JP2008118607A - Network decoder apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image which is easy to see even in switching sources, when a plurality of incoming intra-frame coded video data items are selectively received, decoded and displayed. <P>SOLUTION: A network decoder apparatus 12 includes: a data size variation rate calculation section 206 for calculating a rate of change of data size for each frame of received coded video data; and a control section 201 which controls to perform gamma correction of frame data using a luminance correction curve of an LUT stored in an image processing section 205 when the calculated rate of change of data size is lower than or equal to a threshold, or controls not to perform the gamma correction processing of the frame data by resetting the luminance correction curve of the LUT by outputting an initialization signal to the image processing section 205 when the rate of change exceeds the threshold. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a network decoder device for receiving encoded video data transmitted from a plurality of network cameras, performing image processing, and displaying the encoded video data on a monitor.

  Along with the development of IT technology and network technology in recent years, a network camera monitoring system in which a plurality of network cameras and a network decoder device are connected via a network and a monitor is connected to the network decoder device is often used in the security field. Has come to be. In this network camera monitoring system, image data captured by each network camera is encoded and sent to the network, and the network decoder device receives these encoded image data, decodes them, and selectively selects each image. Or on a monitor as a multi-screen. Further, each network camera described above is capable of pan / tilt / zoom (PTZ) operation, and the network decoder device is provided with the PTZ operation function and control function of each network camera, so that the supervisor can remotely control each network camera. Some can be manipulated.

  Some general television receivers and display devices have an image quality correction function. In these apparatuses, since image data to be input and processed is expected to be relatively continuous frame data, image quality correction / improvement processing such as gamma correction and noise reduction is executed across continuous frames. Is.

  As a more specific example of this, there is known a video signal processing apparatus capable of generating a gradation correction curve according to the characteristics of an image of an input video signal and optimally correcting the image quality based on this (for example, , See Patent Document 1). The invention described in Patent Document 1 is characterized in that histogram data based on a luminance signal component of an input video signal is generated, and thereby dynamic gamma correction is performed.

  And this patent document 1 shows the example which used the leak type | mold integration circuit as an implementation | achievement means of an image quality correction function. This is because the distribution of the histogram data changes greatly when a significant change occurs in the image, such as a scene change, but when a large change occurs in the histogram, the luminance signal corrected by the gradation correction unit suddenly changes. It is a means to improve this because it changes and becomes unnatural. That is, in order to make the update of the histogram data distribution moderate to some extent, leak type integration processing is performed in the time direction at the time of data update. It is also disclosed that the gradation correction curve is reset to be a straight line when the histogram data changes suddenly.

In addition, an example is known in which a technique for displaying a temporal transition of the amount of change in an image and displaying an image in association with the temporal transition of the amount of change when a change above a certain level is detected is applied to a monitoring system. (For example, refer to Patent Document 2).
JP 2005-217574 A JP 2005-78572 A

  However, when the gradation correction function by the leaky integration circuit described in Patent Document 1 is applied to the security field, the following problems arise particularly when the frame rate of the network camera is lowered. For example, when the image quality correction function processing that outputs a correct corrected image within 1 second by leak integration for a bit rate of 30 fps is applied to the security field as it is, a low frame rate frequently used in the security field, for example, a frame of 1 fps is used. In a network camera that is processing at a rate, a correct corrected image is output after 30 times (that is, 30 seconds). As described above, in the security field, the image quality correction function using the leaky integration circuit described in Patent Document 1 is insufficient.

  In the technique described in Patent Document 2, the amount of change in units of frames can be easily recognized, and the image is automatically saved where the amount of change is large. can do. However, since the threshold value of the change amount is a fixed value, the threshold value should be changed when the resolution of the image data input from the camera is changed or the compression rate is changed. Is not disclosed.

