Robust Spread Spectrum Based Digital Video Watermarking Scheme in Frequency Domain Nisha Chaudhary 1 Savita Shivani 2

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1 IJSRD Internatonal Journal for Scentfc Research & Development Vol. 2, Issue 6, 2 ISSN (onlne): Robust Spread Spectrum Based Dgtal Vdeo Watermarkng Scheme n Frequency Doman Nsha Chaudhary Savta Shvan 2 B.Tech, M.Tech 2 B.Tech, M.Tech, Ph.D,2 Department of Computer Engneerng,2 Suresh Gyan Vhar Unversty, Jagatpura, Japur, Rajasthan Abstract There s an exploson of data exchange on the Internet and the extensve use of dgtal meda. Consequently, dgtal data owners can quckly and massvely transfer multmeda documents through the Internet. It has aroused ntense nterest n multmeda securty and multmeda copyrght protecton, and ths has become a crtcal ssue n the modern dgtal era. The problem s severe n case of dgtal vdeo as several copes of duplcate vdeos can be made on optcal dsks even wth cheap commodty computers. Ths results n recordng, edtng and replcaton of multmeda contents, thereby provdng revenue losses. Dgtal watermarkng technque s the process of embeddng nosetolerant sgnal n the carrer sgnal. Ths dssertaton focuses on the embeddng of watermark bts nto the vdeo frames. A gven vdeo sample s splt nto frames for watermark embeddng. A frame s frst transformed nto frequency doman usng Dscrete Fourer Transform. A watermark, modulated wth PN sequence s transformed and added to the Fourer coeffcents and then the nverse s obtaned of modfed Fourer Coeffcents to get watermarked frame. Ths process s repeated to the entre length of vdeo to get watermarked vdeo. The vdeo watermarkng algorthm proposed s robust aganst the attacks of frame droppng, averagng and statstcal analyss. Peak Sgnal to Nose Rato (PSNR) s used as the qualty metrc for watermarkng scheme. Mathematcal technques are presented and smulaton are carred out usng MATLAB. Key words: Watermarkng, DFT, FFT, Spread Spectrum, m sequences I. INTRODUCTION The rapd prolferaton of multmeda over nternet demands sophstcated technque for secure and effcent access to nformaton. There s growng need to dscourage unauthorzed duplcaton and use of dgtal data. Watermarkng refers to hdng a message sgnal nto a host sgnal, wthout any perceptual dstorton of the host sgnal []. As the word watermarkng suggests, the mark tself s transparent or unnotceable for the human percepton system. Usually, the host sgnal s a dgtal meda, lke audo, vdeo or mages. Dgtal watermarkng embeddng refers to the method of nsertng nformaton nto multmeda data, called orgnal meda or cover meda e.g. text, audo, mage or vdeo. The embedded nformaton or watermark can be a seral number or a random number sequence, ownershp dentfer, copyrght message, control sgnal, transacton date, nformaton about the creators of the work, blevel or gray level mage, text or other dgtal data format. As the Human Vsual System (HVS) [2], s far from beng perfect for mages and vdeo so t s possble to modfy the pxel values wthout the watermark beng vsble. Provded that a certan HVS threshold s not exceeded, the modfed (watermarked) mage or vdeo wll be ndstngushable to the human eye compared wth the orgnal. After embeddng watermark, the watermarked meda are sent over Internet or some other transmsson channel. Whenever the copyrght of the dgtal meda s under queston, the embedded nformaton s decoded to dentfy copyrght owner. The decodng process can extract the watermark from the watermarked meda (watermark extracton) or can detect the exstence of watermark n marked content (watermark detecton). Watermarkng vdeo content mportant to avod pracy and llegal manpulaton. However, watermarkng ndvdual frames of vdeo n spatal doman [3] n fragle and s subjected to varous knds of attacks. Also, wth a lttle modfcaton, the watermark gets destroyed and cannot be detected at the recever end. Frequency doman watermarkng s more robust as compared to spatal doman watermarkng. Also, frequency