KR100877747B1 - Digital Video Recorder and, apparatus and method for protectiong input image of the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video recorder and an input image protection device and method thereof, in which an important image of an individual can be protected by selectively masking a region in which an image of a video security device may invade privacy of an individual.

The configuration is a digital video recorder which processes and transmits or stores image data received from at least one surveillance camera, wherein the extraction method and the masking method of the masking area of the image data are set, and the image data is set from the image data. And an input image protection processor for extracting and selectively masking a masking area, and masking a set area before transmission or storage is performed.

Video Protection, DVR, Masking, Area Extraction, Object Tracking, ASM

Description

Digital video recorder and its input image protection device and method {Digital Video Recorder and, apparatus and method for protectiong input image of the same}

1 is a block diagram of an input image protection device of a digital video recorder according to the present invention.

2 is a detailed configuration diagram of an input image protection processor according to the present invention;

3A and 3B are detailed configuration diagrams of a masking region extracting unit of the input image protection device according to the present invention.

4 is a flowchart illustrating an input image protection method according to an exemplary embodiment of the present invention.

5 is a flowchart illustrating an ASM object tracking flow for an input image protection method according to the present invention.

<Explanation of symbols for main parts of the drawings>

102. Input image protection processing unit 212. Masking area setting unit

213. Masking area extraction unit 213a. Setting coordinate area capture

213b. Object detection unit 213c. Area extractor

213d. Object Extraction Section 214. Masking Section

215. Masking image storage unit

The present invention relates to a video security device, and more particularly, to a digital video recorder (Digital Viedo Recorder) to selectively protect the area in the input image that may infringe the privacy of the individual to protect important information of the individual (Digital Viedo Recorder; DVR) and its input image protection device and method.

At present, the digital video recording system called digital video recorder (DVR) is attracting attention in the field of security surveillance based on digital video compression technology.

Since the digital video recorder uses a hard disk (HDD) or a digital video disk (DVD) instead of a video tape, it is easy to play or search a stored screen.

In addition, they are stored as digital signals, making them convenient for editing and transferring images.

Typical digital video recorders include motion detection, sensor and connection recording, auto pan, tilt, zoom, control, and image magnification / editing functions. There are various selection menu functions and the function to keep data semi-permanently.

In addition, it can be used as a security device of a financial institution that can cause crimes because it can perform zooming in and out, printing remotely by default, as well as quick and easy searching.

However, when receiving and recording video data using a digital video recorder in places where privacy is controversial, for example, in a bathroom or a dressing room, there is a restriction on the use of the digital video recorder in a general place because of an invasion of privacy. Will receive.

As described above, the digital video recorder system of the related art has a problem that installation is difficult due to the controversy of privacy of a person, although a surveillance camera must be installed for security.

In the case of unattended stores of banks, surveillance cameras are installed for security purposes. If financial information is recorded and stored or transmitted as it is, the financial information of an individual may be leaked. There is a risk.

Therefore, there is a need for an invention that can utilize a digital video recorder without exposing such a privacy infringement issue or exposing a risk of leakage of important personal information.

The present invention is to solve the problems of the prior art digital video recorder system, and the digital video to protect the important information of the individual by selectively masking the area that may infringe the privacy of the individual in the input image It is an object of the present invention to provide a digital recorder (DVR) and an input image protection device and method thereof.

The present invention has a configuration of selectively masking an area to be masked from an input image and extracting an area to be masked from the input image, and masking by a user through various masking methods such as a filtering method, a blur method, and a mosaic method. Provide a technical configuration to regulate the water level.

In addition, the present invention provides a video security device and method that can install a surveillance camera even in a place that is not generally installed by implementing various masking methods.

The present invention provides a video security device and method for reducing the additional costs incurred in the conventional method of masking after recording, since the masking of the portion to be protected is performed in the video input step.

According to an aspect of the present invention, there is provided a digital video recorder including: an image receiver configured to receive image data input from at least one surveillance camera; An input image protection processor configured to extract a partial region from the received image data and selectively mask the extracted region; And an encoder for encoding the protected image data and a file system for sequentially storing the encoded image data.

Here, the input image protection processor extracts a masking region corresponding to a partial region of the image data by using the fixed coordinate value of the received image data, and masks the extracted masking region.

