Subliminal message protection

• US 6,122,322 A
• Filed: 05/13/1999
• Issued: 09/19/2000
• Est. Priority Date: 11/19/1996
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Jandel, Magnus
• Primary Examiner(s): Britton, Howard
• Assistant Examiner(s): DIEP, NHON THANH
• Application Number:
  US09/310,739
• Time in Patent Office: 495 Days
• Field of Search: 346/46, 346/94, 358/908, 348/699, 348/700, 348/473, 348/475, 348/553, 348/154, 348/155
• US Class Current: 375/240.13
• CPC Class Codes: H04N 21/433 Content storage operation, e.g. storage operation in response to a pause request, caching operations
• CPC Class Codes: H04N 21/44008 involving operations for analysing video streams, e.g. detecting features or characteristics in the video stream arrangements characterised by components specially adapted for monitoring, identification or recognition of video in broadcast systems H04H60/59
• CPC Class Codes: H04N 21/454 Content or additional data filtering, e.g. blocking advertisements
• CPC Class Codes: H04N 21/47 End-user applications
• CPC Class Codes: H04N 21/4882 for displaying messages, e.g. warnings, reminders arrangements for providing short real-time information to substation in data switching networks H04L12/1895
• CPC Class Codes: H04N 21/812 involving advertisement data advertising per se G06Q30/02
• CPC Class Codes: H04N 5/147 Scene change detection
• CPC Class Codes: H04N 7/52 Systems for transmission of a pulse code modulated video signal with one or more other pulse code modulated signals, e.g. an audio signal or a synchronizing signal assembling of a multiplex stream by combining a video stream with other content or additional data, remultiplexing of multiplex streams, insertion of stuffing bits into the multiplex stream, assembling of a packetised elementary stream at server side H04N21/236; disassembling of a multiplex stream, remultiplexing of multiplex streams, extraction or processing of Service Information, disassembling of packetised elementary stream at client side H04N21/434
• CPC Class Codes: Y10S 358/908 Pause control, i.e. "commercial killers"

Abstract

The present invention relates to a method and to a system for detecting a first context change between two frames. When a second context change between a further two frames occurs within a predetermined time interval, the frames accommodated within the two context changes are defined as a subliminal message. An alarm is sent to an observer upon detection of a subliminal message.

Claims

1. A method of distinguishing between messages in a sequence of frames that include image information, the method comprising:

detecting a first context change between a first and a second frame,

detecting a second context change between a third and a fourth frame,

comparing the time period between the first and the second context changes with a first threshold value, and

indicating said message in dependence on said comparison.

2. A method according to claim 1, characterized in that relevant data related to the first and second context changes and data relating to the source of the frame sequence are stored in a memory.

3. A method according to claim 1, characterized in that a second message is indicated in dependence on whether a third context change between said first and said fourth frame is detected.

4. A method according to claim 1, characterized in that said first context change is detected by measuring the energy difference between said first and said second frames.

5. A method according to claim 1, characterized in that said second context change is detected by measuring the energy difference between said second and said third frames.

6. A method according to claim 4, characterized in that the energy is measured by calculating, for each frame point, the difference between the value of a frame point in a first frame and the value of the corresponding frame point in a second frame, calculating the square of the calculated difference, and forming the sum of the calculated square values for all frame points.

7. A method according to claim 1, characterized in that said first context change is detected by measuring the energy in a first displaced frame difference (DFD), and using the measured energy to calculate the second frame from the first frame.

8. A method according to claim 1, characterized in that said second context change is detected by measuring the energy in a second displaced frame difference (DFD), and using the measured energy to calculate the fourth frame from the third frame.

9. A method according to claim 7, characterized by comparing the energy in the displaced frame difference with a second threshold value, and indicating a context change in dependence on said comparison.

10. A method according to claim 8, characterized by comparing the energy in the displaced frame difference with a second threshold value, and indicating a context change in dependence on said comparison.

11. A method according to claim 7, characterized in that the energy in the displaced frame difference (DFD) is measured by calculating the square of the value in each frame point in the displaced frame difference and forming the sum of the calculated values for all frame points.

12. A method according to claim 7, characterized in that the energy in the displaced frame difference (DFD) is measured by calculating the absolute magnitude of the value in each frame point in the displaced frame difference and forming the sum of the calculated values for all frame points.

13. A method according to claim 1, characterized in that the first context change is indicated when an I-frame in an MPEG-stream is detected.

14. A method according to claim 1, characterized in that the second context change is indicated when an I-frame in an MPEG-stream is detected.

15. A method according to claim 1, characterized by comparing the second frame with a fifth frame stored in a frame library, and indicating the first message in dependence on said comparison.

16. A method according to claim 2, characterized by storing in said memory the frame sequence between the first and the second context change.

17. A method according to claim 2, characterized in that a user is able to examine the contents of said memory.

18. A method according to claim 1, characterized in that said second frame and said third frame are one and the same frame.

19. A system for automatically detecting subliminal messages in a frame sequence, the system comprising:

means for measuring context changes between two frames in the frame sequence;

means for initiating an alarm;

means for storing a frame sequence;

means for calculating a time difference between two context changes;

means for comparing a measured time difference with a threshold value; and

means for initiating an alarm in response to the outcome of said means for comparing.