doman watermarkng usng spread spectrum uses correlaton based analyss at the tme of watermark detecton, whch provdes a way for blnd watermarkng. In ths technque, the orgnal unmarked vdeo s not requred at the recever end and therefore, s useful n a broad category of applcatons. As the case wth all watermarkng systems, the perceptual fdelty of the marked content must be as low as possble. Also, the markng scheme should be robust enough to handle attacks and vdeo edtng to greatest possble extent. In ths work, a tradeoff between PSNR and robustness s derved by embeddng watermark n frames of the orgnal vdeo. Intellectual property protecton [] s one of the greatest concerns of nternet users today. Dgtal vdeos are consdered a representatve part of such propertes so are consdered mportant. There s a crtcal need of development of technques that prevent malcous users from clamng ownershp, motvatng nternet users to feel more safe to publsh ther work onlne. In ths work an effcent and easly mplemented technque for watermarkng vdeo fles s presented. The proposed watermarkng process embeds the watermark n the frequency doman, by alterng the Fourer Coeffcents [5] of a sub mage of the orgnal mage. The embedded data can be extracted usng a denosng process wthout the need of the orgnal unmarked content. Thus, t provdes a way of blnd watermarkng whch s much more convenent and desrable as compared to nonblnd watermarkng. Moreover, usng Frequency doman for watermark embeddng, one can acheve a much more robust watermark as compared to spatal doman watermarks. Also, wth spread spectrum technque, the watermark energy s dstrbuted unformly over the host sgnal thereby provdng much more mperceptblty as compared to spatal doman technques. All rghts reserved by 5

2 Robust Spread Spectrum Based Dgtal Vdeo Watermarkng Scheme n Frequency Doman (IJSRD/Vol. 2/Issue 6/2/) II. RESEARCH APPROACH Ths work proposes a technque of watermarkng n the frequency doman. A gven vdeo s frst dvded nto frames for watermark embeddng. Each frame s then dvded nto RGB color planes for the purpose of watermark embeddng. The color plane frame s then transformed usng Dscrete Fourer Transform to obtan the DFT coeffcents. The watermarkng bts to be embedded n the frame are frst spreaded and modulated wth a chosen PN sequence [6] and then added n the Fourer coeffcents usng the embeddng algorthm. Each frame s separately watermarked wth the content. The nverse Fourer Transform s then appled to get the watermarked color plane frame. All the three color planes are then tested to fnd out the mnmum value of the PSNR. Fnally, the one wth the least value of the PSNR s selected and the other two color plane frames are kept unchanged. The watermarked frames are recombned to get back the watermarked vdeo. III. PROPOSED WORK A. Proposed Vdeo Watermarkng usng PN sequences The current work focuses on vdeo watermarkng n frequency doman usng Dscrete Fourer Transform. A gven vdeo s segregated nto the frames whch are then separately processed. The embeddng algorthm works as follows: ) Embeddng Algorthm () Separate the gven vdeo nto frames. The frame rate typcally depends on the format of the vdeo as well as vdeo qualty. (2) Let the frame sze be m X n. Each frame s then dvded nto red, green and blue planes for the purpose of watermark embeddng. (3) A bnary watermark s modulated wth a gven PN sequence and embedded n magntude of the Fourer Coeffcents of the RGB planes one by one. () The color plane s selected for watermark embeddng whch provdes the hghest value of PSNR. (5) Inverse Fourer Transform s obtaned for the plane to get back the watermarked plane. (6) The planes are combned agan to get back the watermarked frame. () The process s repeated for all the frames of the vdeo to get the watermarked vdeo. The process of watermark embeddng s llustrated n the fgure 3.. 