  As described above, when the network camera monitoring system is used in the security field, each network camera is often set to various frame rates depending on the monitoring target, the monitoring time zone, and the like. Also, there are cases where a plurality of types of resolutions of images output from each network camera are mixed, such as SXGA size, VGA size, and QVGA size. Furthermore, each network camera is automatically PTZ controlled with a predetermined imaging direction and viewing angle by a timer function or the like.

  That is, the network decoder device applied to the security field differs from the general television receiver as described above in that the frame rate is increased by the network camera when continuous frame data input can be expected and when it cannot be expected. When receiving different image data, it is characteristic that the resolution may be different depending on the network camera. Further, it is also characteristic that continuous image data similar to “scene change” is received by PTZ control even for images from the same network camera.

  The present invention has been made in view of the above circumstances, and the object thereof is, for example, supplied when intra-frame encoded video data having different frame rates and resolutions are supplied from a plurality of network cameras. An object of the present invention is to provide a network decoder device capable of performing appropriate image quality correction for each source and obtaining an easy-to-view image even when the source is switched when the intra-frame encoded video data is arbitrarily switched.

The present invention provides the following means [1] to [3] in order to solve the above problems.
[1] One of a plurality of intra-frame encoded video data supplied via a network is selectively received, sequentially input to a decoding unit in units of frames, and subjected to decoding processing. In a network decoder device that outputs frame data,
The frame data decoded by the decoding means is input, a luminance component histogram is calculated, and a luminance correction parameter is determined and held based on the luminance distribution, and the held luminance according to the input of the initialization signal A brightness holding means for changing a correction parameter to a non-correction parameter, and correcting a brightness component of the frame data based on the held or changed parameter;
Data size fluctuation rate calculating means for calculating a data size fluctuation rate for each frame of the received intra-frame encoded video data;
When the calculated variation rate of the data size is equal to or smaller than the threshold value, the luminance component of the frame data is corrected using the luminance correction parameter held in the luminance correction unit, and when the variation rate exceeds the threshold value, Control means for outputting an initialization signal to the brightness correction means and correcting the brightness component of the frame data using the changed non-correction parameter;
A network decoder device comprising:
[2] Any one of a plurality of intra-frame encoded video data supplied via the network is selectively received, sequentially input to the decoding means in units of frames, and decoded. In a network decoder device that outputs frame data,
The frame data decoded by the decoding means is input, a luminance component histogram is calculated, and a luminance correction parameter is determined and held based on the luminance distribution, and the held luminance according to the input of the initialization signal A brightness holding means for changing a correction parameter to a non-correction parameter, and correcting a brightness component of the frame data based on the held or changed parameter;
Received data interval measuring means for measuring a time interval between each frame of the received intra-frame encoded video data;
When the measured time interval is less than or equal to a predetermined time, the luminance component of the frame data is corrected using the luminance correction parameter held in the luminance correction means, and when the time interval exceeds the predetermined time, Control means for outputting an initialization signal to the brightness correction means and correcting the brightness component of the frame data using the changed non-correction parameter;
A network decoder device comprising:
[3] Intra-frame encoded video data corresponding to one specified identifier among a plurality of intra-frame encoded video data each including an identifier supplied via the network is received and sent to the decoding unit in units of frames. In a network decoder device that sequentially inputs and decodes, and outputs these sequentially decoded frame data,
A parameter holding unit for inputting the frame data decoded by the decoding unit, calculating a histogram of luminance components, determining a luminance correction parameter based on the luminance distribution, and holding the parameter in correspondence with the identifier, and specifying Luminance correction means for correcting the luminance component of the frame data based on the identifier and the held luminance correction parameters;
Control means for inputting the designated identifier to the brightness correction means and correcting the brightness component of the frame data using the brightness correction parameter corresponding to the identifier held in the parameter holding unit;
A network decoder device comprising:

