Patent Application
20100129055
The invention relates to the field of digital data media such as DVDs.
More particularly, the invention relates to access of the content of these digital data media.
It can be useful to control the access of the content of a DVD in order to:
Therefore, a first application of the invention is to prevent or dissuade any illegal copying of DVDs.
Copying a video DVD on a DVD R is made easy for the general public through copy software (better known as “ripping software” or “rippers”), leading DVD publishers to deplore a substantial shortfall.
In defining the DVD-video standard, protection solutions have been defined, such as CSS or CGMS. Yet these non-upgradable solutions have quickly shown their limits when confronted with the new ripping software developed at the time.
In order to dissuade illegal copying, the DVD according to the document WO 2006/044301 integrates corrupted data in sectors normally used for CSS, in order to be undetectable when the original DVD is played, but to get revealed on a copied DVD. Thus this document teaches how to make hardly readable the contents of a fraudulently copied DVD.
However, these corrupted cells are recognizable by recent ripping software.
In order to dissuade or prevent illegal copying, the document WO 2005/050638 proposes a DVD that includes one or both following solutions:
The ripping software would then be unable to read the DVD or, to the best, would copy an unplayable DVD.
However, the first solution offered by this technique involves the presence of corrupted cells that are recognizable by recent ripping software.
The second solution typically generates on the original DVD a discontinuous playback (non “seamless”) of the stream, and consequently the stream playback quality suffers from that.
The current copy-protection solutions are thus not satisfactory.
A second application of the invention proposes to control access to digital data in order to implement, for instance, services providing a single access to DVDs (this activity is best known as “pay-per-view DVD”).
A user can traditionally watch a DVD either by purchasing or by renting it in a video store or on the Internet. The first solution is expensive if one wants to watch the film a limited number of time, and the second requires returning to the video store to give back the watched DVD, or retuning it by mail, which is boring.
The pay-per-view DVD concept consists in reconciling the advantages of DVDs purchased and rented, by allowing displaying, with a pay per view, a content stored on a durable medium, permanently kept by the user.
To this end, a reliable single access control of the DVD content is necessary.
There are numerous digital access control methods, especially those that implement static or dynamic keys.
For instance, the principle of “public key and secret key” can be applied to DVDs as follows:
In this system, running the algorithm embedded in the plug-in is subject to a paying for view by the user.
Such a system applied to DVDs is for instance described in FR 2 866 749.
This public key-secret key technique needs to use enough memory to store both second keys (which are typically complex codes).
But this technique has a certain protection level, nevertheless insufficient for certain more complex ripping software, which can remove the access control module while keeping the video and audio contents.
WO 2004/109680 discloses a method for single access to a DVD stream, via an access code entered by the user. This access code can calculate the address, on the DVD, of a series of cells. If the code is correct, the read cell series will conform to the user's wish. Otherwise, the sequence will not be the good one, and will correspond to a sequence of uninteresting or non-viewable cells.
However, a skilled ripper will be able, without much difficulty, to regain the good cell series of an original DVD. He will then be able to play them back directly through its remote if they correspond to a particular chaptering or title number; he will also be able, after selecting those good cell series with a ripping software, to perform illegal copying which does not require a return of the access code.
An object of the invention is to remedy these problems relating to single access.
Another object of the invention would be to find a technical solution to prevent or dissuade illegal copying, while allowing permitted private copying.
In order to achieve these objects, the invention provides, according to a first aspect, a digital data medium for storing at least one content stream, comprising:
Optional aspects of this medium are as follows:
It is also proposed a data medium set, characterized in that it comprises a digital data medium as defined above and a medium protective cover provided with a display means reproducing the symbol allowing an access to a normal medium playing if it is selected, the display means being such that the symbol appears in one of the following ways: it is located in the bottom of the cover; it is provided with metal flakes; it is covered with a photoreflective material; it is made with a fluorescent or metallic ink; it has so fine patterns or watermarks ignored by the blurring of a conventional copying system; it is a hologram; it is a fractal; it is a nameless face; it is a design requiring at least a special filter to be understandable, e.g. a color or polarized filter, an independent filter for each user's eye—3D image for instance—, a filter to overlay, etc.
