WAVELET DOMAIN VIDEO INFORMATION EMBEDDING

Transcription

1 WAVELET DOMAIN VIDEO INFORMATION EMBEDDING Mng Yang, Monca Trfas, Candce Trutt, and Guoun Xong Department of Mathematca and Computer Scences Jacksonve State Unversty, Jacksonve, AL 3665 {myang, atrfas, ABSTRACT Wth the proferaton of dgta mutmeda content, such as mage, audo, vdeo, and anmaton, nformaton hdng technques have attracted more and more research nterests. Hgh btrate nformaton hdng s dfferent from dgta watermarkng n that t tres to hde reatvey arge amount of auxary nformaton nstead of just one or a few verfcaton bts. Ths research s many focused on waveet doman hgh btrate nformaton hdng wthn dgta vdeo content. Channe capacty and the robustness of hdden nformaton aganst ossy vdeo codec represent our man concern. Impact of embedded nformaton on the performance of bock-matchng based moton estmaton and compensaton s another ssue. In the proposed agorthm, bt s hdden wthn each DWT coeffcent bock by means of vector quantzaton. LL (Low-Low) band coeffcents are chosen for nformaton embeddng due to ther reatvey arge amptudes and the correspondng sma quantzaton step szes on owfrequency coeffcents. The proposed agorthm s tested under H.6/AVC (Advanced Vdeo Codec), whch s the state-of-the-art vdeo codng standard. Expermenta resuts have shown that the proposed agorthm s very robust to H.6/AVC codec. Keywords: Informaton Hdng, Waveet, Vdeo, Channe Capacty, Btrate, H.6/AVC.. INTRODUCTION Informaton hdng technques have attracted more and more research nterests. Informaton hdng not ony hdes the content and ocaton of the protected data, but aso conceas the very exstence of nformaton [][]. Hgh btrate nformaton hdng embeds a reatvey arge amount of auxary nformaton wthn the host meda. The man goa of hgh btrate nformaton hdng n our study s to embed redundant nformaton wthn dgta vdeo for captonng, speech-n-vdeo, vdeo-n-vdeo, and covert communcaton. The most common attack to the hdden nformaton s JPEG/JPEG000 compresson (for st mage) or MPEG-x, H.6x, Moton-JPEG (for dgta vdeo). As such, for hgh btrate nformaton hdng, we are many concerned wth the foowng Hube Huanyu Auto-Lghtng Co., Ltd. Xangfan 0, Hube, P.R. Chna guoun0@yahoo.com.cn performance metrcs: () transparency,.e., the embeddng of hdden nformaton shoud not degrade the vsua quaty of the orgna mage/vdeo content [3]; () data capacty,.e., how many bts can be effectvey embedded wthn the host data [][5][6]; (3) robustness to JPEG/MPEG compresson,.e., how much hdden nformaton can survve the ossy JPEG/MPEG compresson [7]. Accordng to modern nformaton hdng theory, the embeddng capacty of the host vdeo frames provdes an addtona communcaton channe wth a certan amount of capacty. Accordngy, a major task n hgh btrate nformaton hdng research s to successfuy dever the nformaton bts through ths communcaton channe. Hgh btrate nformaton hdng agorthms fa nto two categores: spata-doman and transform-doman. The most straghtforward spata-doman technque for dgta mage - east-sgnfcant-bt (LSB) agorthm - s very senstve to ossy compresson. Manccam and Bourbaks proposed a spata-doman agorthm based on the texture anayss of each 3x3 neghborhood wthn the mage [8] that obtaned hgher robustness aganst compresson because the modfcatons on non-lsb bts are more robust to ossy compresson. Transform-doman agorthms embed the nformaton nto transformed host mage/vdeo. The vector projecton based hgh btrate nformaton hdng agorthm proposed by Swanson, Zhu, and Tewfk [9] embeds data by projectng the DCT coeffcents vector to a certan drecton. The method proposed by Aturk and Mersereau embeds the data by whtenng the mage and quantzng a DCT coeffcents [0]. Ther agorthm sgnfcanty mproved the securty eve and data capacty. Chae and Manjunath make use of a attce structure to code the nformaton and pace the nformaton n the md-frequency coeffcent ocatons of the DWT bock [][]. Yang and Bourbaks [3][] have proposed an nformaton hdng agorthm that proves to be robust to JPEG compresson. In ths research, we are tryng to desgn and mpement a transparent, robust, and hgh bt-rate nformaton hdng agorthm for dgta vdeo. Waveet doman s chosen for nformaton embeddng. Our goa s tryng to reach a baance between transparency, channe cty, and