  According to the present invention, when a plurality of intra-frame encoded video data supplied via a network is selectively received, decoded, and output, the image quality after decoding of each intra-frame encoded video data is improved. It is possible to output frame data with optimum image quality by performing a corresponding luminance correction process. According to the present invention, since the luminance correction process can be initialized once by detecting the switching timing of the intra-frame encoded video data, even when the intra-frame encoded video data is arbitrarily switched, a special It is possible to output frame data that has been subjected to image quality correction without giving a sense of incongruity.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic overall configuration of a network camera monitoring system to which an embodiment of the present invention is applied. In the figure, the network camera monitoring system includes a network camera 11-1 to 11-n installed at a place where a monitoring target is imaged and a network decoder device 12 installed on the monitor side via a network 14. Each is connected, and a monitor 13 is connected to the network decoder device 12.

  The network decoder device 12 and the monitor 13 may be integrated to form a network camera viewer device.

  Each of the network cameras 11-1 to 11-n (hereinafter sometimes referred to as the network camera 11) has a camera number as an identifier in advance, and digital image data obtained by imaging is represented by a code (not shown). The encoding unit performs intra-frame encoding processing (for example, JPEG compression processing), and includes the encoded video data together with the camera number of the network camera or the camera number included in the header portion of the encoded video data. The interface (I / F) unit has a function of converting the format into packet data and sending it to the network 14. The network camera 11 includes a control unit (not shown) and a pan / tilt / zoom (PTZ) drive unit, and the network I / F unit receives the PTZ control command transmitted from the network decoder device 12. By executing the PTZ control command by the control unit, the PTZ driving unit is driven to change each direction of pan / tilt or perform zooming.

  The network decoder device 12 receives the encoded video data and the camera number converted into packet data sent from the network cameras 11-1 to 11-n, executes a decoding process, and performs a gamma correction described later on the decoded image data. It has a function of executing the processing and outputting it as a video output signal to the monitor 13. The network decoder device 12 has a function of generating a PTZ control command including a camera number and sending it to the network 14 by a PTZ operation on a desired network camera 11 by a supervisor (operator). The internal configuration and operation of the network decoder device 12 will be described later.

  The monitor 13 inputs the video output signal from the network decoder device 12 and displays it on the screen. The network 14 is a network based on IP (Internet Protocol) control, and the Internet or a LAN (Local Area Network) can be applied.

  Next, a first example of the network decoder device in the network camera monitoring system to which the embodiment of the present invention is applied will be described. FIG. 2 is a schematic internal configuration diagram of the network decoder device 12 in this embodiment. In the figure, a network decoder device 12 includes a network interface (I / F) unit 200, a control unit 201, a ROM 202, a RAM 203, a user interface (I / F) unit 204, an image processing unit 205, a data A size variation rate calculation unit 206 and a variation rate determination unit 207 are provided, and each block is connected as shown in FIG.

  The network I / F unit 200 transmits the encoded video data and camera number converted from packet data (when the camera number is included in the header of the encoded video data) sent from the network cameras 11-1 to 11-n, respectively. And the encoded video data and the camera number are extracted from the packet data and supplied to the control unit 201. The network I / F unit 200 has a function of converting the PTZ control command generated by the control unit 201 into packet data and sending it to the network 14.

  The control unit 201 has a function of controlling the entire network decoder device 12 by loading control software stored in advance in the ROM 202 into the RAM 203 and executing it. In particular, the control unit 201 includes the network I / F unit 200. For the encoded video data and camera number supplied from, the encoded video data is supplied to the image processing unit 205 in correspondence with the camera number. Further, the control unit 201 has a function of generating a PTZ control command in accordance with an operator instruction input from the user I / F unit 204 and supplying the PTZ control command to the network I / F unit 200.

  In addition to the control software, the ROM 202 previously stores attribute information of the network camera 11, such as camera-specific information such as camera number, model number, manufacturer name, serial number, and setting information related to camera operation such as resolution, frame rate, and color balance. I remember it. It is desirable that various information stored in the ROM 202 can be rewritten via the network 14 in order to cope with a version upgrade of the control software and a change in the connection state or setting state of the network camera 11. The RAM 203 is used to temporarily store various variables and various data when the control unit 201 executes the control software.

