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
  • H04N21/234—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs
  • H04N21/23418—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs involving operations for analysing video streams, e.g. detecting features or characteristics
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/30—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using hierarchical techniques, e.g. scalability
  • H04N19/31—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using hierarchical techniques, e.g. scalability in the temporal domain
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/48—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using compressed domain processing techniques other than decoding, e.g. modification of transform coefficients, variable length coding [VLC] data or run-length data
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
  • H04N19/61—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding in combination with predictive coding
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
  • H04N19/62—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding by frequency transforming in three dimensions
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
  • H04N19/63—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding using sub-band based transform, e.g. wavelets
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/70—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by syntax aspects related to video coding, e.g. related to compression standards
• • 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
  • H04N21/234—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs
  • H04N21/2347—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs involving video stream encryption
• • 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
  • H04N21/234—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs
  • H04N21/2347—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs involving video stream encryption
  • H04N21/23476—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs involving video stream encryption by partially encrypting, e.g. encrypting the ending portion of a movie
• • 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]
  • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
  • H04N21/45—Management operations performed by the client for facilitating the reception of or the interaction with the content or administrating data related to the end-user or to the client device itself, e.g. learning user preferences for recommending movies, resolving scheduling conflicts
  • H04N21/462—Content or additional data management, e.g. creating a master electronic program guide from data received from the Internet and a Head-end, controlling the complexity of a video stream by scaling the resolution or bit-rate based on the client capabilities
  • H04N21/4621—Controlling the complexity of the content stream or additional data, e.g. lowering the resolution or bit-rate of the video stream for a mobile client with a small screen
• • 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]
  • H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client 
  • H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
  • H04N21/631—Multimode Transmission, e.g. transmitting basic layers and enhancement layers of the content over different transmission paths or transmitting with different error corrections, different keys or with different transmission protocols
• • 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]
  • H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client 
  • H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
  • H04N21/647—Control signaling between network components and server or clients; Network processes for video distribution between server and clients, e.g. controlling the quality of the video stream, by dropping packets, protecting content from unauthorised alteration within the network, monitoring of network load, bridging between two different networks, e.g. between IP and wireless
  • H04N21/64784—Data processing by the network
  • H04N21/64792—Controlling the complexity of the content stream, e.g. by dropping packets
• • 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]
  • H04N21/80—Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
  • H04N21/83—Generation or processing of protective or descriptive data associated with content; Content structuring
  • H04N21/835—Generation of protective data, e.g. certificates
  • H04N21/8355—Generation of protective data, e.g. certificates involving usage data, e.g. number of copies or viewings allowed
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/16—Analogue secrecy systems; Analogue subscription systems
  • H04N7/167—Systems rendering the television signal unintelligible and subsequently intelligible
  • H04N7/1675—Providing digital key or authorisation information for generation or regeneration of the scrambling sequence
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding

Definitions

• the present invention relates to the field of processing video sequences encoded using video coders based on wavelet technology.
• the present invention relates more particularly to a device capable of securely transmitting a set of video streams of high visual quality to a viewing screen such as a television screen and / or to be recorded on the hard disk or on any other medium.
• recording of a box connecting the remote transmission network to the display screen such as a television screen or a personal computer monitor while preserving the audiovisual quality but avoiding any fraudulent use such as the possibility of making pirated copies of films or audiovisual programs recorded on the hard disk or any other recording medium of the set-top box.
• the invention also relates to a client-server system, the server providing the stream allowing viewing of the secure digital video film and the client reading and displaying the digital audiovisual stream.
• patent application EP0734164 presenting a method and a device for increasing the coding efficiency, carried out by video encoders based on classified vector quantization by optimizing the coding so as not to have to transmit the classification information. in the encoded bit stream.
• This prior art applies to video streams resulting from the transformation into DCT or wavelet.
• the incoming video signal is divided into a plurality of sub-bands, for example the DC coefficients are arranged in a sub-band and the AC coefficients in remaining sub-bands, followed by formatting in size blocks. identical, each block including a DC coefficient and a multitude of AC coefficients.
• a selection signal is then generated, representing the vector quantization class corresponding to each assembled block.
