KR102271118B1 - Apparatus and method for recording video data - Google Patents

Abstract

An image storing device and a method thereof are disclosed. The image storing device includes: a transcoder which transcodes at least a portion of a first bitstream provided from a video transmitter and processes the same into a second bitstream having an updated IDR period of a time length different from that of the IDR period of the first bitstream; and a storage unit configured to store the second bitstream. The image storing device can significantly reduce the construction cost of a CCTV system.

Description

Video storage device and method {Apparatus and method for recording video data}

The present invention relates to an image storage device and method.

Recently, the installation of CCTV systems for the purpose of video surveillance and security is increasing in government and public institutions, and these CCTV systems are being expanded to various locations such as intersections and alleys in residential areas to collect traffic volume or secure a social safety net.

In general, the CCTV system is configured to include a camera group 110, an image distribution device 120, and an image storage device 130 consisting of IP cameras installed in each designated location as illustrated in FIG. An image captured by each IP camera may be checked at the control center 140 located at a remote location.

Here, the image distribution device 120 may be, for example, a device that monitors and manages digital image data of a plurality of IP cameras, and the image storage device 130 records, monitors, and events images of IP cameras installed on a network. It may be a device for management.

As shown, each IP camera is connected to a video distribution device 120 that is, for example, a VMS (Video Management System) through a wired/wireless communication network, and the video distribution device 120 is connected to an image ( That is, the video of each channel) is received in the form of a bitstream and provided to the control center 140 .

In addition, the video distribution device 120 provides the received bitstream to the video storage device 130 , which is, for example, a Network Video Recorder (NVR) device so that the bitstream is stored, and also requested from the control center 140 . The bitstream may be read from the image storage device 130 and provided to the control center 140 .

The image storage device 130 receives and stores the bitstream. The image storage device 130 may be connected to a monitor to check whether the bitstream is being normally received. The image storage device 130 may include a decoder to output an image corresponding to a bitstream to a monitor.

In general, the image storage device 130 is set to store and maintain the received bitstream for a predetermined period (eg, 30 days).

However, recent CCTV images are processed in FHD level, so a large-capacity storage space is required. For example, to store one hour of 30 fps (frames per second) information as an FHD image, about 2 GB of storage space is required. Therefore, to store data for 30 days of 24 hours as one channel information, about 1.44 TB storage space is required. Similarly, in the case of a CCTV system targeting 800 channels, the image storage device 130 must have a storage space of at least 1,152 TB.

Therefore, if a plurality of IP cameras in which the bitstream is to be stored are set, that is, a plurality of channels, a large-capacity storage space proportional to the number of channels must be sufficiently secured in the image storage device 130, which reduces the cost of constructing a CCTV system. causing a significant increase. In addition, as CCTV images are gradually being improved to 4K and 8K grades, it will be required to secure a larger storage space in the long term, which inevitably increases the construction cost of the CCTV system exponentially.

However, technology development related to the CCTV system so far has focused only on encryption of the bitstream to be stored due to the need for information security, and development efforts for technology for more efficiently compressing and storing the bitstream are insufficient.

Korean Patent Registration No. 10-2012037

An object of the present invention is to provide an image storage apparatus and method that can significantly reduce the construction cost of a CCTV system by effectively compressing, storing, and using large amounts of high-resolution and high-definition image data without deterioration in image quality.

Objects other than the present invention will be easily understood through the following description.

According to an aspect of the present invention, by transcoding at least a portion of a first bitstream provided from an image transmitter, a second having an updated IDR period of a time length different from that of an IDR period of the first bitstream Transcoder that processes bitstream; and a storage unit configured to store the second bitstream.

The transcoder converts one or more intra frames into an inter frame by using one or more intra frames as a frame to be transcoded so that the second bitstream has an updated IDR period, wherein the updated IDR period is the second bit It may be determined by analyzing the first bitstream according to a predetermined bitstream characteristic interpretation rule that is equally applied as a whole within the stream.

