CN1134174C - Video error concealing method in ground digital TV broadcast - Google Patents
Video error concealing method in ground digital TV broadcast Download PDFInfo
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Abstract
The present invention belongs to the technical field of multimedia transmission in ground digital television broadcasting. When the method decodes video signals at a receiving end, video image information lost due to transmission errors is effectively restored according to the correlativity between the time domain and the spatial domain of video compression data. The method comprises the steps: time domain compensation in a current frame or a reference frame, block match searching in the reference frame and hiding of error macro-blocks. The reliability of the video transmission of a ground digital television broadcasting system is obviously enhanced by utilizing the method, so the technology is one of the reliable reception techniques for ground digital television broadcasting systems.
Description
Technical field the invention belongs to the radio multimedium transmission technique field, relates to the reliable reception technology that adopts multimedia transmission in MPEG-2 video compression standard and the relevant ground system of digital television broadcast.
Background technology is current, the U.S., Europe and Japan have worked out corresponding ground digital television broadcast (Digital Terrestrial TV Broadcasting:DTTB) standard, and China also works out the ground digital television broadcast agreement that is suitable for China at positive tissue.In received terrestrial digital broadcasting, shadow effect, multipath fading, Doppler frequency shift and various noise and interference can make received signal power produce very big fluctuation, its fluctuating range can reach 10dB even higher, and this will have a strong impact on the reliability of digital signal transmission.Video source in the ground digital television broadcast adopts the MPEG-2 compression standard, yet does not comprise the relevant details of the information source coding and decoding method of antagonism overland propagation mistake in the current standard.Therefore, the video transmission error hidden algorithm based on MPEG-2 is extremely important and a need to be resolved hurrily technology of DTTB system.
Propose some concealing video errors algorithms in the existing research paper, comprised following a few class:
Time domain motion compensation: utilize the relativity of time domain of video image, the image information of predicting and recovering to lose according to the motion vector information that correctly receives image information on every side because of mistake.This algorithm has error concealment effect preferably for the low bit-rate video packed data, but and is not suitable for high bit-rate video image.
The block matching motion search: the image information of utilizing motion search to find best match position to recover to lose, can reach good mistake recovery effects, but its practicality is owing to high computational complexity is restricted.
Spatial domain error concealment technology: this class technology tends to produce significantly " blocking effect " at the more image section of details, and its image recovery effects is unsatisfactory.
Summary of the invention the objective of the invention is to, for overcoming the weak point of prior art, propose a kind of new video error concealing method, can realize that effective mistake image recovers by less relatively computation complexity, thereby improve the reliability of video transmission in the ground system of digital television broadcast.
Video error concealing method in a kind of ground system of digital television broadcast that the present invention proposes is characterized in that, when the receiving terminal video decode is found mistake, carries out error concealment, may further comprise the steps:
1) according to the motion vector of the correct macro block around the present frame erroneous macroblock, perhaps in the reference frame with the motion vector of the correct macro block of erroneous macroblock same position and location about thereof, come the time domain compensation vector of prediction error macro block, the time domain compensation vector representation that obtains of prediction the relative position displacement vector between present frame erroneous macroblock position and the reference frame compensated position, the position of present frame erroneous macroblock is added that the time domain compensation vector has just obtained the time domain compensation position in the reference frame:
2) the reference frame time domain compensation position that previous step is obtained is as original position, in the certain limit of reference frame, the piece match search is carried out in the zone above or below the erroneous macroblock position, obtain mating vector and corresponding matched position, the certain limit of said reference frame is meant that the time domain compensation position that obtains with previous step is the square area at center, the distance at each limit and center is a W pixel, W is an integer, the length of side of whole square area is that (2 * W+1) individual pixels comprise (2 * W+1) altogether
2Individual pixel;
3) the reference frame compensated position is added the coupling vector that previous step obtains, just obtained the position of coupling macro block in the reference frame, the macro block that will be arranged in reference frame coupling macro block position copies present frame to and substitutes erroneous macroblock, thereby realizes the error concealment of present frame erroneous macroblock.
Effect of the present invention is under relatively low computation complexity, to have improved the effect of error concealment, thereby improved the reliability of video transmission in the ground system of digital television broadcast.
