A NEW AUDIO WATERMARKING METHOD BASED

Transcription

1 A NEW AUDIO WATERMARKING METHOD BASED ON DISCRETE COSINE TRANSFORM WITH A GRAY IMAGE Mohammad Ibrahm Khan 1, Md. Iqbal Hasan Sarker 2, Kaushk Deb 3 and Md. Hasan Furhad 4 1,2,3 Department of Computer Scence & Engneerng, Chttagong Unversty of Engneerng & Technology,Chttagong-4349, Bangladesh. 4 Department of Computer Engneerng & Informaton Technology, EUCS Lab, Unversty of Ulsan, South Korea. 1 muhammad_khan@cuet.ac.bd, 2 qbal@cuet.ac.bd, 3 debkaushk99@cuet.ac.bd, 4 hfurhad@gmal.com ABSTRACT Many effectve watermarkng algorthms have been proposed and mplemented for dgtal mages and dgtal vdeo. However, a few algorthms have been proposed for audo watermarkng. Ths s due to the fact that, human audtory system (HAS) s far more complex and senstve than human vsual system (HVS). In ths research work, a new method of embeddng mage data nto the audo sgnal and addtve audo watermarkng algorthm based on Dscrete Cosne Transformaton (DCT) doman s proposed. Frst, the orgnal audo s transformed nto DCT doman. The DCT coeffcents are dvded nto a fxed number of subsectons and the energy of each subsecton s calculated. Next, watermark s generated from mage by mage processng algorthm. Watermarks are then embedded nto selected peaks of hghest energy subsecton. Expermental results demonstrate that the watermark s naudble and ths algorthm s robust to common operatons of dgtal audo sgnal processng, such as nose addton, re-samplng, requantzaton and so on. To evaluate the performance of the proposed audo watermarkng method, subjectve and objectve qualty tests ncludng Bt Error Rate (BER) and Sgnal to Nose rato (SNR) are conducted. KEYWORDS Audo watermarkng, Dscrete Cosne Transformaton, Arnold Transformaton, BER, SNR. 1. INTRODUCTION Along wth the rapd growth of Internet, the transmsson of audovsual meda becomes easer. It leads to the problems regardng copyrght protecton. Among them, copyrght protecton s the prmary concern and the hotspot of nternatonal area n recent areas. Dgtal product nformaton hdng and dgtal watermarkng technology s generated on ths bass and developed along wth the protecton of copyrght; ths technology s wdely used n protectng the copyrght of mage, audo and vdeo by means of extractng or detectng the watermark for ts varous applcaton ncludng copyrght protecton, broadcast and publcaton montorng, authentcaton, copy control. Audo watermarkng should satsfy the followng features. They are as followng: DOI : /jcst

2 I. Imperceptblty: The dgtal watermark should not affect the qualty of orgnal audo sgnal after t s watermarked. II. Robustness: The embedded watermark data should not be removed or elmnated by unauthorzed dstrbutors usng common sgnal processng operatons and attacks. III. Capacty: Capacty refers to the numbers of bts that can be embedded nto the audo sgnal wthn a unt of tme. IV. Securty: Securty mples that the watermark can only be detectable by the authorzed person. In ths paper, we propose a new watermarkng technque usng Dscrete Cosne Transformaton (DCT) for audo copyrght protecton. The watermarks are embedded nto the selected peaks of the hghest energy segment of DCT coeffcents. Expermental results ndcate that the proposed watermarkng method provde strong robustness aganst several knds of attacks such as nose addton, re-samplng, re-quantzaton and so on and acheves Bt Error Rate (BER) almost zero. In addton, our proposed method acheves SNR (sgnal -to-nose rato) values rangng up to 29 db. The rest of the paper s organzed as follows: Secton 2 provdes a bref descrpton of prevous works related to audo watermarkng. Secton 3 ntroduces tradtonal Arnold transformaton. Secton 4 ntroduces our proposed watermarkng method ncludng watermark embeddng process and watermark detecton process. Secton 5 and 6 dscusses the performance of our proposed method n terms of mperceptblty and robustness. Fnally, secton 7 concludes ths paper. 2. RELATED RESEARCH A sgnfcant number of watermarkng technques have been reported n recent years n order to create robust and mperceptble audo watermarks. Le et al. [1] propose a method of watermarkng system for audo sgnals n the tme doman. Ths proposed algorthm uses dfferental average-of-absolute-ampltude relatons. In whch samples are kept n group and each group of audo samples uses to represent one-bt nformaton. Ths method also uses the low frequency ampltude modfcaton technque so that t can scale the ampltudes n selected sectons of samples. In [2], authors propose a blnd audo watermarkng method whch nserts watermark nto audo sgnal n the tme doman. For watermark detecton, the strength of the audo sgnal modfcatons s lmted by the necessty for producng an output sgnal. The watermark s generated usng a key. The watermark embeddng also depends on the ampltude and frequency of audo sgnal so that t mnmzes the audblty of the watermarked sgnal. In [3], authors explan a blnd watermarkng method whch nserts watermarks nto Dscrete Cosne Transform ( DCT) coeffcents usng quantzaton ndex modulaton method. In [4], authors propose a blnd audo watermarkng method by usng adaptve quantzaton aganst synchronzaton attack. In addton the multresoluton characterstcs of dscrete wavelet transform (DWT) and the energy compresson characterstcs of dscrete cosne transform (DCT) are combned n ths method. It also mproves the transparency of dgtal watermark. Watermark s then nserted nto low frequency components usng adaptve quantzaton accordng to human audtory system (HAS). In [5], authors propose a watermarkng method n cepstrum doman for audo sgnal n whch a pseudo-random sequence s used as a watermark. The watermark s then weghted n the cepstrum doman accordng to the dstrbuton of cepstrum coeffcents and the frequency maskng characterstcs of human audtory system (HAS). In [6], authors propose a blnd watermarkng system whch takes the advantages of the attack-nvarant feature of the cepstrum doman and error-correcton capablty of BCH code to ncrease the mperceptblty and robustness of audo watermarkng. In [7], authors propose a survey of watermarkng systems 120

