KR20050023421A - Copy control using digital speed bumps - Google Patents

Abstract

A digital media recorder and its control method are shown. During attempts to copy media content, such as audio or video sequences, subsequences are extracted from the input media sequence. The digital fingerprint of the sub-sequence is calculated and compared with at least one first reference fingerprint from the database. The result of the comparison determines the action taken in other processing. Recording of an input medium sequence on a medium carrier is allowed or blocked, eg disallowed. In this case, recording of the sequence is allowed, and the database is updated with the information on which the digital medium sequence is recorded. This has the effect of "speed bump", which limits the speed at which their copies of the media content can be made, ie the effect is to prohibit more than a number of copies given in a given time frame.

Description

Copy control using digital speed bumps

The present invention relates generally to the field of copy protection of digitally recorded media, and in particular to digital media recorders and methods of controlling such recorders.

Some unauthorized copying of copyrighted media content has become an important issue for long periods of time. For example, audio records are recorded on cassette tapes and television programs and movies are copied into video. Unauthorized copies of such formats of analog recording media are all corrupted by at least a slight deterioration of quality when compared to the original records.

However, the problem has become more and more important as the media industry enters the "digital age". Music and movies are currently distributed in digitally encrypted form, copies of which are typically indistinguishable from the original, creating a larger market for "pirates" of media content.

To illustrate the situation, a compact recordable disc, i.e., CD, can be considered. These are typically used for recording audio content. However, any media content can be recorded on such discs. Further, while the following discussion is illustrated by the CD-R, there are other digital recording media capable of recording the medium, for example in the form of movies that are equally relevant to the discussion.

Since its introduction, the CD-R has been an overwhelming success story. One of the main factors contributing to its rapid compliance is that consumers now have the possibility to make digital quality copies of the most popular audio forms — compact discs — played on any CD player. On the other hand, CE style CD recorders, i.e. dedicated digital audio copying devices, limit the copying of the copyrighted disc to first generation copies, and have built-in limitations for a PC based on CD recorders. You must run a Serial Copy Management System (SCMS). The latter has been a big problem from the point of view of content owners, for example, immediately after the release of a new music album, a number of CD-R copies are released for exchange and sale on school campus-like environments. Face the scenario. As a result, and especially in conjunction with the mp3 configuration on the Internet, content owners view CD-R as a major factor in the slowing growth of CD sales.

Technical measurements thus prevent misuse of the recorders, such as making it very desirable to make multiple copies. At the same time, the convenience of the devices is not impaired, for example if copying is allowed by the owner of the content, then it should be possible to process at high speed.

Previous technical solutions within the technical field of copy protection of digital data have been disclosed in the international patent application published under WO 00/04688. A method and system for protecting digitally watermarked media content includes generating digital tickets in combination with the media content. The ticket holds information regarding the copy protection status of the content as well as the receiver and digital watermark. The content of the ticket is processed by the receiver to determine whether to allow the receiver to copy the content.

1 and 2 are schematic diagrams of a digital media recorder according to the present invention;

3 is a flow chart of a method according to the invention.

It is an object of the present invention to provide a solution to the problem of a method for providing a more adaptive operation of copy protection of digital media content.

According to a first aspect, the invention as claimed in claim 1 below provides a solution as a method of controlling a digital media recorder capable of recording digital media sequences on a digital media carrier. Sub-sequences are extracted from an input medium sequence, such as an audio or video sequence. The digital fingerprint of the sub-sequence is calculated and compared with at least one first reference fingerprint, which is taken from the primary database of fingerprints. The result of the comparison yields a first comparison value used when determining the action taken in another process. Depending on the first comparison value, writing of the input medium sequence on the medium carrier is allowed or blocked, eg disallowed. If recording of the sequence is allowed, then the primary database is updated with the information on which the digital medium sequence is recorded on the medium carrier.