According to a third aspect of the invention, it is provided a method for playing a digital data medium such as defined above, using a playing device for this medium type, characterized in that it comprises the following steps:
Certain optional aspects of this process are as follows:
Other features, objects and advantages will emerge from the following description, which is merely illustrative and not exhaustive and should be read in light of the accompanying drawings, in which:
A system according to the invention comprises:
Referring to
The DVD (1) is dedicated to store at least one content stream, and interactive menus to organize and access content streams in accordance to chapters of the video work (main content), bonuses, advertising, previews (secondary contents), languages, subtitles, etc.
This or these content stream(s) are stored in the DVD (1) in one or more content cells each grouping one or more stream portions. The portions contained in one cell typically represent together a typical content scene, such as for example a movie scene. A content scene contains a video portion and/or one or more audio stream portions associated with the video portion (for instance one audio portion per language) and/or one or more sub-picture stream portions associated with the video portion (for instance one subtitle portion per language).
According to the DVD-video standard specifications, a cell is a stored video, audio and/or subtitle unit having a length that can range from a split second to several hours.
A cell can optionally be linked undividedly to at least another cell in a “block of cells”, each cell of a block containing then a video stream portion (such as a video angle) different from the video stream portion (such as another video angle) of another cell of the block, and/or at least a portion of at least an audio stream and/or at least a portion of at least a sub-picture stream, and each can be different from those of another cell of the block. The undivided link is created by multiplexing these different portions together.
For reasons of convenience, a “block of cells” will be called “multi-angle cell” in the following. In contrast, a “single-angle cell” consists of a single cell.
During production (or authoring) of a DVD, multiple content streams can be interleaved, multiplexed together, to ultimately provide a unique set of linked cells which succeed without even contain a same stream portion.
Finally, since cells of a same video stream are not necessarily adjacent, an additional step for the authoring (called scenario publishing) will help define an organization and cell playback controls in order to allow termination of a particular reading order thereof, to reconstitute each content stream without interference or reading disturbance.
At least one instruction sequence or program chain (“Program Chain”, denoted “PGC”) and at least one program (“Program”, denoted “PG”) may then be created during authoring, a PG being a cell series that is used for example to form a movie chapter, a PGC being a set of at least one PG or cells linked together to create a sequential presentation.
In a PGC can be found one or more navigation data or controls allowing navigation and at least one PG.
The authoring software allows in particular arranging the cells in the PGCs, define the PGs, program certain controls (PCG pre-controls, PGC post-controls, cell controls and button controls). During the DVD encoding, this software will use this information configured to define navigation data which consist in components and controls intended in particular to implement the DVD navigation, the navigation allowing transitions between cells.
Depending on various conditions (e.g. the physical distance that may separate two cells to be played successively, any cell of button controls to be executed during the transition between these two cells, the actual characteristics of the cell contents), the transition will be continuous (“seamless”), almost continuous (“quasi-seamless”) or non continuous (“non seamless”). Advantageously according to the invention, transitions are arranged to be “seamless” or “quasi-seamless”.
It will be noted here that “quasi-seamless” readings, although not guaranteed by the DVD video standard, are the result of a set of conditions producing transitions between cells that are in practice almost imperceptible by a viewer watching the DVD. The person skilled in the art will know how to adjust said different conditions to achieve this effect. Here are a few examples of quasi-seamless transitions:
Referring to
As it will be discussed below, the module (5) for controlling access to the DVD content (1) when playing it may be arranged according to the invention so that setting of the read table (4) is not the same as defined during the authoring, in fact of being incomplete or corrupted, for instance because of a ripping or a denied access.
In order to add confusion in the DVD (1) playback where the read table (4) is not properly set, the DVD (1) advantageously comprises a number of particular cells.