When an update IDR period of the same time length is designated and applied in advance in the second bitstream, the transcoder is configured to select one of a plurality of Groups of Pictures (GOPs) belonging to each updated IDR period in the first bitstream. In the second GOP, only the intra frames included in the last GOP are limited to the transcoding target frame, and the intra frames included in each of the plurality of GOPs included in each update IDR period have a reference relationship of a predetermined structure. The bitstream is processed, but the reference relationship of the predetermined structure may be any one of an IPPP structure, an IBBB structure, and an IBBP structure.

The length of time of the update IDR cycle includes the number of channels through which the bitstream to be stored in the storage unit is provided, the total storage capacity size of the storage unit, the free storage capacity size of the storage unit, and the bitstream is stored and maintained in the storage unit It can be calculated by a predefined equation to have one or more of the time periods as a factor to be considered.

The bitstream characteristic interpretation rule for adaptively determining the update IDR period is for each of the intra frames included in each of the second GOP to the last GOP among a plurality of Groups of Pictures (GOPs) belonging to the first bitstream. It may be to calculate a difference value from a corresponding pixel of an intra frame in the first GOP or a frame to be referenced, and specify the frame to be transcoded as a frame to be transcoded and change it to an inter frame only when the difference between frames is less than or equal to a predetermined threshold value .

The transcoder may be configured to change an intra frame designated as a transcoding target frame into an inter frame using a lossless coding technique.

In order for the encoder unit of the transcoder to operate in a lossless coding scheme, one or more flag values of a sequence parameter set (SPS), a picture parameter set (PPS), a picture header (PH), and a CU syntax (Coding Unit Syntax) can be adjusted have.

According to another aspect of the present invention, there is provided a computer program stored on a computer-readable medium for performing an image storage method, the computer program causing a computer to perform the following steps, the steps comprising: (a) an image transmitter receiving a first bitstream from and (b) transcoding at least a part of the first bitstream into a second bitstream having an updated IDR period of a time length different from that of an IDR period of the first bitstream. However, in step (b), one or more intra frames are used as transcoding target frames so that the second bitstream has an updated IDR cycle, and are changed to an inter frame, but with an updated IDR cycle. A computer program stored in a computer-readable medium is provided, which is determined by interpreting the first bitstream according to a pre-specified bitstream characteristic interpretation rule that is equally applied as a whole within the second bitstream.

When an update IDR period of the same length of time is designated and applied in advance in the second bitstream, in step (b), a plurality of Group of Pictures (GOPs) belonging to each updated IDR period in the first bitstream ), only intra frames included in each of the second to last GOPs are limited to the transcoding target frame, and intra frames included in each of a plurality of GOPs belonging to each update IDR period have a reference relationship of a predetermined structure. It is processed into the second bitstream, and the reference relation of the predetermined structure may be any one of an IPPP structure, an IBBB structure, and an IBBP structure.

The length of time of the update IDR cycle includes the number of channels through which the bitstream to be stored in the storage unit is provided, the total storage capacity size of the storage unit, the free storage capacity size of the storage unit and the bitstream is stored and maintained in the storage unit. It may be calculated by an equation predefined to have one or more of the periods as a factor to be considered.

The bitstream characteristic interpretation rule for adaptively determining the update IDR period to be applied is applied to each of the intra frames included in each of the second GOP to the last GOP among a plurality of Groups of Pictures (GOPs) belonging to the first bitstream. In the first GOP, the difference value with the corresponding pixel of the intra frame or frame to be referenced is calculated, and only when the difference value between frames is less than or equal to a predetermined threshold value, it is specified as a frame to be transcoded and changed to an inter frame. have.

Other aspects, features and advantages other than those described above will become apparent from the following drawings, claims, and detailed description of the invention.

According to an embodiment of the present invention, it is possible to effectively compress, store, and use massive data of high-resolution and high-definition images without deterioration in picture quality, thereby significantly reducing the construction cost of a CCTV system.