Preferably, the primary database of fingerprints includes a copy count number and a copy limit number combined with the fingerprints in the list. Comparing the sub-sequence fingerprint with the first reference fingerprint includes a copy count number and a copy limit number, and updating the primary database includes updating the copy count number in combination with the fingerprint. Include.

In order to precisely adjust the multiple events of the sub-sequence in the medium sequence, the invention preferably further comprises comparing the sub-sequence fingerprint with at least one second reference fingerprint, wherein the second reference fingerprint Is taken from the secondary temporary database of the fingerprint. This comparison yields a second comparison value, which is used to determine another process. Depending on whether the second comparison value indicates whether a fingerprint exists in the secondary database, the fingerprint is stored in the secondary database. The primary database is finally updated with information from the secondary database when recording is complete.

If a record is made, recorder checks are made in advance by checking the fingerprint in the primary database. If so, some appropriate action is taken, such as stopping recording or adding noise. Since the database is of limited size, older entries are removed for newer ones, preferably on a first-in first-out basis, which means that they will be granted again after blocked records. This means that within a predetermined time, determined by the size of the database, prohibits copy records, but is independent of the speed at which the records are made.

Note that the addition of copy count and copy limit with each database entry allows copies to be made more than one record in the series. For example, if the copy limit is set to 3, a series of three copies can be made. The user then has to make a number of different copies, and then a new series of new copies can be made and so on.

For any new record, it is verified that the database does not contain its fingerprint, or if it does, the maximum number of copies has not yet been made. Otherwise, recording is prohibited, continue with reduced quality, or other appropriate action will be taken. That is, the recorder stores that the record is made by storing fingerprints in the first database.

In other words, the technical effect of the present invention can be defined by the concept of "speed bump", which does not block the made copies, but limits the speed when those copies can be made. In its basic form the concept is: Recorders are prohibited from making more than a given number of copies to be made within a given time frame.

In order to make the presented speed bump machine efficient, especially in the PC world, it is not easily disturbed by making undetectable changes to the digital content of the medium. This excludes executions that rely solely on cryptographic hash functions. However, a viable alternative to use is the following paper: Robust Audio Hash, disclosed in "Robust Audio Hash for Content Identification," by Ton Calker and Job Ostivin, Jean Heitzma, 2001, Brescia, Content-Based Multimedia Indexing Council Or a fingerprinting technique. This technique allows the extraction of robust features from the recorded media content, which the recorder can store in an internal database.

The advantage of the presented machine is that no particular preliminary preparation of the original media content is required as is the case with prior art systems that rely on signaling by embedded watermarks. This is also correct for the records (eg no remarking is needed). Thus, audibility does not play a role. In addition, there are also no planned signal distortion threats, for example to remove watermarks.

Another advantage of the present invention is that the use for (small-) business purposes is substantially frustrated while the use for personal purposes is achieved only to a small extent-depending on the allowable emissivity.

Another advantage is also that in PC based recorders the speed bump machine can be operated spontaneously, i.e. without assistance from the PC's main processor, when realized as a separate hardware module in its own recorder as will be described in more detail below.

Another advantage of the speed bump machine according to the invention is that the fingerprinting technique itself does not need to be standardized-it is the very concept of ownership and speed bumps, that is, of the series and time that passes until other series of copies are allowed. This can give a competitive advantage to ensure the efficiency of the maximum number of copies of the quantity.

According to a second aspect, as claimed in claim 7, the present invention provides a solution by means of a digital media recorder capable of recording digital media sequences on a digital media carrier, the technical effects and advantages of which are mentioned above. Corresponds to the first aspect of the invention as described above.

The digital media recorder and the method by which such a recorder can be controlled are shown immediately in connection with FIGS.

Although embodiments will only discuss audio sequences and use terminology relating to audio recordings, other types of media may be considered equivalents and discussed separately. It should also be understood that the present invention is applicable to other types of digital recording media other than the illustrated CD-R, such as a medium based on magnetic recording techniques.

