Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
  • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
  • H04N21/238—Interfacing the downstream path of the transmission network, e.g. adapting the transmission rate of a video stream to network bandwidth; Processing of multiplex streams
  • H04N21/2389—Multiplex stream processing, e.g. multiplex stream encrypting
  • H04N21/23892—Multiplex stream processing, e.g. multiplex stream encrypting involving embedding information at multiplex stream level, e.g. embedding a watermark at packet level

Definitions

• the present invention relates to the insertion of information in still or moving images.
• Content digitization techniques such as still or moving images make it possible to make copies of these contents in unlimited quantity and without degradation of quality.
• the development of computer networks and personal computers leads to uncontrolled dissemination of these contents. It is becoming increasingly difficult to enforce the rights of the authors of these contents.
• the first category brings together cryptographic techniques which consists in applying to digitized content an encryption that renders it unreadable without a decryption key.
• the second category brings together the techniques of insertion of non-perceptible watermarks carrying information to identify a legal copy of a work or a code limiting the possibilities of duplication.
• watermarks For a watermark insertion technique to be effective, watermarks must not be able to be removed from the content without substantially degrading the quality of the images. In particular, it should not be possible to delete watermarks by combining multiple copies of the same content. Furthermore, images, and in particular video sequences, are currently undergoing numerous treatments such as digital / analog and digital / digital conversions, compression / decompression treatments, scaling or cropping processes or adjusting brightness, contrast and colors. Watermarks must also withstand these treatments.
• the technique employed must also allow to insert a sufficient amount of information, knowing that the more one increases this quantity, the more the watermark insertion will affect the quality of the images, and therefore the robustness of the watermark.
• this method although generic, is not optimal in the case of images and requires the prior encoding of the message to be inserted in the image by means of an error correction coding, which helps reduce the bandwidth or the amount of useful information that can be inserted into the image.
• the present invention aims to eliminate this disadvantage.
• This objective is achieved by providing an information insertion method comprising a predetermined number of symbols, in a sequence of images of at least one image having a predetermined number of lines each gathering a predetermined number of pixels.
• this method comprises the steps of:
• this method further comprises a step of interleaving the symbols of the information to be inserted, prior to the phase shift of each function of the set of functions.
• this method comprises, prior to the phase shift modulation of each function of the set of functions, generating steps of a pseudo-random sequence comprising a respective symbol for each symbol of the information to be used. insert, and stir symbols of the information to be inserted with the pseudo-random sequence.
• the stirring step consists of combining, by an exclusive OR operation, symbols of the information to be inserted and the pseudo-random sequence.
• the functions of the set of functions have respective main spectral lines spaced at a constant pitch corresponding to the line frequency of the image sequence.
• the image sequence has a comb-shaped spectrum, the comb-shaped spectrum of the function set being shifted with respect to the spectrum of the image sequence of a frequency that is adjusted.
• the combination of the pixels of the image sequence to the result of the superposition of the out-of-phase functions is performed by a modulation of the luminance of the pixels of the image sequence.
• the combination of the pixels of the image sequence to the result of the superimposition of the out-of-phase functions is performed by a rotation of the color components of the pixels of the image sequence.
• this method comprises in in addition to a step of preprocessing the image to avoid saturation phenomena of the pixels of the image sequence when the combination thereof to the result of the superimposition of the out-of-phase functions.
• this method further comprises a step of encoding the symbols of the information to be inserted, to obtain a distinct symbol sequence for each color component of the pixels of the image sequence, the functions of the set of functions being out of phase by each of the sequences of symbols obtained, superimposed and then combined respectively with the color components of the pixels of the image sequence.
• the coding applied to the symbols of the information to be inserted, to obtain a distinct symbol sequence for each color component is a convolution type coding.
• the combination of the pixels of the image sequence to the result of the superposition of the out-of-phase functions is performed so as to be not very visible in the image sequence.
• the combination of the pixels of the image sequence to the result of the superposition of the out-of-phase functions is performed so as to scramble the images of the image sequence.
• the invention also relates to a method of extracting information from a sequence of images of at least one image comprising a predetermined number of lines each gathering a predetermined number of pixels. According to the invention, the information has been inserted according to the insertion method defined above.
• the invention also relates to a method of descrambling a sequence of images of at least one image comprising a predetermined number of lines each gathering a predetermined number of pixels.
• the image sequence has been scrambled according to the insertion method defined above.
• the invention further relates to an information insertion device comprising a predetermined number of symbols, in a sequence of images. at least one image having a predetermined number of lines each gathering a predetermined number of pixels.
• this device comprises means for implementing the information insertion method defined above.