  The user I / F unit 204 is an operation input unit for inputting an instruction from the operator. The user I / F unit 204 includes a power on / off switch of the network decoder device 12 and performs a desired PTZ operation of the network camera 11 on the operator. For example, one-screen display, multi-screen display such as 4-screen display or 16-screen display, multi-screen display, etc. are specified and supplied to the image processing unit 205. Is to do. As the operation means, a keyboard or a mouse can be used. When the network decoder device 12 and the monitor 13 are integrated to form a network camera viewer device, a touch panel can be used.

  The image processing unit 205 has a function of executing gamma correction processing which is image quality correction processing after decoding encoded image data for each frame data sequentially supplied from the control unit 201 to obtain decoded image data. As image quality correction processing, not only gamma correction processing but also chroma correction may be executed. The image processing unit 205 has a function of configuring the image data that has been subjected to the image quality correction processing in sequence according to the screen designation from the user I / F unit 204 and outputting it as a video output signal.

  Next, the gamma correction process will be described. The image processing unit 205 generates and has a LUT (Look Up Table) for correcting the luminance value as shown in FIG. 3 (parameter holding unit). The LUT generation method may be the method described in Patent Document 1. The LUT in the figure has a luminance correction parameter for determining the output luminance value Yout with respect to the input luminance value Yin. In the initial state of the network decoder device 12, a non-correction characteristic (non-correction parameter) in which Yout = Yin, that is, the input luminance value Yin becomes the output luminance value Yout as it is, as shown by the straight line shown in FIG. The curve shown in the figure is a correction curve for performing an optimal gamma correction. According to this example, when the input luminance value Yin is small, the output luminance value Yout is increased, and the input luminance value Yin is When the value is large, a correction characteristic that reduces the output luminance value Yout is applied. This correction curve is desirably determined based on the luminance histogram distribution of the input image as described in Patent Document 1.

  Returning to the description of FIG. 2, the data size variation rate calculation unit 206 has a function of calculating the variation rate of the data size in units of frame data for the encoded image data supplied from the control unit 201 to the image processing unit 205. . The data size fluctuation rate calculation unit 206 executes processing as shown in the flowchart of FIG. That is, the data size of the encoded image data per frame supplied last time is held, and the variation rate of the data size with the data size of the encoded image data per frame supplied this time is calculated (step). S401). Next, the data size of the encoded image data per frame received this time is updated and stored as the previously supplied data size (step S402).

  When the encoded image data is JPEG data that is intra-frame encoded image data, the data size of the JPEG data when the dark place is imaged with the same compression rate and resolution setting, and the JPEG when the bright place is imaged In comparison with the data size of data, the data size of JPEG data in the dark is usually smaller. In addition, when capturing subjects with a lot of high-frequency components such as detailed landscapes, objects, and people's clothes that correspond to complex patterns, the data size is a subject with relatively little high-frequency components, such as a covered pattern. Is larger than the data size when the image is captured. Therefore, the result of the data size variation rate calculation unit 206 can detect not only the scene change at the boundary between two frame data having different camera numbers, but also the case where the network camera 11 greatly changes the subject by the PTZ operation.

  By calculating the data size variation rate in this way, the possibility of a so-called scene change has been predicted. As in step S402, the data size of the encoded image data per frame received this time is set to the previous time. By updating and holding the supplied data size, comparison with the previous frame data is performed, so that the detection accuracy of the scene change is high.

  The variation rate determination unit 207 has a function of determining whether or not the variation rate of the data size that is the output result of the data size variation rate calculation unit 206 is within a predetermined range. For example, the case where the rate of change> 60% is out of the range, and the case where the rate of change ≦ 60% is set within the range. If the variation rate of the data size is out of the specified range, the variation rate determination unit 207 determines that the subject has been significantly changed due to a scene change or a PTZ operation and the data size of the encoded image data has greatly varied, and image processing is performed. An initialization signal is output to the unit 205.