Advantageously, at least certain of these particular cells show a total memory capacity and are so poorly compressible, compared to the whole content cells, that a copy data medium, for instance a single layer DVD-R, which typically has a smaller storage capacity than the storage capacity of an original DVD, for instance a DVD-9, would not have sufficient capacity to store both of these particular cells and the content cells.
Thus these particular cells can prevent a ripping.
Furthermore, a particular cell can be multi-angle or single-angle and can for example provide one or more of the following features:
“Bait” means a video angle and/or an audio stream portion and/or a sub-picture stream portion arranged to give a bad execution to the DVD user if it is called instead of an angle or a content portion. Particular cells containing bait may have been written one at a time in the DVD (1), or initially be part of at least one stream called “bait” interleaved with at least one content stream.
Advantageously, all the cells and stream portions stored by the cells comply with the same data medium standard, such as the DVD Video standard, so that particular cells cannot be distinguished from other cells by a ripper. Thus, illegal copying is not necessarily prevented, but the copied DVD can be rendered unusable (i.e. non viewable or, at least, unpleasant to watch) if it is managed that it has a closed access to content or that its read table (4) is not correctly set—certain techniques employed for this purpose will be described later.
Advantageously, at least a particular stream portion and/or particular cell has been switched with the content portion of the same cell and/or with a content cell, so that if the read table (4) is correctly set, it is the content portion that is read and, if the at least one cell is read without read table (4) or with an incorrectly set read table (4), it is the particular stream portion that can be read. If the particular stream portion is a bait, its playing will make the film non-viewable or unpleasant.
Consequently, a normal stream reading can be obtained only if the read table (4) is correctly set, and by “normal reading” it is meant a reading allowing reading cells in an appropriate order to reconstitute a complete stream (for instance a title, such as for example a film).
On the contrary, if the read table (4) is incorrectly set, a stream (corresponding to a normal reading) cannot be correctly reconstructed, and reading according to this table (4)—then incomplete or corrupted—will lead to an error or a reading of cells not containing the required stream, such as bait cells. The reading then leads to a failure or a non viewable or unpleasant watching or a watching inconsistent with the required stream.
Once the authoring done, the so created DVD (1) is inserted in the DVD player (100) by the user, and then the player (100) runs the booting sector (2) that triggers playback of the access control module (5).
Reading the access control module (5) triggers positioning of the memory (51) in a determined state by storing internal variables therein. This memory (51) can be of GPRM (“General Purpose Registry Memory”) type.
According to the determined state of memory (51), the access control module (5) allows or does not allow a normal reading of at least one content stream, by:
According to the invention, a state is determined by the nature and the storage order of the internal variables that have been loaded in the memory (51) during positioning thereof. This state leads to said normal playing authorization only if the internal variables are preset values stored in a preset order during the authoring.
Advantageously, the access control module (5) carries out said authorization step by:
Thus this technique allows a DVD controlled playback.
Moreover, if, during the authoring, transitions (41) are arranged to be seamless or quasi-seamless, the DVD playback has a high quality (i.e. without any perceptible freezing of the audio/video display).
Various embodiments of the invention are presented below, concerning:
1. Managing the Content Access Control
1.1. Permanent Access Control
This particular embodiment of the invention is intended to dissuade or prevent illegal copies of original DVDs.
To this end, it provides a restricted content access only if the DVD (1) has been illegally copied.
Various non limiting examples of embodiments are shown below:
1.1.1. Manipulating the Controls
Here, the DVD includes at least one preliminary content to which access controls are associated, these access controls being involved, at least in part, to positioning of memory (51).
The preliminary content is chosen so that it is automatically read at the very start of the DVD and corresponds to a typically non copied content in case of an illegal copying (e.g. the legal display against copying).
In this case, said access controls are not copied in case of an illegal copying, and therefore are not executed when someone tries to play the fraudulent DVD.
Since the memory (51) cannot be positioned, the read table (4) is not available or, at least, is corrupted.
1.1.2. Manipulating the Data
Since original video DVDs typically have a memory capacity far superior to copy DVDs (e.g. an 8.5 Go original DVD (DVD-9) and a 4.7 Go copy DVD (DVD R), ripping software must usually compress and delete certain data.