• This step is followed by classification for vector quantization by the generation of parameters relating to the evolution of the DC coefficients in the horizontal and vertical direction, and of the differential entropy encoding of the DC coefficients relating to the assembled blocks to generate a first encoded video signal.
• the AC coefficients are classified and encoded separately using entropy encoding based on the selection information to generate a second encoded video signal.
• the two signals thus generated are formatted for transmission. For decoding, no classification information is transmitted, it is reconstructed from the DC coefficients encoded and transmitted to the decoder.
• This solution relates to a process relating to digital compression and the encoding of video streams resulting from the transformation into DCT and wavelets.
• the description of the process indicates the steps to be applied to implement a classified vector quantization, increasing the compression and the efficiency of the encoding. Only one stream is transmitted to the receiver.
• the technical problem and the objective posed in this document are to optimize the digital format and it aims to obtain a digital stream formatted at the output of a digital encoder.
• the process described in this solution does not make it possible to secure the video stream and does not provide any protection against illicit uses of video streams originating from wavelet encoding.
• This prior art represents an encryption solution using keys, therefore, a single stream is transmitted to the receiver and all the elements constituting the original stream are inside the protected stream.
• This document relates to a solution that does not respond satisfactorily to the protection of the transmitted video stream.
• the statistical properties are modified and the size of the stream and the bit rate increase. Consequently, this prior art does not meet the high security objectives guaranteeing a lossless process which is the subject of the present invention.
• a first part of the image is compressed at low quality, without encryption, and a second part of the image is encrypted.
• the second part is encrypted and includes two sections, encrypted differently.
• the decryption of the first section and its combination with the first part restores the initial image with average quality.
• the decryption of the second section, its combination with the first section and the first part restore the image original at maximum quality.
• the image can also be partitioned into multiple independent sections, each section being encrypted with its own method and its own key.
• the protection method in this prior art is encryption, therefore, all the original elements of the flow remain inside the protected flow, the restitution of the entire content from the only protected flow is possible in the case where a person is ill. intentioned finds or simulates the encryption keys.
• this solution does not provide satisfactory security against pirating of the video stream.
• the size of the protected stream is different from the size of the original stream. This prior art therefore does not solve the problem of high security, while providing fine granularity in the quality of the reconstructed video sequences treated in the present invention.
• US patent 2001/0053222 A1 proposes a method and a system for the protection of video streams encoded according to the MPEG-4 standard.
• the audiovisual stream is composed of several audio and video objects, managed by a scenic composition.
• One of the objects in the video stream is encrypted using a key generated in four encryption stages which is renewed periodically.
• Protected objects are video objects.
• the encrypted object is multiplexed with the other objects and the entire stream is sent to the user.
• the MPEG-4 stream is reconstructed on the destination equipment by the decryption module, which reconstitutes the original video stream, from the encrypted video stream, and by regenerating the encryption key from encryption information sent beforehand and from information contained in the encrypted stream. Since all the content protected from video objects is in the stream sent to the user, a malicious person who finds the encryption keys can decrypt this protected content and view or broadcast it. This prior art therefore does not entirely solve the problem of securing the video stream.
• the method according to the invention provides a high level of protection while reducing the volume of information necessary to access the original content from the protected content.
• the protection carried out in accordance with the invention, is based on the principle of deletion and replacement of certain information coding the original visual signal by any method, namely: substitution, modification, permutation or displacement of the information. This protection is also based on knowledge of the structure of the bit stream at the output of the wavelet-based visual encoder.
• the present invention relates to the general principle of a method for securing an audiovisual stream.
• the objective is to authorize video-on-demand and pay-per-view services across all broadcasting networks and local recording in the user's digital set-top box, as well as live viewing of television channels .
• the solution consists in permanently extracting and storing outside the user's home, in fact in the broadcasting and transmission network, part of the digital audiovisual stream recorded at the customer's premises or broadcast live, this part being essential for viewing said digital audiovisual stream on a television screen or monitor type, but being of a very low volume compared to the total volume of the stream digital audiovisual recorded at the user's home or received in real time.
• the missing part will be transmitted via the broadcasting or transmission network when viewing said digital audiovisual stream.