  Here, FIG. 5 shows an example in which the data size of the encoded image data per frame data and the variation on the time axis are represented in a graph. In the figure, it is assumed that the network camera 11 that has taken an image of a specific monitoring place changes the subject by the PTZ operation. First, before the time of scene change 1, although the data size is relatively small, there is a slight fluctuation of the data size. In the data size variation rate calculation unit 206, the data size fluctuation can be absorbed and the scene change with respect to the immediately previous frame data can be detected by sequentially updating and holding the immediately previous data size. Moreover, the possibility of outputting an extra initialization signal is extremely reduced by absorbing the shaking.

  The scene change 1 is an example corresponding to the variation rate> 60% in the variation rate determination unit 207, and at this timing, the initialization signal is output before the image processing unit 205 refers to the LUT. Upon receiving this initialization signal, the image processing unit 205 changes the LUT correction curve shown in FIG. 3 to a straight line for initialization. The scene change 2 is also an example corresponding to the change rate> 60% in the change rate determination unit 207, and the initialization signal is output to the image processing unit 205 at this timing as in the case of the scene change 1.

  Next, a second example of the network decoder device in the network camera monitoring system to which the embodiment of the present invention is applied will be described. FIG. 6 is a schematic internal configuration diagram of the network decoder device 12a in the present embodiment. In addition, about the same thing as the block demonstrated in 1st Example, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  The network decoder device 12a in the figure has a configuration in which a reception data interval measuring unit 209 is added to the configuration of the network decoder device 12 in the first embodiment. The reception data interval measurement unit 209 measures the input time interval of the encoded image data in units of frame data supplied from the control unit 201 to the image processing unit 205, and the encoded image data is converted into the image processing unit 205 within a predetermined time. If not supplied, the initialization signal is output to the image processing unit 205.

  FIG. 7 is a schematic diagram for explaining camera switching when the network decoder device 12a receives encoded video data having a plurality of different frame rates. Note that the image processing unit 205 generates an LUT for correcting the luminance value as shown in FIG.

  In FIG. 7, when the network decoder device 12a receives the encoded video data 1 of 30 fps transmitted from the network camera 11-1 that captures a dark place, the bright place is captured at a certain timing. It is the figure which showed typically the state when switched to reception of 1 fps encoded video data 2 transmitted from the network camera 11-2. When the encoded video data 1 is gamma-corrected, the image processing unit 205 applies luminance correction for brightly displaying the dark portion by the correction curve A in the LUT generated as shown in FIG.

  Here, it is assumed that the video data is switched to the encoded video data 2 from the network camera 11-2 at a certain timing as shown in FIG. Since the picked-up image of the network camera 11-2 is a bright image, it must be corrected by the correction curve B in the LUT in FIG. However, when the correction curve B is not generated in time at the time of switching and the correction curve A is applied as before, inappropriate luminance correction is performed and the video of the network camera 11-2 is output as an excessively bright video. . In addition, since a video that is too bright continues to be output until the next frame is decoded, a situation that is very difficult for the supervisor to see can occur when switching the network camera.

  Therefore, in the network decoder device 12a in this embodiment, the reception data interval measurement unit 209 measures the input interval of encoded image data in units of frame data supplied to the image processing unit 205, that is, the interval of decoding processing, If the decoding process is not executed within this time, an initialization signal is output to the image processing unit 205, and the image processing unit 205 that has received this initialization signal changes the correction characteristic to a linear non-correction characteristic with reference to the LUT. To do. The timing for outputting this initialization signal may be output (1) every time a predetermined time is not received, or (2) only when the decoding interval is extended, that is, only when the camera image is switched. May be. In the case of (1), since the initialization signal is always output when the frame rate is low, the LUT continues to have uncorrected characteristics, and the input luminance value Yin becomes the output luminance value Yout as it is. On the other hand, in the case of (2), the input luminance value Yin becomes the output luminance value Yout as it is at the time of switching, but after the switching, a gamma correction process using a correction curve is executed.