Here, the input image protection processing unit may extract an object to be masked by tracking a pattern of an object included in the image data and mask the extracted object.

Here, the input image protection processing unit includes a masking area setting unit for setting an area to be masked from the received image data, a masking area extraction unit for extracting the set area, and a masking unit for selectively masking the extracted area. It is characterized by.

An input image protection apparatus of a digital video recorder according to the present invention for achieving another object is a digital video recorder for processing and transmitting or storing image data received from at least one surveillance camera, the image of the masking area of the image data; And an input image protection processor configured to set an extraction method and a masking method and selectively extract a masking area from the image data according to the setting content, and mask the set area before the transmission or storage is performed.

Here, the input image protection processing unit, a masking area setting unit for setting a masking area and a masking method in the image received from the at least one surveillance camera, a masking area extraction unit for extracting the set area, and the extracted area It characterized in that it comprises a masking portion to selectively mask the.

Here, the masking area may be set by setting a coordinate value of the extracted area or extracting an object to be tracked by an object tracking method having an active type algorithm in order to extract an area to be masked from an input image. .

The masking area extracting unit may include a set coordinate area capturing unit for extracting a corresponding area by a set coordinate value.

The masking area extractor may include an object detector that detects a specified object in a received image, an area extractor that extracts an area including a setting object when an object is detected, and an object part from an area that includes an object. It is characterized in that it comprises an object extracting unit.

Here, the masking unit may include a filtering method for filtering the extracted region and blackening the image processing method, a blur method for mapping the R, G, and B values of the extracted region to an average value of neighboring pixels, and adjusting the number of pixels in the extracted region. It is characterized in that the extraction area is masked by any one of the mosaic method of mosaic processing.

According to another aspect of the present invention, there is provided a method of protecting an input image of a digital video recorder, the method of protecting an input image of a digital video recorder, the method including: Setting an extraction method of an area to be masked from the received image and a masking method of the extracted area; And extracting a set region from the received image according to the set contents and masking the extracted region.

Here, the masking region extraction method and the masking method may be set differently for each received channel.

Here, in the masking of the extracted region, when the set masking scheme is a filtering scheme, the extracted region may be filtered and blackened.

Here, in the masking of the extracted area, when the set masking method is a blur method, the R, G, and B values of the extracted area may be mapped to an average value of surrounding pixels.

Here, in the masking of the extracted region, when the set method is a mosaic method, mosaicing may be performed by adjusting the number of pixels of the extracted region.

According to another aspect of the present invention, there is provided a method of protecting an input image of a digital video recorder, the method comprising: detecting a designated object included in received image data; Extracting an area corresponding to the extracted object; And masking the extracted region of the image data.

The detecting of the designated object may include detecting an object using coordinate values corresponding to the fixed object when the object is a fixed object, and using pattern tracking of the moving object when the object is a moving object. Detecting an object.

Hereinafter, a preferred embodiment of an input image protection device and method of a digital video recorder according to the present invention will be described in detail.

Features and advantages of the input image protection device and method of the digital video recorder according to the present invention will become apparent from the detailed description of each embodiment below.

1 is a block diagram of an input image protection device of a digital video recorder according to the present invention.

Referring to FIG. 1, the digital video recorder includes an image processor 100, a main board 110, a front board 140, and a back board 130.

The image processor 100 includes an image receiver 101, an input image protection processor 102, and an MPEG encoder / decoder 103.

The image receiver 101 receives image data from each camera of at least one channel.

The input image protection processor 102 selectively masks an area in which the image received by the image receiver 101 may infringe an individual's privacy.

This is for protecting personal privacy information or important information, and has a configuration of setting an area to be masked from an input image, selectively extracting an area to be masked from the input image, and selectively masking a filtering method and a blur method. The user may adjust the masking level through various masking methods, such as a mosaic method.

The digital video recorder according to the present invention may perform the operation of masking the portion to be protected by the input image protection processing unit 102 in the previous step of storing (recording) the input image.

The configuration of the input image protection processor 102 will be described in more detail with reference to FIGS. 2, 3A, and 3B as follows.

2 is a detailed configuration diagram of an input image protection processing unit according to the present invention, and FIGS. 3A and 3B are detailed configuration diagrams of a masking area extraction unit of the input image protection device according to the present invention.

