in the flame | frame image | photographed by one sequence and the compression strength which compresses a flame | frame is shown typically. In this sequence, moving image shooting starts at time t0, and moving image shooting ends at time t5. In this sequence, shooting is started in a state where the zoom lens of the lens system 221 is controlled to the wide end position. Zooming is performed from the wide end to the tele end from time t1 to t2, and then from the tele end to the wide end in two stages from time t3 to t4 and from time t4 to t5. Returned.

  When the depth of field is relatively deep at the wide end, the frame contains a relatively large amount of high-frequency components. On the other hand, when the depth of field becomes shallow by zooming to the tele end, the high-frequency component contained in the frame decreases. On the other hand, when returning from the tele end to the wide end, the high frequency component increases. The time evolution of the high frequency component obtained in this sequence is schematically indicated by reference numeral 400.

  Here, reference numeral 410 schematically shows the temporal development of the compression strength when trial shooting is performed in this sequence and encoding is performed in real time. Here, the compression strength in the quantization unit 330 is shown. From time t0 to t1, a frame with a relatively high frequency component is captured. Since the amount of generated code increases as the number of high frequency components increases, the value of the quantization step is set large so that the amount of code generated per unit time does not greatly exceed the target bit rate during the period from time t0 to t1. That is, the compressive strength is relatively high.

  On the other hand, when the high frequency component decreases during the period from time t1 to t2, the generated code amount decreases. For this reason, the value of the quantization step gradually decreases according to the target bit rate. That is, the compressive strength decreases. Similarly, in the period from time t3 to t4 and in the period from time t4 to t5, the high-frequency component gradually increases, so that the compression strength gradually increases. Therefore, in the period from time t0 to t1, the image quality of the compressed frame is low, and the image quality increases from time t1 to time t2. In addition, the image quality of the frame gradually decreases from time t3 to t5. That is, the feedback based on the amount of code generated per unit time makes the bit rate fluctuation relatively gradual, but the image quality fluctuation becomes large.

  The encoding parameter determination unit 280 allocates a relatively large amount of code during a period in which the generated code amount is predicted to increase based on a change in the compression strength of the preliminary shooting data, and the generated code amount decreases. A relatively small amount of code is allocated during a period in which the value is predicted. Specifically, the encoding parameter determination unit 280 sets a relatively small quantization step during a period in which the generated code amount is predicted to increase, and the generated code amount is predicted to decrease. A relatively large quantization step is set during the period. That is, the encoding parameter determination unit 280 sets the value of the quantization step for each time so that the change in compression strength is reduced over one sequence, as indicated by reference numeral 420 in the figure. As a result, it is possible to prevent the image quality of the main shooting from fluctuating greatly.

  As described above, the parameter determination unit 280 is a code that makes the ratio of the compression strength applied in the second period to the compression strength applied in the first period smaller than the ratio applied in the pre-shooting data encoding process. Determine optimization parameters. For this reason, the image quality can be made more uniform over time.

  In this example, it has been described that the amount of generated code varies as the high frequency component varies due to zooming. However, the generated code amount may also be caused by time variations of various shooting environments such as zooming change, focus position change, image pickup device 10 position change, image pickup device 10 orientation change, and lighting device 40 blinking.

  FIG. 5 schematically shows changes in the code amount due to the control of the quantization step. In this figure, the horizontal axis represents the value of the quantization step, and the vertical axis represents the change coefficient indicating the change rate 500 of the generated code amount. The generated code amount is predicted by a value obtained by multiplying the code amount by a change coefficient corresponding to the value of the quantization step. Based on the rate of change shown in the figure and the amount of generated code in the preliminary shooting data, the encoding control unit 300 changes the allocation of the amount of code relative to each other as described in FIG. The value of the quantization step is determined for each time so that the total value of the code amount over the sequence approaches the target code amount. That is, the encoding control unit 300 determines the quantization step value for each time so that the average value of the code amount over one sequence approaches the average value of the target code amount.