2 robustness to H.6/AVC vdeo codec. Here we have objectves: () Hgh Bt-rate: bt per * bock; () Bnd nformaton retreva; (3) None or mnmum vsua degradaton; () Robustness to ossy vdeo codec. The proposed agorthm dffers from prevous work n that t uses vector quantzaton nstead of scaar quantzaton to embed the nformaton, whch makes the hdden data more robust to quantzaton nose. Rather than usng a coeffcents for data embeddng, ony the ow-frequency coeffcents n the approxmaton subband of the waveet decomposton are modfed to hde nformaton. Based on the quantzaton procedure of H.6/AVC compresson, a mathematca mode has been proposed to predct the BER of the agorthm.. INFORMATION HIDING STRATEGIES Tempora/Spata Locaton of Hdden Informaton Vdeo nformaton hdng s smar to mage nformaton hdng snce dgta vdeo s a sequence of st mages. Lke most of the state-of-art vdeo codecs, the H.6/AVC standard uses the Group-Of-Pctures (GOP) structures. Ths structure contans three dfferent knds of frames: I-frame, P-frame, and B-frame, each of whch s compressed wth dfferent strateges. Due to dfferent compresson agorthms, t s expected that I-frames have the hghest channe capacty for nformaton hdng, whe B-frames have the owest channe capacty for nformaton hdng. In vdeo compresson, the source pcture and the decoded pcture are both comprsed of three sampe arrays: umnance (uma) array and two chromnance (chroma) arrays. In order not to ead to any coor dstorton, ony the uma sampe array s chosen as the host of nformaton hdng. The uma array w be modfed as a gray-eve mage to hde nformaton. Waveet Anayss In ths study, waveet doman s chosen for nformaton embeddng. In waveet anayss, we obtan approxmatons (or trends) and detas (fuctuatons). The approxmatons are the hgh-scae, ow-frequency components of the sgna. The detas are the ow-scae, hgh-frequency components. A one-eve waveet transform of an MxN mage f can be descrbed as: f LL LH HL HH where the subbands LL, HL, LH and HH each has M/ rows and N/ coumns. Fg. dspays the subbands produced by -eve waveet transform apped to the Lena mage. As one can notce, most of the energy s concentrated n the LL subband, whch makes t a good canddate for nformaton embeddng. Fg. One-eve Waveet Decomposton Informaton Hdng Doman As can be seen n Fg., ow-frequency coeffcents present hgher amptudes than hgh-frequency coeffcents. Thus, the LL subband has been seected for nformaton hdng. The ratonaes are: Waveet and DCT both transform the mage or vdeo frames nto frequency doman. Ths w overcome the probems wth spata doman nformaton embeddng,.e., senstvty to transform-based ossy compresson. Approxmaton coeffcents n LL subband have reatvey arger amptudes compared to deta coeffcents, so they offer more room for nformaton embeddng; The hdden nformaton on approxmaton coeffcents w have a better chance to survve ossy compresson, snce the quantzaton step sze for the approxmaton coeffcents s sma; Hgh-frequency DWT coeffcents w be easy removed by ossy compresson due to ther reatvey ower energy and arger quantzaton step sze. We embed the nformaton wthn the LL band of the waveet decomposton. Snce texture detas of the mage and frames are contaned n LH, HL, and HH components, modfyng LL coeffcents w not change the texture detas. Wthn the approxmaton subband, we have chosen to embed nformaton bts by means of vector quantzaton, nstead of scaar quantzaton. Vector quantzaton has proven to be more robust to quantzaton nose than the scaar method. The approxmaton coeffcents w be grouped nto vectors, whose norms w be modfed to host nformaton bts. If one or more coeffcents have been corrupted by nose, the nformaton bt can st be devered correcty due to the others who work jonty to carry the nformaton bt.

