|Publication number||US3004104 A|
|Publication date||Oct 10, 1961|
|Filing date||Apr 29, 1954|
|Priority date||Apr 29, 1954|
|Publication number||US 3004104 A, US 3004104A, US-A-3004104, US3004104 A, US3004104A|
|Inventors||Hembrooke Emil Frank|
|Original Assignee||Muzak Corp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (11), Referenced by (114), Classifications (16)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Oct. 10, 1961 E. F. HEMBROOKE IDENTIFICATION OF SOUND AND LIKE SIGNALS Filed April 29, 1954 mnPC ESZ FREQUENCY f' looo IOO . E M T moat E24 LOUDSPEAKERW AMPLIFIER :PLAYBAOK' RECORD l l. l
' FILTER \NVENTOR Emil Fran/r, Hemraoie BY MWMf I! 7 ATTORNE q TRANSDUCER EILTER 3,004,104 IDENTIFICATION OF SOUND AND LIKE SIGNALS Emil Frank Hembrooke, Brooklyn, N.Y., assiguor to Muzak Corporation, New York,'N.Y., a corporation of New York Filed Apr. 29, 1954, Ser.'No. 426,465 6 Claims. (Cl. 1792) 'vides for the identification of recorded music or other audio signals by coded signals which are not evident to a listener but which nonetheless can easily be detected and which are such an integral part of the audio signals.
that they are difficult if not impossible to obliterate.
The unauthorized recording and rebroadcasting of musical performances, for example, has been difiicult to prevent because of the inability to detect positively whether the rebroadcast is an exact reproduction of the original or a different performance. tion makes possible the positive identification of the origin of a musical presentation and therebyconstitutes an effective means of preventing such piracy, ie it may be likened to a watermark in paper.
The invention may be used for the identification of any kind of signal, whether audio, or other, comprising a number of dilferent frequency components, although for purposes of illustration it is shown and described herein as applied to the identification of audio signals.
It is well known that a complex audio signal, such as music or speech, is composed of a number of frequency components extending over a wide range of frequencies.
In accordance with the present invention such a signal is identified by suppressing a selected frequency, or narrow band of frequencies, within the frequency spectrum of the signal at timed intervals accordingto apredeterimined code. Because of the insensitivity of the ear in detecting the absence of a particular frequency or narrow band of frequencies in a sound signal, the identifying code will be imperceptible to the listener.
The suppression of a selected frequency or narrow band of frequencies is accomplished, in a specific embodiment of the invention, by converting the signal into a complex electrical voltage and then passing this voltage through a very narrow band-reject electrical filter which passes all but a very narrow range of frequencies in the complex voltage.
In the accompanying drawings:
FIGURE 1 is a graph of the spectrum of frequencies in a typical sound signal at an instant of time when a predetermined narrow range of frequencies is being suppressed;
FIGURE 2 is a graph of the amplitude of the sound signals in said predetermined narrow range of frequencies, plotted versus time to portray an illustrative coding sequence;
FIGURE 3 is an electric circuit, in block form, for impressing an identifying code on a signal in accordance with one embodiment of this invention;
FIGURE 4 is an electric circuit, in block form, for detecting the identifying code.
In FIGURE 1 the horizontal scale represents the fre- The present invenquencies of the various components in a typical sound signal while the vertical scale represenst the amplitude of these various components at a particular instantof time. The audible frequency range of the sound signal, as indicated in this figure, extends approximately from 20 cycles per second to 20,000 cycles per second.
The amplitudes of frequency components of the signal over a very narrow range of frequency, for example, 10 cycles per second, at some place in the frequency spectrum are attenuated, in accordance with the invention,
in order to identify the signal. The attenuation of these.
for example, in the vicinity of 1000 cycles per second,
that can be accommodated in even the cheapest reproducing systems since the permanence as an identifying mark of the attenuated harmonic components when so placed is greater than if frequency i were placed at one edge of the signal frequency range. If it were placed at one edge, for example, at approximately 20,000 cycles per second, the identifying effect could be entirely eliminated simply by filtering out all of the very high frequencies of the sound signal. Moreover, in this regard, the frequency i should be placed at a frequency which is generally present in the signal to be identified. ,This frequency will of course depend upon the signal, but for music approximately 1000 cycles per second has been found to be satisfactory.