Description of drawings
Fig. 1 is a concealing video errors algorithm flow chart of the present invention.
Fig. 2 is the schematic diagram of time domain compensation method of the present invention;
Wherein, a is in the present frame, and b is in the reference frame
Fig. 3 is the schematic diagram of erroneous macroblock hidden method of the present invention.
Fig. 4 is for adopting the MPEG-2 video decode flow chart of concealing video errors algorithm of the present invention.
Fig. 5 rebuilds the effect contrast figure through the video image after the transmission in the embodiment of the invention.
Embodiment is elaborated to principle of the present invention below in conjunction with each drawings and Examples.
The present invention proposes the video error concealing method in a kind of ground system of digital television broadcast.At first in the receiving terminal video decoding process, carry out error detection occurs, adopt error detecting method in general, judge whether mistake has taken place in the video code flow based on the grammatical and semantic of compressed video stream.If wrong in the discovery code stream, when the receiving terminal video decode, carry out following error concealment treatment step (as shown in Figure 1) successively:
1) time domain compensation in present frame or the reference frame, prediction obtains the time domain compensation vector of erroneous macroblock and corresponding compensation position in reference frame;
2) the piece match search in the reference frame, with the center of the compensated position in the reference frame that obtains in the previous step time domain compensation as the hunting zone, in certain hunting zone of reference frame to erroneous macroblock above or below macro block carry out the piece match search, obtain mating vector;
3) erroneous macroblock is hidden, and the compensated position in the reference frame that obtains with first step time domain compensation is a starting point, and the macro block of matched position copies present frame to and substitutes erroneous macroblock in the reference frame of the coupling vectors directed that previous step piece match search is obtained.
Said time domain compensation is the time domain compensation vector that comes the prediction error macro block according to the motion vector of erroneous macroblock (EMB) correct macro block on every side, and its computational methods are as follows,
MV wherein
EMBPredict the outcome MV for erroneous macroblock time domain compensation vector
iBe the motion vector of correct macro block around the erroneous macroblock, k is for adopting the number of the correct macro block of inter prediction encoding on every side.When erroneous macroblock adopts inter prediction encoding, choose the correct macro block that does not comprise the left and right sides in the present frame around the erroneous macroblock, as the macro block among Fig. 2 a 1, macro block 2 ..., macro block 6, k is 6 to the maximum; When erroneous macroblock adopts intraframe coding, choose and comprise current location and correct macro block on every side thereof in the reference frame, as the macro block among Fig. 2 b 0 be in the reference frame with the macro block of erroneous macroblock same position, and the macro block 1 among Fig. 2 b, macro block 2 ..., macro block 8 is 8 macro blocks around the macro block 0, k is 9 to the maximum.Prediction obtains MV
EMBAfter, the macro block on the then corresponding compensated position that obtains in the reference frame.
Said match search be meant in the certain limit search, for the macro block of each locational N * N size, according to the average absolute value error criterion (Mean Absolute Difference MAD) carries out following matching detection,
Wherein, F
c(. .) for being arranged in the pixel value of the macro block above or below the erroneous macroblock, F in the present frame
p(. .) expression is arranged in the pixel value of the macro block above or below the macro block of current detection position, (K in the reference frame, l) represent the coordinate of current detection piece top left corner pixel, (x, y) expression current detection piece is with respect to the skew of search original position, and N is the length of side (pixel number) of macro block.By detecting the whole positions in the hunting zone, can obtain minimum position of average absolute value error (MAD) and corresponding coupling vector.That is to say that we are to the macro block above or below the erroneous macroblock in the present frame, carry out match search in the certain limit of reference frame to obtain mating vector.Certain limit in the reference frame here is meant that the compensated position that obtains with previous step is the square area at center, the distance at each limit and center is a W pixel, W is an integer, so the length of side of whole square area is that (2 * W+1) individual pixels comprise (2 * W+1) altogether
2Individual pixel.