3 H.6/AVC Advanced Vdeo Codec The proposed data embeddng methodoogy s tested under H.6/AVC vdeo codec. H.6/AVC, aso known as MPEG- part 0, s the atest deveopment of vdeo codng standard. Ths standard was proposed by Jont Vdeo Team (JVT) formed by ITU-T Vdeo Codng Experts Group (VCEG) and ISO Moton Pcture Expert Group (MPEG). In H.6/AVC, many new features have been added n order to mprove the codng performance. In H.6/AVC, a pcture may be spt nto one or more sces. A sce coud be parsed and decoded ndependenty wthout usng the data from other sces. Sces can be coded wth dfferent codng types: I sce, P sce, B sce, SP sce, and SI sce. After moton estmaton, each resdua macrobock s transformed, quantzed, and entropy-coded. H.6 uses nteger transform, whch s an approxmaton of DCT transform. 3. INFORMATION HIDING AND BLIND RETRIEVAL Informaton Hdng Agorthm The nformaton hdng agorthm ustrated n Fg. can be summarzed nto the foowng steps: (a) Perform a one-eve waveet transform of the orgna host mage; (b) Group the coeffcents wthn the approxmaton subband nto 6-eement vectors; (c) Quantze the vectors to embed the nformaton bts; (d) Perform an nverse waveet transform to the modfed waveet coeffcents to obtan the stego-mage. (e) Repeat the same procedure for every frame n the vdeo sequence. Orgna Image Stego-Image DWT IDWT DWT Decomposton LL Subband In step (c), the foowng procedure w be used: () Let us consder the transform apped to a generc - D vector V: V c, c, c,..., c, ) ( 0 c5 T: the threshod for vector quantzaton V : the norm of vector V [] : round-off operaton Vector Quantzaton Message LL Fg. Basc Structure of Informaton Hdng Agorthm V T V T 5 0 c 5 0 T c () One bt s embedded by modfyng : T ' T ± 0.5 (+0.5 to embed, and -0.5 to embed 0); (3) ' T '* T, V ' ' * V ; () Put the vector V ' back to ts orgna ocaton n the approxmaton subband; (5) Repeat the same operaton for each 6-eement vector unt a the nformaton bts have been embedded. Bnd Retreva wthout Orgna Image In most of the hgh btrate nformaton hdng appcaton scenaros, the presence of the orgna mage/vdeo content at the recever can not be expected. In ths case, the retreva of the embedded nformaton n the absence of the orgna mage (bnd retreva) s hghy desred. The agorthm for nformaton retreva s descrbed n the foowng: () Perform a one-eve waveet decomposton to the stego-mage (the mage contanng the hdden nformaton); () Reshape the approxmaton subband nto a -D vector; group ts coeffcents nto6-eement vectors n exacty the same order as n nformaton hdng; (3) Denote one of these 6-eement vectors wth : " V" " V" T " T T I T " T " [ ] V" If I>0, the s extracted as the nformaton bt; If I<0, then 0 s extracted as the nformaton bt. () Repeat the same operaton to each DWT vector unt a the nformaton bts have been extracted. Wth ths approach, the hdden nformaton can be extracted wthout the orgna mage. Ths feature s very mportant n many appcaton scenaros.. PERFORMANCE ANALYSIS Reduce Vsua Dstorton The embedded nformaton w nevtaby resut n quantzaton nose to the host vdeo content. If pxes next to each other are grouped nto bocks for nformaton embeddng, the quantzaton nose w appear as strps n the stego- vdeo content and cause bockng effects. In order to address ths ssue, a checkerboard bockng T

4 pattern has been apped to reduce vsua degradaton. Here s an exampe of the pattern that has been apped: Effectve Area for V Integer Mutpe of T Locaton of V Fg. Survva Regons of the Hdden Informaton As shown n Fg. 3, wth the checkerboard bockng approach, pxes n dfferent ocatons wth the same pattern (nstead of pxes n cose proxmty) are grouped nto bocks for nformaton embeddng. Wth ths approach, quantzaton nose caused by nformaton embeddng has been dspersed. The vsua dstorton appears more ke random nose and thus becomes ess vsbe. Robustness to ossy compresson The hdden nformaton w be nevtaby dstorted by the ossy H.6/AVC coded (more precsey, by the quantzaton). Vector quantzaton was used as a