Method for processing error code of compressed image during transmission

FIELD: image transferring equipment engineering, possible use in multimedia communications.

SUBSTANCE: in accordance to method, when error codes are detected on receiving side, data of code stream of image with error codes are refused prior to decoding of data of code stream of image, and refused data of code stream of image are replaced with data of code stream of image, positioned in appropriate position of previous frame, and data of code stream of image are encoded continuously. Also, an array of marks is set up for data of code stream of image prior to encoding on receiving side, to perform recording of positions, where error codes have been detected.

EFFECT: possible avoidance of transfer of internal frame images on transmitting side and of frozen images on receiving side, or decrease of their occurrence periods, thus improving quality of image.

7 cl, 2 dwg

 

The technical field

The invention relates to the transmission of images in multimedia communications, and more specifically to a method of processing error codes received when transferring compressed coded image.

Level, prior to the invention of

Technology transfer images, especially the technique of transmission of the compressed coded images, widely used in video conferencing and video phones. In bidirectional video communication in real time, such as video conference, video data is compressed in the form of code data stream for transmission in accordance with international standards. Standards NH proposed by the International telecommunication Union ITU-T, such as N and n are common standards that are currently used to encode images. Standards NH a digital video format that is defined as a common intermediate format CIF and quarter common intermediate format QCIF, which are the formats of standardized images for video conferencing. These image formats can be used in various international television standards such as PAL, NTSC and SECAM, and so on.

For example, the format CIF will be briefly described the structure of the digital video formats defined in the standards NH. Figure 1 and figure 2 shows respectively the composition fo the Mat H.261 CIF and CIF format H.263. As shown in figure 1 and figure 2, each frame image is divided into numerous groups of blocks GOB, and each GOB is divided into multiple macroblocks MB. MB can continue to divide, but because it does not relate to the present invention, and the description of this in the future is not given. In accordance with the format of the image data code stream of the compressed encoded image formed according to the standards NH are placed at multiple levels during transmission. Among these levels, the level of the image consists of a header image level and data level GOB, the level GOB consists of a header level GOB and data at the level of the MB, the MB level consists of a header level MB and data at the next level, and so on. Because of the redundancy in the compressed code stream is low, the image quality at the receiving side much stronger impact on the error codes of the transmission channel, obtained by transfer.

At the receiving side is commonly used detection method the error code, such as forward error correction FEC. Upon detection of an error code displays the image at the receiving side is "frozen", that is, stops the decoding process of the image data in the video data that can be directly broadcast. At the same time from the reception side to the lane is the giver send a team to Bystroobnovlathan (FastUpdate) through management conference. After taking command Bystroobnovlathan the transmitting side encodes the current frame through the encoding inside a frame, and sends the encoded frame and sets the bit location permissions "freezing" in the code flows as reliability. After detecting the location of the bits permissions "freezing" in the code flow is set as the reliability, the receiving side cancels the freeze display and decodes the image data in the video data that can continuously stream.

The disadvantage of the prior art is that, even if there are multiple error codes the frozen image and the intra-frame encoded images of low quality will often appear during decoding of the image data. Especially in a multipoint videoconference, when the terminal performs broadcast transmission if the error codes that appeared on the lines of a certain receiving terminal, intra-frame encoded images of low quality will often be all terminals used in video conferencing due to the above-mentioned processing method for error codes. Typically, this is unacceptable for users.

The invention

The objective of the invention is to perform a method of handling code is in error when transferring compressed coded image. This method prevents transmission of intra-frame images on the transmission side and the frozen image on the receiving side, or to reduce the periods of occurrence. Thus, it is possible to improve the image quality.

In order to solve this problem, the method according to the present invention includes the steps according to which: the presence of a detected error codes on the receiving side reject code data image stream error code before decoding the data code stream image and replace rejected data code stream image to image data located in the corresponding location of the previous frame, then continuously decode the data code stream of the image.

It is preferable that the method further comprises a step, in accordance with which set the array of labels for the data code stream image before decoding at the receiving side in order to record the locations, where they found the error codes.

It is preferable that the data code stream image with error codes that will be rejected before decoding the data code stream image at the receiving side, data are in GOB with the error codes provided that the coding standard image is Oia is N.