  FIG. 6 shows an example of a quantization table applied to DCT coefficients in a table format. Each frequency component of the DCT coefficient calculated by the conversion unit 320 is divided by a corresponding value in the quantization table 600. The encoding control unit 300 may change the value of the quantization step for quantizing each frequency component by changing the value of each quantization step in the quantization table. For example, the encoding control unit 300 may change the value of the quantization step with time by switching the entire quantization table with time. Also, the encoding control unit 300 may change the quantization step value with time by changing the quantization parameter, which is a coefficient by which the value of each quantization step in the quantization table is multiplied, to 0. Good. That is, examples of the encoding parameter determined by the encoding parameter determination unit 280 include the quantization table itself and the quantization parameter.

  FIG. 7 shows an example of an operation flow in the imaging system 50. This flow is started when the operation input unit 32 is instructed to start shooting one scene. In step S <b> 702, the controller 34 reads control data for controlling the imaging device 10, the carriage device 20, and the lighting device 40 from the control data storage unit 36. The main control data is control data for controlling the operations of the imaging device 10, the carriage device 20, and the lighting device 40 when performing the main photographing described later.

  Subsequently, when a user instruction to start trial shooting is given to the operation input unit 32, the controller 34 instructs the imaging device 10 to start trial shooting (step S704). During the trial shooting, the controller 34 transmits a control signal for controlling each device of the imaging device 10, the carriage device 20, and the lighting device 40 to each device based on the read control data. The moving image data obtained by trial shooting is compressed and encoded in real time by the compression unit 270. In the trial shooting, the encoding control unit 300 may control the value of the quantization step by feedback based on the generated code amount per unit time.

  When the trial shooting is completed, the system control unit 250 records the preliminary shooting data compressed by the compression unit 270 as a moving image file on the recording medium 209 (step S706). Subsequently, the encoding parameter determination unit 280 analyzes the preliminary moving image file recorded on the recording medium 209, determines the value of the quantization step, and stores it in the internal memory 235 (step S708). This process will be described with reference to FIG.

  When a user instruction to start main shooting is given to the operation input unit 32, the controller 34 instructs the imaging device 10 to start main shooting (step S710). During the actual photographing, the controller 34 transmits a control signal for controlling each device of the imaging device 10, the carriage device 20, and the lighting device 40 to each device based on the control data read in step S702. Therefore, the main shooting is performed under substantially the same conditions as the trial shooting. The compression unit 270 performs compression encoding in real time by applying the value of the quantization step stored in the internal memory 235 to the quantization during the main photographing. This process will be described with reference to FIG.

  Subsequently, when the main photographing is completed, the system control unit 250 records the main moving image data compressed by the compression unit 270 on the recording medium 209 as a moving image file (step S712). When the recording on the recording medium 209 is completed, this flow ends.

  FIG. 8 shows an example of a process for determining the quantization step. That is, the process flow in step S708 of FIG. 7 is shown. In step S802, the encoding parameter determination unit 280 calculates the entire code amount of the preliminary shooting data. Subsequently, the encoding parameter determination unit 280 calculates an average value of the code amount from a predetermined target code amount (step S804).

  Subsequently, the encoding parameter determination unit 280 calculates a quantization step value (step S806). Specifically, the value of the quantization step at each time is calculated so that the average value of the code amount over one sequence of the generated generated code amount approaches the average value of the code amount calculated in step S804.

  Here, when the total code amount calculated in step S802 is smaller than the target code amount by a predetermined threshold value, the quantization step is performed so that the compression strength applied at the time of actual shooting is reduced as an average over one sequence. Calculate the value. On the other hand, when the total code amount calculated in step S802 is larger than the target code amount exceeding a predetermined threshold, the value of the quantization step is set so that the compression strength applied at the time of actual shooting is high as an average over one sequence. calculate. In any case, as described with reference to FIG. 4, a quantization step with a small value is determined during a period when the code amount is large, and a quantization step with a large value is determined during a period when the code amount is small. As a result, a sufficient amount of code is allocated to a period in which a high frequency component of a frame is predicted to increase in the main shooting or a period in which the image content of the frame is predicted to change greatly, and prediction within one sequence is performed. The average value of the code amount can be brought close to the average value of the target code amount. As described above, the parameter determination unit 280 determines the compression strength for each time of the moving image data based on the entire code amount and the target code amount of the preliminary shooting data.