As shown in FIG. 2, the input image protection processor 102 according to the present invention uses a masking area setting unit 212, a masking area extracting unit 213, a masking unit 214, and a masking area storage unit 215. Included and configured.

In the encoding of the video signals received from the plurality of surveillance cameras, an area to be masked is extracted in a manner set by a user, and the extracted area is masked by a set masking method.

To this end, in an embodiment of the present invention, a method of setting a coordinate value of the extraction area may be used.

In another embodiment of the present invention, a method of setting an object to be tracked by an object tracking method having an algorithm of an active type may be used.

The input image protection processor 102 may include a masking area setting unit 212 for setting a masking method of the extracted image, and an image received through the image receiving unit 101 by a setting method through the masking area setting unit 212. And a masking region extracting unit 213 for extracting a setting region, a masking unit 214 for masking the extracted region, and a masking image storage unit 215 for storing a masking image.

The masking image storage unit 215 overwrites and stores the extracted region masked by the masking unit 400 in the original image received by the image receiving unit 101, or masks the entire image. To the terminal selected by the user.

The masking area setting unit 212 presets and stores the coordinates of the area to be masked, the designation of the object to be tracked, and the masking method.

As we saw earlier, the setting of the masking area is

First, as a fixed area masking method, when masking of an area fixedly output to a specific part is required, the user may preset the coordinates of the area to be masked to allow masking in a pre-storage step.

For example, in the case of the camera installed in the ATM, the coordinates of the corresponding area may be set in advance so that the password input field may be masked in order to protect the password information of the user. In addition, it is preferable to use a fixed area masking method in order to mask the area that is fixedly output.

Secondly, as a moving area masking method, an object tracking method is set to track a recognition pattern such as a face of a person so as to protect an individual's privacy and to mask the corresponding part. It is necessary to specify a target to be set and to set judgments for determining the target.

For example, in the case of a camera installed in a parking lot, the pattern of the parking lot user is traced to recognize that the person is a person, and the face of the person or a part of the face is masked to protect the privacy of the user, or the pattern of the car is recognized to be the car and the corresponding car The license plate pattern can be set to mask the license plate.

In addition, in order to mask the area photographed by moving, it is preferable to use a moving area masking method using object tracking.

The masking area extracting unit 213 is configured as follows according to an area setting method for extracting a masking area.

If the masking area setting method uses the fixed area masking method, as shown in FIG. 3A, the masking area extracting unit 213 sets the capturing coordinate area capturing unit 213a to capture the corresponding area according to the set coordinate value. ).

When the masking area is set using the moving area masking method, as shown in FIG. 3B, the object detecting unit 213b for detecting a specified object in the received image, and when the object is detected, the corresponding area (the setting object is And an area extracting unit 213c for extracting an included area) and an object extracting unit 213d for extracting an object part from an area containing an object.

Here, the object detector 213b determines whether there is a part in the masking area setting unit 212 that matches the feature of the object selected by the user.

For example, if the license plate of the vehicle is selected as a masking region, the object detector 213b determines whether there is an area having a pattern similar to that of the license plate of the vehicle.

If it is determined that there is a part matching the feature of the selected object, the area extractor 213c extracts the corresponding area, and the object extractor 213d extracts the object part from the extraction area including the object.

And the setting of the masking method,

First, a filtering method of filtering and extracting the extracted region black may be used. The filtering method is a method of processing black from a certain region (x, y) to (x ', y'). In the filtering method, since the selected area is blacked out, the user cannot adjust the level of masking, but since the recovery of the selected area is impossible, it is useful as a method for completely protecting the privacy of the individual.

Second, a blur method of mapping the R, G, and B values of the extracted region to the average value of the surrounding pixels may be used. The blur method is a method of blurring an image by mapping three primary colors of an image, that is, R (red), G (green), and B (blue), to an average value of surrounding pixels.

The formula used as an example of the blur method is as follows.

(R, G, B) = ((R0, G0, B0) + (R1, G1, B1) + (R2, G2, B2) + (R3, G3, B3) + (R4, G4, B4)) / 5

Here, 0 represents a center coordinate (corresponding pixel), 1 represents an upper coordinate of the pixel, 2 represents a coordinate of the pixel, 3 represents a lower coordinate of the pixel, and 4 represents a right coordinate of the pixel.

