KR20030056276A - A system and method for video coding - Google Patents

Abstract

PURPOSE: A video encoding system and method are provided to accurately detect an error generated in the event of encoding to enable video communication with high picture quality. CONSTITUTION: An image applied to a video encoding system is split into a plurality of blocks and a number is given to each of the blocks(S202). A specific rule for inserting a resynchronization code into the split blocks is designated according to encoding information of the image. The resynchronization code is inserted into the blocks according to the designated rule to encode the blocks(S207). The encoding information includes the bit rate and frame rate of the image, the size of the image, and a video packet size.

Description

Image encoding apparatus and method thereof {A SYSTEM AND METHOD FOR VIDEO CODING}

The present invention relates to an image encoding apparatus and a method thereof, and more particularly, to an image encoding apparatus capable of providing a high quality image communication through accurate error detection by inserting a resynchronization code according to a predetermined rule during image encoding; It's about how.

In general, when a signal to be transmitted or stored is represented by a string of symbols, the representation of each symbol by a predetermined length code is called encoding.

Here, each symbol is represented by fixed length coding (Fixed Length Coding) and the same length is represented by a code of different length is called Variable Length Coding (VLC). Each of these encodings is a procedure for reducing the amount of signal to be transmitted or stored.

In the variable length coding (VLC), when each symbol is represented by a code of a different length, a short length code is assigned to a symbol having a high frequency of occurrence and a relative length is assigned to a symbol having a low frequency of occurrence. As long as you assign a long sign. As a result, it is possible to represent a signal with smaller bits as compared to fixed length coding, which assigns the same length code to all symbols.

However, although variable length coding (VLC) is effective for compressing the amount of information of a signal, it has the following disadvantages compared to fixed length coding in an environment where channel errors frequently occur.

That is, in the case of fixed length coding, when a code representing an arbitrary symbol is contaminated with a channel error, only the symbol is affected. However, in the case of variable length coding, since a unique length exists for each code for each symbol, when a channel error occurs for an arbitrary symbol encoded with a specific length, a code contaminated with the error may be mistaken for a code for another symbol. In other words, because the synchronization information for each code may be lost, not only the corresponding symbol is lost but also the next successive codes.

As a result, there is a need for a method that can compensate for the above disadvantages when compressing and transmitting information using variable length coding in a channel error environment.

Meanwhile, resynchronization codes used in decoding include a picture start code, a video object start code, a GOB start code, a GOB start code, and a resynchronization marker.

The GOB start code has a feature of being inserted for each block at a predetermined position in a frame regardless of the amount of block coded bits. However, in general, the more motion and the more important part, the more bits are generated. In the case of the GOB start code, since the bit generation amount is not taken into account, an error is more likely to occur in the critical part, and thus, the important part cannot be effectively protected. There is this.

In the case of the resynchronization marker, a method of inserting the resynchronization marker after accumulating the amount of bits generated during block encoding and reaching a predetermined threshold is used. In this case, since the probability of an error is independent of the motion of the image, the disadvantage of the GOB start code can be compensated for.

However, since the location of the resynchronization marker in the screen does not have a predetermined rule, there is a problem in that the decoder cannot detect the resynchronization marker due to the propagation of a generation error and resynchronization marker emulation due to the generation error.

Accordingly, there is a need for an image encoding system that minimizes loss due to an error in a frame and minimizes a period in which image degradation continues, so that image communication can be performed with excellent image quality even in a high channel error rate environment.

The present invention has been made to solve the above problems, and an object of the present invention is to insert a resynchronization code according to a predetermined rule in consideration of the size of the bit stream of each block and the number of the corresponding block according to video encoding, It is an object of the present invention to provide an image encoding apparatus and method for maximizing error robustness according to error detection and re-decoding performed, and to provide excellent image communication through accurate error detection.

1 is a block diagram of an overall image encoding apparatus according to an embodiment of the present invention.

2 is a flowchart sequentially illustrating an operation process of an image encoding apparatus according to an embodiment of the present invention.