3 whch are appled to Multmeda. In [8], watermarks are embedded nto the hghest m DCT coeffcents of the whole sound excludng the DC component by the followng equaton: v = v ( 1+ x ) (1) Where, m s the length of the watermark sequence, v s a magntude coeffcent nto whch a watermark s embedded, x s a watermark to be nserted nto v, s a scalng factor, v s an adjusted magntude coeffcent. The watermark sequence s extracted by performng the nverse operaton of (1) represented by the followng equaton: x v = ( 1) / v (2) In [9], the authors ntroduce a new method for nsertng watermarks nto audo sgnals by usng components whch have low frequency. Ths proposed method uses lftng-based wavelet transform (LBWT). The novel technology of nsertng mage data nto the audo sgnal and addtve audo watermarkng algorthm based on DCT doman s proposed n [10]. In [11], the authors propose a watermarkng method where DCT coeffcents are used. In [12], the authors ntroduce a watermarkng method whch nserts synchronzaton sgnals n tme doman. In [13] and [14], the authors propose a new watermarkng system usng Dscrete Fourer Transform (DFT) and Frst Fourer Transform (FFT) of dgtal contents for copyrght protecton respectvely. In [15], the authors propose a novel method to generate a unque personalzed watermark whch can act authentcatng nformaton for any watermarkng algorthm. In [16], the authors descrbe the watermark constructon process where scrambled verson of watermark s obtaned wth the help of Arnold transform. 3. TRADITIONAL ARNOLD TRANSFORM A dgtal mage can be consdered as a two unt functon f(x,y) n the plane Z. It can be represented as Z = f(x,y) where x,y {0,1,2,3...N-1}. Hence, N represents order of dgtal mage. The matrx of mage can be changed nto a new matrx by usng the Arnold transform whch results n a scrambled verson to offer better securty. It s a mappng functon whch changes a pont (x,y) to another pont ( x, y ) by usng the equaton (3) and (4). x = (x + y) mod N (3) y = (x + 2y) mod N (4) If the orgnal mage teratve n tmes to come to some scrambled state, the scrambled mage also need to teratve n tmes usng new ant-arnold transform to come to orgnal mage. 4. PROPOSED WATERMARKING METHOD In ths secton, we propose our algorthm based on a Dscrete Cosne Transform (DCT) on audo sgnal n whch a watermark mage s embedded. The algorthm conssts of two procedures; watermark embeddng procedure and watermark extracton procedure. 121