1 is a diagram schematically showing the configuration of a general CCTV system.
2 is a block diagram of an image storage device according to an embodiment of the present invention;
3 is a diagram for explaining a bitstream of an IPPP structure;
4 is a diagram illustrating a surveillance image captured by an IP camera in a fixed position.
5 is a diagram for explaining a bitstream transcoding technique according to an embodiment of the present invention.
6 is a diagram for explaining a reconstructed HEVC encoder structure according to an embodiment of the present invention.

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to a specific embodiment, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

The terms used herein are used only to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In this specification, terms such as "comprises" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

FIG. 2 is a block diagram of an image storage device according to an embodiment of the present invention, FIG. 3 is a diagram for explaining a bitstream of an IPPP structure, and FIG. 4 is a surveillance image captured by an IP camera in a fixed position. It is an exemplified drawing. 5 is a diagram for explaining a bitstream transcoding technique according to an embodiment of the present invention, and FIG. 6 is a diagram for explaining a structure of a reconstructed HEVC encoder according to an embodiment of the present invention.

Referring to FIG. 2 , the image storage device 130 according to the present embodiment may include a decoder 210 , a transcoder 220 , and a storage unit 230 .

The decoder 210 provides a decoded image of the received bitstream to the monitor so that it can be checked whether the bitstream of each channel is normally received from the video transmitter (Network Video Transmitter, NVT) 240 . The administrator will be able to easily check whether the bitstream is normally received by referring to the image output from the monitor.

Here, the image transmitter 240 is a device that provides a bitstream to be stored in the image storage device 130 , and may be, for example, one or more of the image distribution device 120 and an IP camera. If the video transmitter 240 provides both a high-resolution bitstream and a low-resolution bitstream corresponding to the captured image, the decoder 210 decodes the low-resolution bitstream to improve processing efficiency and displays it on the monitor. will be able to provide

The transcoder 220 is a general configuration and is implemented including a decoder unit and an encoder unit, and as will be described later, transcodes an input bitstream into a bitstream that has a relatively small data amount and maintains the same image quality. The obtained bitstream is stored in the storage unit 230 .

In general, in the compressed video format in the bitstream generated and transmitted by the IP camera, an intra frame and an inter frame are arranged in an IPPP structure as illustrated in FIG. 3(a), and the I frame is is an IDR frame, which is arranged at a predetermined time interval (ie, an IDR period (Period)). For convenience of explanation, in this specification, the case of the IPPP structure will be mainly described, but as is well known, the video format is various, such as an IPPP structure, an IBBB structure, an IBBP structure, etc., and the present invention is the same without any limitation for various video formats. Of course, it can be applied.

For example, in a bitstream of 30 fps in which the IDR period is set to 1 second, one I frame and the following 29 P frames are located within a time interval of 1 second.

Here, the I frame is an essential frame to reduce image quality degradation caused by camera movement or scene change, or to enable random access. Accordingly, in the case of encoding general content such as a drama or a movie, the encoding is performed so that about one frame per second is included.

I-frames are encoded independently from other images, whereas P-frames are encoded non-independently with reference to other preceding frames. Accordingly, as illustrated in (b) of FIG. 3 , the compressed I frame has a significantly larger amount of data than the compressed P frame.

4 exemplifies four surveillance images captured by an IP camera in a fixed position. For reference, the exemplified surveillance images are taken at intervals of about 30 seconds to 1 minute by an IP camera installed in an intersection area.

As seen in the surveillance images, only some moving objects change their positions and shapes over time, while most of the background images remain fixed. This is a typical characteristic in the captured image of an IP camera installed to continuously capture a designated surveillance area at a fixed location.

In addition, such an IP camera basically hardly causes camera movement or scene change, but also has a feature that the need for random access to a specific visual position of an image captured by the IP camera is remarkably low.

By reflecting the characteristics of the image generated by the CCTV system as described above, the image storage device 130 according to the present embodiment operates to significantly reduce the data amount of the bitstream stored in the storage unit 230 .

5 is a diagram illustrating a bitstream transcoding technique by the transcoder 220 of the image storage device 130 .