2) Extracton Algorthm () Separate the gven vdeo nto frames. Obtan the Red, Green and Blue planes of frame. (2) Obtan the DFT of each of the color plane. (3) Gven a PN sequence, perform the correlaton analyss wth each of the plane, and correspondng de spreadng. A value well above threshold gves the watermark bts. () Repeat the process for all the frames to ensure the presence of watermark even n the case of frame droppng. As watermark s embedded n all the frames, the scheme provdes a robust watermarkng technque. ` Fg. 3.: Proposed Archtecture of Embeddng Process Fg. 3.2: Proposed Archtecture of Extracton Process B. Watermark Embeddng Scheme In ths research, the watermarkng scheme s carred out over 2 bt color vdeos. Consder an arbtrary frame of sample vdeo to be watermarked, as shown n table 3.. All rghts reserved by 6

3 Robust Spread Spectrum Based Dgtal Vdeo Watermarkng Scheme n Frequency Doman (IJSRD/Vol. 2/Issue 6/2/) Each frame s specfcally an mage and can be vsualzed n some format. Also, each pxel of the mage s a 2 bt value comprsng of bts each of Red, Blue and Green color. Pxel value separaton n RGB color planes s performed to embed the watermark. Fgure 3.3 s a sample vdeo frame to be watermarked (frame number 9 n the frames dsplayed n chapter ). Fgure 3.2, 3.3 and 3. shows the Red, Green and Blue planes of the frame. The proposed method takes the Fourer Transform of each of these planes and embed the watermark modulated wth PN sequence to each one of the R, G and B plane. PSNR value of each of these frames s computed and fnally the one wth hghest value of PSNR (or least value of Mean Square Error) s selected. The rest two bt planes are kept ntact. All the color planes are these merged to get the watermarked frame. All such frames are then combned to get the watermarked vdeo. Fg 3.3 Orgnal Color Frame and Decomposton nto Red, Green and Blue color Planes C. Watermark Detecton At the recever end, the watermarked vdeo s agan parttoned nto frames. Each frame s then further separated nto Red, Green and Blue planes. The Fourer Coeffcents of each of the color planes are computed and the presence of watermark s ensured by a correlaton test wth the same PN sequence. If the value of correlaton between PN sequence and the extracted PN sequence s greater than a certan threshold, then one can ensure the presence of watermark n the gven mage plane. However, proper embeddng of the modulated PN sequence n the Fourer coeffcents s a trcky ssue and can be done n several ways. The two dmensonal Dscrete Fourer Transform of a set of n numbers gves n complex number of the form ab, where a, b ϵ R, and =. In ths dssertaton, Bnary phase only flter (BPOF) sgnature s used to embed watermark n the Fourer Coeffcents. D. Watermark Embeddng n Fourer Coeffcents Consder an magnary pxel matrx of dmenson X as llustrated n fgure All the above values le n the range [,625].The above table can be converted nto bnary values of length 2 bt n whch the frst bts represent Red, the next bts represents Green and the last bts represents the Blue color. The correspondng RGB bt planes are as shown n fgure 3., 3.9 and 3.. Red Plane All rghts reserved by

4 Robust Spread Spectrum Based Dgtal Vdeo Watermarkng Scheme n Frequency Doman (IJSRD/Vol. 2/Issue 6/2/) Green Plane Blue Plane The correspondng decmal values of each of the planes are: Red Plane Green Plane Blue plane The two dmensonal FFT of the Blue plane can be obtaned as shown n the fgure gven below: Table 3.: Fft Coeffcents For Blue Plane Of Jpg Image Of Frame The magntude of these Fourer coeffcents are shown n fgure 3. below: Table 3.2: Magntude Of Fourer Coeffcents The phase of the coeffcents are shown n the table 3.5 gven below: Table 3.3: Phase of Fourer Coeffcents Usng the modulus and the phase of the complex numbers, each of these can be wrtten n the Euler form The Bnary Phase Only Flter for the Fourer coeffcents can be obtaned by settng up the value f tangent of angle of phase s equal to, f t s negatve and f t s postve. Fgure 3.5 shows the BPOF flter values. All rghts reserved by