• the invention also relates to a device for extracting information from a sequence of images of at least one image comprising a predetermined number of lines each gathering a predetermined number of pixels.
• this device comprises means for implementing the information extraction method defined above.
• the invention also relates to a device for descrambling a sequence of images of at least one image comprising a predetermined number of lines each gathering a predetermined number of pixels.
• this device comprises means for implementing the image descrambling method defined above.
• FIG. 1 represents the spectrum of a video sequence of images
• FIG. 2 diagrammatically represents a device according to the invention for inserting information in a still image or in a sequence of images
• FIG. 3 diagrammatically represents a device according to the invention for extracting information inserted in a still image or in a sequence of images, using the device represented in FIG. 2;
• FIG. 4 diagrammatically represents a device according to the invention for rendering scrambled images using the device represented in FIG. 2;
• FIG. 5 schematically shows a variant of the device shown in Figure 2
• FIG. 6 schematically represents a device according to the invention for extracting information inserted in a still image or in a sequence of images, using the device represented in FIG. 5;
• FIG. 7 schematically represents a device according to the invention for rendering scrambled images using the device represented in FIG. 5.
• the present invention is based on the exploitation of the spectral shape of an image or sequence of digital images in baseband (unmodulated) as illustrated in FIG. 1.
• the spectrum energy of a sequence of images is distributed in sets of lines spaced from the image frequency, each set of lines having a maximum of energy at a frequency nf H which is a multiple of the line frequency f H of the lines of the picture. Two consecutive maximum energy are therefore spaced from the line frequency f ⁇ (H for horizontal).
• the present invention proposes to use the spectrum intervals between the energy peaks corresponding to multiples of the line frequency f H to insert information forming a mark. It is also possible to insert information between the lines spaced from the frequency of the images.
• FIG. 1 represents a device according to the invention for inserting a mark in an image or a sequence of images.
• This device comprises a module 1 for extracting the image parameters producing synchronization signals for locating the lines and the pixels in the image, and if it is a sequence of images, the images of the sequence.
• the synchronization signals at the line and pixel frequency are applied to a function generator 3, these functions having the particularity of being orthogonal to each other, the orthogonality being defined here in the sense of the scalar product of the functions. In addition, they must form an orthogonal base in the vector space of the functions so as to form a comb spectrum interspersed in the image spectrum as illustrated in FIG. 1.
• the number of functions is variable and related. the number of symbols constituting the message to be inserted in the image.
• the orthogonal functions used are sinusoidal functions whose respective frequencies are spaced from the line frequency f H and offset in frequency by a certain step, for example equal to H / 2 relative to the maximum energy located at the frequencies nf H of the image.
• wavelet functions such as Haar or Hadamard functions, or windowed sinusoids.
• windowed sinusoids Such functions are of the form:
• Re (c) is the real part of the complex number c
• F (t) is a periodic windowing function such as a Hanning, Hamming, Blackmann, or raised cosine function or a truncated Gaussian function, or a wavelet function such as Haar.
• the set of orthogonal functions produced by the generator 3 is for example generated in the form of a software table or an indexed memory. It is also possible to envisage orthogonal functions spaced apart not from the line frequency f H , but from the image frequency, which is generally a few tens of Hertz.
• the message to be inserted in the image or the image sequence is processed by a module 4 which completes the message with mark start and end signals, and in the case of a sequence of images, which distributes the message in N successive images, by copying or cutting the message.
• Each message portion to be inserted in each image may be processed by an interleaving module 7 which performs a permutation of the bits of the message portion.
• Interleaving makes it possible to distribute the symbols of the message in a balanced way over the basic functions. Interlacing is done during a period equivalent to a number T lines. All T lines, the permutation law is changed.
• the device shown in FIG. 2 may also comprise a module 2 for generating a pseudo-random sequence used as a brewing sequence from an initial value and the line synchronization signal received as input.
• the generated brewing sequence is combined with the output message of module 4 or 7 by an Exclusive OR operation producing the elementary symbols of the message.
• the processing of the message by a brewing sequence makes it possible to avoid the redundancies detectable by the eye or by electronic means.
• the brewing takes place for a time equivalent to a number L b of lines. All L b lines the brewing sequence is changed.
• the elementary symbols of the message at the output of the operation 5 are applied to a phase-shifter 6 also receiving as input the set of basic functions produced by the generator 3.
• the phase-shifter 6 uses each of the elementary symbols of the message, derived from the operation 5 to determine a phase at the origin of each of the basic functions. In the case of a base of sinusoidal functions, this amounts to applying on each of the functions a phase modulation of BPSK (Binary Phase-shift Keying) whose rate depends on the parameters L e , L b and a signal of synchronization related to the message.
• BPSK Binary Phase-shift Keying
• phase-shifted functions delivered by the phase-shifter 6 are superposed or summed by an adder 9, so as to obtain a resultant function which is then sampled and then mixed with the image by an image transformation module 10 applying to the pixels of the image. image a transformation dependent on a respective sample of the resulting function.