3 is a flowchart sequentially illustrating a decoding process of an encoded image.

4A to 4C are diagrams for describing an error detection occurring during an image decoding process and a recovery process therefor.

※ Explanation of code about main part of drawing ※

100: video encoding device

110: encoding information input unit

120: video input unit

130: resynchronization code information

140: encoder

150: image transmission unit

130: decoding device

A feature according to the video encoding method of the present invention for realizing the above object is a method for encoding a video applied from the outside with a variable length using a resynchronization code, wherein a plurality of the video applied from the outside A first step of dividing into blocks and assigning a block number; A second step of designating a predetermined rule for inserting a resynchronization code into the divided block according to encoding information of the applied image; And a third step of inserting and encoding the resynchronization code into the divided block according to the predetermined rule specified in the second step.

In this case, the third step may include: checking whether a sum of bit generation magnitudes generated during encoding of each divided block is equal to or greater than a specific bit generation threshold; Determining whether a number of a corresponding block for encoding is a specific integer multiple if the sum of the identified bit generation amount sizes is equal to or greater than a specific bit generation amount threshold; And encoding the resynchronization code by inserting the resynchronization code into the block if the identified block number is a specific integer multiple.

In addition, the image encoding apparatus for transmitting a bitstream generated using the image encoding method, characterized in that for transmitting the specific integer to the decoding apparatus.

A feature according to the video encoding apparatus of the present invention is a device for encoding a video applied from the outside into a variable length using a resynchronization code, wherein the externally divided video is divided into a plurality of blocks and assigned a block number. A block divider; A resynchronization code insertion designation unit which designates a predetermined rule for inserting a resynchronization code into the divided block according to the encoding information of the applied image; And an encoder for inserting and encoding a resynchronization code into the divided block according to the specified rule, and an image transmitter for transmitting an encoded image applied from the encoder to an external decoding apparatus.

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

1 is a block diagram of an overall image encoding apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the image encoding apparatus 100 according to the present invention uses the encoding information input unit 110, the image input unit 120, the resynchronization code information unit 130, the encoding unit 140, and the image transmission unit 150. It is characterized in that it is connected to the decoding device 160 through a wireless channel or the like.

The encoding information input unit 110 receives encoding information of a corresponding video input from the outside, that is, a bit rate, a frame rate, an image size, and a video packet size (if MPEG-4), which are parameters required for encoding.

The resynchronization code information unit 130 uses the encoding information of the corresponding image received from the encoding information input unit 110 to determine a specific position and a predetermined rule into which the resynchronization code can be inserted and store / manage information thereof.

The present invention is characterized in that a resynchronization code is inserted into a corresponding block if the number of the corresponding block is an integer multiple of a specific integer and the size of the bit stream generated for each block is greater than or equal to a predetermined specific bit.

Here, the resynchronization code is a code used for error detection and decoding at the time of decoding. When the error is detected by the decoding unit 160, a starting point for starting decoding can be started again, and the starting point is the resynchronization code.

As described above, the reason why a new starting point is required when decoding according to an error detection is that the corresponding image is encoded by a variable length coding (VLC) method represented by codes having different lengths.

The encoder 140 performs encoding of the corresponding block according to the encoding information of the corresponding image transmitted from the encoding information input unit 110 and the resynchronization code information transmitted from the resynchronization code information unit 130.

That is, the resynchronization code is inserted and encoded according to a result of comparing the sum of the size of the bit stream of each block of the image received through the image input unit with a threshold (predetermined reference value) and the number of the corresponding block.

The image transmitting unit 150 transmits the specific integer to the decoding apparatus 160 so that the decoding apparatus 160 may use the resynchronization code by using the specific integer when decoding the encoded image, and then transmits the encoded image to the wired / wireless communication network. Through the transmission to the decoding device 160.

The decoding apparatus 160 decodes the encoded image received from the image transmitting unit 150 in the encoding apparatus 100 and provides the encoded image to the corresponding user terminal, and inserts an error occurrence block detected during decoding according to a predetermined rule. Re-decode using sync code and specific integer.