As illustrated in (a) of FIG. 5 , the compressed image format in the bitstream corresponding to the image captured by the IP camera is an IPPP structure, and is an I frame (ie, IDR frame) every predetermined IDR period (IDR Period). ) is arranged in the best position. In the present specification, for convenience of description, a case in which the reference frames of all P frames are set to one preceding frame will be described as an example, but the present disclosure is not limited thereto, and it is natural that the P frames may be set to have a plurality of reference frames.

Here, since the amount of compressed data of the I frame is significantly larger than that of the P frame, the transcoder 220 according to the present embodiment applies a relatively long updated IDR period, and one I frame within the updated IDR period. The amount of data of the bitstream stored in the storage unit 230 is reduced by reprocessing the bitstream so that only the bitstream exists.

As an example of the methods that can be considered at this time, as illustrated in FIG. 5( b ), the transcoder 220 includes all of the GOPs from the second GOP to the last GOP among Groups of Pictures (GOPs) in the updated IDR period. A method of reducing the amount of data in the bitstream to be stored may be considered by transcoding the frames into P frames that are non-independently encoded with reference to the immediately preceding frame.

At this time, in order to reprocess the frames belonging to the second GOP into P frames, the preceding I frame is decoded and then encoded as _{a P T10 frame referring to the immediately preceding P frame (ie, the last P frame of the first GOP).}

In this case, even in the case of a P frame to reference the existing I-frame in the second GOP, whereby the existing I-frame change in P _T10 frame because the restored pixel value for P _T10 frame changed from the existing I frame mismatch ( In order to prevent mismatch), the corresponding P frame must also be decoded and then changed to _{a P T11} frame re-encoded with reference to the _{P T10 frame.} Such processing must be commonly performed not only for the remaining P frames of the second GOP, but also for GOPs that follow within the updated IDR period.

_{In addition, in the case where the P frame preceding the P T10} frame is to be referred to during the transcoding process by the transcoder 220 , the decoding operation for all preceding frames up to all frames in the first GOP due to the reference relationship between the frames this is required

In this way, to reprocess all of the frames included in the second GOP to the last GOP included in the updated IDR period into P frames each referencing the previous frame, decoding and encoding of each target frame must be performed individually, and Also, since a separate decoding process must be performed for frames before the target frame, there is a problem in that the complexity of transcoding is significantly increased. Also, there is a problem in that image quality may be deteriorated in the process of decoding and re-encoding a plurality of frames.

In order to improve the above problems and reprocess the bitstream with a significantly smaller data amount, the transcoder 220 according to the present embodiment reprocesses the bitstream using typical characteristics found in the surveillance image captured by the IP camera. have characteristics.

That is, the transcoder 220 corresponds to Transform, quantization, Inv. Transform, Inv. Transform, and In-loop Filter for the I frame, which is a reprocessing target. The lossless encoding process is performed on the P frame by applying a simple encoder structure in which the operation of the module is disabled (refer to (b) of FIG. 6). Through this, it is possible to remarkably improve complexity that may occur in the transcoding process, and also to solve the problem of image quality degradation.

Specifically, the transcoder 220 limits only I frames after the second GOP among the frames belonging to the updated IDR period as the target frame to be transcoded and changes them to P frames by lossless encoding, respectively, but the updated IDR It is reprocessed into a bitstream having a reference relationship of an IPPP structure between I frames in a period (refer to (c) of FIG. 5).

That is, the transcoder 220 decodes the I frame of the second GOP among Groups of Pictures (GOPs) in the updated IDR period, and then encodes it into _{a P T1 frame referring to the I frame of the first GOP.}

At this time, since a lossless coding process is performed so that the encoding target pixel value and the pixel value obtained after encoding and restoring the pixel value become the same, the restored value of the I frame, which is the transcoding target frame (that is, , the encoding target pixel value) and the value obtained by reconstructing the _{reprocessed P T1 frame have the same characteristics.}

Accordingly, since mismatch does not occur in pixel values referenced by the P frame immediately after referring to the I frame in the existing second GOP, it is sufficient to transcode only the I frame, which is the frame to be transcoded.

