KR100385620B1 - Improved MPEG coding method, moving picture transmitting system and method thereof - Google Patents

Abstract

The present invention relates to an improved MPEG encoding method for encoding a video signal received from a video input device, a system for transmitting video data encoded using the same, and a method thereof.

The improved MPEG encoding method according to the present invention is characterized in that an object selected as a reference frame of inter frames is fixed to an intra frame.

The video transmission system using the improved MPEG encoding method according to the present invention comprises: an image processing unit for receiving an image signal from a moving image input device and performing signal processing, and encoding the signal processed data by the improved MPEG encoding method; And a transmission unit adapted to transmit the video data encoded by the image processing unit in real time by adapting to a change in network transmission rate.

According to the present invention, video data input and received from a remote fixed camera can be transmitted in real time according to a flexible transmission rate of a network, and additionally set by a user according to the type and capacity of a storage medium and the importance of a storage image. Data encoded at one storage rate can be recorded.

Description

Improved MPEG coding method, video transmission system using same and method thereof {Improved MPEG coding method, moving picture transmitting system and method}

The present invention relates to an improved MPEG (Moving Picture Experts Group) encoding method and a video processing system using the same. More particularly, the present invention compresses image data input through a remote fixed camera using an improved MPEG encoding method and improves MPEG encoding. The present invention relates to a video transmission system and a method for transmitting a video data adaptively compressed to a network environment to a decoder at a remote location using a wide data loss rate by the method.

MPEG, which is used as the basis technology of the present invention, is a standard organization established under the ISO (International Organization for Standardization) by the Video Coding Standards Committee for storage media, and at the same time, it refers to a standard standard of a video encoding and decoding algorithm. The video information encoding principle used in MPEG consists of three parts according to the spatial relationship, the temporal correlation and the bias of the code occurrence probability. ) Is a technology borrowed. JPEG is a lossy compression method that performs a DCT (Discrete Cosine Transform) to divide the spatial frequency of an image into high frequency components and low frequency components, and to lose high frequency components that are difficult to be recognized by human sensory organs through quantization. Encoding according to the bias relationship between code generation probabilities is a technique using entropy coding that gives a short code to a high occurrence probability of the constituent data of an image and a long code to the other.

However, when transmitting the entire compressed frame (for example, 30 frames per second) by applying the MPEG encoding method according to the prior art, it may not be able to transmit the entire frame in real time due to the characteristics of the wired / wireless channel. In particular, when transmitting video data encoded using a PSTN network or an ISDN network, it is common to transmit only a limited number of frames due to a limitation of a supported transmission rate.

Meanwhile, in the MPEG encoding scheme according to the related art, encoding is performed using temporal correlation, and encoding using temporal correlation is performed using an inter-picture (I picture) and an inter-picture (Predictive-Picture). We apply the structure of Bidirectionally predictive-Picture (P picture and B picture). In this case, when the I / P frame structure is applied, an arbitrary frame is discarded by referring to the state of the transmission channel, which makes it difficult to restore a normal image. This is because reconstruction is impossible without adjacent frames because the conventional MPEG coding method uses correlation between adjacent frames. In addition, in the case of applying the I / P / B frame structure, even if the B frame is discarded, the received image can be normally restored, but in general, one GOP (Group Of) is required due to the reordering delay and the necessity of the reordering frame memory. There is a predetermined limit on the number of B frames. That is, in the conventional MPEG encoding scheme, there is a significant limitation on the allowable loss rate of frames.

As described above, according to the conventional coding scheme, due to the low allowable frame loss rate, it is difficult to select various compression rates according to the amount of storage space, and it is difficult to adapt to changes in the transmission speed on the network, thereby making it difficult to transmit in real time. there was.

In particular, in applications such as security systems, images captured by fixed cameras have a very close temporal correlation, and existing video encoding and transmission systems do not properly use such characteristics of storage media. And it is difficult to adaptively adjust the amount of data according to the characteristics of the transmission medium.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned general problems, and an object of the present invention is that even if the temporal adjacent correlation between the input images is large due to the use characteristics or mechanical characteristics of the image input apparatus, the image data may be lost after the loss. Since there is a lot of data that can restore the original image, we provide an improved MPEG encoding method to increase the allowable frame loss rate, and by using the improved MPEG encoding method, the real-time video encoding is adaptively adapted to the fluid environment of the network. The present invention provides a video transmission system and a method for transmitting data and additionally allowing a user to flexibly adjust a storage rate of video data according to a capacity of a storage medium.

1 shows a comparison between each frame and a reference frame in the improved MPEG encoding method according to the present invention compared with the MPEG encoding method according to the prior art.