The user can adjust the masking level of the image by applying the blur method in duplicate. For example, if you want to recognize the contour level, you can apply the blur method only once. If you want to recognize the shape only, you can apply the blur method twice or three times.

Third, a mosaic method of mosaicing by adjusting the number of pixels of the extracted region may be used. The mosaic method divides the selected image into pixels of a certain size and changes the position of the pixels by using a random function to make it difficult to recognize the original image.

Increasing the number of pixels in the mosaic method makes it more difficult to recognize the original image, and thus it is easy for the user to adjust the masking level of the image.

In addition, it can be selected according to the purpose of use in various masking schemes applicable from the known technique.

The MPEG encoder / decoder 103 performs encoding on the image data masked by the input image protection processor.

In this case, the image data includes not only image data photographed by each camera, but also channel information and time information.

The encoded image data is stored in the file system 111 as multimedia data in correspondence with the photographing time of each of the plurality of cameras through the record task unit 117.

A redundant array of inexpensive disk (RAID) driver 112 provides a function for smoothly driving the file system 111.

In general, RAID file system management is a method of dividing data and processing a plurality of storage media in parallel. By using several storage media in parallel, access speed and data preservation reliability are excellent.

The reproduction task unit 118 processes to reproduce the multimedia data stored in the file system 111. That is, the playback task unit 118 reads out multimedia data corresponding to the capturing time of the camera from the file system 111 according to a playback request from the user.

At this time, the playback task unit 118 decodes the digital signature of the read multimedia content, and decodes and reproduces the read multimedia data by using the MPEG encoder / decoder 103.

The digital video recorder according to an embodiment of the present invention may provide communication with a user terminal through the Ethernet task unit 119.

For example, the Ethernet task unit 119 may receive a command to execute the multimedia data from a user terminal located at a remote location, or may transmit a video and audio of the multimedia data to be played back to the user terminal. In addition, in order to drive the Ethernet task unit 119, the digital video recorder includes an Ethernet driver 113.

The event task unit 120 processes an event for image data input from the camera. The event task unit 120 may generate a corresponding event according to the input of the image data to notify the start of recording or an alarm.

The digital video recorder according to an embodiment of the present invention includes a sensor task unit 121. The sensor task unit 121 may detect heat, noise, etc. generated in the digital video recorder in advance, and may minimize physical deterioration of the stored image data. The serial communication task unit 122 may provide a communication function with the digital video recorder and another device connected through a serial interface.

For example, the serial communication task unit 122 may include a USB port, store the multimedia data in another storage medium connected with a USB cable, or read data backed up to the storage medium.

In order to drive the serial communication task unit 122, a serial port driver 116 is used. For example, the digital video recorder may be connected to the administrator's notebook using serial communication.

At this time, the serial communication task unit 122 and the serial port driver 116 provide a connection function with the serial interface of the notebook.

In addition, the digital video recorder according to an embodiment of the present invention may further include an email task unit 123 for receiving an email from a predetermined mail server or transmitting an email to the predetermined mail server.

The main task unit 124 supports retrieval of the corresponding multimedia data according to a user command input through the front board 140, or controls not only an image such as brightness and contrast of an image output through the display device, but also a display horizontal and vertical. Supports the user interface related to the display, such as its aspect ratio.

In addition, the main task unit 124 supports various functions to determine the overall operating state of the system.

The digital video recorder according to an embodiment of the present invention provides serial standard interfacing for connection with a peripheral device through a small computer system interface (SCSI) driver 115.

Accordingly, the SCSI driver 115 can be compatible with the specifications for the instruction set around all peripheral devices and mechanical and electrical requirements for connecting the input and output buses. The SCSI-based interface uses device numbers of peripheral devices to prevent device-to-device collisions, providing stable performance of digital video recorders.

The VGA driver 114 processes the multimedia data to be displayed on the display device according to the resolution. The front board 140 may provide various display-related user interfaces displayed on the display device through the VGA driver 114. The front board 140 provides a function for controlling an LED for notifying a remote controller input from a user, an input of a touch key, and an operation state of various devices in the digital video recorder.

In addition, the back board 130 supports a function that is not used as frequently as the front board 140. For example, the operator interface can be supported by controlling functions for maintenance such as board replacement or changing the system environment.