  Subsequently, the calculated quantization step value is stored in the internal memory 235 (step S808), and the process is terminated.

  FIG. 9 shows an example of processing in actual photographing. That is, the process flow in step 710 of FIG. 7 is shown. When the main flow is started, main photographing is started in step S902 (step S902). When the moving image shooting is started, the frame data preprocessed by the preprocessing unit 260 is sequentially stored in the internal memory 235. The compression unit 270 sequentially selects the frame data stored in the internal memory 235 according to the control from the memory control unit 233 and performs compression encoding (step S904).

  When the selected frame data is compression-encoded, the encoding control unit 300 determines the difference between the generated code amount and the predicted code amount when the quantization step stored in the internal memory 235 is applied to the quantization. It is determined whether or not the value is smaller than a predetermined reference value (step S906). The expected code amount may be a generated code amount predicted from the preliminary shooting data and the value of the quantization step determined by the encoding parameter determination unit 280.

  When the difference between the generated code amount and the predicted code amount is smaller than the reference value, the compression unit 270 performs compression encoding by applying the quantization step stored in the internal memory 235 (step S908). When the difference between the generated code amount and the predicted code amount is equal to or larger than the reference value, the encoding control unit 300 should apply the quantization unit 330 based on the average value of the current generated code amount and the target code amount. A quantization step is determined (step S910). That is, the encoding control unit 300 calculates the quantization step mainly by feedback control based on the generated code amount per unit time.

  In the determination in step S906, a predetermined maximum value allowed as the generated code amount may be applied as the predicted code amount. In addition, in the determination in step S906, an average value of the code amount generated within a predetermined period may be applied as the generated code amount. In step S906, the generated code amount is monitored, and when the difference from the predicted code amount is equal to or larger than the reference value, the value of the quantization step is determined in units of time mainly based on the generated code amount and the target code amount. . For this reason, when the actual shooting is performed under an operation condition temporarily different from that at the time of trial shooting, it is possible to prevent the code amount from being significantly increased by applying the predicted quantization step. Even when the timing at which each device is operated is shifted in time from the time of trial shooting, if the shift is eliminated, the quantization control by the predicted quantization step can be restored. Note that the predicted code amount may be corrected based on the generated code amount after the start of the main photographing and applied to the determination in step S906. In addition, the encoding control unit 300 specifies the corresponding timing between the main shooting and the trial shooting based on the generated code amount after starting the main shooting, and the quantization stored in the internal memory 235 from the specified timing. You may start applying steps.

  As described above, the encoding control unit 300 stores the generated code amount generated by encoding the main shooting data according to the encoding parameter in the internal memory 235 when the generated code amount matches the predetermined prediction code amount. The main photographing data is encoded according to the quantization step. In addition, when the generated code amount does not match the predetermined predicted code amount, the encoding control unit 300 controls the encoding parameter for encoding the moving image data according to the generated code amount.

  When the compression encoding process of step S908 and step S910 is completed, it is determined whether or not the compression encoding of all the frames has been completed (step S912). When the compression encoding of all the frames has been completed, this flow ends. If the compression encoding of all frames has not been completed, the process proceeds to step S904, and the frame selection and encoding processing is performed until the compression encoding of all frames is completed.

  As described above, the code amount and the change in the code amount of one sequence can be calculated in advance from preliminary shooting data obtained by trial shooting. Therefore, it is possible to optimally assign the code amount of each period at the time of actual photographing in view of the change in the code amount of the entire sequence. For this reason, for example, a sufficient code amount can be allocated in real time during a period in which rapid zooming or the like is performed. On the other hand, for example, during the period of shooting at the tele end, the code amount allocation can be reduced in real time. Therefore, as a whole sequence, the overall stable image quality can be maintained while the generated code amount approaches the target code amount.

  The processing described in relation to the imaging apparatus 10 according to the present embodiment is realized by each unit of the imaging apparatus 10, for example, a processor functioning as the system control unit 250, the image processing unit 237, and the like operating according to a program. Can do. That is, the process can be realized by a so-called computer device. The computer device may load a program for controlling the execution of the above-described process, operate according to the read program, and execute the process. The computer device can load the program by reading a computer-readable recording medium storing the program.