As shown in FIGURE 2, the identifying mark is discontinuous and eliminates the selected frequency components of the signal only at certain intervals of time, according to a predetermined, coded pattern.
FIGURE 3 shows a specific illustrative embodiment of a coding apparatus according to the invention comprising an electric circuit for impressing upon the signal to be marked a code of the type illustrated in FIG- URE 2. The audio signal voltage, comprising a number of frequency components extending over a wide range of frequency, is applied at input terminal 11. This voltage is switched by means of an encoding switch 12' either directly from terminal 11 to terminal 13 or through a band-reject filter 14 to terminal 13, depending upon whether the switch,12 is open or closed. The switch 12 is opened and closed in sequence according to a predetermined coding pattern, for example, the name of the orchestra or the trademark of the recording company may be spelled out in International Code, or any other suitably identifiable sequence of pulses may be utilized as a proprietary code. The encoding switch may be actuated mechanically, as by means of a coding cam, so that the coding equipment is fully automatic and may be employed continuously at very slight expense. The band-reject filter 14 preferably has a very high Q that is, it is sharply tuned to reject only the frequency components within an extremely narrow range on either side of its resonant frequency, 13,, so that the absence of the rejected frequency components will be imperceptible to the listener. This necessitates, of course, that the reduction in the total power of the audio signal due to the deletion of said selected frequency components be less than approximately 3 decibels.
The output voltage from terminal 13 may be broadcast concurrently or it may be recorded and reproduced at. a later time, as illustrated in FIGURE 3, by means of.
a playback head, amplifier and speaker.
The code impressed on the signal by switch 12 will serve to identify thereafter the origin of the audio signal so marked.
FIGURE 4 shows a specific illustrative embodiment Patented Oct. 10, 1961v of an apparatus for detecting the identifying code in the audio signal. This apparatus includes an input terminal 20 to which may be applied an audio signal voltage similar to that obtained at terminal 13 or terminal 13 in FIGURE 3. This voltage is amplified by means of an amplifier 21 and fed through a band pass filter 22, which has a transmission characteristic such that it will pass. only frequency components within the same narrow range of frequency which the band-reject filter 14 will reject, as previously described. In'other words, the transmission characteristics of the band-pass filter 22' are substantially opposite to those of the bandreject' filter '14. The output of the band-pass filter 22 is connected to a suitable transducer 23, such as a recording meter, oscilloscope, Or the like. As the voltage applied to terminal 20 passes through the filter 22, all frequency components of the signal lying outside the pass band are eliminated and only those within this band are passed. Since these frequencies were alternately suppressed and passed by the encoding circuit illustrated in FIGURE 3, the voltage applied to the transducer 23 will be intermittent. If transducer 23 is a recording meter containing a rectifier which converts these audio frequency alternating current voltages to direct current voltages, it can plot a graph oftheir amplitude versus time. Thus, a graph of the type illustrated in FIGURE 2 is plotted, in which the coding pattern, as indicated at 24 in FIG- URE 2, is readily apparent. Alternatively, transducer 23 may be a loudspeaker to convert the identifying code into sound.
The foregoing is intended in illustration and not in limitation. Changes or modifications inthe embodiments illustrated will occur to those skilled in the art and these changes or modifications may be made without departing from the spirit or scope of the invention as set foith.
' I claim:
1. In combination, an input terminal, means for supplying to said terminal an electric signal corresponding to an original signal and having a plurality of frequency components each having a respective frequency and amplitude, an output terminal, encoding means for impress ing a distinctive code on said electric signal for identifying the origin of said original signal, said encoding means including a narrow-band-reject filter adapted to attenuate said components of said electric signal within a very narrow frequency range, and also including a switch for connecting and for disconnecting said filter between said terminals in a predetermined time sequence to form said distinctive code.