  Next, a third example of the network decoder device in the network camera monitoring system to which the embodiment of the present invention is applied will be described. As the schematic internal configuration of the network decoder device 12b in the present embodiment, either FIG. 2 or FIG. 6 can be applied. In the present embodiment, the control unit 201 executes processing according to the flowchart shown in FIG.

  That is, for example, when the encoded video data 1 supplied from the network camera 11-1 is switched to the encoded video data 2 from the network camera 11-2, the control unit 201 decodes the encoded video data 1. In addition, the timing process is started by the built-in timer (step S100), and the process waits until a predetermined time elapses (step S101). At this time, as the time for the supervisor to view the video, the predetermined time is set to at least 3 seconds, for example. Next, when 3 seconds have elapsed, the control unit 201 sets the camera number corresponding to the network camera 11-2 as a variable of the control software in order to switch from the encoded video data 1 to the encoded video data 2. At the same time, an initialization signal is output to the image processing unit 205 (step S102).

  Then, the image processing unit 205 receives the initialization signal and changes the correction characteristic to a linear non-correction characteristic with reference to the LUT.

  Note that the operator may specify a camera number from the user I / F unit 204. Along with this, the user I / F unit 204 transmits the designated camera number to the control unit 201, and the control unit 201 that has received this notification outputs an initialization signal to the image processing unit 205. Then, the image processing unit 205 changes the gamma correction to the non-correction characteristic according to the received initialization signal. Thereby, even when the operator changes the camera number, it is possible to perform image quality correction processing according to an appropriate switching timing.

  Next, a fourth example of the network decoder device in the network camera monitoring system to which the embodiment of the present invention is applied will be described. The first to third embodiments are examples in which the image processing unit 205 executes gamma correction processing using one LUT, and can be configured with a relatively small memory capacity. However, in these examples, even if it is not necessary to return to the initial state, the correction calculation result may be wasted because there is a case where the non-correction characteristic occurs due to the generation of the initialization signal. For example, in the implementation in the security field, when images from four network cameras 11-1 to 11-4 are sequentially displayed on the monitor 13, camera number 1 → camera number 2 → camera number 3 → camera number 4 → There are many cases of patrol such as camera number 1 →. Therefore, if each network camera 11 can hold the correction calculation result, it is not necessary to return to the initial state one by one, and the gamma correction process can be executed using the previous correction calculation result, which is efficient.

  FIG. 10 is a schematic internal configuration diagram of the network decoder device 12c in the present embodiment. In addition, about the same thing as the block demonstrated in 1st Example, the same code | symbol is attached | subjected and the description is abbreviate | omitted. The image processing unit 205 generates and holds the gamma correction LUT array 210 (parameter holding unit). The gamma correction LUT array 210 is configured such that the LUT illustrated in FIG. 3 corresponds to each camera number corresponding to the number of network cameras 11. Even when chroma correction is performed for each network camera 11, it is desirable to generate and hold a chroma correction array such as the gamma correction LUT array 210.

  The control unit 201 notifies the image processing unit 205 of the camera number corresponding to the received encoded video data. Then, the image processing unit 205 selects the corresponding LUT from the gamma correction LUT array 210 according to the camera number notified from the control unit 201, and executes gamma correction processing.

  Next, a fifth example of the network decoder device in the network camera monitoring system to which the embodiment of the present invention is applied will be described with reference to the flowchart of FIG. In this embodiment, the control unit 201 of the network decoder device 12d loads the control software stored in the ROM 202 into the RAM 203 and executes it, thereby realizing the main functions of the network decoder device 12d. Note that the control unit 201 includes an image processing unit as a software function block.

  First, the network decoder device 12d receives the JPEG file converted into packet data sent from the network cameras 11-1 to 11-n connected via the network 14 by the network I / F unit 200, and receives the control unit. (Step S200).