According to this particular embodiment of the invention, video, audio and/or sub-picture bait scenes having at low throughput (for instance 1.2 Mbps), normally unseen by the final user and the ripper, and typically without any commercial interest, are provided in the DVD. These low throughput scenes are poorly compressible.
As a rule, the term “compressibility rate” in the whole present disclosure means the ratio, expressed in percent, between the smallest size achievable after compression of the file, and the size of the original file. Thus, a file that can be strongly compressed has a low compressibility rate, while a file that cannot be strongly compressed has a high compressibility rate, the impossibility of compression corresponding to a compressibility rate of 100%. The “compressibility rate” is the ratio between the size of the compressed file actually obtained and the size of the original file.
For instance, memory of an original medium (DVD-9, 8.5 GB) is employed as follows by MPEG-2 data:
Low throughput scenes (2.5 GB)+commercial content (6.0 GB)
And memory of a copy (DVD R, 4.7 GB) is employed as follows:
Low throughput scenes×T1+commercial content×T2
T1 and T2 being the compression rates to be achieved by ripping for a successful storing on a DVD-R.
As low throughput scenes have been chosen so that T1 cannot be less than a compressibility rate of 99%, T2 in the example should fall to 36%, which is lower than the compressibility rate that can be achieved:
This method thus allows dissuading copying a video DVD on a recordable DVD.
Low throughput scenes may be inserted at a preliminary content (as defined in 1.1.1.), for instance:
Alternatively or in combination, these low throughput scenes can be inserted in certain cells belonging to the set of linked cells (3) as a bait video track, possibly multiplexed into a multi-angle cell. Certain bait tracks could have been switched with content scenes in certain cells.
A correct reading (as determined in the read table (4) during authoring) thus corresponds to the following angular reading: A1+B1+C2.
Generally, ripping software not identifying the content of different angles will interpret the project as follows:
The ripper not recognizing the right path thus cannot delete angles as this would lead to the removal of:
Therefore, this DVD leads to a deadlock if it is expected that all the low throughput scenes lead to the situation shown in
According to another alternative or in combination, low throughput scenes can be inserted in a VTS, a title, a set of additional PGCs, PGs or cells that are not played.
1.1.3. Associating Bait Cells with Access Controls
Bait cells or cell series are defined herein as “critical elements” to which are associated:
Controls are such that the access control module (5) must validate the presence of critical elements in all the linked cells (3), to allow a normal playback of the DVD, for instance as follows (see
Access to a normal DVD playback can then be denied.
1.1.4. Access Control Awaiting User Action
It may be desirable in some cases that the access control module (5) put the DVD playing on standby of an external event, for instance triggered by the DVD user.
For this purpose, and with reference to
Each digital picture (11) may for example be comprised of 36 symbols or pictograms each corresponding to a button associated with a control. Items for presenting this picture (11) to the user may also include a sub-picture (12) superimposed on one of the 36 pictures (indicating the current selection), and which can be moved by using the remote control unit (300). Preferably, the images are present in a random order.
One of the buttons associated with one of the symbols triggers a control allowing access to or setting of the read table 4, by positioning the memory (51).
This latter image reproduces a symbol (22) which is in addition provided to the user on a medium (21), such as for example the cover (21) sold with the original DVD.
In case of erroneous selection, the access control module (5) will position the memory so that the DVD is not read or is partially read in a degraded manner (the read table (4) being incorrectly set).
Advantageously, symbol (22) on the cover (21) is presented in a form non reproducible by conventional reproduction means (copier, scanner, etc.).
This technique can then allow the private copying of the DVD while preventing copying of a borrowed or rented copied DVD, because the cover (21) of these latter DVDs may be different from the original DVD.
Here are examples of non reproducible symbols (22):
1.2. Single Access Control
In this embodiment of the invention, the access control module (5) is arranged to standby for at least one external instruction to the DVD and the DVD player, before being able to wholly position the memory (51). This at least one external instruction, taking the form of a code to be stored in memory (51), will allow the module (5) to enable or not accessing to or correct setting of the read table (4).