It is preferable that the step of rejecting data code image stream error code before decoding data coded image stream provided that the coding standard image is n, includes the sub-steps according to which:

if error codes were found in the first GOB of the frame, reject all data in the entire frame, or

if error codes were found in a GOB, other than the first GOB of the frame and if the frame identifier (GFID) GOB error code is identical to the GFID of the next GOB reject data in GOB with error codes, or

if error codes were found in a GOB, other than the first GOB of the frame, and if the GFID GOB error code is not identical to the GFID of the next GOB, do a reverse search of the next frame header at the receiving side and reject all data between the start position of the GOB with error codes and the initial position of the next frame header.

It is preferable that the method further comprises a step, in accordance with which set a fixed number of MB each frame in the intraframe coding mode on the transmission side and creates MB of adjacent frames, which will be located next to the screen.

It is more preferable that the number of MB that are installed in the intraframe coding mode in each ka is re for CIF images, is three, and the number of their images to other formats can be proportionally adjusted in accordance with the size of the images.

It is preferable that the various principles of treatment apply in the situation of codes with a large number of errors in the case of codes with fewer errors. In the situation of codes with a large number of errors special image is displayed on the receiving side.

Compared with the prior art real user requirements and actual situation videoconferencing considered to a greater extent in the present invention that prevents transmission of intra-frame images on the transmission side and the frozen image on the receiving side, or to reduce the periods of appearance with the present invention. As the scene of the conference are small changes, error codes can be hidden and, thus, improve the quality of images.

Brief description of drawings

Figure 1 depicts the structure, which includes the format In CIF. Figure 2 depicts the structure, which includes the format HYPHA n CIF.

Detailed description of the invention

Below is a more detailed description of the invention with reference to the accompanying drawings and options for implementation.

In prior art receiving immediate side is about to freeze the displayed image after detection of the error codes and sends a command to Bystroobnovlathan to the transmitting side via the conference management. When receiving the command, the transferor immediately encodes the current frame through the encoding inside a frame and sends it, and sets bit permissions "freezing" in the code stream as reliability. After the discovery location bits permissions "freezing" is set as the reliability, the receiving party shall permit the display of frozen images. With this way of handling error codes, even if there are small errors codes, freeze image and the intra-frame coded image of low quality will often appear during decoding of the image data that does not satisfy the users.

The authors of the present invention have found that as the scene changes quite strongly during video conferencing or video telephony, data, error code, you can replace the data arranged in the same location of the previous frame in many cases without the need to freeze the image and re-transmitting the data. With this processing method can improve the image quality at the receiving side, and it is more acceptable for users compared with the prior art.

In a preferred embodiment of the invention adopted a code stream at the receiving side first is raverat the cyclic redundancy code CRC. The video data is then passed to the level of videodatabase through videotranny buffer. Video in videoframes buffer data are FEC frame. Once the data has been verified, and the decoder has received their frame formats, data clean code image stream are extracted from the data. Data clean code image stream is buffered clean code thread to wait for the decoding. In this preferred embodiment, the buffer clean code stream is set to the array of labels used to record the location where they found the error codes. For an array of labels can be set per element according to the buffer clean code stream. This means that the length of the array of labels is equal to the data length code stream in the buffer clean code stream, and each value of the array element label indicates whether the corresponding bit of the data code stream error code.

In this embodiment, the situation associated with error codes can be divided into two categories: the situation with codes with a large number of errors and codes with a small number of errors, and in accordance with this produce processing.

For codes with multiple errors error detection is first produced using the FEC method, which is recommended with the public standards N and n. If there are error codes, the FEC frame is rejected and the corresponding location of the array of labels are marked with representing an error code.

When processing data clean code flow without FEC frame first check to see whether there is any sign that represents the error code in the array of labels. If the error code is absent, the data is sent directly to the module decoding the code stream. If there is an error label or tag errors, it is necessary to perform processing for rejecting data. When using standard n this processing includes the following three stages:

A. determine the sequence number of GOB, where they found the error codes, and the initial position of the GOB in the buffer, which can be performed using a direct search title GOB,

C. if GOB is the first GOB of the frame, then do a reverse lookup of the frame header of the next frame and reject all data in the entire frame, where they found the error codes, and

C. if the GOB is not the first GOB of the frame, produce a direct search frame header of the previous GOB and make an entry GFID, meanwhile, produce a reverse lookup of the frame header of the next GOB and make an entry GFID; if these two GFID identical, then reject the data in GOB with the error code, otherwise do a reverse lookup of the frame header of the next frame and reject all the data between the starting position of the GOB with error codes and all data of the next frame header. The above GFID is a mark bit, which is defined in the standard Ne, it represents the frame number, which is GOB. If two GFID are different, then show that the two GOB are located in different frames. On the contrary, if two GFED identical, we show that two GOB are in the same frame.