1 and 2 respectively show digital recorders 100 and 200, memory 103 and 203 and processing units 104 and 204, which include input / output units 102 and 202 connecting to digital media sources 101 and 201, respectively. And recording units 105 and 205 capable of receiving removable blank recording media 108 and 208 such as CD-R.

As FIG. 2 shows, a separate control unit 209 can be present in addition to the processing unit 204. As those skilled in the art will understand, all units are connected via buses 106 and 206 and may also include a connection 207 to a computer, as shown in FIG. 2. The media content controlled by the recorders 100, 200 begins at the media source 101, 201. As will be appreciated by those skilled in the art, such media sources 101 and 201 may be in the form of data streams from external computers, digital outputs from digital playback devices, and the like.

As will be apparent from the description for carrying out the method according to the invention, the speed bump mechanism does not necessarily act on the level of albums or tracks, but on the basis of recording time, i.e. sub-sequences of tracks or albums. do. The flowchart in FIG. 3 shows a schematic overview of the algorithm. There are two databases that play a role: The primary database contains fingerprints of records made on disks before the current one, and the secondary database contains those on the current disk. Both databases are realized in the memory 103, 203 of the recorder, as those skilled in the art will understand.

With regard to the arrangement in FIGS. 1 and 2 as well as the flowchart in FIG. 3, the method according to the invention will be described immediately. The method is preferably realized in the form of control sequences, ie software stored in the memory 103, 203 of the recorders 100, 200. The software is operated by cooperating the processor 104, 204, the copy control unit 209 and / or the processor 104, 204 with the control unit 209.

Further, the method assumes that the recording medium 108, 208 is inserted into the recorder according to the present invention in the form of a disc (e.g., CD-R), such as the recorder disclosed in Figs. In addition, the criteria will be primary and secondary databases.

In the input and extraction step 301, beginning the method of the invention, fingerprints are extracted on a continuous basis from audio content received from the media source 101, 201 and used for recording.

Each extracted fingerprints are compared with the primary database for matching in matching step 302. If no match is found that includes recording of the sequence is authorized, the method continues with a storage decision step 305. During the storage decision step 305, it is determined whether the fingerprint is to be stored in the secondary database. The decision is preferably based on the features in terms of time intervals, ie the duration of the sub-sequence in the query. Other features for selecting a fingerprint for storage may be based on the characteristics of the fingerprint itself. Any combination of features can also be used. These features will be described below in more detail.

Continuing the method of the invention, if a matching entry that has reached the copy limit is found in matching step 302, then a check is calculated whether the copy limit has been reached in check step 303. Proper action will be taken in operation step 303 if the copy limit is reached. The action taken in step 304 preferably has the effect of degrading the recording, thus reducing the " value " of the recording, not only notifying the user of the action taken, but also continuing the recording process at a reduced quality. Operations such as stopping processing.

However, if the matching entry has not yet reached the copy limit, when checked in the copy limit check step 303, the fingerprint is stored in the secondary database as indicated in the save step 307. If the fingerprint already exists in the secondary database, it does not need to be stored again, as indicated by check step 306.

The step of writing then takes place in writing step 308 and proceeds according to procedures known in the art.

In inspection step 309, it is determined whether or not the recording is finished. If not, control returns to the stage of input and to extraction 301.

All records are correctly executed and also checked in check steps 310 and 311, when the current disk is detached from the drive, the primary database is updated from the secondary database in the updating step 12. Therefore, the updating step 312 includes incrementing copy counters of fingerprints occurring in both databases, and moving the fingerprints that hold from the secondary database to the primary database using first in, first out.

The algorithm correctly processes frequently occurring, eg classical music, within a portion of the audio. Basically, the idea is that it doesn't matter how many copies are on a single disk, because they can't be sold or given separately. Therefore, they are treated as a single example.

The database is divided into two parts, as already indicated, that is, the previous history of fingerprints in the primary database, and the fingerprints of the current disk in the secondary database. In order to ensure that the speed bump machine is not activated for failed records according to the invention, only the primary database can be used for verification purposes. Updating this database does not occur until the disk is detached and all records on that disk are correct.