4 4.1. Watermark Embeddng Procedure The embeddng procedure performs three major operatons; watermark pre-processng, DCTbased frequency decomposton of the audo sgnal and watermark embeddng n the DCTtransformed audo sgnal. The operatons are descrbed n the followng steps. 1. Express the gray-sale watermark mage as a two-dmensonal matrx whose sze s M1 M2. Image = { Image(k,j), 0 k<m1, 0 j<m2 } (5) 2. Convert the gray scale watermark mage nto bnary format and also perform Arnold transform to scramble the watermark mage and get scrambled mage. 3. Convert two-dmensonal mage matrx nto a one-dmensonal vector W of length M1 M2. W = { W() = Image(k,j), 0 < M1 M2, 0 k<m1, 0 j<m2} (6) 4. Apply DCT to the orgnal host sgnal to calculate the DCT coeffcents. Audo host sgnal Watermark mage Apply DCT to audo sgnal Convert bnary format Dvde nto sub sectons Arnold Transformaton Calculate Energy Watermark generaton Sub secton Selecton Perform Embeddng algorthm Apply Inverse DCT Watermarked Audo sgnal Fgure 1: Watermark embeddng process 5. Absolute values of the DCT coeffcents are dvded nto subsectons. 6. Energy of each secton s then calculated usng the followng equaton; 122

5 2 E = v( ) (7) 7. Fnd the most promnent peaks from the hghest energy secton usng peak detecton algorthm. 8. The watermark s then embedded nto the selected N peaks of the selected secton by usng the equaton (1) shown n [8], where N s the length of normalzed one dmensonal vector of mage. 9. Apply the nverse Dscrete Cosne Transformaton (IDCT) to obtan the watermarked audo sgnal Watermark Extracton Procedure Audo host sgnal Apply DCT to audo sgnal Dvde nto sub sectons Calculate Energy Watermarked sgnal Pre-embeddng Process Sub secton Selecton Pre-embeddng Process Perform Detecton algorthm Convert two dmensonal matrx whch represents scrambled bnary mage Ant-Arnold Transform Convert to gray mage Watermark mage Fgure 2: Watermark extracton process 123

6 The extracton process s mplemented n the followng steps: 1. The watermarked audo sgnal s transformed nto DCT doman. 2. Extract the hghest promnent peaks from the DCT coeffcents whch are located at the same poston n the embeddng process above. 3. The watermarked vector s then calculated by performng the extracton algorthm usng the nverse operaton of (1) represented by equaton (2). 4. Convert extracted watermarked vector back nto two dmensonal matrx whch represents scrambled mage. 5. Apply ant-arnold transform to get the orgnal mage of bnary format. 6. Convert bnary mage to gray-scale mage. 5. PERFORMANCE EVALUATION FRAMEWORK In ths secton, we ntroduce performance evaluaton of our proposed system Bt Error Rate (BER) The robustness s measured as the BER correspondng to correctly formed bnary values of the mage. The BER (n present) s gven by k BER = a (8) k n= 0 If ( w [ n] = w[ n] ) then a = 0 otherwse a =1, where w [n] represents the set of bnary values formed from the watermarked audo host sgnal and w[n] ndcates the set of the bnary values of the orgnal mage Perceptual Qualty Perceptual qualty refers to the mperceptblty of embedded watermark data wthn the host sgnal. In most applcatons t s mportant that the watermark s undetectable to a lstener or a vewer. Ths ensures that the qualty of the host sgnal s not percevably dstorted and does not ndcate the presence or locaton of a watermark. In ths paper, the sgnal-to-nose rato (SNR) of the watermarked sgnal versus the host sgnal was used as a qualty measure. In order to evaluate the qualty of watermarked sgnal, the followng sgnal-to-nose rato (SNR) equaton s used. N 2 S ( n) n= 1 SNR = 10 log10 N (9) 2 [ S( n) S ( n)] n= 1 where S(n) s a host audo sgnal of length N samples and S (n) be watermarked audo sgnal Subjectve Qualty Evaluaton The naudblty of our watermarkng method has been done by lstenng tests nvolvng ten persons. Each lstener was presented wth the pars of orgnal sgnal and the watermarked sgnal and was asked to report whether any dfference could be detected between the two sgnals. The ten people lsted to each par for 10 tmes and they have a grade for ths par, usng the ITU-R BS.1284 standardzed 5-pont gradng scale. The average grade for of each par from all lsteners s the fnal grade for ths par. 124