The same is true for the subsequent GOP. However, the I frame, which is the transcoding target frame in the existing third GOP, is transcoded _{into the P T2} frame with reference to the P _T1 frame transcoded in the previous GOP, that is, from the third GOP, the transcoding target frame is the immediately preceding transcoding target. A rule of transcoding with reference to a frame is applied so that I frames in the updated IDR period have a reference relationship of the IPPP structure.

Therefore, in order to encode the transcoding target frame, it is sufficient to selectively refer only to the I frame and/or the preceding transcoding target frame in the first GOP regardless of the preceding P frame. This is to make it possible to refer to the preceding I frame, which is temporally separated, paying attention to the typical characteristics of the image captured by the IP camera of the CCTV system (that is, the point that most of the images contain a significant part of the same background area). .

As described above, the transcoder 220 according to the present embodiment performs a transcoding process on only the target transcoding frame (ie, I frames after the second GOP), and at the time of restoration, the independently coded I frame Therefore, by independently decoding and encoding only the I frame in the first GOP and/or the preceding transcoding target frame, there is an advantage of remarkably improving the compression rate while remarkably improving the complexity of the transcoding process. In addition, by applying a lossless coding technique in the transcoding process, there is an advantage in suppressing image quality degradation that occurs during decoding of I-frames and encoding of P-frames.

An arithmetic comparison of the compression performance of a conventional image storage device for storing a bitstream corresponding to an image captured by an IP camera and an image storage device according to the present embodiment is as follows. For reference, it is assumed that the compressed image format is an IPPP structure as an FHD video at 30 fps and the IDR period is 1 second. In general, the data amount of the P frame compared to the I frame is estimated to be about tens to 1, but for convenience of calculation, the data amount of the I frame is set to 20 and the data amount of the P frame is set to 1 as a ratio of 20:1.

In addition, for the convenience of comparison, it is specified that the update IDR period is changed to 10 seconds in consideration of the characteristics of the CCTV system image.

In this case, since there are one I frame and 29 P frames per second in the conventional imaging apparatus, the data amount corresponds to 49 (ie, 20x1+1x29), and since it is a 10-second period, the total data amount corresponds to 490.

However, in the image storage device 130 according to the present embodiment, since I frames of the subsequent GOP are transcoded into P frames to correspond to the update IDR period by the transcoder 220, there is one I frame in the 10-second interval, There are 299 P frames (that is, 29 of the first GOP and 270 of the remaining 9 GOPs), and the total data amount is 319 (ie, 20x1+1x299), which is about 35% of compression compared to the conventional image storage device. It shows the performance improvement effect.

Here, as the update IDR period is set to be relatively large, the compression performance may be relatively remarkably improved even though the random access restriction increases.

Accordingly, as an example, the update IDR period may be fixed to a specific value set by an administrator in consideration of typical characteristics of an image captured by an IP camera.

Also, as another example, the update IDR period may be adaptively determined in the bitstream by the controller included in the image storage device 130 in consideration of the characteristics of the bitstream.

That is, the controller provided in the image storage device 130 adaptively determines whether or not to change the transcoding target intra frame (ie, I frame) into an inter frame (ie, P frame or B frame) in the received bitstream. By determining, a plurality of different update IDR periods (eg, an update IDR period adaptively determined with a time length of 3 seconds, 10 seconds, 7 seconds, 20 seconds, etc., respectively) may be applied in the reprocessed bitstream.

At this time, the controller calculates a difference value between the intra frame to be transcoded and the intra frame in the first GOP or a reference frame (intra frame or inter frame), and sets the calculated difference value to a predetermined threshold. If it exceeds, transcoding is omitted to maintain an intra frame, but if it is less than a threshold value, the transcoder 220 may perform transcoding to control processing into an inter frame. The controller can adaptively adjust the update IDR period, and the difference between frames is SAD (Sum of Absolute Difference), MSE (Mean Squared Error), SSE (Sum of Squared Error), SAE (Sum of Absolute Error), etc. It may be calculated using an error measurement technique of calculating a difference value between corresponding pixels.