2 is a block diagram showing the overall configuration of a first embodiment of a video transmission system using the improved MPEG encoding method according to the present invention.

3A is a flowchart illustrating an embodiment of a video transmission method using an improved MPEG encoding method according to the present invention.

3B illustrates the internal structure of a transmission buffer in a video transmission system using the improved MPEG encoding method according to the present invention.

4 is a block diagram showing the overall configuration of a second embodiment of a video transmission system using the improved MPEG encoding method according to the present invention.

5A is a flowchart illustrating an embodiment of a video storing method using the improved MPEG encoding method according to the present invention.

5B illustrates a structure of a data string for explaining an operation of a storage frame selector of a moving picture storage system using an improved MPEG encoding method according to the present invention.

<Explanation of symbols for main parts of drawing>

10: image processor 12: signal processor

14: MPEG encoder 20: transmission unit

22: transmission frame selector 24: transmission buffer

26: transmission processing unit

In order to achieve the above object, a system for encoding a video signal received from a video input device according to the present invention and transmitting the encoded video data through a network includes an inter frame in a group of picture (GOP) coding unit. By fixing an object to be selected as a reference frame of frames as an intra frame, a frame that does not affect the reconstruction of the original image even if it is lost as needed among the encoded data is extended to the entire inter frame. And an improved MPEG encoding method characterized by the above.

As described above, a system for encoding a video signal received from a video input device by using an improved MPEG encoding method and transmitting the encoded video data through a network receives a video signal from the video input device, processes the signal, and processes the data. An image processor which encodes the signal using the improved MPEG encoding method; And a transmission unit adapted to transmit the video data encoded by the image processing unit in real time by adapting to a change in network transmission rate.

In addition, the video transmission system using the improved MPEG encoding method includes a storage frame selection unit for receiving the image data encoded by the image processing unit, and selecting a frame to be stored based on the number of storage frames per unit time set by the user; And a storage unit having a video database storing the frames selected by the storage frame selection unit.

In order to achieve the above another object, a method of encoding a video signal received from a video input device according to the present invention by an improved MPEG encoding method, and transmitting the encoded video data through a network (a) from a video input device Converting the received video signal into aligned data by processing the received video signal and encoding the same by the improved MPEG encoding method; And (b) real-time transmission of the encoded image data at a data loss rate adapted to a change in network rate.

The video transmission method using the improved MPEG encoding method may further include (c) storing the encoded image data at a preset number of storage frames per time.

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

The improvement of the MPEG method according to the present invention is achieved in the encoding step according to the temporal correlation. The image input through the image input device is transformed into a digital data stream maintained through signal processing, and undergoes a coding step according to spatial correlation using a still image coding technique in which DCT (Discrete Cosine Transform) transformation is the main algorithm. MPEG consists of a signal multiprocessing system structure of a sequence layer, a GOP layer, a picture layer, a slice layer, a macroblock layer, and a block layer, among which a reference frame is selected from a GOP, a coding unit for each frame, and changes according to temporal correlation. By extracting only the part, encoding is realized once more by the motion vector technique.

In general, an image from a camera photographed in real time has a high correlation between adjacent frames. In particular, when the camera is fixed and the background does not change, the correlation between adjacent frames is very high. Therefore, since the camera applied in the security field is photographed in a fixed state, the close correlation is very high. On the other hand, the mobile camera has a relatively low correlation with the fixed camera since the fixed and moving are repeated.

1 shows a comparison between each frame and a reference frame in the improved MPEG encoding method according to the present invention compared with the MPEG encoding method according to the prior art.

The conventional MPEG encoding method considers a mobile camera and encodes a GOP, which is a coding unit, by using a temporal correlation between an I picture as an intra frame that encodes all information on the screen and surrounding frames. It consists of an inter frame B picture (Bi-directionally predictive Picture) and P picture (Predictive Picture). P picture is a forward-predictive encoding of the adjacent P or I picture as a reference frame to obtain a motion vector (meaning that the information of the back picture is obtained from the previous picture). The B picture is a coded video obtained by bi-prediction-encoding the front and rear adjacent P or I pictures as reference frames.

In the improved MPEG encoding method according to the present invention, each GOP is composed of one I picture and a plurality of P pictures in order to take advantage of characteristics of an input image from a fixed camera having a low implementation and ease of implementation. In this case, the reference frame due to the temporal correlation of the P picture is limited to an I picture in the same GOP and encoded. Therefore, the loss target frame, which has been limited to the B picture in the past, is enlarged to all the frames except the I picture, thereby increasing the allowable loss rate of the frame.