The operation of the video encoding apparatus of the present invention having the above structure will be described using the flowchart of the attached video encoding method as follows.

2 is a flowchart sequentially illustrating an overall operation of an image encoding apparatus according to an embodiment of the present invention.

Referring to FIG. 2, the encoder 140 divides a plurality of blocks from an image received from the image input unit 120 (S201) and assigns a number to each block (S202).

Subsequently, the encoding process for each divided block is performed. Before this, it is determined whether to insert a resynchronization code. In the determination, the resynchronization code information unit 130 determines whether the predetermined rule is satisfied and inserts the resynchronization code.

In this case, the inserted resynchronization code is inserted into the corresponding block according to a predetermined rule according to the present invention. First, the calculation result of [Equation 1] considering the encoding information of the corresponding image received from the encoding information input unit 110. Determine a specific integer according to

In Equation 1, Fr is a frame rate, VPThr is a bit amount threshold between resynchronization codes, MBNum is a number of blocks in a frame, and Br is a bit rate.

According to the calculation result of [Equation 1], a resynchronization code is inserted into a block of a number corresponding to an integer multiple of a specific number (N). In this case, another rule to consider is to insert a resynchronization code into the corresponding block when the amount of bits generated during encoding becomes more than a predetermined bit.

That is, in the encoding apparatus according to the present invention, in reinsertion of a resynchronization code used for error detection and re-decoding, if the block number is an integer multiple of a specific integer and the amount of bits generated during encoding is more than a specific bit, the resynchronization code It characterized in that to insert.

First, it is determined whether the sum of the bit stream sizes per block generated before the encoding of the corresponding block is a predetermined reference value, that is, a predetermined specific bit or more (S203).

As a result of the determination, if the sum of the bit stream sizes per block is equal to or less than a predetermined specific bit, block encoding is performed (S207). On the other hand, if the sum of the bit stream sizes per block is more than the predetermined specific bit, the resynchronization code information unit ( Check whether the schedule rule received from 130 is satisfied.

That is, it is checked whether the number of the corresponding block is a multiple of a specific integer (for example, 5, etc.) (S204), and if the result of the check is not a multiple of the specific integer 5 of the number of the corresponding block, block encoding is performed ( On the other hand, if the number of the corresponding block is a multiple of the specific integer 5, the sum of the bit stream sizes for each block is initialized (S205). That is, to make the accumulated bit zero.

Thereafter, after the resynchronization code is inserted (S206), the macroblock is encoded (S207).

After the encoding of the macroblock is finished, the cumulative number of bits is updated (S208), and then it is determined whether the current block which has been encoded is the last block of the frame (S210).

As a result of the determination, if it is not the last block, block encoding is performed through the above process, whereas if it is the last block, it is determined whether the current frame that has been encoded is the last frame (S210).

As a result of the determination, if it is not the last frame, the next frame is received from the image input unit 120 and the encoding is performed through the above process, whereas if the last frame, the encoding is terminated.

3 is a flowchart schematically illustrating an overall operation of an image communication system for transmitting an encoded image according to an embodiment of the present invention.

Referring to FIG. 3, the image transmitter 150 transmits a specific integer to be used for resynchronization code detection to the decoding apparatus before transmitting the encoded image (S301), and then decodes the encoded image through the wired / wireless communication network 160. (S302).

Thereafter, the decoding apparatus 160 decodes the encoded image received from the image transmitter 150 (S303) and transmits the encoded image to the user terminal (S306).

The decoding apparatus 160 searches whether an error due to a wired / wireless channel or an error occurs during transmission while decoding the encoded image (S304).

As a result of the check, if an error is detected, a starting point is required to start decoding again. Since the starting point is a resynchronization code inserted according to a predetermined rule, the decoding is performed using the resynchronization code (S305) and then the corresponding image is transmitted to the user terminal. It is transmitted (S306).

4A to 4C are diagrams for describing an error detection and deletion process occurring during an image decoding process.