When using standard N treatment for rejected data as follows. Determine the initial position of the GOB, where they found the error codes, and the initial position of the next GOB in the buffer, and reject all data between the two initial positions. This can be done by forward and reverse search titles GOB.

Once the data has been rejected, perform a coverage error on the side of decoding, i.e. rejected the image data is replaced with the corresponding data in the previous frame.

After the above processing, since the scenes video conferencing have small changes, you can have a good cover codes with small errors. But when, after the above processing, the image has a large moving object, the moving parts will remain visible mark. How to force vnutribruchnogo coding can be used to resolve the increasing footprint. For CIF image regardless of what the initial mode to the financing is interframe encoding mode or a mode with no coding forced three MB per frame using the intraframe coding. Three MB frame can be placed next to, for example, three MB are arranged one after another in a row, in a column or on an orthogonal line. Three MB can also be located separately, but the three MB of available frame should be located on the screen next to the MB of the previous frame. For example, three MB of the current frame are selected in accordance with MB of the previous frame to increase or decrease the sequence number MB. Since the increase in the error image is always next time for MB, the increase in footprint is most effectively removed by using serial mode, not arbitrary mode.

For codes with a large number of errors, even if processed, the image quality is still bad. In this scenario, you receive a special image, such as blue screen savers showing what occurred error codes.

Compared with the prior art real user requirements and the actual situation of the conference were discussed more fully in the present invention that allows the present invention to avoid freezing of the image at the receiving side, or to reduce the periods of occurrence. As the scene of the conference who have small changes, the error codes can be well hidden and, thus, improve the quality of images.

Although the present invention has been described with reference to specific exemplary embodiments of, it is clear that various modifications and changes may be made in these embodiments implement without deviating from the broader scope of the invention as set forth in the claims. Accordingly, the description and drawings should be considered in the illustrative sense and not in a restrictive sense.

1. The way to handle error codes when sending compressed coded image between a transmitting party and a receiving party, comprising stages, whereby in the presence of a detected error codes on the receiving side reject code data image stream error code before decoding the data code stream image, and replace rejected data code stream of the image data coded image stream, located in the corresponding location of the previous frame, and then continuously decode the data code stream of the image.

2. The method according to claim 1, characterized in that it further comprises the step, in accordance with which set the array of labels for the data code stream image before decoding at the receiving side for the button to record the locations, where were detected error codes.

3. The method according to claim 1, characterized in that the data code stream image with error codes that will be rejected before decoding the data code stream image at the receiving side, data are in the group of blocks (GOB) error code, provided that the coding standard image is N.

4. The method according to claim 1, characterized in that the step of rejecting data code image stream error code before decoding data coded image stream provided that the coding standard image is n includes a step, in accordance with which, if the error codes were found in the first GOB of the frame, reject all data in the entire frame, or if you have detected the error codes in a GOB, other than the first GOB of the frame and if the frame identifier (GFID) GOB error code is identical to the GFID of the next GOB, then reject the data in GOB with error codes, or, if the error codes were found in a GOB, different from the first GB of the frame, and if the GFID GOB error code is not identical to the GFID of the next GOB, then do a reverse search of the next frame header at the receiving side and reject all data between the start position of the GOB with error codes and the initial position of the next frame header.

5. The method according to claim 1, characterized in that it further contains the inhabitants stages, under which set a fixed number of macroblocks (MB) in each frame in the intraframe coding mode on the transmission side and creates MB of adjacent frames, which will be located next to the screen.

6. The method according to claim 5, characterized in that the number of MB that are installed in the intraframe coding mode in each frame for images common intermediate format (CIF), is three, and the number of MB that are installed in the intraframe coding mode in each frame for images to other formats, can be proportionally adjusted in accordance with the size of the images.

7. The method according to claim 1, characterized in that it further comprises the step, in accordance with which perform different processing for codes with a large number of errors and the situation of codes with fewer error codes and if we have a situation with codes with a large number of errors display a special image at the receiving side.



 

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