The remote terminal user accesses a predetermined application program managed by the file system 111 of the digital video recorder or retrieves multimedia data backed up to the digital video recorder using a predetermined application program that can be executed on the remote computer itself. And can be read.

In particular, in the present invention, the user can create a playback file of a new structure that can be reproduced by itself without a separate player from the multimedia data backed up to the digital video recorder through the application program.

A masking process of a specific area of the input image protection device of the digital video recorder according to the present invention having such a technical configuration will be described.

4 is a flowchart illustrating an input image protection method according to an exemplary embodiment of the present invention.

The user sets the masking area extraction method and the masking method using the masking area setting unit 212 (S401).

Naturally, the masking region extraction method and the masking method may be set differently for each channel.

For example, it is natural that the masking method and the area extraction method of the image by the surveillance camera of the cash machine and the surveillance camera in the bathroom should be different.

After the masking area extraction method and the masking method are set through the image receiving unit 211, the masking area extraction method is determined (S402), and the image information of the area set by the masking area extraction unit 213 is set according to the setting method. Extract

For example, when the set masking area extraction method is a fixed area masking method using the set coordinate value, the set coordinate area is extracted from the received image (S403).

In case of the moving area masking method, it is determined whether an object to be masked is detected in the received image (S404).

FIG. 5 is a flowchart illustrating an ASM object tracking flow for an input image protection method according to the present invention. An object tracking method for moving area masking will be described in detail with reference to FIG. 5.

The active shape model object tracking applied to the present invention is performed by the motion detection step (S500), the area tracking step (S510), and the active contour tracking step (S520). Predetermines the object type and recognizes it as a tracking object by bringing the shape most similar to the setting object type in the image.

The motion detection step S500 includes a color filtering process, a difference image processing process for detecting differential motions, a motion image extraction process, and an area detection process.

When motion detection is performed by performing the motion detection step S500, the area tracking step S510 is performed.

The region tracking step consists of a process for region tracking, obtaining static regions and dynamic regions, matching them, region filing and region filling and merging.

After the motion detection and area tracking are performed, the active contour tracking step is performed. The active shape tracker is a method of calculating shape initializations, calculating the average of the contours (medium value), and PCA training (Principal Component). The tracking results are output through analysis training, model fitting, local edge search, and Mahalanovis Optimal Search Direction.

Naturally, other object tracking methods may be applied in addition to the object tracking method.

If it is determined that there is an object to be masked by performing the above process, an area including the object is extracted (S405).

The object portion is extracted from the extraction region including the object (S406).

When the area to be masked is extracted from the received image by the set method as described above, the masking operation is performed by determining the set masking method (S407).

If the masking method is set as the filtering method, the extracted area is filtered and blackened (S408). In the case of the blur method, the R, G, and B values of the extracted area are mapped to the average value of the surrounding pixels (S409).

In the case of a mosaic method, a mosaic process is performed by adjusting the number of pixels of the extracted region (S410).

When the masking operation of the extracted region is performed as described above, the masking region and the original image are mixed and stored or transmitted to the host terminals (S411).

The apparatus and method for protecting an input image of a digital video recorder according to the present invention as described above selectively masks a region in which an input image may be infringed on the privacy of an individual, thereby protecting important personal information.

In the present invention, the masking of the part to be protected is performed in the video input step, so that the masking after the recording does not require additional work.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art may of course make modifications without departing from the essential characteristics of the present invention. Therefore, the technical idea of the present invention is not limited to the above embodiment.

The apparatus and method for protecting an input image of a digital video recorder according to the present invention as described above have the following effects.

First, by setting an area to be masked from the input image and extracting an area to be masked from the input image, masking only a predetermined part selected by the user, thereby preventing the possibility of privacy infringement and protecting important personal information or image information. There is.

Second, the user can adjust the masking level through various masking methods such as filtering method, blur method, mosaic method, etc., so that it can be installed even in places where installation is generally impossible.

In addition, by performing the masking in the image input step, there is an effect of reducing the additional cost incurred in the masking method after recording.