2. A system of reproducing a continuous sound such as a musical selection and of permanently but unchtrusively identifying its origincomprising: means for continuously generating an electric signal corresponding to said sound and having frequency components extending substantially over the audio range of frequencies, means for variably attenuating in accordance with an identifying code frequency components of said signal lying within a very narrow band of frequency within said audio range, and means for then utilizing said identified electric-signal whereby either said sound substantially in original form without the audible presence of said code or said code alone can be reproduced.
3. The system as in claim 2 wherein said' means for utilizing includes means for eliminating all frequency components of said electric signal except those remaining in said narrow band. 1
4. The system as in'claim 2 wherein said narrow band of frequency has a width of only a few cycles per second, and is near the center of said band.
5. A method of unobtrusively identifying a sound signal such as a musical selection, said method'comprising the steps of taking a sound signal having frequency components within the audio range, and attenuating the components in a very narrow frequency band within said range in accordance with an identifying pattern so that said signal will be permanently marked with an easily detectable pattern but a person hearing said marked-- signal will be unaware of audible change in it.
6. The method as in claim 5 wherein said narrow frequency band has a width of the order of ten cycles per second and lies in said audio range near a frequency of one thousand cycles per second.
References Cited in the file of this patent UNITED STATES PATENTS 1,724,938 Jammer Aug. 20, 1929 2,116,172 Hyneman et al May 3,. 1938 2,335,335 Zenner Nov. 30, 1943 2,352,918 Smith July 4, 1944 2,376,275 Rhoads May 14, 1945 2,398,755 Shepherd Apr. 16, 1946- 2,406,034 Phelps Aug. 20, 1946 2,474,191 Reid et al. June 21, 1949 2,503,701 Baughman Apr. 11, 1950 2,580,973 Sueur Jan. '1, 1952 2,636,936 Goldsmith Apr. 28, 1953-
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US1724938 *||Nov 20, 1926||Aug 20, 1929||Western Electric Co||Carrier-wave transmission|
|US2116172 *||Dec 27, 1935||May 3, 1938||Western Union Telegraph Co||Composite set|
|US2335335 *||Jan 18, 1941||Nov 30, 1943||Teletype Corp||Communication system|
|US2352918 *||Oct 30, 1942||Jul 4, 1944||Rca Corp||Two-way telephone and telegraph system|
|US2376275 *||Mar 24, 1944||May 15, 1945||American Telephone & Telegraph||Signaling system|
|US2398755 *||Jun 17, 1943||Apr 16, 1946||O'd Shepherd Judson||Communication system|
|US2406034 *||Aug 24, 1943||Aug 20, 1946||Bell Telephone Labor Inc||Carrier wave signaling system|
|US2474191 *||Jun 6, 1947||Jun 21, 1949||Avco Mfg Corp||Tone control|
|US2503701 *||Nov 26, 1946||Apr 11, 1950||Union Switch & Signal Co||Simplexed line circuit system for remote-control systems|
|US2580973 *||Aug 7, 1947||Jan 1, 1952||Rene Sueur||Pulse signaling means|
|US2636936 *||Sep 10, 1946||Apr 28, 1953||Rca Corp||Television secrecy system|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3210864 *||Dec 6, 1962||Oct 12, 1965||Meyer Jerome C||Electronic device and method for testing and teaching|
|US3360873 *||Oct 1, 1965||Jan 2, 1968||James A. Tillotson||Electronic device and method for testing and teaching|
|US3639839 *||Sep 16, 1969||Feb 1, 1972||Masayuki Fukata||Broadcast system for a control signal|
|US3735048 *||May 28, 1971||May 22, 1973||Motorola Inc||In-band data transmission system|