strategy of nformaton hdng n order to make the procedure more robust to nose. Suppose the DWT coeffcents vector wth the embedded nformaton bt s: V ' ( c0', c ', c',..., c n ', cn '), then the vector obtaned after H.6/AVC compresson w be: V ( c ' + q, c ' + q, c ' + q,..., c ' + q, c ' q ), where " 0 0 n n n + n q represents the nose caused by compresson. Accordng to the nformaton retreva agorthm: ' V' 0 ( c ') " V" ( c ' 0 + q Fg. 3 Checkerboard Bockng Approach ) In order to extract the correct nformaton bt, one must make sure that: sgn( T -[ T ])sgn( T -[ T ]). The embedded nformaton w be abe to survve quantzaton nose as ong as ths condton hods. The above condton (n the case that an nformaton bt s embedded) s graphcay ustrated n Fg.. As one can notce, as ong as V" s ocated n the green shaded areas, the hdden nformaton w be extracted correcty. T he condton mentoned above can be converted to: " ( ' + m) ( m 0, ±, ±, ± 3,... ), whch T T can be further converted to: n q ( c ' q ) ( m ) T 0 + ) ( c ' ) ( m T 0 + and n q ) ( ') ( ) 0 ( c ' + q ) ( m + T c m T Suppose the probabty densty functon of q (c ' + q ) s f Q (x) (pease note 0 that ( x) 0 ), then the p robabty of extractng a f Q wrong nformaton bt,.e. BER, s: S " S ' P e p ( ( + m ) T T m ( ( m + ) T ( m ) T n 0 ( c ') + ( m + ) T n 0 ( c ') + ( m ) T ) f Q ( x )) As can be seen, n order to mnmze P, T needs to be maxmzed. Ths means that the vector quantzaton threshod T has to be maxmzed under the constrant that acceptabe vsua dstorton s resuted. In the mpementaton, the quantzaton step sze T was ncreased graduay unt the quaty degradaton o f the mage starts to be vsbe. In ths case, quantzaton threshod s maxmzed, and thus BER s mnmzed. 5. EXPERIMENTAL RESULTS The proposed agorthm was mpemented wth Mathworks Matab R006 and Waveet Toobox. The transparency of the nformaton hdng agorthm has been subjectvey tested. The comparson between the orgna vdeo frames and the stego- frames for the vdeo sequence foreman_cf.yuv s ustrated n Fg. 5. As can be seen, no vsua dstorton s detected under subjectve testng, so the transparency of the nformaton hdng agorthm has been reaby ensured. The channe capacty s evauated wth bts per pxe (bpp),.e., the number of hdden nformaton bts dvded by the number of pxes n the mage. The nta data rate was /6 bpp. e

5 (a) (b) Fg. 5 Compar son between Orgna and Stego Frames (a) Orgna Frames (b) Stego Frames After nformaton hdng, the stego-vdeo was tested wth H.6/AVC reference software JM3. under dfferent quantzaton parameters (QP). In the testng, the robustness of the proposed agorthm to H.6/AVC compresson s measured wth Bt-Error-Rate (BER,.e. how many percents of the hdden nformaton coud survve the vdeo codec) by comparng the extracted bt strng wth the orgna message bt strng. A GOP structure of IBBPBB s adopted. Fg. 6 dspays the performance of the agorthm apped to the frst 6 frames of the vdeo sequence foreman_cf.yuv. Fg. 7 contans the resut of appyng the same agorthm to the frst 6 frames of a dfferent vdeo sequence tempete_cf.yuv. Fg. 6 Performance of Informaton Hdng Agorthm Fg. 7 Performance of Informaton Hdng Agorthm In Fg. 6 and Fg. 7, the frame ndex s represented on the X-axs and the correspondng survva rate (.0-BER,.e., how many percents of the embedded nformaton survve the ossy codec) of hdden nformaton s shown on the Y- axs. As can be seen from Fg. 6 and Fg. 7, the BER s very ow when QP s ower than 5. Ths means that the proposed agorthm s very robust to H.6/AVC codec. When QP reaches 5 (correspondng to bt rate of Mbps), the BER starts to ncrease sgnfcanty. The perodca spkes refect I-frames n the GOP structure beng used. As expected, nformaton wthn I-frame has the best chance to survve H.6/AVC. Between the two adjacent spkes, we can see there s a smaer spke, whch corresponds to the P-frame between B-frames. In order to ncrease the channe capacty and reaby hde more nformaton bts wthn the mage, smaer bocks (8- eement vector and -eement