  Next, the control unit 201 refers to the header information of the JPEG file, compares the file size data recorded therein with the data size of the actually received JPEG file, and confirms that there is no difference in data size. The validity of the Huffman table included in the data, and the data format (Y: Cb: Cr ratio should be 4: 2: 0, 4: 2: 4, or 4: 1: 1), etc. (Step S201), and if any abnormality is detected in this step, the process is terminated.

  If the control unit 201 determines that decoding is possible in step S201, the control unit 201 compares the data size with the previously received JPEG file based on the flowchart of FIG. 4 (step S202). Next, when the control unit 201 determines that the variation rate of the compared data size has exceeded a predetermined threshold (for example, 60% as in the first embodiment), the control unit 201 requests the image processing unit to perform a reset request. Is output to change the brightness correction value to the initial state (step S204). On the other hand, if the variation rate of the data size is equal to or smaller than the threshold, the process proceeds to the following step S205 without outputting a reset request to the image processing unit.

  The image processing unit of the control unit 201 decodes JPEG data in units of MCU (Minimum Coded Unit), and generates a luminance component and a chroma component for each pixel (step S205).

  Next, the image processing unit, from the decoded luminance component and chroma component, features such as histogram distribution, total number of luminance values, number of pixels, maximum luminance value, minimum luminance value, etc. by the method described in Patent Document 1. The amount is calculated (step S206). Each process of step S205 and step S206 is repeated until decoding of all the MCUs is completed (step S207). When the decoding process for all the MCUs is completed, the LUT is calculated from the feature amount calculated in step S206 and stored in the RAM 203 (step S208). This LUT is referred to when the next JPEG file is received.

  Here, when performing image processing with reference to the LUT in step S206 described above, for example, the following two methods can be applied.

<Method 1>
In this method, image processing is performed using an LUT that does not reflect the feature amount of image information being decoded. This is a method according to the flowchart of FIG. 11 described above, and even if decoding of all the MCUs is not completed, the LUT is calculated based on the previous JPEG data. Image processing can be executed in parallel, and high-speed processing can be performed.

<Method 2>
This is a method of performing image processing using an LUT reflecting the feature amount of image information being decoded. In this case, image processing such as luminance value correction of all pixels is performed after decoding of all MCUs is completed. That is, in step S206, the feature amount is calculated and stored in the LUT, and step S208 is performed, and image processing such as luminance correction is performed in another loop. Since this is a sequential process, it is likely to be a lower speed process than method 1, and the cost is increased to increase the speed. However, according to this method 2, it is easy to determine the optimum LUT correction value for the image being decoded, and it is possible to output a video that is very easy for the monitor to see.

  As described in detail above, according to the first to fifth embodiments, the plurality of intra-frame encoded video data transmitted from the network cameras 11-1 to 11-n are converted into the network decoder device 12 (12a, 12b). , 12c, 12d) are selectively received, decoded and output to the monitor 13, the network decoder device 12 (12a, 12b, 12c, 12d) receives the frame data after decoding of each encoded image data. Can be obtained by performing luminance correction processing according to the image quality. Since the luminance correction process can be initialized once by detecting the switching timing of the intra-frame encoded video data, even if the intra-frame encoded video data is arbitrarily switched, a particular sense of incongruity is given to the monitor. Therefore, it is possible to output the frame data whose image quality has been corrected to the monitor 13.

  The processing by the image processing unit 205, the data size variation rate calculation unit 206, the variation rate determination unit 207, and the reception data interval measurement unit 209 in the first to fourth embodiments described above is performed by, for example, a DSP (Digital Signal Processor). The digital signal processing circuit as shown in FIG.

  The present invention is particularly useful in a network camera monitoring system in the security field.