For this purpose, and with reference to
The external control device (200) preferably includes an electronic computer, possibly equipped with a keypad and/or a segment display monitor, able to compute a complex code based on a simple code received or entered.
The communication interface (150) may in particular include a display (400) involved in the transmission of information between the player (100) and the external control device (200), through the user, as follows:
Production Phase (
This phase corresponds to the authoring of such a DVD.
A film number 70 is defined by any sequential number assigned to each film, having from four to eight digits.
This film number (70) is processed into an eight digit film key (72) by an “expansion” function (71) which is a reproducible algorithm (not a random variable).
This film key (72) is encoded (74) by using a single and reversible function, with a fixed secret key (73) stored in the DVD (1), in order to position (75) a first series of internal variables (eight GPRMs between 0 and 7) seemingly not linked to the film number (70). This “fixed” secret key (74) can be attributed to a film, a production series, an assignee, etc.
This first series of internal variables (75) is re-encoded (76) by using the same reversible single function from the film key (72). This provides a second series of internal variables (77) (eight GPRMs numbered between 8 and 15) which either does not appear to be linked with the film number (70).
Thus, even if only 10,000 different series of internal variables among 100,000,000,000,000,000 (one hundred million billion) possible combinations are generated, it is impossible to infer them simply from the film number (70).
Watching Phase (
Once the DVD is created, viewing its contents by inserting it in the player (100) is attempted.
This phase corresponds to the positioning of internal variables in memory (51).
The access control module (5) can operate as follows: at the startup, the DVD combines (79) the film number (70) and the random code (78) and then performs an addition—carries out a “checksum” (80). Then the film number (70) is encoded with a four digit random code (78) in order to produce an eight digit simple code (81) (“SSSS SSSS”), possibly supplemented by a two digit control code (“XX”).
This simple code (81) is transmitted (82) via the communication interface (150) to the external control device (200) which sends back (83) via the communication interface (150) an eight digit complex code (84) (“TTTT TTTT”), possibly supplemented by a two digit control code (“XX”).
This complex code (84) is then encoded (85) by using the reversible single function, with the simple code (81), which allows to form a second series of internal variables (86). This second series (86), encoded in turn ((76−1) by using the reversible single function submitted to a reversion, i.e. an inverse code of code (76)), by using the film key (72), allows to regain a first series of internal variables (88).
The film key (72) allowing to regain the first series of internal variables (88) is itself rebuilt (71) from the film number (70) by using the same algorithm as implemented during the DVD production phase (
It is noteworthy that the reversible single functions used to perform the encodings 74, 76 (
Control Phase with External Control Device (
This phase corresponds to steps carried out at the external control device (200).
The external control device (200) is initialized (90) with the secret key (73) of the film or series it must protect, or directly with the second series of internal variables (86) if it must protect only one film. As to the film number (70), it can be introduced into the external control device (200) during initialization (90) or be deduced (89), on an ad hoc basis, from the simple code (81) received (82) from the DVD.
As in the production phase, the film number (70) and the secret key (73) allow rebuilding step by step (encoding (76′) using a reversible single function to create a first series of controls (88′) then encoding (74′) using the same reversible single function) the second series of controls (86′). Encoding (85′) using the same reversible single function of this second series of internal variables (86′) by means of the simple code (81) produces the complex code (84) which is sent back (83) to the DVD.
Synthesis
There is an asymmetry in the access control process if encodings (74′), (76′) and (85′) carried out by the external control device (200) are not respectively similar to encodings (74), (76), and (85) provided on the DVD during authoring.
In particular, encoding (85) is so correlated with the conversion mode (79)-(80) of the simple code (81) that a second series of values (86) is systematically found, whatever the random code (78), according to a same determined order (during authoring), only when the encoding (85′) embedded in the external control device (200) is identical to the DVD encoding (85).
The access control module (5) is then arranged to permit access to the read table (4) only if the internal variables (86) and (88) stored in memory (51) are those initially planned during the DVD authoring.