7 Table 1. Gradng Scale (ITU-R) Grade Qualty Imparment 5 Excellent Imperceptble 4 Good Perceptble but not annoyng 3 Far Slghtly annoyng 2 Poor Annoyng 1 Bad Very Annoyng 6. EXPERIMENTAL RESULTS In ths secton, we evaluate the performance of our watermarkng system for four dfferent types of 16 bt mono audo sgnals sampled at 44.1 khz: (a) an nstrumental song Hey Jude played by a Korean tradtonal muscal nstrument called the gayageum; (b) the song Let t Be by the Beatles; (c) the begnnng of Symphony No. 5 n C mnor, Op.67, by Ludwg van Beethoven; (d) a human voce provdng TOEIC (Test of Englsh for Internatonal Communcaton) lstenng test nstructon. A gray-scale mage shown n fgure 3 was used as watermark for embeddng n the audo fles. We choose gray-scale mage as watermark mage. The sze of the watermark mage was chosen after takng nto consderaton the length of the audo fles Fgure 3: The orgnal watermark mage Performance of audo watermarkng algorthm s commonly evaluated wth respect to two common metrcs: (a) Imperceptblty (Inaudblty) and (b) Robustness Imperceptblty Test Imperceptblty s related to the perceptual qualty of the watermarked sgnal. It ensures that the qualty of the sgnal s not perceptble to a lstener. To measure mperceptblty, we use Sgnalto-Nose rato (SNR) as an objectve measure and a lstenng test as a subjectve measure. Table 2. SNR and Average ITU-R grade value of the proposed watermarkng system Type of Sgnal Sgnal-to-Nose rato (SNR) Average Grade(ITU-R) Hey Jude Let t be Symphony No Human Voce Robustness Test The robustness of a watermarkng method s defned as the ablty of watermark detector to extract the embedded watermark after common sgnal processng operatons and attacks. In ths paper, robustness s measured n terms of the Bt Error Rate (BER). 125

8 Table 3. Bt Error Rate (BER) of the proposed method wthout attack Hey Jude Let t be Human Voce Table 4. Bt Error Rate (BER) of the proposed method aganst re-samplng Hey Jude Let t be Human Voce Table 5. Bt Error Rate (BER) of the proposed method aganst re-quantzaton Hey Jude Let t be Human Voce Table 6. Bt Error Rate (BER) of the proposed method aganst flter attacks Hey Jude Let t be Human Voce Table 7. Bt Error Rate (BER) of the proposed method aganst random nose Hey Jude Let t be Human Voce Table 8. Bt Error Rate (BER) of the proposed method aganst AWGN Hey Jude Let t be Human Voce