5 Robust Spread Spectrum Based Dgtal Vdeo Watermarkng Scheme n Frequency Doman (IJSRD/Vol. 2/Issue 6/2/) Table 3.: Magntude Of Fourer Coeffcents E. PN sequence Generator Consder the followng crcut to generate a PN sequence: Fg. 3.: LFSR Crcut for generaton of PN sequence R, R 2, R 3 and R are the regsters that hold bt of nformaton. The contents of the R and R 2 are exored and the result s agan exored wth R 3 and the result s agan fed to the R 3 regster. The above crcut s an example of Lnear Feedback Shft Regster (LFSR) Crcut. Let the ntal contents of the regsters be (,,,), then the output can be generated n the followng way. Tme LFSR States Output,,,,,, 2,,, 3,,,,,, 5,,, 6,,,,,, Table 3.5: Lnear Feedback Shft Regster O/P For M Sequences The last row s the same as the frst one and therefore ndcates that the same pattern would repeat thereafter. Thus, the perod of the LFSR consstng of 3 regsters s 2 3 =. Denotng wth to keep the values n polar format, the PN sequence obtaned s,,,,,,. Consder the watermark to be bt sequence. Convertng t nto polar form, the watermark can be represented as. The speeded sequence obtaned to embed n the host sgnal s: Watermark Bt PN Sequence Spread Sequence Table 3.6: Embeddng Of Bts Correspondng To Psnr Values Fg. 3.5: The watermark to be embedded (represented as a sgnal). Horzontal axes shows the tme and the vertcal axes shows the ampltude. All rghts reserved by 9

6 Robust Spread Spectrum Based Dgtal Vdeo Watermarkng Scheme n Frequency Doman (IJSRD/Vol. 2/Issue 6/2/) Fg. 3.6: The spreadng correspondng to a one bt data. Horzontal axes shows the tme and the vertcal axes shows the ampltude. Fg 3. The spreadng correspondng to a sequence. Horzontal axes shows the tme and the vertcal axes shows the ampltude. Thus, the sequence to be embed s,,,,,,,,,,,,,,,,,,,,. These watermark bts are to be added n such a way so as to mantan the symmetry of the Fourer transform. F. Proposed Algorthm for watermark embeddng The data to be embedded s used to modulate the magntude of the Fourer coeffcents n such a way so as to mantan the symmetry of the magntudes. In the example shown above, the hypothetcal frame conssts of 6 pxels (X matrx) and the watermark s to embedded n all the bts of the frame, such that the symmetry s preserved. In can be easly observed that the frst row of the transform conssts of all the real values, whereas the other seven values of each row are symmetrcally separated. Thus, keepng the two rows, the frst one and the mddle, on can have a total of pxels n whch the values are to be modfed. Also, as the symmetry s to be preserved, a total of 2 bts can be embedded n the magntude of the coeffcents. The spreaded code to be embed s to be appended wth paddng bts to make t 2 bts long. Let α be the maskng threshold value above whch denotes a and below whch denotes a. Ths value s sutably chosen as per the magntude of the Fourer coeffcents. Consder the table for magntude of Fourer coeffcents repeated here for ready reference The two rows whch are hghlghted are to be kept ntact and the embeddng s performed n half of the remanng bts, as the other half s to be modfed to mantan the symmetry of Fourer Transform. Let α =.2, whch ndcates that a value equal to or below.2 denotes a and a value above t denotes a. An nteger multple of a step sze β s to be added (or subtracted) to (from) the magntude to change t to denote the value t should represent. Consder the data stream,,,,,,,,,,,,,,,,,,,,,±,±,±. The last three are paddng bts whch can ether be or. One possble embeddng wth β=. s Table 3.: Embedng In Magntude Values Of Fft Coeffcents (Changed Values Are Shown In Red) The Fourer coeffcents can be constructed from these modfed magntudes and the orgnal phase of the frame, usng the Euler Formula All rghts reserved by