• modified main stream The digital audiovisual stream being modified and separated into two parts, most of the modified audiovisual stream, called “modified main stream” will therefore be transmitted via a conventional broadcasting network while the missing part called “additional information” will be sent to the request via a narrowband telecommunications network such as conventional telephone networks or cellular networks of the GSM, GPRS or UMTS type or by using a small part of a DSL or BLR type network, or even by using a subset of the shared bandwidth over a wired network.
• the original digital audiovisual stream is reconstructed on the recipient equipment (decoder) by a synthesis module from the modified main stream and additional information.
• the invention provides a protection system, comprising an analysis - scrambling and descrambling module based on a digital format resulting from the encoding of a video stream based on wavelet transforms.
• the analysis and scrambling module proposed by the invention is based on the substitution by “decoys” or the modification of part of the coefficients resulting from the transformation into wavelets. The fact of having removed and substituted a part of the original data of the original digital stream during the generation of the modified main stream, does not allow the restitution of said original stream from only the data of said modified main stream.
• the invention relates, in its most general sense, to a method for the secure distribution of video sequences according to a digital stream format resulting from an encoding based on wavelet processing, consisting of frames comprising blocks containing coefficients d wavelets describing the visual elements, characterized in that before the transmission to the client equipment, a flow analysis is carried out to generate a modified main flow, by deleting and replacing certain information coding the original flow and presenting the format of the original stream, and additional information of any format, comprising said digital information coding the original stream capable of allowing the reconstruction of said modified frames, then separately transmitting said modified main stream and said complementary information thus generated from the server to the destination equipment.
• Protection is carried out by deleting the original elements and replacing them with decoys, the extracted original elements being stored separately in the additional information.
• the fact of having removed and substituted part of the original data of the original video stream during the generation of the modified main stream does not allow the restitution of said original stream from only the data of said modified main stream.
• the video stream is fully protected (all sub-bands) and fully transmitted via the network or via physical media to the user, regardless of their rights.
• the partial reconstruction is carried out by sending part of the additional information, containing the original elements, either directly or in progressive mode.
• the analysis and scrambling module decides how to visually degrade the video stream according to its structure and scalability properties resulting from the wavelet transform.
• the study focuses on the impact of the modification of different parts of the flow (coefficients, sub-bands, scalability layers, areas of interest) on visual degradation.
• the scrambling is carried out by modifying wavelet coefficients belonging to at least one temporal sub-band resulting from the temporal analysis.
• the scrambling is performed by modifying wavelet coefficients belonging to at least one spatial sub-band resulting from the spatial analysis of a temporal sub-band.
• scrambling is carried out by modifying wavelet coefficients belonging to at least one temporal sub-band resulting from a temporal analysis of a spatial sub-band.
• the wavelet coefficients to be modified are chosen according to random laws and / or defined a priori.
• the parameters for scrambling depend on the properties of temporal scalability and / or spatial scalability and / or qualitative scalability and / or flow scalability and / or scalability by regions of interest offered by digital streams generated by wavelet-based coders.
• the visual intensity of the degradation of the video sequences obtained is determined by the quantity of wavelet coefficients modified in each space-time sub-band.
• the intensity of the visual degradation of the video sequences decoded from the modified main stream is a function of the position within the original digital stream of the modified data, said data representing, according to their positions, the values quantified according to different precisions of the wavelet coefficients belonging to a space-time sub-band.
• the intensity of the visual degradation of the video sequences decoded from the modified main stream is determined according to the membership in the quality layer of the wavelet coefficients modified in each space-time sub-band.
• the modification of the wavelet coefficients is carried out directly in the bit stream.
• the modification of the wavelet coefficients is carried out with partial decoding. According to another variant, the modification of the wavelet coefficients is carried out during coding or by carrying out a decoding then a complete re-encoding.
• the size of the modified main stream is strictly identical to the size of the original digital video stream.
• the substitution of the wavelet coefficients is carried out with random or calculated values.
• the duration of the visual scrambling obtained within a group of frames is determined as a function of the time sub-band to which the modified wavelet coefficients belong.
• the visual scrambling obtained within a group of frames is spatially limited in a region of interest of each frame.
• the additional information is organized into layers of temporal and / or spatial and / or qualitative and / or flow and / or scalability scalability.
• the stream is gradually descrambled with different levels of quality and / or resolution and / or frame-rate and / or according to a region of interest via the sending of certain parts of the additional information corresponding to the scalability layers respectively qualitative and / or spatial and / or temporal and / or for a region of interest.