In some cases, if all the difference values between frames are less than or equal to a threshold value, only one intra frame exists in the processed bitstream as a whole, and thus, it may belong to one update IDR period. In this case, since a disadvantageous situation may occur in terms of random access, it is natural that the maximum value of the update IDR period that can be adaptively selected can be pre-determined so that the bitstream can be processed into a bitstream capable of random access above the minimum level. .

In addition, as another example, the controller (not shown) provided in the control center 140 and/or the image storage device 130 determines the number of channels in which the bitstream is to be stored in the image storage device 130 , the storage unit ( The total storage capacity size of 230 , the free storage capacity size of the storage unit 230 , and the period during which the bitstream is stored and maintained in the storage unit 230 are taken into consideration by a pre-defined equation It may be possible to adaptively calculate and apply an optimal update IDR period at a time point.

In this case, when the number of channels is relatively large or the storage and maintenance period of the bitstream is long compared to the size of the total storage capacity or the size of the free storage capacity of the storage unit 230, the update IDR period may be calculated relatively large. will be. Of course, the limit range of the update IDR period calculated by the equation may be preset, and may be limited in advance so that the update IDR period within the limit range is applied.

Next, the image storage device 130 according to the present embodiment may have processing complexity compared to the conventional image storage device because transcoding processing is performed by the transcoder 220 .

The transcoder 220 transcodes (ie, decodes and encodes) only one I frame out of 30 frames per second, and assuming that the complexity of the encoding process for one frame is about 5 times the complexity of the decoding process, The coder 220 may estimate that about 6 frames are decoded based on the decoding processing complexity.

Accordingly, the transcoder 220 induces complexity of processing 6 frames more by additional transcoding compared to the conventional image storage device. Therefore, when the conventional image storage device decodes 30 frames per second, it can be seen that the image storage device 130 according to the present embodiment decodes 36 frames, and in this case, the complexity increases by up to 20%. can be calculated.

However, compared to the increase in processor cost when the transcoder 220 is included in the conventional image storage device to cause complexity, the amount saved by increasing the compression rate of the bitstream to prevent expansion of the storage capacity is significantly large. Industrial applicability of the image storage device according to the embodiment will be sufficient.

When the transcoder 220 according to the present embodiment is mounted on the image storage device 130 , the encoder unit of the transcoder 220 may be newly developed to perform the above-described processing. In this case, the configuration and operation structure of the encoder unit of the transcoder 220 can be easily understood by those skilled in the art through the foregoing description, and thus a detailed description thereof will be omitted.

In another method, the encoder unit of the transcoder 220 uses the same conventional encoder structure as illustrated in FIG. 6( a ), but by setting a flag, it is modified so that the operation according to the present embodiment is possible. You may.

6A illustrates an HEVC encoder structure. As shown, the modules forming the encoder structure include Block Structure, Intra Prediction, Inter Prediction, Transform, Quantization, and Inverse Transform. , inverse quantization, in-loop filter, and entropy coding.

The encoder composed of the above-described blocks is generally processed by a lossy coding method, which causes loss in the final encoding result. In particular, a lot of loss may occur in the quantization block, and some loss may also occur in the transform and in-loop filter.

Accordingly, SPS (Sequence Parameter Set), which is a parameter set including sequence level information, PPS (Picture Parameter Set), which is a parameter set including picture level information, PH (Picture Header), which is picture header information, and/ Alternatively, by adjusting a flag value of a CU syntax (Coding Unit Syntax), the encoder unit of the transcoder 220 may be adjusted to perform lossless encoding processing.

Specifically, transquant_bypass_enabled_flag (that is, a flag that specifies on/off of the transquant bypass function) in the PPS, which is the parameter set of the HEVC encoder, is turned on to enable transquant bypass for each coding unit (CU), and to be transcoded cu_transquant_bypass_flag, which is a flag for a coding unit of a CU syntax, is turned on to losslessly encode all blocks (ie, coding units) in a frame.