7 Robust Spread Spectrum Based Dgtal Vdeo Watermarkng Scheme n Frequency Doman (IJSRD/Vol. 2/Issue 6/2/) Table 3.: Reconstructon Of Fourer Coeffcents From Modfed Magntude And Phase Values whch on nverse Fourer Transform gves Table 3.9: Reconstructon Of Pxel Values From Modfed Fourer Coeffcents The orgnal blue plane pxel values are shown n the table Table 3.: Orgnal Pxel Value Of The Blue Plane Of Image The MSE fr the above hypothetcal vdeo frame s 62 gvng PSNR value 2.2db. The PSNR value for Suresh Gyan Vhar Unverse convocaton vdeo (also provded n CD ROM enclosed) s computed n Chapter.. IV. CONCLUSION AND FUTIRE SCOPE Ths dssertaton proposes a technque of watermark embeddng n vdeo n frequency doman n whch the vdeo s segregated nto frames. Each frame s then converted to mage format and then separated nto Red, Green and Blue Planes. The pxel matrx of each of the color planes s then subjected to two dmensonal Fourer Transform. The text strng to be used as watermark s frst converted nto ASCII code, and then modulated usng PN sequence. The Fourer Coeffcents are then converted nto Euler Form by decomposng nto magntude and phase. Ths modulated strng s then embedded nto the magntude of the Fourer Coeffcents wthout affectng the phase. To keep the fdelty of the watermark vdeo as hgh as possble, the proposed technque embed the watermark n only one of the three planes, vz red, green and blue, whch gves the hghest value of PSNR. Later, at the tme of detecton, the extracted strng s to be demodulated wth the same PN sequence to get back the watermark, or the presence of watermark s ensured. It turns out that the PSNR value s a functon of length of the watermark. PSNR values are nversely proportonal to the length of the watermark message. The proposed technque for vdeo watermarkng presents a robust technque aganst frame droppng attacks. As the dfferent frames of the vdeo, conssts of watermark n any of red, green or blue planes, the watermark presence s unaltered aganst frame droppng. However, an addtonal computaton cost s nculcated as the detector has to decompose the frame nto RGB planes and each one s separately operated for the presence of watermark. A. Future Scope The proposed future work on the ths technque of vdeo watermarkng embed the watermark selectvely n the transtonal frames of the vdeo. Transtonal frames are the frames n whch the locaton of a sequence of frame changes. These are the frames n whch some content of the new scene s supermposed on some content of the prevous scene. However, n such a technque, there s a serous drawback of robustness of the embedded watermark. However, embeddng selectvely n the transtonal frames and some ntermedate frames wll serve the purpose of robustness and at the same tme, optmzng the fdelty of the watermarked vdeo. REFERENCES [] B. Chen and G. Wornell, Achevable performance of dgtal watermarkng systems, n Proc. Int. Conf. Multmeda Comput. Syst., Florence, Italy, June 2, pp. 3. [2] Lesa M Kennedy, Mtra Basu, "Image enhancement usng a human vsual system model", Volume 3, Issue 2, December 99, Pages 2 2. [3] Qngtang Su, Yugang Nu, Qngjun Wang, Guoru Sheng, " A blnd color mage watermarkng based on DC component n the spatal doman", Internatonal Journal for Lght and Electron Optcs, Volume 2, Issue 23, December 23, Pages [] K.Hll, "A Perspectve: The Role of Identfers n Managng and Protectng Intellectual Property n the Dgtal Age", Proceedngs of the IEEE, Vol., No., July 29, pp [5] Frank Y. Shh, Scott Y.T. Wusdsd, "Combnatonal mage watermarkng n the spatal and frequency domans", Pattern Recognton, Volume 36, Issue, Aprl 23, Pages [6] Sant P. Maty, Malay K. Kundu, Trtha S. Das, "Robust SS watermarkng wth mproved capacty", Pattern Recognton Letters, Volume 2, Issue 3, February 2, Pages [] Ruben Ros, Jose A. Oneva, Javer Lopez, "Covert communcatons through network confguraton messages", Computers & Securty, Volume 39, Part A, November 23, Pages 36 [] ChengCh Lee, HongHao Chen, HungTng Lu, GuoWe Chen, ChweShyong Tsa, "A new vsual cryptography wth multlevel encodng", Journal of All rghts reserved by

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