As discussed above in connection with the storage decision step 305, the fingerprints of the sub-sequences are stored in the secondary database at some regular time intervals. Their effect is to introduce frequent degradation of the quality of the recording, reducing the "value" of the unauthorized recording of the media sequence.

A more detailed discussion of the features regarding the regularity of fingerprint storage will follow immediately. As discussed previously, when the copy limit reaches a particular media sequence, the fingerprint is stored in a secondary database. The regularity of these storage operations, i. E. The time scale, preferably depends on the type of content controlling the copy and partly on the fingerprinting algorithm used. The time scale for the sub-sequence is considerably shorter than the complete medium sequence under consideration. For example, for modern popular music where songs typically last only a few minutes, the one minute sub-sequence may be appropriate. This may result in several examples (eg, with predefined or adaptive durations and intensities) of operation step 304 in the record, which substantially reduces the (unauthorized) record if an unauthorized record is attempted. Distortions of the recorded signal). For video sequences, a sub-sequence time interval of 5 or 10 minutes would be appropriate because the movie generally lasts over an hour. Alternatively, additional random time intervals may also be used.

The regularity of the storage of sub-sequence fingerprints also depends on the fingerprinting algorithm used. For example, the algorithms of previously referenced papers (Italy, Brescia, Content-Based Multimedia Indexing Conference 2001, "Robust Audio Hashing for Content Identification", Jean Heightsma, Tone Kalker, and Job Oustbin) can be used for a short time. Generate a substantial amount of information. As a result such a method is preferably used in "burst mode", ie, fingerprint information is stored in the secondary database only for a short piece of content. Other fingerprinting algorithms can be thought of producing information at a slower speed; It may rather be possible to store all the information in a database, which implies that the interval is reduced to zero and the sub-sequence is actually a complete medium sequence.

One example of the implementation of the method as described above will be reported briefly immediately.

Based on the fingerprinting method disclosed in the previously referenced paper (Italy, Brescia, Content-Based Multimedia Indexing Conference 2001, "Robust Audio Hashing for Content Identification", Jean Heightsma, Tone Kalker and Job Oustbin), Subsequent estimates of the performance of the speed bump algorithm, as indicated, can be made. Of course, this is only one example and is included here for illustrative purposes only. Other uses and choices are possible, as would be understood by one skilled in the art.

Fingerprint information is generated at a rate of 1 kB per 3 audio seconds. During each audio-minute, the continuous 3/8 audio-second portion of the fingerprint is stored in a database, which occupies about 16 bytes using a suitable utilization technique. If a velocity bump of 16 real-time times is obtained, recording occurs at a single velocity, and the primary and secondary database sizes are about 15 kB and 1 kB, respectively. While searching the database, the bit-error rate in one of the eight fingerprints is a common signal processing "attack" (eg, all-band filtering, equalization, subsequent D / A and A / D conversion). , And sufficient tolerance against mp3 compression at 128 kbps). Assuming a blind search strategy, it takes on average 4 bytes per fingerprint to determine that there is no match, which delivers up to the memory bandwidth required for a database of about 320 kB / audio-seconds. As a result, a false positive rate can be estimated at about 2 x 10 ^-12 per audio-second. Note that the drawings for the first database size, memory bandwidth, pseudo position rate at higher write speeds must be adjusted accordingly to maintain the efficiency of the speed bumps.

Thus, to summarize; A digital media recorder and its control method are shown. During attempts to copy media content, such as audio or video sequences, subsequences are extracted from the input media sequence. The digital fingerprint of the sub-sequence is calculated and compared with at least one first reference fingerprint from the database. The result of the comparison determines the action taken in other processing. Recording of an input medium sequence on a medium carrier is allowed or blocked, eg disallowed. In this case, recording of the sequence is allowed, and the database is updated with the information on which the digital medium sequence is recorded. This has the effect of "speed bump", which limits the speed at which their copies of the media content can be made, ie the effect is to prohibit more than a number of copies given in a given time frame.