1 is a schematic overall configuration diagram of a network camera monitoring system to which an embodiment of the present invention is applied. FIG. 2 is a schematic internal configuration diagram of a network decoder device in the first embodiment. It is the figure which represented typically the LUT for correct | amending a luminance value in a 1st Example. It is a flowchart for demonstrating operation | movement of the data size fluctuation rate calculation part in a 1st Example. It is the figure which represented the data size of the encoding image data per frame data in 1st Example, and the fluctuation | variation on a time axis in the graph. It is a schematic internal block diagram of the network decoder apparatus in the second embodiment. It is a figure for demonstrating camera switching in the 2nd Example when the network decoder apparatus receives the encoding video data of several different frame rates. It is the figure which represented typically the LUT for correct | amending a luminance value in 2nd Example. It is a flowchart for demonstrating the process which a control part performs in 3rd Example. FIG. 14 is a schematic internal configuration diagram of a network decoder device in a fourth embodiment. It is a flowchart for demonstrating the process which a control part performs in 5th Example.

Explanation of symbols

11-1 to 11-n Network camera 12, 12a, 12b, 12c Network decoder device 13 Monitor 14 Network 200 Network interface unit 201 Control unit 202 ROM
203 RAM
204 User interface unit 205 Image processing unit 206 Data size variation rate calculation unit 207 Variation rate determination unit 209 Received data interval measurement unit 210 Gamma correction LUT array

Claims (3)

Any one of a plurality of intra-frame encoded video data supplied via the network is selectively received, sequentially input to the decoding means in units of frames, and subjected to decoding processing. In the output network decoder device,
The frame data decoded by the decoding means is input, a luminance component histogram is calculated, and a luminance correction parameter is determined and held based on the luminance distribution, and the held luminance according to the input of the initialization signal A brightness holding means for changing a correction parameter to a non-correction parameter, and correcting a brightness component of the frame data based on the held or changed parameter;
Data size fluctuation rate calculating means for calculating a data size fluctuation rate for each frame of the received intra-frame encoded video data;
When the calculated variation rate of the data size is equal to or smaller than the threshold value, the luminance component of the frame data is corrected using the luminance correction parameter held in the luminance correction unit, and when the variation rate exceeds the threshold value, Control means for outputting an initialization signal to the brightness correction means and correcting the brightness component of the frame data using the changed non-correction parameter;
A network decoder device comprising: Any one of a plurality of intra-frame encoded video data supplied via the network is selectively received, sequentially input to the decoding means in units of frames, and subjected to decoding processing. In the output network decoder device,
The frame data decoded by the decoding means is input, a luminance component histogram is calculated, and a luminance correction parameter is determined and held based on the luminance distribution, and the held luminance according to the input of the initialization signal A brightness holding means for changing a correction parameter to a non-correction parameter, and correcting a brightness component of the frame data based on the held or changed parameter;
Received data interval measuring means for measuring a time interval between each frame of the received intra-frame encoded video data;
When the measured time interval is less than or equal to a predetermined time, the luminance component of the frame data is corrected using the luminance correction parameter held in the luminance correction means, and when the time interval exceeds the predetermined time, Control means for outputting an initialization signal to the brightness correction means and correcting the brightness component of the frame data using the changed non-correction parameter;
A network decoder device comprising: Intra-frame encoded video data corresponding to one specified identifier among a plurality of intra-frame encoded video data each including an identifier supplied via the network is received and sequentially input to the decoding means in units of frames. In the network decoder device that performs decoding processing and outputs the sequentially decoded frame data,
A parameter holding unit for inputting the frame data decoded by the decoding unit, calculating a histogram of luminance components, determining a luminance correction parameter based on the luminance distribution, and holding the parameter in correspondence with the identifier, and specifying Luminance correction means for correcting the luminance component of the frame data based on the identifier and the held luminance correction parameters;
Control means for inputting the designated identifier to the brightness correction means and correcting the brightness component of the frame data using the brightness correction parameter corresponding to the identifier held in the parameter holding unit;
A network decoder device comprising:

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