• the stream is partially descrambled according to different levels of quality and / or resolution and / or frame-rate and / or according to a region of interest via the sending of part of the additional information corresponding to the (aux) scalability layer (s) respectively qualitative and / or spatial and / or temporal and / or for this region of interest.
• a summary of a digital stream in original format is calculated on the recipient equipment as a function of said modified main stream and of said additional information.
• the transmission of said modified main stream is carried out through a physically distributed hardware medium [CD-ROM, DVD, hard disk, flash memory card].
• the modified main stream undergoes transcoding, rearrangement and / or extraction of frames or groups of frames during its transmission.
• the transmission of said additional information is carried out through a physically distributed hardware medium [flash memory card, smart card].
• the modification of the wavelet coefficients is perfectly reversible (lossless process) and the digital stream reconstituted from the modified main stream and the additional information is strictly identical to the original stream.
• the modification of the wavelet coefficients is perfectly reversible (lossless process) and the portion of the digital stream reconstructed from the modified main stream and the additional information is strictly identical to the corresponding portion in the original stream.
• the reconstruction of a descrambled video stream is controlled and / or limited in terms of predefined frame-rate and / or resolution and / or bit rate and / or quality, according to the rights of
• the reconstruction of a descrambled video stream is limited in terms of frame rate and / or resolution and / or bit rate and / or quality depending on the display device on which it is viewed.
• the reconstitution of the descrambled video stream is carried out gradually in stages until the reconstruction of the original video stream.
• the invention also relates to a system for manufacturing a video stream, comprising at least one multimedia server containing the video sequences. original and comprising a device for analyzing the video stream, a device for separating the original video stream into a main stream modified by deleting and replacing certain information coding the original visual signal and into additional information as a function of said analysis, and at at least one device on the recipient equipment for the reconstruction of the video stream as a function of said modified main stream and of said additional information.
• a video coder based on wavelet processing performs a temporal and spatial decomposition of an initial video sequence in order to obtain a set of spatio-temporal wavelet coefficients. These coefficients are then quantified and then coded by an entropy coder in order to generate one or more nested bit streams which have properties of temporal scalability and / or spatial scalability (or resolution) and / or qualitative scalability and / or flow scalability and / or scalability of regions of interest.
• temporal scalability is the possibility of decoding from a single or several nested bit streams, video sequences whose frame display frequency (number of frames per second) is variable.
• the spatial scalability property is the possibility of decoding from a single or from several nested bit streams video sequences whose spatial resolution (size) of the frames is variable.
• the qualitative scalability property is the possibility of decoding from a single or several nested bit streams video sequences whose visual quality of the frames, measured according to objective and / or subjective criteria, is variable.
• the rate scalability property is the possibility of decoding from a single or several nested bit streams video sequences according to a variable average rate (average number of bits of information per second).
• the region of interest scalability property is the possibility of decoding from one or more nested bit streams one or more targeted areas within the video sequence.
• GOF Group Of Frames
• the spatiotemporal wavelet coefficients are generated in two successive stages and according to a spatial and temporal analysis of the GOF frames.
• the first step consists in carrying out a temporal analysis of the N frames of each GOF according to the estimated direction of movement (temporal analysis with motion estimation), this in order to remove the temporal redundancies and to focus spatially in the frames resulting from the temporal analysis energy and information due to movement.
• This temporal analysis can be carried out according to different spatial resolutions and after decomposition into wavelets of each frame of the GOF, the motion estimation being carried out independently within each spatial sub-band (ulti-resolution motion estimation).
• the second step consists in performing a spatial analysis of the N frames resulting from the temporal analysis using a wavelet decomposition in order to remove the spatial redundancies and to concentrate the energy due to the spatial discontinuities present in each frame.
• the temporal analysis is carried out in several iterations.
• p successive frames of the original GOF are analyzed by means of wavelet filters f L and f H predefined of length p and after estimation and compensation of the movement for each frame and with respect to one or more frames called reference frames.
• a subset tL x of frames of type L of length N / 2 and a subset t-Hj are thus generated .