Said erroneous macroblock is hidden and to be meant with a macro block in the reference frame and to substitute erroneous macroblock in the present frame.As shown in Figure 3, at first being starting point with the macro block of erroneous macroblock (EMB) same position in the reference frame, the compensation vector that obtains according to first step time domain compensation obtains compensated position, be starting point with this compensated position again, the coupling vector that obtains according to previous step piece match search obtains matched position, and the macro block on this matched position just is used to substitute the erroneous macroblock in the present frame.
The present invention is further illustrated below in conjunction with embodiment.
Table 1. information source feature
| The video source sequence | The Moving Picture Experts Group-2 cycle tests |
| Video image brightness frame resolution | 720 * 576 pixels |
| Chroma format | Y∶U∶V＝4∶2∶2 |
| The source encoding frame rate | 25 frame/seconds |
| The source encoding bit rate | 5M bps |
In the present embodiment, source code stream packets length is 188 bytes, and the average mistake packet rate that channel error code causes is 3 * 10
-2Given source properties is as shown in table 1, video source is the Moving Picture Experts Group-2 video sequence, and the resolution of each luminance frame is 720 * 576 pixels, and chroma format is Y: U: V=4: 2: 2, the source encoding frame rate was 25 frame/seconds, and the source encoding bit rate is about 5M bps.
In the present embodiment, the MPEG-2 video decode flow process of employing as shown in Figure 4.In decode procedure, the compressed video stream of input is carried out error detection occurs based on the video code flow grammatical and semantic, if do not find mistake then carry out normal video decipher reestablishment.If find wrongly, at first carry out again synchronously, promptly skip the code stream of the whole video image layer (Slice) that comprises mistake, it is synchronous to find the original position of next video image layer bit stream to recover video decode, continues the video code flow of back is decoded; Simultaneously, in comprising the video image layer of mistake, comprised many image macro, all thought erroneous macroblock, and it has been carried out error concealment handle for each such image macro.Error concealment is handled needs not find wrong code stream information as reference information that its concrete steps are described, and will be described further below in the above.
In the present embodiment, Video Decoder can detect many macro blocks that make a mistake, and all adopts error concealment algorithm described above to handle for each erroneous macroblock, the image macro information of recovering to lose.The example that is treated to so that an erroneous macroblock is carried out further specifies the error conceal method that the present invention proposes below.
In the present embodiment, the length of side of all macro blocks is 16 pixels.The erroneous macroblock of choosing is in second frame, and the pixel in its upper left corner is positioned at several from the top down the 161st row, several from left to right the 145th row, and promptly its top left corner pixel is arranged in (145,161) pixel position of second frame.
The first step is carried out time domain compensation.Because this erroneous macroblock adopts inter prediction encoding, predict the time domain compensation vector so adopt inherent its 6 the correct macro block on every side of present frame, macro block 1 as shown in Fig. 2 left hand view, macro block 2 ..., macro block 6, k=6, can obtain its time domain compensation vector according to formula 1 is MV
EMB=(20,0) then obtain corresponding time domain compensation position and are (165,161) the pixel position in the reference frame.
Second step was carried out the piece match search.In this embodiment the macro block that is positioned at the erroneous macroblock top is carried out the piece match search, choose with reference frame (165,161) the pixel position is the center, the length of side is the square region of search of 5 pixels, calculate MAD according to formula 2, promptly calculate macro block directly over the macro block that top left corner pixel in the reference frame is arranged in this square area and the average absolute value error (MAD) between the macro block of erroneous macroblock top, find a macro block position of MAD minimum.Actual result is that the macro block that top left corner pixel is positioned at the macro block top of reference frame (165,159) pixel position is the macro block of MAD minimum, promptly mates vector and is (0 ,-2), and corresponding error macroblock match position is (165,159).
The 3rd step carried out erroneous macroblock and substitutes.According to top two results that step obtains, the macro block that is positioned at (165,159) with top left corner pixel in the reference frame copies present frame to and substitutes erroneous macroblock.