According to FIG. 2, a first embodiment of a video transmission system using the improved MPEG encoding method according to the present invention includes an image processing unit 10 and a transmission unit 20.

The image processor 10 includes a signal processor 12 and an MPEG encoder 14, and converts an image signal received from a video input device (not shown) into a series of image digital data. In general, a video input device converts an analog signal into a digital signal and outputs the digital signal. Otherwise, the signal processing unit 12 performs an A / D conversion function first, and then removes the noise signal and arranges the signal to the MPEG standard. Function and other filtering functions. The MPEG encoder 14 encodes the signal-processed video data by using the improvement method described with reference to FIG. 1 and sends it to the transmission unit 20.

The transmission unit 20 includes a transmission frame selection unit 22, a transmission buffer 24, and a transmission processing unit 26 to adapt the moving image data encoded by the image processing unit 10 to changes in the network transmission rate in real time. send.

The transmission frame selector 22 receives the image data encoded by the image processor 10, selects the image data encoded in units of frames according to the remaining capacity of the transmission buffer 24, and transmits the image data to the transmission buffer 24. .

The transmission buffer 24 temporarily stores the encoded image data selected by the transmission frame selecting unit 22, and the transmission processing unit 26 fetches the encoded image data temporarily stored in the transmission buffer 24 to match the network condition. Transmit by converting to transmission standard.

The transmission rate of the bitstream fetched from the transmission buffer 24 and transmitted by the transmission processing unit 26 varies depending on the type and state of the transmission medium. Accordingly, the transmission frame selector 22 selects a frame to be stored in the transmission buffer 24 according to the remaining capacity of the transmission buffer 24 determined according to the change of the transmission speed, and loses the frames not selected.

Operation of the transmission frame selector 22 will be described in more detail below with reference to FIGS. 3A and 3B.

In FIG. 3B, the total storage space of the transmission buffer 24 is Bmax, the limit number of bits for selecting a transmission frame is M, the number of bits filled in the transmission buffer 24 is L, and the total number of bits that can be generated in one frame. Twofold is defined as Fmax.

Referring to FIG. 3A, first, the transmission frame selector 22 receives the image data encoded by the image processor 10, searches for the image data, and finds the starting point of the current frame using picture_start_code (steps S100 and S110).

Thereafter, the transmission frame selector 22 compares the L value of the transmission buffer 24 with the M value (step S120), and performs the following operation according to the result.

1) When L ≤ M

All bit streams of the current frame are transferred to the transmission buffer 24 and stored (step S130).

2) If L> M, the following operation is performed according to the type of the current frame (step S140).

① If the current frame is an inter frame,

The current frame is lost (step S150).

② If the current frame is an intra frame,

If the frame immediately transmitted to the transmission buffer 24 is an interla frame, all the frames of the GOP to which the current interla frame belongs are lost (steps S160 and S170), and the frame immediately transmitted to the transmission buffer 24 is interleaved. In the case of a frame, the current interla frame is transmitted to the transmission buffer 24 and stored (steps S160 and S130).

Thereafter, the above-described step S100 is repeated to transmit the bitstream of the encoded image data received from the image processing unit 10 through the network. At this time, if the previous process is continued in step S170, in step S110 to find the starting point of the I frame of the new GOP using GOP_start_code.

In order to prevent the transmission buffer 24 from overflowing, (Mmax-M) = Fmax should be more than twice the total number of bits that can occur in one frame, and the M value determined for this is It can be determined experimentally according to the video signal input through.

The second embodiment of the video transmission system using the improved MPEG encoding method according to the present invention adds a storage unit for storing additionally encoded video in addition to the above-described functions.

According to FIG. 4, the second embodiment of the video transmission system using the improved MPEG method according to the present invention includes an image processing unit 10a having a signal processing unit 12a and an MPEG encoder 14a, and a transmission frame selection unit 22a. ), A transmission unit 20a having a transmission buffer 24a and a transmission processing unit 26a, and a storage unit 30 having a storage frame selection unit 32 and an image database 34. Here, the image processing unit 10a and the transmission unit 20a perform the same functions as the image processing unit 10 and the transmission unit 20 of the first embodiment of the video transmission system using the improved MPEG method described above. Will be omitted.

The storage frame selector 32 receives the image data encoded by the image processor 10a and selects a frame to be stored in the video database 34 based on the number of storage frames per unit time set by the user.

A process of selecting a frame to be stored by FIG. 5A will be described in more detail.