Claims (25)

In a digital video recorder, An image receiver configured to receive image data input from at least one surveillance camera; An input image protection processor configured to extract a partial region from the received image data and selectively mask the extracted region; And An encoder for encoding the protected image data and a file system for sequentially storing the encoded image data, And the input image protection processor extracts a masking region corresponding to a partial region of the image data using a fixed coordinate value of the received image data, and masks the extracted masking region. delete delete The method of claim 1, wherein the input image protection processing unit, A masking area setting unit for setting an area to be masked from the received image data; A masking area extracting unit extracting a set area; And a masking unit for selectively masking the extracted region. The method of claim 4, wherein the masking region extraction unit, And a set coordinate region capture unit for extracting a corresponding region by a set coordinate value. delete The method of claim 4, wherein the masking portion, Filtering method for filtering the extracted area black and processing, Blur method for mapping the R, G, B value of the extracted area to the average value of the surrounding pixels, and Mosaic method for controlling the mosaic by adjusting the number of pixels of the extracted area A digital video recorder, characterized in that for masking the extraction area with any of the following. A digital video recorder for processing and transmitting or storing image data received from at least one surveillance camera, An input image protection processor configured to set an extraction method and a masking method of a masking area of the image data, and selectively extract and mask a masking area from the image data before processing and transmitting the image data. Including, The setting of the masking area may include setting coordinate values of the extraction area to extract an area to be masked from an input image, or setting an object to be tracked by an object tracking method having an active algorithm. Input video protection device of the recorder. The method of claim 8, wherein the input image protection processing unit, A masking area setting unit for setting a masking area and a masking method in an image received from at least one surveillance camera; A masking area extracting unit extracting a set area; And a masking unit for selectively masking the extracted region. delete delete delete The method of claim 9, wherein the masking portion, Filtering method for filtering the extracted area black and processing, Blur method for mapping the R, G, B value of the extracted area to the average value of the surrounding pixels, and Mosaic method for controlling the mosaic by adjusting the number of pixels of the extracted area Masking the extraction area with any one of the input image protection device of the digital video recorder. In the input video protection method of the digital video recorder, Before processing and transmitting or storing image data received from multiple surveillance cameras, Setting an extraction method of an area to be masked from the received image and a masking method of the extracted area; And Extracting a set region from a received image according to the set contents and masking the extracted region; The masking region extraction method and the masking method may be set differently for each received channel. delete The method of claim 14, wherein the setting of the extraction method of the area to be masked comprises: A method of protecting an input image of a digital video recorder, characterized by setting a coordinate value of an extraction area or setting an object to be tracked by an object tracking method having an active type algorithm. The method of claim 14, wherein the extracting the set area from the received image comprises: A method of protecting an input image of a digital video recorder, comprising extracting a corresponding coordinate region using a set coordinate value from a received image. The method of claim 14, wherein the extracting the set area from the received image comprises: Determining whether an object to be masked is detected in the received image; If it is determined that there is an object to be masked, extracting an area containing the object; And extracting an object portion from an extraction area including the object. The method of claim 14, wherein the setting of the method of masking the extracted region comprises: An input video protection method of a digital video recorder, characterized in that the filtering method, the blur method, and the mosaic method. The method of claim 14, wherein in masking the extracted region, If the masking method is a filtering method, the input image protection method of the digital video recorder, characterized in that the extracted area is filtered and blackened. The method of claim 14, wherein in masking the extracted region, If the masking method is set as a blur method, the R, G, and B values of the extracted region are mapped to average values of surrounding pixels. The method of claim 14, wherein in masking the extracted region, If the set method is a mosaic method, the input image protection method of the digital video recorder, characterized in that the mosaic processing by adjusting the number of pixels of the extracted region. delete In the input video protection method of the digital video recorder, Detecting a designated object included in the received image data; Extracting an area corresponding to the extracted object; And Masking the extracted area of the image data; The detecting of the designated object may include detecting an object by using a coordinate value corresponding to the fixed object when the object is a fixed object, and detecting an object by using pattern tracking of the moving object when the object is a moving object. And detecting the input video of the digital video recorder. In the input video protection method of the digital video recorder, Detecting a designated object included in the received image data; Extracting an area corresponding to the extracted object; And Masking the extracted area of the image data; The masking may include: a filtering method of filtering the extracted area and blackening the filter; a blur method of mapping the R, G, and B values of the extracted area to an average value of neighboring pixels; and adjusting the number of pixels of the extracted area. A method of protecting an input video of a digital video recorder, characterized in that the masking is performed using one of mosaic methods of mosaicing.

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