For detected each erroneous macroblock, handle according to being similar to top step.For this algorithm effects is carried out objective evaluation, adopt the Y-PSNR of reconstructed image that this algorithm performance is assessed here.(Peak Signal to Noise Ratio PSNR) is defined as Y-PSNR
Wherein, PSNR is the Y-PSNR of image, f (i, the j) pixel value of each pixel in the expression original image, f
r(M and N are respectively the wide and high of image for i, j) each pixel value in the expression reconstructed image.It among Fig. 5 the PSNR curve of the reconstruction video image of present embodiment.Wherein, uppermost curve is Y-PSNR (Peak Signal to Noise Ratio, PSNR) curve, the just errorless PSNR curve that transmits the back at the reconstruction video image of Video Decoder end of the video image of video encoder end reconstruction; Nethermost curve is the PSNR curve of the reconstruction video image that decoder end obtains when not carrying out error concealment; Middle curve is the PSNR curve of the reconstruction video image that decoder end obtained after the error concealment above adopting was handled.The mean P SNR of these three curves is respectively 27.6dB, 24.0dB and 26.9dB.
Claims (1)
1, the video error concealing method in a kind of ground system of digital television broadcast is characterized in that, when the receiving terminal video decode is found mistake, carries out error concealment, may further comprise the steps:
1) according to the motion vector of the correct macro block around the present frame erroneous macroblock, perhaps in the reference frame with the motion vector of the correct macro block of erroneous macroblock same position and location about thereof, come the time domain compensation vector of prediction error macro block, the time domain compensation vector representation that obtains of prediction the relative position displacement vector between present frame erroneous macroblock position and the reference frame compensated position, the position of present frame erroneous macroblock is added that the time domain compensation vector has just obtained the time domain compensation position in the reference frame;
4) the reference frame time domain compensation position that previous step is obtained is as original position, in the certain limit of reference frame, the piece match search is carried out in the zone above or below the erroneous macroblock position, obtain mating vector and corresponding matched position, the certain limit of said reference frame is meant that the time domain compensation position that obtains with previous step is the square area at center, the distance at each limit and center is a W pixel, W is an integer, the length of side of whole square area is that (2 * W+1) individual pixels comprise (2 * W+1) altogether
2Individual pixel;
5) the reference frame compensated position is added the coupling vector that previous step obtains, just obtained the position of coupling macro block in the reference frame, the macro block that will be arranged in reference frame coupling macro block position copies present frame to and substitutes erroneous macroblock, thereby realizes the error concealment of present frame erroneous macroblock.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103957413A (en) * | 2014-01-13 | 2014-07-30 | 南京达鹏信息技术有限公司 | Real-time error-code concealment method and device for mobile network video communication application |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003259369A (en) * | 2002-02-28 | 2003-09-12 | Techno Mathematical Co Ltd | Error concealment method employing electronic watermark of moving picture |
| KR100531895B1 (en) * | 2004-02-26 | 2005-11-29 | 엘지전자 주식회사 | Apparatus and method for concealing block error of image in mobile communication system |
| WO2006122313A2 (en) * | 2005-05-11 | 2006-11-16 | Qualcomm Incorporated | A method and apparatus for unified error concealment framework |
| BRPI0710093A2 (en) * | 2006-04-20 | 2011-08-02 | Thomson Licensing | redundant video encoding method and apparatus |
| CN101101753B (en) * | 2006-07-07 | 2011-04-20 | 乐金电子（昆山）电脑有限公司 | Audio frequency frame recognition method |
| CN102098517B (en) * | 2006-08-28 | 2014-05-07 | 汤姆森许可贸易公司 | Method and apparatus for determining expected distortion in decoded video blocks |
| JP4427086B2 (en) | 2006-12-27 | 2010-03-03 | パナソニック株式会社 | Video decoding device |
| JP2009081576A (en) * | 2007-09-25 | 2009-04-16 | Toshiba Corp | Motion picture decoding apparatus and motion picture decoding method |
| CN101287128B (en) * | 2008-05-29 | 2010-10-06 | 中兴通讯股份有限公司 | Error recovery method for video decoding |
| CN103648048B (en) * | 2013-12-23 | 2017-04-05 | 乐视网信息技术（北京）股份有限公司 | Intelligent television video resource searching method and system |
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| CN103957413A (en) * | 2014-01-13 | 2014-07-30 | 南京达鹏信息技术有限公司 | Real-time error-code concealment method and device for mobile network video communication application |
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