• H type frames of length N / 2 such as tL- L ⁇ (L 0 , L x , ..., L N / 2 ), tH- L ⁇ (H 0 , E ⁇ , ..., H N 2 ).
• the motion estimation / compensation and the time filtering are iterated over the subset of frames tL k-1 of type L obtained in iteration k-1 and are generated two new sub- sets of frames tL k and tH k whose length (number of frames) is reduced by a factor of 2 compared to tL k-1 .
• the iteration also relates to the subset of frames tH ⁇ .
• n ⁇ The total number of iterations during the time analysis is noted n ⁇ . It is between 1 and N / 2.
• n ⁇ + l temporal sub-bands are generated.
• Sub-band tL 4 1 frame of type L: LLLL 0
• Sub-band tH 4 1 frame of type H: LLLH 0
• Sub-band tH 3 2 frames of type H: LLH 0 , LLH ⁇
• Sub-band tH 2 4 frames of type H: LH 0 , ..., LH 3
• Sub-band tE ⁇ 8 frames of type H: H 0 , ..., H 7.
• the spatial analysis is then carried out on each of the frames belonging to each temporal sub-band t-Li and t-Hi: each frame is decomposed using a discrete wavelet transform at D levels, thus generating 3xD + l spatial sub-bands of wavelet coefficients for each frame.
• spatial sub-bands are denoted s-LL 0 , s- HL ⁇ S-LI ⁇ , s-HH lf s-HL 2 , s-LH 2 , s-HH 2 , ..., s — HL D , s — LH D , S — HH D. temporal and spatial analyzes,
• space-time sub-bands of wavelet coefficients are available: tL nT (s-LL 0 ), tL nT (s-HL 1 ), tL nT (s- HHI), ..., tL nT (S HL-D), tL nT (S-D LH), tL nT (S-D HH), "Nos tH (s-LL 0) tH nT (s-HL 1 ), tH nT (s-LH x ), tH nT (s- 1 ), ..., tH nT (S-HL D ), tH nT (S-LH D ), tH nT ( S-HH D ), m ...
• the wavelet coefficients of each space-time sub-band are then progressively compressed by bit plane using an entropy coder whose aim is to remove the statistical redundancies existing within a fixed set of wavelet coefficients.
• the entropy coder generates, for each set of independently coded wavelet coefficients, a binary f lux which can be divided into several substreams distributed according to different quality layers.
• the analysis and scrambling module makes modifications (by permutation and / or substitution and / or threshold threshold) of a subset coef f hereents d Wavelets belonging to one or more space-time sub-bands. These modifications introduce a visually perceptible degradation (scrambling) of the video sequence decoded from these modified coefficients.
• the choice of the type of spatial sub-band to which the Wavelet coefficients belong makes it possible to control the visual aspect of the scrambling: for the s-HL sub-band of the vertical direction artifacts appear on the frames (degradation of vertical spatial discontinuities), for the s-LH subband of horizontal artefacts appear (degradation of horizontal spatial discontinuities) and for the s-HH subband of checkerboard type artifacts »Appear (joint degradations of horizontal and vertical spatial discontinuities).
• the choice of the resolution level r to which the spatial sub-band belongs makes it possible to control the spatial extent of the scrambling generated by the modification coefficients wavelets: the closer r is to 0, the larger the spatial extent.
• a modification of the wavelet coefficients belonging to a sub-band of resolution r ⁇ 0 generates a scrambling which will be visible on all the decoded frames with higher spatial resolution r + 1, r + 2, ...
• a modification of the wavelet coefficients belonging to a quality layer q generates a scrambling which will be visible on all the decoded frames by considering at least the first q quality layers.
• the modification of the spatio-temporal wavelet coefficients is carried out after a partial decoding of the bit stream generated according to a standard or norm or an algorithm or an encoding format. Once the modification has been carried out, a re-encoding of the coefficients is carried out in order to generate a bit stream of identical size and which respects the conformity with respect to the standard or the norm or the algorithm or the encoding format. having generated the original bitstream.
• subsets of bits inside the original bit stream representing the coefficients of coded spatio-temporal wavelets are modified without decoding and without disturbing the conformity of the stream vis-à-vis the standard or norm or of the algorithm or encoding format that generated the original bitstream.