The storage frame selector 32 receives the number of recording frames from the user (step S200), and determines a value X obtained by dividing the maximum output frame number of the encoded image data by the number of recording frames (step S210).

In this case, if the X value is an integer value, only one frame is stored for each number of X frames for each GOP among the encoded image data (steps S220 and S230). If the X value is not an integer value, only one frame is stored for each number of frames corresponding to the value corresponding to the integer part of X, and the frames corresponding to the rest are lost (steps S220 and S240).

Thereafter, the process initializes to the next GOP and repeats steps S230 or S240 (step S250).

Hereinafter, the processes of FIG. 5A will be described with reference to FIG. 5B.

If the maximum number of output frames output from the MPEG encoder 14a is 30 frames per second (= one GOP), and the user sets the number of recording frames to 7 frames per second, the X value becomes approximately 4.3. Accordingly, when one frame is stored every four or five frames regardless of the GOP unit, a large number of I frames are lost, and all P frames having lost I frames as reference frames are lost. In order to prevent such a result, in the present invention, seven frames are stored in one frame per four frames per GOP unit, and the last 29th and 30th frames are lost. In this way, I frames included in all GOPs can be stored without being lost at all times.

In a second embodiment of the video transmission system using the improved MPEG method according to the present invention, another feature is that the storage unit 30 and the transmission unit 20a described above can operate simultaneously regardless of the external environment. You can do

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

According to the present invention, in using a remote fixed camera for security purposes or for other special purposes, the encoded video can be transmitted in real time by adapting to a change in network transmission rate on a network, and the type, capacity, and storage video of a storage medium can be transmitted. It is possible to record the encoded video at different storage rates according to the importance of. This allows for more flexible remote integrated security management.

Claims (11)

delete delete delete delete delete delete In encoding the video signal received from the video input device by temporal correlation, the object selected as the reference frame of the inter frames in each GOP is fixed to the intra frame by encoding using the improved MPEG encoding method. In a system for transmitting a video data through a network, A signal processor that receives a video signal from the video input device and converts the video signal into video digital data when the video signal is a video analog signal; And an MPEG encoder which encodes the image digital data processed by the signal processor by the improved MPEG encoding method. And A transmission buffer for temporarily storing the encoded image data; If the remaining capacity of the transmission buffer is greater than or equal to a predetermined value, the frame received from the image processor is transmitted to the transmission buffer. If the remaining capacity of the transmission buffer is less than a predetermined value, the frame received from the image processing unit is an inter frame. If the frame is lost, if the frame transmitted to the transmission buffer immediately before the interla frame is an interla frame, all the frames of the GOP to which the current interla frame belongs are lost and the frame transmitted to the transmission buffer immediately before A transmission frame selector configured to transfer a current interla frame to the transmission buffer in the case of the inter frame; And a transmission unit for extracting the encoded image data temporarily stored in the transmission buffer, converting the encoded image data into a transmission standard suitable for a network state, and transmitting the same. And Determines an integer value obtained by receiving the number of recording frames from a user and dividing the maximum number of output frames output from the image processor by the number of recording frames, and determining the number of integer values for each GOP of the encoded image data received from the image processor. A storage frame selector which stores one frame per frame and loses the remaining frames; And a storage unit having a moving image database for storing the frames selected by the storage frame selecting unit. delete delete delete In encoding the video signal received from the video input device by temporal correlation, the object selected as the reference frame of the inter frames in each GOP is fixed to the intra frame by encoding using the improved MPEG encoding method. In a method for transmitting a video data through a network, (a) converting the video signal received from the video input device into signal-aligned data and encoding the same by the improved MPEG encoding method; (b) (b1) checking a remaining capacity of the transmission buffer when a new frame starts in the encoded image data; (b2) if the remaining capacity of the transmission buffer is greater than or equal to a predetermined value, transmitting the current frame through the transmission buffer; (b3) if the remaining capacity of the transmission buffer is less than a predetermined value and the current frame is an inter frame, losing the frame; And (b4) when the remaining capacity of the transmission buffer is less than a predetermined value and the current frame is an interla frame, when the frame transmitted immediately through the transmission buffer is an interla frame, all the frames of the GOP to which the current interla frame belongs. And transmitting the current interla frame through a transmission buffer in the case of an inter frame, and transmitting the encoded image data at a data loss rate adapted to a change in network transmission rate. And (c) (c1) receiving an input number of recording frames from a user and determining an integer value obtained by dividing the maximum output frame number of the image data encoded in the step (a) by the recording frame number; And (c2) storing one frame for each integer number of frames for each GOP of the coded image data and losing the remaining frames. And a video transmission method using the improved MPEG encoding method.