Marking a digitally encoded video and/or audio signal

• US 6,131,161 A
• Filed: 10/03/1996
• Issued: 10/10/2000
• Est. Priority Date: 10/04/1995
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Linnartz, Johan P. M. G.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US08/723,653
• Time in Patent Office: 1,468 Days
• Field of Search: 380/3, 380/4, 380/5, 380/9, 380/10, 380/11, 380/12, 380/13, 380/14, 380/15, 380/16, 380/17, 380/18, 380/19, 380/20, 380/49, 380/50, 380/51, 380/54, 380/55, 380/59, 380/200, 380/201, 380/203, 380/287, 382/232, 382/276, 382/282, 382/283, 713/150, 713/168, 713/176, 713/177-179, 713/200, 713/201
• US Class Current: 713/176
• CPC Class Codes: G06F 2211/007 Encryption, En-/decode, En-/decipher, En-/decypher, Scramble, (De-)compress
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 1/0085 Time domain based watermarking, e.g. watermarks spread over several images
• CPC Class Codes: G06T 2201/0053 Embedding of the watermark in the coding stream, possibly without decoding; Embedding of the watermark in the compressed domain
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/0021 involving encryption or decryption of contents recorded on or reproduced from a record carrier
• CPC Class Codes: G11B 20/00405 the key being stored by varying characteristics of the recording track, e.g. by altering the track pitch or by modulating the wobble track
• CPC Class Codes: G11B 20/00884 involving a watermark, i.e. a barely perceptible transformation of the original data which can nevertheless be recognised by an algorithm
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 2005/91321 the copy protection signal being a copy protection control signal, e.g. a record inhibit signal
• CPC Class Codes: H04N 2005/91335 the copy protection signal being a watermark
• CPC Class Codes: H04N 2005/91342 the copy protection signal being an authentication signal
• CPC Class Codes: H04N 21/23892 involving embedding information at multiplex stream level, e.g. embedding a watermark at packet level
• CPC Class Codes: H04N 21/8358 involving watermark protecting executable software by watermarking G06F21/16; image watermarking in general G06T1/0021; watermarks inserted in still images for transmission purposes H04N1/32144; inserting watermarks during video coding H04N19/467
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection

Abstract

An electronic watermarking scheme is proposed that can significantly increase the security of copy protection mechanisms. The watermarking methods works at high level in the hierarchy of the (MPEG) source signal. This ensures that the watermark is easily detectable, but difficult to erase without significant transcoding effort. Such transcoding is considered a difficult and expensive task that may furthermore lead to loss of quality or increase in bit rate.

Claims

1. A method of watermarking a digitally encoded signal which is decoded prior to being displayed, comprising the steps of:

assigning a predetermined value to a selected encoding parameter of a digitally encoded signal having a plurality of coding parameters, the selected encoding parameter relating to encoding a signal and which, when modified, requires at least two other encoding parameters of the signal to be modified in order to maintain the format of the signal or prevent errors in the decoding of the signal; and

encoding the signal with the predetermined value so as to produce a detectable watermark in the signal which prevents copying of the signal and that cannot be removed unless the signal is decoded and reencoded without the predetermined value.

2. The method as claimed in claim 1, wherein the digitally encoded signal is an MPEG signal, and wherein the predetermined value is the number of slices in a frame.

3. The method as claimed in claim 2, wherein successive frames alternately comprise a modulo-N and a modulo-M number of slices in which N and M are integers.

4. The method according claim 3, wherein N and M have different values.

5. A method of decoding a digitally encoded signal which has been encoded by setting an encoding parameter to a predetermined value, comprising the steps of:

detecting, in the digitally encoded signal, the predetermined encoding parameter used to encode the signal;

preventing copying of the digitally encoded signal if the signal contains the predetermined value; and

decoding the digitally encoded signal if the signal does not contain the predetermined value.

6. The method as claimed in claim 5, wherein the digitally encoded signal is an MPEG signal, and wherein the predetermined value is the number of slices in a frame.

7. The method as claimed in claim 6, wherein successive frames alternately comprise a modulo-N and a modulo-M number of slices in which N and M are integers.

8. The method according claim 7, wherein N and M have different values.

9. An encoder for watermarking a digitally encoded signal which is decoded prior to being displayed, the encoder comprising;

assigning means for assigning a predetermined value to a selected encoding parameter of a digitally encoded signal having a plurality of coding parameters, the selected encoding parameter relating to encoding a signal and which, when modified, requires at least two other encoding parameters of the signal to be modified in order to maintain the format of the signal or prevent errors in the decoding of the signal; and

encoding means for encoding the signal with the predetermined value so as to produce a detectable watermark in the signal that cannot be removed unless the signal is decoded and reencoded without the predetermined value.

10. A decoder for decoding a digitally encoded signal which has been encoded by setting an encoding parameter to a predetermined value, the decoder comprising:

detecting means for detecting, in the digitally encoded signal, the predetermined encoding parameter used to encode the signal;

preventing means for preventing copying of the digitally encoded signal if the signal contains the predetermined value; and

decoding means for decoding the digitally encoded signal if the signal does not contain the predetermined value.

11. A system comprising:

an encoder which to assigns a predetermined value to a selected encoding parameter of a digitally encoded signal having a plurality of coding parameters and encode a signal which is decoded prior to being displayed with the predetermined value so that, when modified, at least two other encoding parameters of the signal must be modified in order to maintain the format of the signal or prevent errors in the decoding of the signal so as to produce a watermark in the signal, the encoding parameter relating to encoding the signal; and

an electronic storage medium which stores the signal encoded by the encoder.

12. A system as claimed in claim 11, wherein the encoded signal is an MPEG signal, and wherein the predetermined value is the number of slices in a frame.

13. A system as claimed in claim 12, wherein successive frames of the MPEG signal alternately comprise a modulo-N and a modulo-N number of slices in which N and M are integers.

14. The system according claim 13, wherein N and M have different values.

15. A system comprising:

an encoder for assigning a predetermined value to a selected encoding parameter and for encoding a signal with the predetermined value so as to produce a watermark in the signal, the encoding parameter relating to encoding the signal;

an electronic storage medium which stores the signal encoded by the encoder; and

an electronic device which reads the encoded signal from the electronic storage medium, which decodes the signal if the predetermined value is not detected, and which prevents decoding of the signal if the predetermined value is detected.