  In this embodiment, an example of the imaging system 50 has been described by taking up the imaging apparatus 10 for studio photography. However, as an imaging device, various lenses having an imaging function such as an interchangeable lens single-lens reflex camera, a compact digital camera, a mirrorless single-lens camera, a video camera, a mobile phone with an imaging function, a portable information terminal with an imaging function, etc. Equipment can be targeted.

  In the present embodiment, the moving image data is taken up and described. However, not only moving image data but also various data such as audio data can be applied. That is, not only the imaging device but also an electronic audio device such as a recording device can be applied. That is, an encoding parameter that acquires information indicating a change in the code amount of the first data and controls the code amount of the second data obtained after the first data for each time based on the change in the code amount. The electronic device that determines the value can be the target of application. In addition, an electronic device that takes in various data such as moving image data and audio data and performs processing related to encoding, such as a personal computer, can also be applied.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

DESCRIPTION OF SYMBOLS 10 Imaging device, 20 Carriage device, 30 Control device, 32 Operation input part, 34 Controller, 36 Control data storage part, 38 Recording medium, 40 Illumination device, 50 Shooting system, 60 Studio, 201 Display part, 202 Operation member, 208 power supply unit, 209 recording medium, 219 optical axis, 221 lens system, 231 imaging device, 232 A / D converter, 233 memory control unit, 234 timing generation unit, 235 internal memory, 236 system memory, 237 image processing unit, 238 Display control unit, 239 D / A converter, 240 recording medium IF, 241 external IF, 243 lens drive control unit, 270 compression unit, 300 encoding control unit, 310 subtraction unit, 320 conversion unit, 330 quantization unit, 340 variable length coding unit, 332 inverse quantization unit, 322 inverse transform unit, 3 2 adding unit, 360 deblocking unit, the prediction unit between 370 frames, 350 intra-frame prediction unit, 380 prediction control unit, 600 a quantization table

Claims (11)

An information acquisition unit for acquiring information indicating a change in the code amount of the first data;
A parameter determining unit that determines an encoding parameter for controlling the code amount of the second data obtained after the first data for each time based on the change in the code amount;
A parameter determination device comprising: The information acquisition unit acquires information indicating a change in the code amount of the first moving image data obtained by shooting in advance,
The parameter determination device according to claim 1, wherein the parameter determination unit determines an encoding parameter for controlling a code amount of second moving image data obtained by shooting after the first moving image data for each time. The parameter determination apparatus according to claim 2, further comprising an encoding unit that encodes the second moving image data in accordance with the encoding parameter. The parameter determination device according to claim 2 or 3, wherein the parameter determination unit determines a parameter for controlling a compression strength for irreversibly compressing the second moving image data as the encoding parameter. The information acquisition unit acquires the first moving image data subjected to an encoding process including quantization,
The parameter determination unit is a coding parameter for reducing a ratio of the compression strength applied in the second period to the compression strength applied in the first period, which is smaller than the ratio applied in the encoding process of the first moving image data. The parameter determination device according to claim 4, wherein the parameter is determined. The parameter determination device according to claim 4 or 5, wherein the parameter determination unit determines a compression strength for each time of the second moving image data based on an entire code amount and a target code amount of the first moving image data. The parameter determination device according to any one of claims 2 to 6, wherein the parameter determination unit determines a value of a quantization step for quantizing the second moving image data as the encoding parameter. A code for encoding the second moving image data according to the encoding parameter when a generated code amount generated by encoding the second moving image data according to the encoding parameter matches a predetermined prediction code amount. The parameter determination device according to any one of claims 2 to 7, further comprising an optimization control unit. The encoding control unit controls an encoding parameter for controlling a code amount of the second moving image data according to the generated code amount when the generated code amount does not match the predetermined prediction code amount. The parameter determination device according to claim 8. An imaging unit that performs video imaging to generate the first video data and the second video data;
The parameter determination device according to any one of claims 2 to 9,
An imaging apparatus comprising: Obtaining information indicating a change in the code amount of the first data;
Determining a coding parameter for controlling the code amount of the second data obtained after the first data for each time based on the change in the code amount;
A program that causes a computer to execute.

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