vector) coud be used for nformaton embeddng. Obvousy, the step sze for vector quantzaton needs to be adjusted correspondngy n order to avod vsua dstorton. Wth ths approach, channe capacty coud be ncreased to /3bpp or /6bpp, at the prce of sghty hgher BER. 6. CONCLUSION AND FUTURE WORK In ths paper, a waveet doman hgh btrate nformaton hdng agorthm that hdes arge amount of data wthn dgta vdeo content has been proposed. The approxmaton subband n waveet doman s frst dvded nto bocks (wth checkerboard pattern), each of whch w then be modfed through vector quantzaton to embed hdden data. Hdng nformaton wthn the approxmaton subband has sgnfcant advantages compared to the smar procedure apped to the other subbands. The proposed agorthm has ganed a very hgh eve of robustness to H.6/AVC compresson wthout causng unacceptabe vsua dstorton. In the future, error correcton code w be apped to further suppress bt error rate. Snce most of the state-of- art vdeo codecs use hybrd bock-matchng archtecture, the embedded nformaton s key to mpact the

6 performance of bock-matchng based moton estmaton. Such mpact w be quanttatvey anayzed through ratedstorton testng. The proposed agorthm w aso be apped to vdeo streamng appcatons for vdeo-ondemand, and thus t w be tested under a packet-swtch network transmsson envronment. The proposed agorthm s gong to be very usefu n practca appcaton such as sde nformaton devery, captonng, vdeo-n-vdeo, speech-n-vdeo, error conceament, and etc. References [] M. Yang, S. L, and N. Bourbaks, Data-magevdeo encrypton, IEEE Potentas Magazne, Aug/Sept. 00, pp.8-3. [] N. Bourbaks, and A. Doas, SCAN based mutmeda nformaton on demand, IEEE Mutmeda Magazne, Sept. 003, pp [3] A.B. Watson, DCT quantzaton matrces vsuay optmzed for ndvdua mages, Human Vson, Vsua Processng, and Dgta Dspay IV, Bernce E. Rogowtz, Edtor, Proc. SPIE 93-. [] M. Barn, F. Barton, A. de Rosa, and A. Pva, Capacty of the watermark-channe: how many bts can be hdden wthn a dgta mage? Proc. of SPIE, Vo. 3657, San Jose, CA, Jan. 999, pp [5] C.Y. Ln, and S.F. Chang, Watermarkng capacty of dgta mages based on doman-specfc maskng effects, Proceedng of Internatona Conference on Informaton Technoogy: Codng and Computng (ITCC '0), Apr 0-0, Las Vegas, NV. [6] D. Kundur, Impcatons for hgh capacty data hdng n the presence of ossy compresson, Proceedng of Internatona Conference on Informaton Technoogy: Codng and Computng, pp. 6-, March, 000. [7] C. Fe, D. Kundur, and R. Kwong, The choce of watermark doman n the presence of compresson, Proceedng of Internatona Conference on Informaton Technoogy: Codng and Computng, pp. 79-8, Las Vegas, NV, 00. [8] S.S. Manccam, and N. Bourbaks, Lossess mage compresson and encrypton usng SCAN, Pattern Recognton Journa, Vo. 3, 00, pp [9] Swanson, M.D., Zhu, B., and Tewfk, A.H., 997, Data hdng for vdeo-n-vdeo, Proceedngs of the 997 Internatona Conference on Image Processng (ICIP 97), Vo., pp , Santa Barbara, Caforna, October, 997. [0] F. Aturk, and R. Mersereau, A nove approach for ncreasng securty and data embeddng capacty n mages for data hdng appcatons, Proceedng of Internatona Conference on Informaton Technoogy: Codng and Computng, pp [] J.J. Chae, and B.S. Manjunath, Data hdng n vdeo, Proceedng of the 6th IEEE Internatona Conference on Image Processng (ICIP'99), Kobe, Japan, vo., pp. 3-35, Oct [] D. Mukherjee, J.J. Chae, and S.K. Mtra, A source and channe codng approach to data hdng wth appcaton to hdng speech n vdeo, Proceedng of IEEE Internatona Conference on Image Processng, Part I, Chcago, IL, pp , October 998. [3] M. Yang and N. Bourbaks, A hgh btrate mutmeda nformaton hdng agorthm n DCT doman, Proceedng of Word Conference of Integrated Desgn and Process Technoogy (IDPT 005), Bejng, Chna, Jun. 3 th -7 th, 005. [] M. Yang and N. Bourbaks, A hgh btrate nformaton hdng agorthm for dgta vdeo content under H.6/AVC compresson, Proceedng of IEEE Internatona Mdwest Symposum on Crcuts and Systems, Cncnnat, OH, Aug., 005.