• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.1
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• pp.404-421
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• 2020

A reversible data hiding scheme in JPEG compressed bitstreams is proposed, which could avoid decoding failure and file expansion by means of removing of bitstreams corresponding to high frequency coefficients and embedding of secret data in file header as comment part. We decode original JPEG images to quantified 8×8 DCT blocks, and search for a high frequency as an optimal termination point, beyond which the coefficients are set to zero. These blocks are separated into two parts so that termination point in the latter part is slightly smaller to make the whole blocks available in substitution. Then spare space is reserved to insert secret data after comment marker so that data extraction is independent of recovery in receiver. Marked images can be displayed normally such that it is difficult to distinguish deviation by human eyes. Termination point is adaptive for variation in secret size. A secret size below 500 bits produces a negligible distortion and a PSNR of approximately 50 dB, while PSNR is also mostly larger than 30 dB for a secret size up to 25000 bits. The experimental results show that the proposed technique exhibits significant advantages in computational complexity and preservation of file size for small hiding capacity, compared to previous methods.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.75-77
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• 2006

In this paper, the technology of the conformance test for Broadcast Web Site Service (BWS) which is one of the data services of the T-DMB (Terrestrial Digital Multimedia Broadcasting) is proposed. First, the standard of the BWS Service is introduced and then the method of the conformance test of BWS bitstream and BWS receiver module is provided. A BWS bitstream analyzer is implemented for use in verifying the transmitted BWS bitstreams. To provide a means for the receiver manufactures to verify their own BWS receiver modules, a receiver test suite is developed including BWS test bitstreams and a BWS reference receiver module. The BWS bitstream analyzer includes the analysis function for the conformance test of MOT protocol, HTML, PNG, MNG, JPEG, and Ecma Script. Also, it was actually used for verifying the BWS test bitstreams. In the course of developing a HWS receiver module, 4he BWS receiver module under test can be verified by comparing the results of the BWS reference receiver module with those of the receiver module under test. when the same BWS test bitstreams are fed into the two receiver modules.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.298-301
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• 2012

This paper presents a graph-based method of detecting and tracking moving objects in H.264/SVC bitstreams for video surveillance applications that makes use the information from spatial base and enhancement layers of the bitstreams. In the base layer, segmentation of real moving objects are first performed using a spatio-temporal graph by removing false detected objects via graph pruning and graph projection, followed by graph matching to precisely identify the real moving objects over time even under occlusion. For the accurate detection and reliable tracking of moving objects in the enhancement layer, as well as saving computational complexity, the identified block groups of the real moving objects in the base layer are then mapped to the enhancement layer to provide accurate and efficient object detection and tracking in the bitstreams of higher resolution. Experimental results show the proposed method can produce reliable results with low computational complexity in both spatial layers of H.264/SVC test bitstreams.

• Journal of Korea Multimedia Society
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• v.3 no.4
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• pp.333-338
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• 2000

MPEG2(or some situations, MPEG is mostly used to change the raw image into the compressed bitstreams for digital image processing. Also these bitsreams are stored in computer for several applications such as multimedia area. Transmission channels have various capacities according to the application area, and the bitstreams stored in computer should be converted in order not to exceed the capacities of a transmission channel. So the problem is how to convert compressed bitstreams of a given bit-rate into compressed bitstreams of other bit-rates. Such a specific transcoding problem in this paper is referred to as bit-rate conversion. Several researches have been done on bit-rate conversion for the bitstreams compressed by MPEG. But the existing schemes are not suitable fort MPEG4 applications because it needs to transmit shape information( which is not necessary for MPEG2) as well as texture information in MPEG4 system. So we propose a new bit-rate converter which considers both texture and shape information.