• the choice of the space-time wavelet coefficients to be modified within a space-time sub-band is conducted randomly and / or according to rules defined a priori.
• the modified main stream has a size identical to that of the original video stream.
• the scrambling thus generated has properties of temporal, spatial, qualitative, flow and area of interest scalability.
• the additional information relating to said scrambling thus generated is organized into layers of temporal, spatial, qualitative, flow rate scalability and on area of interest.
• the scrambling has a temporal scalability between: "all the frames of all the GOFs (maximum scrambling)" and "no frame of no GOF ”(sequence not scrambled).
• the scrambling has a qualitative scalability ranging from: “the whole of each frame is scrambled”, “certain spatial regions of each frames are scrambled ”(regions of interest) and“ no scrambling is applied to the frames ”.
• said descrambling will make it possible to address the various stated scalabilities (temporal, spatial, qualitative, bit rate and area of interest), by sending certain parts of the additional information corresponding to different layers of scalability (temporal, spatial, qualitative, bit rate and area of interest), thus giving access to different levels of quality / resolution / frame-rate for the video sequence decoded from the partially descrambled stream.
• the different levels of quality / resolution / frame rate of the video sequence are obtained from the partially descrambled flow by sending part of the additional information by scalability layer (temporal, spatial, qualitative, bit rate and area of interest).
• the figure represents a particular preferred embodiment of the client-server system according to the invention.
• the original stream (1) is directly in digital form or in analog form. In the latter case, the analog stream is converted by a wavelet-based encoder not shown in a digital format (2).
• the video stream that we want to secure (2) is passed to an analysis and scrambling module (3) which will generate a modified main stream (5) in the same format as the input stream (2) outside that some of the coefficients have been replaced by values different from the original ones, and is stored in the server (6).
• the additional information (4), of any format, is also placed in the server (6) and contains information relating to the elements of the images which have been modified, replaced, substituted or moved, and their value or location in the original feed.
• the stream (5) in the format identical to the original stream is then transmitted, via a broadband network (9) of the radio type, cable, satellite, etc., to the viewer's terminal (8), and more precisely to its hard disk ( 10).
• a broadband network (9) of the radio type, cable, satellite, etc. When the viewer (8) requests to view the film on his hard drive (10), two possibilities are possible: either the viewer (8) does not have all the rights necessary to see the film, in this case, the video stream (5) generated by the scrambling module (3) present on the hard disk (10) is passed to the synthesis system (13), via a read buffer memory (11), which does not modify it and transmits identically to a display reader capable of decoding it (14) and its content, visually degraded by the scrambling module (3), is displayed on the display screen (15).
• the video stream (5) generated by the scrambling module (3) is passed directly via a network (9) to the read buffer memory (11) then to the synthesis system (13).
• the video stream (5) undergoes in the network (9) a series of operations for transcoding and rearranging its frames or groups of frames.
• the server decides that the viewer (8) has the rights to correctly view the film.
• the synthesis module (13) makes a viewing request to the server (6) containing the additional information necessary (4) for the reconstruction of the original video (2).
• the server (6) then sends via the telecommunication network (7) of analog or digital telephone line type, DSL (Digital Subscriber Line) or BLR (Local Radio Loop), via DAB (Digital Audio Broadcasting) networks or via networks.
• the synthesis module (13) restores the scrambled video stream which it reads in its playback buffer memory (11), modified fields of which it knows the positions as well as the original values are restored, thanks to the content of the additional information read in the descrambling buffer (12).
• the amount of information contained in the additional information (4) which is sent to the descrambling module is specific, adaptive and progressive for each spectator and depends on their rights, for example single or multiple use, right to make one or more copies private, late or anticipated payment.
• the level (quality, quantity, type) of the additional information is also determined according to the visual quality required by the user. Wavelet-based video coding characterized by the previously described scalability enables the video stream to be reproduced with different quality, resolution and frame rate levels.
• the modified main stream (5) is passed directly via a network (9) to the read buffer memory (11) then to the synthesis module (13).
• the modified main stream (5) is written (recorded) on a physical medium such as a CD-ROM, DVD, hard disk, flash memory card, etc. (9a).
• the modified main stream (5) will then be read from the physical medium (9bis) by the disk drive (10bis) of the box (8) to be transmitted to the read buffer memory (11) then to the synthesis module (13) .