During the decoding process of the encoded image data, if an error is detected as shown in FIG. 4A, subsequent data 411 is not decoded. That is, if there is no point for resynchronization from the picture start code 410 to the next picture start code 410 ', the data 411 after error detection is not decoded at all.

To do this, by inserting a resynchronization code that can be resynchronized in the middle of the video packet, the amount of information lost is reduced.

That is, as shown in FIG. 4B, a resynchronization code is inserted between the picture start codes 410 and 410 'to reduce the amount of information 411' lost.

On the other hand, decoding the bit stream with the actual error occurs as shown in FIG. 4C. That is, the number of blocks where an error is detected is 29, and the next block number is found by checking the next resynchronization code.

In such a case, an error occurs before the video packet 1 430, thereby erroneously decoding the preceding block number 25, and an error is detected in the video packet 2 440 portion due to the error propagation, or the video packet 3 (450). An error in the header may have caused the block number to be decoded incorrectly.

In order to find out the cause of the detected error, the video encoding apparatus according to the present invention regularly inserts a resynchronization code into a block number corresponding to an integer multiple of a specific integer (for example, 5) during encoding. Using this, after the error is detected, the next resynchronization code is found to confirm the block number, and as a result, it can be seen that an error occurs in the third video packet 450 in which 19 is searched instead of an integer multiple of 5. Therefore, the third video packet 450 is immediately removed and the next decoding process is subsequently performed.

As described above, the re-decoding start point is easily found through the resynchronization code inserted according to a predetermined rule during encoding, thereby minimizing the loss portion caused by the error and minimizing the section where the degradation of image quality continues. It enables high quality video communication even in high environments.

The drawings and detailed description of the invention are merely exemplary of the invention, which are used for the purpose of illustrating the invention only and are not intended to limit the scope of the invention as defined in the claims or in the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The video encoding apparatus and the method according to the present invention inserts and encodes a resynchronization code according to a predetermined rule in consideration of the size of the bit stream of each block and the corresponding block number according to the video encoding, and then transmits the same to the decoding apparatus. In addition, it is possible to not only maximize the error robustness effect by easily searching for the error detection cause that occurs during decoding, but also to minimize the loss caused by the error in the frame and to minimize the section where the deterioration of image quality continues. There is an effect that can provide a high quality video communication through accurate error detection.

Claims (6)

In the method for encoding a video applied from the outside with a variable length using a resynchronization code, A first step of dividing the image applied from the outside into a plurality of blocks and assigning a block number; A second step of designating a predetermined rule for inserting a resynchronization code into the divided block according to encoding information of an image applied from the outside; And A third step of inserting and encoding a resynchronization code into the divided block according to the predetermined rule specified in the second step Image encoding method comprising a. According to claim 1, The third step, Confirming whether a sum of bit generation magnitudes generated during encoding of each divided block is equal to or greater than a specific bit generation threshold; Determining whether a number of a corresponding block for encoding is a specific integer multiple if the sum of the identified bit generation amount sizes is equal to or greater than a specific bit generation amount threshold; And Inserting and recoding the resynchronization code into the block if the identified block number is a specific integer multiple. Image encoding method comprising a. The method of claim 2, The specific integer is the following equation, And a specific integer = {(frame rate x threshold amount of bits between resynchronization codes x number of blocks in a frame) / bit rate}. According to claim 1, The encoding information is And a bit rate, a frame rate, an image size, and a video packet size of the image. In the device for encoding a video applied from the outside with a variable length using a resynchronization code, A block dividing unit dividing the image applied from the outside into a plurality of blocks and assigning a block number; A resynchronization code insertion designation unit for designating a predetermined rule for inserting a resynchronization code into the divided block according to the encoding information of the image applied from the outside; An encoder which inserts and encodes a resynchronization code into the divided block according to the specified rule; And An image transmitter for transmitting an encoded image applied from the encoder to an external decoding device. An image encoding apparatus comprising a. The method of claim 5, The schedule rule, And inserting the resynchronization code when a bit generation amount generated during encoding of each divided block is equal to or more than a specific bit and the number of the corresponding block is an integer multiple of a specific integer.