• Journal of Broadcast Engineering
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• v.12 no.3
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• pp.214-221
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• 2007

In this paper, we presents conformance test tools for the broadcast web site (BWS) service which is one of the data services for terrestrial digital multimedia broadcasting (T-DMB). First, the methodology for the conformance test is established for both transmitters and receivers of T-DMB BWS services. The test tools consist of three parts: BWS bitstream analyzer, BWS reference decoder (software) module, and BWS test bitstreams. For testing transmitted BWS bitstreams, we developed the bitstream analyzer. For testing BWS receivers, we developed the reference Ifecoder module and created the test bitstreams. Actually the bitstream analyzer developed in this paper was used for the verification of the test bitstreams. The same test bitstreams are fed to a BWS decoder module under test and the reference decoder module and the results from the two are compared for verification. The test tools can be used for the test of all the protocol and textual/image specifications related to BWS including MOT protocol, HTML, PNG, MNG, JPEG, and Ecma Script.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.294-295
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• 2011

The fundamental problem of selective protection scheme for encoded bitstreams is to find an efficient algorithm to select the set of frames required to be encrypted that can maximize protection effect with the minimum amount of protected data is required. In this paper, we propose an optimal selective protection scheme for SVC bitstreams by protecting the best combination of frames for selective protection in the sense that the amount of data required for protection is minimized and the resulting visual quality degradation is maximized. The selection of the frames to be encrypted is done by first expressing R-Q (protection rate - visual quality) relationship with Lagragian cost model. The experimental results show that, compared to protecting SVC bitstreams layer by layer, the proposed scheme gives superior performance in terms of protection effectiveness due to its better selection of frames for protection given protection bit budgets.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.10
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• pp.83-93
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• 1999

In MPEG-2 video standard, there are many parameters to support profiles and levels. It is necessary to verify that a decoder is compliant with the MPEG-2 standard. This paper proposes a design principle of the test bitstreams which confirms that an MPEG video decoder is correct by observing the final image of the decoder under test. The presented test bitstream is composed of two parts. The first part generates a test pattern by varying a selected test parameter. And the following predictive coded picture generates a complementary pattern to the previous image by motion compensation and DCT coefficients. Then it will result in a uniform pattern. We present several bitstreams following the proposed principle. Also we analyze and compare the characteristics of the test bitstreams presented in the MPEG conformance test and the proposed test bistreams.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.1
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• pp.69-78
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• 2001

MPEG-4 visual conformance standard specifies methods to verify whether bitstreams and decoders meet the requirements at the specified profile and level. The test of decoders can be divided into two parts: the static test and the dynamic test. The static test can be performed by examining the decoder output with that of a reference decoder. This paper proposes design methods of test bitstreams for static test of texture decoding, and shows the test results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1384-1392
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• 1999

A high compression rate is required to transmit video sequences over low bit rate networks such as low bit rate communication channels. When highly compressed videos are transmitted over mobile channels of high error rate, bitstreams corrupted by channel errors are not only difficult to be decoded, but also have fatal effects on the other parts of the bitstreams. In this Paper, we propose an error concealment algorithm for recovering the blocks which can not be decoded due to damaged bitstreams. The proposed error concealment algorithm recovers the damaged blocks using the information of adjacent blocks which are correctly decoded. In the proposed algorithm, the motion vector of the damaged block is estimated using the overlapped block motion compensation(OBMC) and block boundary matching(BBM) techniques. Experiment results show that the proposed algorithm exhibits better performance in PSNR than existing error concealment methods.

• Journal of Broadcast Engineering
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• v.6 no.1
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• pp.82-97
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• 2001

In this paper, we describe a software implementation of a digital TV stream analyzer that can be used for analyzing and verifying digital TV bitstreams on personal computes. It accepts as input MPEG-2 transport streams (TS's) already stored on hard disks and doesn't require any special hardware. After classifying TS packets into program specific information(PSI) TS section auido, video, program clock reference (PCR) private data and null packets, it displays their contents through a graphic user interface along with the syntax elements of the TS header. Also it displays the decoded I frame nearest in time axis the TS packet currently shown This feature helps pin pointing the specific location of problematic parts in bitstreams. The bitsteam analyzer provides the compliance test of MPEG-2 Systems standard and the data injection functionality with which one can easily insert additional data to existing MPEG-2 bitstreams. Using the resulting system one can produce at low test streams for interactive broadcasting and data broadcasting for laboratory use.