9 7. CONCLUSIONS In ths paper, we have presented a new watermarkng system usng Dscrete Cosne Transform (DCT) for copyrght protecton of audo sound. Expermental results ndcate that our proposed watermarkng system has compromsed audblty and robustness better. Ths method also shows strong robustness aganst several knds of attacks such as nose addton, re-samplng, requantzaton, flterng etc. Ths results obtaned verfy the effectveness of audo watermarkng as a relable soluton to the copyrght protecton problem whch s facng the musc ndustry. REFERENCES [1] W. N. Le and L. C. Chang, (2006) Robust and Hgh -Qualty Tme-Doman Audo Watermarkng Based on Low Frequency Ampltude Modfcaton, IEEE Transactons on Multmeda, Vol. 8, No. 1, pp [2] P. Bassa, I. Ptas and N. Nkolads, (2001) Robust Audo Watermarkng n the Tme doman, IEEE Transactons on Multmeda, Vol. 3, No. 2, pp [3] G. Zeng and Z. Qu, (2008) Audo watermarkng n DCT; Embeddng Strategy and Algorthm, n Proceedngs of 9th Internatonal Conference on Sgnal Processng, (ISP 09), pp [4] X. Y. Wang and H. Zaho, (2006) A novel Synchronzaton Invarant Audo Watermarkng Schem e Based on DWT and DCT, IEEE Transactons on Sgnal Processng, Vol. 54, No. 12, pp [5] S. K. Lee and Y. S. Ho, (2000) Dgtal Audo Watermarkng n the cepstrum doman, IEEE Transactons on Consumer Electroncs, Vol. 46, No. 3, pp [6] S. C. Lu and S. D. Ln (2006) BCH code based robust audo watermarkng n the cepstrum doman, Journal of Informaton Scence and Engneerng, Vol. 22, pp [7] S.J. Lee, S. H. Jung (2001) A Survey of Watermarkng Technques Appled to Multmeda, IEEE Transactons on Industral Electroncs, Vol. 12, pp [8] I. Cox, J. Kllan, F. Leghton and T. Ahamoon, (1997) Secure Spread Spectrum Watermarkng for Multmeda, IEEE Transactons on Image Processng, Vol. 6, No. 12, pp [9] E. Erceleb. And L.Batakc., (2009) Audo Watermarkng Scheme Based on Embeddng Strategy n Low Frequency Components wth a Bnary Image., Dgtal Sgnal Processng, Vol. 19, No. 2, pp [10] Yan Yang, Rong Huang and Mntau Xu (2009) A Novel Audo Watermarkng Algorthm for Copyrght Protecton Based on DCT Doman. 2nd Internatonal Symposum on Electronc Commerce and Securty,pp [11] P.K Dhar, M.I.Khan and S. Ahmad (2010) A New DCT-Based Watermarkng Method for Copyrght Protecton of Dgtal Audo., Internatonal Journal of Computer Scence & Informaton Technology(IJCSIT), Vol. 2 No.5. [12] J. Huang, Y. Wang and Y.Q. Sh,(2002) A Blnd Audo Watermarkng Algorthm wth Self Synchronzaton., IEEE Internatonal Symposum on Crcut and Systems, Vol. 3 pp [13] P.K Dhar, M.I.Khan and J.M.Km (2010) A New Audo Watermarkng System usng Dscrete Fourer Transform for Copyrght Protecton., Internatonal Journal of Computer Scence & Network Securty (IJCSNS), Vol. 10 No.6. [14] P.K Dhar and J.M.Km (2011) Dgtal Watermarkng Scheme Based on Frst Fourer Transformaton for Audo Copyrght Protecton., Internatonal Journal of Securty and ts Applcatons (IJSIA), Vol. 5 No.2. [15] T.K. Tewar, V.Saxena and J.P Gupta (2012) A Novel Approach to Generate Watermarks Usng Audtory Features for Audo Watermarkng., Journal of Theoretcal and Appled Informaton Technology (JATIT), Vol. 35 No.2. [16] Dr. M. Sathk and S. S. Sujatha (2010) An Improved Invsble Watermarkng Technque for Image Authentcaton., Internatonal Journal of Advanced Scence and Technology (IJAST), Vol

10 Authors Dr. Mohammad Ibrahm Khan receved the B.S. degree n Electrcal and Electronc Engneerng from Bangladesh Unversty of Engneerng and Technology (BUET), Bangladesh n He receved M.S. degree n Computer Scence and Engneerng from the same Unversty n He receved hs Ph.D. degree n Computer Scence and Engneerng from Jahangrnagar Unversty n Snce 1999, he has been servng as a faculty member n the Department of Computer Scence and Engneerng at Chttagong Unversty of Engneerng & Technology (CUET), Chttagong, Bangladesh. Hs research nterest ncludes Dgtal Image Processng, Graph Theory, Cryptography, Dgtal Watermarkng, Multmeda Systems, and Dgtal Sgnal Processng. Md. Iqbal Hasan Sarker receved the B.Sc degree n Computer Scence & Engneerng from Chttagong Unversty of Engneerng & Technology (CUET), Bangladesh n Currently, he s pursung M.Sc n Computer Scence & Engneerng n the same Unversty. Snce 2010, he has been servng as a faculty member n the same department and unversty. Hs research nterest ncludes Dgtal Watermarkng, Computer Vson, Dgtal Image Processng, Cryptography and data mnng. Dr. Kaushk Deb receved hs B. Tech. and M. Tech. degrees from Department of Computer Scence & Engneerng of Tula State Unversty, Tula, Russa, n 1999 and 2000, respectvely. He receved hs Ph.D. degree n Electrcal Engneerng & Informaton systems from Unversty of Ulsan, Ulsan, South Korea n Snce 2001, he has been servng as a faculty member n the Department of Computer Scence and Engneerng of Chttagong Unversty of Engneerng & Technology (CUET), Chttagong, Bangladesh. Hs research nterests nclude computer vson, pattern recognton, ntellgent transportaton systems (ITSs) and human-computer nteracton. Md. Hasan Furhad receved hs B. Sc degree n Computer Scence & Engneerng from Rajshah Unversty of Engneerng & Technology (RUET), Bangladesh n Currently, he s pursung MS n Unversty of Ulsan, South Korea. He s a Lecturer n Faculty of Engneerng at Unversty of Informaton Technology & Scences (UITS), Chttagong, Bangladesh. Hs research nterests nclude Embedded Systems, Computer Archtecture and Computer Vson. 128