• the transformation applied to the pixels of the image may be, for example, a modification of the luminance by adding the samples of the resulting function obtained by the phase shifter or a rotation of the color components of the image, or any other operation on the elementary components of the images. pixels.
• the amplitude of the transformation will be chosen more or less low.
• this pretreatment may consist of converting the values of the pixel components to be between 16 and 235, for example.
• the parameters L e and L b preferably correspond to an integer number of symbols in the mark to be inserted in the image. However, in the opposite case, you can choose to complete each line of the image with a particular symbol or to repeat the last symbol of the mark until the end of the line.
• FIG. 3 represents a device making it possible to extract a mark from an image or a sequence of images.
• This device comprises a module 21 for extracting the image parameters producing, from the marked image, synchronization signals making it possible to locate the lines and pixels of the image, as well as the start and end marks of the image. message inserted, and if it is a sequence of images, synchronization signals to identify the images of the sequence.
• the pixel and line synchronization signals are applied to a generator 22 of orthogonal functions which is similar to that used in the device shown in FIG.
• the marked image is applied to a module 23 receiving the orthogonal functions and extracting pixel by pixel the symbols of the message by multiplying the orthogonal functions generated by the module 22 respectively to the pixels of the image.
• the symbols of the message obtained are accumulated in a local accumulator 23 synchronized with the frequency of the mark produced by the extraction module 21 and receiving the parameters L e and L b defining the numbers of lines of the image on which the same law permutation and the same brewing sequence are applied.
• the line, picture and mark synchronization signals are applied to a de-interleaving and de-interleaving module receiving as input the brewing sequence and the permutation law used by the device shown in FIG. 2.
• the module performs an inverse processing at that performed by the modules 2, 5 and 7 of the device shown in Figure 2, so as to obtain the bits of the word inserted in the image, which are accumulated in an accumulator 26 finally delivering the word inserted in the image.
• Figure 4 shows a device for decoding a scrambled image.
• This device is identical to that shown in Figure 2, except that the module 4 is deleted, the module 1 is replaced by the module 21 of the device of Figure 3 which extracts, not an image synchronization signal, but a synchronization signal mark, for detecting mark start and end mark in the image, and the transformation module 10 of the image is replaced by a pixel extraction module 31 of the image which performs a transformation inverse to that applied by the module 10 to obtain the pixels of the original image.
• the marking signal obtained at the output of the operator 5 is applied to an encoding module 41 to generate a distinct marking signal for each of the color components of the 'picture.
• the marking signals obtained are applied to the input of a respective phase-shifter 42 producing functions out of phase for each basic function and for each color component of the image. These functions are then superimposed by a respective summator 44 for each color component and applied at the input of a transformation module 43 which combines the functions superimposed respectively on the color components of the pixels of the image.
• the coding carried out by the module of 41 is preferably chosen to introduce more redundancy between the color components of the image, on the mark inserted in the image.
• This coding is for example of convolutive type 1/3.
• the coding carried out by the module 41 is preferably chosen to, on the contrary, eliminate the redundancies between the markings inserted respectively in the color components of the image.
• FIG. 6 represents a device for extracting a mark inserted using the device represented in FIG. 5.
• this device comprises a module for extracting the symbols of the message that delivers message symbols for each of the color components of the pixels of the image.
• This extraction device then comprises a processing chain for each color component comprising a local accumulation module 52, a de-erasing and deinterleaving module and an accumulation module 54, these modules being identical to those of the device shown in FIG. FIG. 3.
• This extraction device furthermore comprises a decoding module 55, performing a function inverse to that of the module 41, so as to restore the marking word from the accumulated marking words for each color component by the modules of FIG. If the coding applied by the coding module 41 is convolutional type 1/3, the decoder 55 may be for example of the Viterbi decoder type.
• FIG. 7 represents a device for decoding a scrambled image by means of the insertion device represented in FIG. 5.
• This device is similar to that represented in FIG. 4 and has the same modifications as those made on the device represented. in FIG. 2 to obtain that of FIG. 5.
• the module 31 for extracting pixels from the image of the device of FIG. 4 is replaced by an extraction module 45 which extracts from the scrambled image, the superposed functions obtained by the summators 44 respectively for the color components.

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• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Editing Of Facsimile Originals (AREA)
• Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
• Compression Or Coding Systems Of Tv Signals (AREA)
• Processing Or Creating Images (AREA)
• Image Processing (AREA)
• Compression Of Band Width Or Redundancy In Fax (AREA)

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• 2004
  • 2004-09-08 FR FR0409521A patent/FR2875090B1/fr not_active Expired - Fee Related
• 2005
  • 2005-09-06 CN CN200580030122A patent/CN100584005C/zh not_active Expired - Fee Related
  • 2005-09-06 US US11/662,290 patent/US20080137905A1/en not_active Abandoned
  • 2005-09-06 JP JP2007530738A patent/JP4444337B2/ja not_active Expired - Fee Related
  • 2005-09-06 EP EP05805568A patent/EP1790153A2/de not_active Withdrawn
  • 2005-09-06 WO PCT/FR2005/002213 patent/WO2006030101A2/fr active Application Filing

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