Through this, the encoder unit of the transcoder 220, as exemplified in FIG. 6(b), has a minimum module that guarantees losslessness (that is, a block structure, an intra prediction, and an inter-screen operation). An encoder structure in which only prediction (Inter Prediction) and entropy coding (Entrophy Coding) operates may be used.

The improved encoder structure can greatly reduce encoding complexity by omitting the operation of a plurality of modules, and, even if the encoder unit of the transcoder 220 is newly developed, a minimum number of modules can be included, thereby simplifying implementation. there is also

In the process of storing the reprocessed bitstream in the storage unit 230 , the image storage device 130 utilizing the improved encoder structure described above modifies header information of a bitstream indicating a reference relation related to transcoding in the above-described manner. After storing the processed bitstream in the storage unit 230 , when a specific image is requested from the control center 140 , the corresponding bitstream is retrieved from the storage unit 230 and provided to the control center 140 . There will be. In this case, management efficiency can be increased by providing the image to the control center 140 in the form of a reprocessed bitstream stored in the storage unit 230 , but relatively random access may be restricted when the video is used in the control center 140 . have.

In addition, the image storage device 130 reprocesses the bitstream received from the image transmitter 240 and stores it in the storage unit 230 , but when a specific image is requested from the control center 140 , it is transcoded from the corresponding bitstream. By transcoding the target transcoding frame changed to the P frame back into the I frame, the bitstream may be reprocessed and provided to the control center 140 . In this case, the processing complexity of reprocessing the bitstream without degrading the image quality by applying the lossless coding technique may be increased, but the random access performance may be relatively improved when the corresponding image is used in the control center 140 .

So far, the description has been focused on the case where the image storage device 130 equipped with the transcoder 220 according to the present embodiment is applied to a CCTV system, but in addition, the present invention provides an image captured by a fixed IP camera without a scene change. It goes without saying that an image storage device for receiving and storing a corresponding bitstream can be applied to various fields without limitation.

It goes without saying that the above-described image storage method may be implemented as a software program or an application embedded in a digital processing device such as an image processing device, and may be performed as an automated procedure according to a time-series sequence. Codes and code segments constituting the program or the like can be easily inferred by a computer programmer in the art. In addition, the program is stored in a computer readable media (computer readable media), is read and executed by the computer to implement the method.

Although the above has been described with reference to the embodiments of the present invention, those of ordinary skill in the art can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention described in the claims below. You will understand that it can be done.

110: camera group 120: video distribution device
130: video storage device 140: control center
210: decoder 220: transcoder
230: storage unit 240: video transmitter

Claims (11)