Claims (12)

A method of controlling a digital media recorder capable of recording digital media sequences on a digital media carrier, the method comprising: Extracting a media sub-sequence from the input media sequence, Calculating a sub-sequence digital fingerprint from the medium sub-sequence, Comparing the sub-sequence fingerprint with at least one first reference fingerprint to produce a first comparison value, wherein the first reference fingerprint is fetched from a primary database of fingerprints. Calculating the Allowing the recording of the input medium sequence on the medium carrier, in dependence on the first comparison value, Blocking the recording of the input medium sequence on the medium carrier, in dependence on the first comparison value, Updating the primary database with the information recorded on the media carrier by the digital medium sequence, at least in dependence on the first comparison value. The method of claim 1, wherein the primary database of fingerprints comprises a copy count number and a copy limit number associated with fingerprints in a list, and comparing the sub-sequence fingerprint with a first reference fingerprint comprises: And comparing the copy count number with the copy limit number, wherein updating the primary database comprises updating the copy count number associated with the fingerprint. The method according to claim 1 or 2, Comparing the sub-sequence fingerprint with at least one second reference fingerprint to produce a second comparison value, wherein the second reference fingerprint is fetched from a secondary database of fingerprints. Calculating the value, Depending on the second comparison value, storing the fingerprint in the secondary database, wherein updating the primary database further comprises information from the secondary database. . 4. A method according to any one of the preceding claims, wherein the updating of the primary database depends on whether or not recording of at least one medium sub-sequence has been completed. The digital medium of claim 1, wherein the blocking of the recording comprises at least one of operations to stop recording, reduce the quality of the recording, and notify the user of the blocking. How to control the recorder. The method of any one of claims 1 to 5, wherein the extraction of the sub-sequence comprises extraction for a predetermined time interval, wherein the time interval has a length that is determined at least in part by the format of the medium sequence. Digital media recorder control method. A digital media recorder capable of recording digital media sequences on a digital media carrier, comprising: Means for extracting a media sub-sequence from the input media sequence, Means for calculating a sub-sequence digital fingerprint from the medium sub-sequence, Means for comparing the sub-sequence fingerprint with at least one reference fingerprint to produce a first comparison value, wherein the first reference fingerprint is fetched from a primary database of fingerprints. Calculating means, Means for analyzing said first comparison value, Means for recording the input medium sequence on the medium carrier, Means for interrupting recording of the input medium sequence on the medium carrier, Means for updating the primary database with information recorded on the medium carrier by the digital medium sequence. 8. The apparatus of claim 7, wherein the primary database of fingerprints includes the copy count number and the copy limit number associated with fingerprints in a list, and means for comparing the sub-sequence fingerprint with a first reference fingerprint. Means for comparing the copy count number with the copy limit number and the means for updating the primary database comprises means for updating the copy count number associated with the fingerprint. Digital media recorder available. The method according to claim 7 or 8, Means for comparing the sub-sequence fingerprint with at least one second reference fingerprint to produce a second comparison value, wherein the second reference fingerprint is fetched from a secondary database of fingerprints. Means for calculating a value, Means for storing the fingerprint in the secondary database, wherein the means for updating the primary database further comprises means for updating with information from the secondary database. . 10. The digital medium of any of claims 7 to 9, wherein the means for updating the primary database comprises means for determining whether recording of the at least one medium sub-sequence is complete. Digital media recorder capable of recording sequences. 11. A method according to any one of claims 7 to 10, wherein the blocking means may perform at least one of the operations of interrupting recording, reducing recording quality, reducing the quality of the recording, and notifying the blocking to the user. And a blocking means capable of recording digital media sequences. 12. The apparatus of any one of claims 7 to 11, wherein the means for extracting the sub-sequences comprises means for extracting for a predetermined time interval, wherein the time interval is at least in part by the format of the medium sequence. A digital media recorder capable of recording digital media sequences having a length determined.