Alternatively, internal variables (86) and (88) stored in memory (51) directly define setting of the read table (4). The latter is therefore incorrectly set if said asymmetry exists.
Such a content access management allows a controlled access to each DVD playing:
Possible Variations of Single Access Control
The external control device (200) can be:
Said external control device (200) can also include a consumption counter:
2. Read Table (4)
As seen above, the read table (4) is created by the authoring software and particularly by a scenario editor that produces notably the cell sequences, the PGCs, the controls, buttons and data necessary for navigation between cells and addressing of intercellular transitions.
Referring to
It is here reminded that a self-forced button simulates the button selection and action by a user on a button in order to automatically control the playback of an angle of cell M.
It is advantageous to use such a button because its running is seamless.
However, all DVD players are not compatible with such running.
Therefore the inventor provides, according to an optional embodiment of the invention, an “emergency title” (“title 2” in
In title 2, the cell H does not contain a self-forced button, but the cell C contains a cell control indicating an angle change, the angle number being given by an internal variable (GPRM)—this number being interpreted for running the next cell M.
This control is arranged so that its running is quasi seamless.
Thus, the scenario consists in the following:
In this example, if GPRM 1=2, GPRM 2=1 and GPRM 3=2, stream portions played in cells M will be successively video 12, video 21 and video 32. Non-played stream portions are baits or are stream portions inconsistent with a stream current reading.
It is thus possible to obtain a seamless or quasi seamless reading according to a full or partial compliance of the DVD player to the DVD standard, interest in watching being conditioned by a correct preliminary positioning of GPRMs by the access control module.
Variations of Read Table 4
a. Doubles
Alternatively, the following programming can be carried out:
b. Multiplication of Baits
It has to be noted that the invention is not limited to a choice of video baits, but is also applicable, in combination with or alternatively to video baits, to audio or even sub-picture baits. In the latter case, since sub-pictures are typically bitmap like pictures, they can especially be used to mask whole or part of the video.
To complicate the fraudster's task, it is possible to multiply baits such as:
When using ripping software, the fraudster will thus see, in that event, a long list of titles without being able to discern the one(s) really useful to a good film running.
c. Multiplexing Correct Tracks
It is possible to multiplex together several parts of audio and video contents in the same cells M. In this case, there will be at least two titles, each running a different part.
There are two different scenarios: one where a cell M is long enough to contain a full audio and video content (typically a full bonus), and the opposite (typically a portion of the movie).
In the first case, both contents can be the subject of two titles, each being seamless.
In the second case, seamless conditions cannot be simultaneously satisfied for both titles; however, it is possible to define conditions under which one title is seamless and the other is quasi seamless. Or even that certain transitions are seamless and others are quasi seamless in both titles.
Since this method allows putting in the same angle certain conventionally suppressed parts (advertising, bonuses, warning, credits), and certain conventionally preserved parts (film) during a ripping, it is possible to effectively prevent removal of these conventionally suppressed parts.
d. Multiplication of Buttons
In PGC normally having buttons, bait buttons can be added (up to 36), which are invisible to the user, but which a ripping software will not distinguish from others, especially if these invisible buttons are associated with controls that resemble to those of effective buttons, but are corrupted.
Thus, a normal DVD playback on a screen and the presence of a real user become necessary, which prevents any automation of new ripping software trying to reconstruct the read table by interpreting controls while normally playing the DVD.
e. Multiplication of DVD Series
Content protection methods can be combined in a different way by DVD series (typically 5000 units) rather than by DVD reference (typically a film title).
Thus it is possible to hinder spreading of ripping software. If the cover, the wafer and the BCA are exactly the same for all DVDs corresponding to one reference, the user will not have any visual reference point to identify his DVD series. He will therefore be embarrassed to know how to set any new ripping software.
| Number | Date | Country | Kind |
|---|---|---|---|
| 07/53667 | Mar 2007 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2008/052723 | 3/6/2008 | WO | 00 | 9/3/2009 |