a transcoder for transcoding at least a portion of the first bitstream so as to process a second bitstream having an update IDR period of a time length different from a time length of an IDR period of the first bitstream; and
A storage unit for storing the second bitstream,
The transcoder converts at least one of intra frames included in each of the GOPs except the first among Group of Pictures (GOPs) consecutively arranged according to the IDR period in the first bitstream as a target frame for transcoding. Processed into the second bitstream having an updated IDR period by selectively transcoding into an inter frame,
An inter frame selected as a target frame to be transcoded and an intra frame transcoded by the transcoder has a reference relationship with at least one of an intra frame and a transcoded inter frame positioned previously. According to claim 1,
The time length of each of the update IDR periods in the second bitstream is equally applied as a whole, or is adaptively determined and applied by analyzing the first bitstream according to a predetermined bitstream characteristic interpretation rule. . 3. The method of claim 2,
When it is previously designated to have an update IDR period of the same time length as a whole in the second bitstream,
The transcoder receives only intra frames respectively included in the second GOP to the last GOP among a plurality of GOPs (Group of Pictures) in the first bitstream corresponding to the time length of each update IDR period in the second bitstream. A video of processing the first bitstream into the second bitstream so as to have the reference relation between the intra frame defined as the transcoding target frame and the intra frame within the first GOP and the transcoding target frame storage device. 3. The method of claim 2,
The length of time of the update IDR cycle includes the number of channels through which the bitstream to be stored in the storage unit is provided, the total storage capacity size of the storage unit, the free storage capacity size of the storage unit, and the bitstream is stored and maintained in the storage unit An image storage device, calculated by a pre-defined equation to have one or more of the periods of time as a factor to be taken into account. 3. The method of claim 2,
The bitstream characteristic interpretation rule for adaptively determining the time length of the update IDR period is,
Among the plurality of groups of pictures (GOPs) belonging to the first bitstream, the intra frame in the first GOP positioned prior to each of the intra frames included in the second GOP to the last GOP, or a frame to be referenced By calculating a difference value, only when the difference value between frames is less than or equal to a predetermined threshold value, it is specified as a frame to be transcoded and changed to an inter frame
The difference value between frames is calculated using one or more of Sum of Absolute Difference (SAD), Mean Squared Error (MSE), Sum of Squared Error (SSE), and Sum of Absolute Error (SAE). According to claim 1,
and the transcoder converts an intra frame selected as a transcoding target frame into an inter frame using a lossless coding technique. 7. The method of claim 6,
In order for the encoder unit of the transcoder to operate in a lossless coding scheme, one or more flag values of a sequence parameter set (SPS), a picture parameter set (PPS), a picture header (PH), and a CU syntax (Coding Unit Syntax) are adjusted. , video storage. A computer program stored on a computer-readable medium for performing an image storage method, the computer program causing a computer to perform the following steps, the steps comprising:
(a) receiving a first bitstream from an image transmitter; and
(b) transcoding at least a part of the first bitstream so that a second bitstream having an update IDR period of a time length different from a time length of an IDR period of the first bitstream is processed including,
In step (b),
At least one of intra frames included in each of the GOPs except for the first among groups of pictures (GOPs) consecutively arranged according to the IDR period in the first bitstream are selected as the transcoding target frame, and the inter frame By transcoding into (inter frame), it is processed into the second bitstream having an updated IDR period,
An inter frame in which the intra frame is transcoded by the transcoder selected as the target frame for transcoding has a reference relationship with at least one of an intra frame and a transcoded inter frame positioned previously,
The time length of each of the update IDR periods in the second bitstream is equally applied as a whole, or is adaptively determined and applied by interpreting the first bitstream according to a predetermined bitstream characteristic interpretation rule. A computer program stored on a capable medium. 9. The method of claim 8,
When it is previously designated to have an update IDR period of the same time length as a whole in the second bitstream,
In step (b), intras included in each of the second GOP to the last GOP among a plurality of GOPs (Group of Pictures) in the first bitstream corresponding to the time length of each update IDR cycle in the second bitstream wherein the first bitstream is processed into the second bitstream to define only frames as to-be-transcoded frames, and to have the reference relationship between intra frames defined as frames to be transcoded. stored in a computer program. 9. The method of claim 8,
The length of time of the update IDR cycle includes the number of channels through which the bitstream to be stored in the storage unit is provided, the total storage capacity size of the storage unit, the free storage capacity size of the storage unit and the bitstream is stored and maintained in the storage unit. A computer program stored on a computer-readable medium, calculated by an equation predefined to have one or more of the time periods as a factor of consideration. 9. The method of claim 8,
The bitstream characteristic interpretation rule for adaptively determining the time length of the update IDR period is,
Among the plurality of groups of pictures (GOPs) belonging to the first bitstream, the intra frame in the first GOP positioned prior to each of the intra frames included in the second GOP to the last GOP, or a frame to be referenced By calculating a difference value, only when the difference value between frames is less than or equal to a predetermined threshold value, it is specified as a transcoding target frame and changed to an inter frame,
The difference value between frames is calculated using one or more of Sum of Absolute Difference (SAD), Mean Squared Error (MSE), Sum of Squared Error (SSE), and Sum of Absolute Error (SAE) on a computer-readable medium. stored computer programs.

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