• the additional information (4) is recorded on a physical medium (7bis) of credit card format, consisting of a chip card or a flash memory card. This card (7bis) will be read by the module (12) of the device (8) which includes a card reader (7ter).
• the card (7bis) contains the applications and the algorithms which will be executed by the synthesis system (13).
• the device (8) is an autonomous, portable and mobile system.
• Sub-band tL 4 1 frame of type L: LLLL 0
• Sub-band tH 4 1 frame of type H: LLLH 0
• Sub-band tH 3 2 frames of type H: LLH 0 , LLH X
• Sub -band tH 2 4 frames of type H: LH 0 / LH 1 ( LH 2 LH 3
• Sub-band tH 1 8 frames of type H: H 0 , H x , H 2 , H 3 , H 4 , H 5 , H 6 , H 7.
• the decomposition into five time sub-bands offers the possibility of reconstructing the initial video sequence according to five different “frame rates”
• the video sequence is scrambled for each GOF as follows:
• the wavelet coefficients of the spatial sub-bands s-HH 2 and s-HH 3 resulting from the spatial decomposition into wavelets of the frame LLLL 0 are extracted and replaced by random or calculated values.
• the wavelet coefficients of the spatial sub-band s-HH 3 resulting from the spatial decomposition into wavelets of the frame LLH 0 are extracted and replaced by random or calculated values.
• the wavelet coefficients of the spatial sub-band s-HH 3 resulting from the decomposition into wavelets of the frame LH 0 are extracted and replaced by random or calculated values.
• the wavelet coefficients of the spatial subband s-HH 3 resulting from the decomposition into wavelets of the frame H 0 are extracted and replaced by random or calculated values.
• descrambling is then carried out for example in five stages, corresponding to different levels of quality obtained after each descrambling stage.
• a descrambling of one or more scalability layers is carried out, the quality of the film viewed being controlled by the server according to the rights of the user and the quality required by him.
• the first descrambling step consists in restoring the wavelet coefficients of the spatial sub-band s-HH 2 for the time sub-band tL 4 .
• the scrambling of the decoded video sequence for a maximum resolution R and at a maximum frame rate of fr 0 is then less spatially extended and more concentrated around the spatial discontinuities of each frame.
• the visual quality of the partially descrambled film is minimal, the film is visually unusable at full resolution and at its original frame rate.
• This step serves to identify the additional information server when establishing the connection.
• the second descrambling step consists in restoring the wavelet coefficients of the spatial sub-band s-HH 3 for the temporal sub-band tL 4 .
• the scrambling of the decoded video sequence for a resolution R and at a frame rate of fr 0 is then much less spatially extended and more concentrated around the spatial discontinuities of each frame.
• the video sequence is now scrambled only for a duration equivalent to half a GOF (8 frames out of 16).
• This step is used for the user (8) to view the video film partially, in order to decide whether he wants to obtain rights to watch the film.
• steps three, four or five are executed.
• the third descrambling step consists in restoring the wavelet coefficients of the spatial sub-band s-HH 3 for the temporal sub-band tH 3 .
• the video sequence is now scrambled only for a period equivalent to a quarter of a GOF (4 frames out of 16).
• the decoded video sequence for the frame rates l / 16xfr 0 , l / 8xfr 0 , l / 4xfr 0 and for the resolutions r R / 16, R / 8, R / 4 is not scrambled.
• the film can be viewed visually, but it is of low quality.
• the fourth descrambling step consists in restoring the wavelet coefficients of the spatial sub-band s-HH 3 for the temporal sub-band tH 2 .
• the video sequence is now scrambled only for a period equivalent to one eighth of a GOF (2 frames out of 16).
• the decoded video sequence for frame rates l / 16xfr 0 , l / 8xfr 0 , l / 4xfr 0 , l / 2xfr 0 and for resolutions r R / 16, R / 8, R / 4 is not scrambled .
• the visual quality of the film returned is average.
• the fifth descrambling step consists in restoring the wavelet coefficients of the spatial sub-band s-HH 3 for the temporal sub-band tH x .
• the yideo sequence is then completely descrambled, whatever the decoding frame-rate and the resolution.
• the reconstructed video stream is strictly identical to the original video stream.

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