|US3969675 *||Dec 30, 1974||Jul 13, 1976||National Research Development Corporation||Single side-band radio|
|US4644422 *||Jun 24, 1983||Feb 17, 1987||Tvi Systems, Ltd.||Anti-copy system|
|US4663674 *||Jan 22, 1986||May 5, 1987||Sony Corporation||Video cassette designed for video theater use|
|US4739398 *||May 2, 1986||Apr 19, 1988||Control Data Corporation||Method, apparatus and system for recognizing broadcast segments|
|US5319735 *||Dec 17, 1991||Jun 7, 1994||Bolt Beranek And Newman Inc.||Embedded signalling|
|US5394274 *||Apr 13, 1993||Feb 28, 1995||Kahn; Leonard R.||Anti-copy system utilizing audible and inaudible protection signals|
|US5450490 *||Mar 31, 1994||Sep 12, 1995||The Arbitron Company||Apparatus and methods for including codes in audio signals and decoding|
|US5574962 *||Dec 20, 1994||Nov 12, 1996||The Arbitron Company||Method and apparatus for automatically identifying a program including a sound signal|
|US5579124 *||Feb 28, 1995||Nov 26, 1996||The Arbitron Company||Method and apparatus for encoding/decoding broadcast or recorded segments and monitoring audience exposure thereto|
|US5581800 *||Jun 7, 1995||Dec 3, 1996||The Arbitron Company||Method and apparatus for automatically identifying a program including a sound signal|
|US5764763 *||Mar 24, 1995||Jun 9, 1998||Jensen; James M.||Apparatus and methods for including codes in audio signals and decoding|
|US5787334 *||Sep 27, 1996||Jul 28, 1998||Ceridian Corporation||Method and apparatus for automatically identifying a program including a sound signal|
|US6289108 *||Feb 10, 2000||Sep 11, 2001||Digimarc Corporation||Methods for detecting alteration of audio and images|
|US6363159||Nov 17, 1999||Mar 26, 2002||Digimarc Corporation||Consumer audio appliance responsive to watermark data|
|US6400827||Jun 29, 1999||Jun 4, 2002||Digimarc Corporation||Methods for hiding in-band digital data in images and video|
|US6404898||Jun 24, 1999||Jun 11, 2002||Digimarc Corporation||Method and system for encoding image and audio content|
|US6430302||Jan 10, 2001||Aug 6, 2002||Digimarc Corporation||Steganographically encoding a first image in accordance with a second image|
|US6496591||Jun 29, 1999||Dec 17, 2002||Digimarc Corporation||Video copy-control with plural embedded signals|
|US6539095||Nov 17, 1999||Mar 25, 2003||Geoffrey B. Rhoads||Audio watermarking to convey auxiliary control information, and media embodying same|
|US6542620 *||Jul 27, 2000||Apr 1, 2003||Digimarc Corporation||Signal processing to hide plural-bit information in image, video, and audio data|
|US6560349 *||Dec 28, 1999||May 6, 2003||Digimarc Corporation||Audio monitoring using steganographic information|
|US6560350 *||Jun 29, 2001||May 6, 2003||Digimarc Corporation||Methods for detecting alteration of audio|
|US6567780||Apr 9, 2002||May 20, 2003||Digimarc Corporation||Audio with hidden in-band digital data|
|US6631165||Sep 1, 1999||Oct 7, 2003||Northrop Grumman Corporation||Code modulation using narrow spectral notching|
|US6654480||Mar 25, 2002||Nov 25, 2003||Digimarc Corporation||Audio appliance and monitoring device responsive to watermark data|
|US6675146||May 31, 2001||Jan 6, 2004||Digimarc Corporation||Audio steganography|
|US6738491 *||Aug 14, 1997||May 18, 2004||Minolta Co., Ltd.||Image forming apparatus and copy management system|
|US6754377||Jun 6, 2002||Jun 22, 2004||Digimarc Corporation||Methods and systems for marking printed documents|
|US6757300||Jun 4, 1999||Jun 29, 2004||Innes Corporation Pty Ltd||Traffic verification system|
|US6871180||May 25, 1999||Mar 22, 2005||Arbitron Inc.||Decoding of information in audio signals|
|US6879652||Jul 14, 2000||Apr 12, 2005||Nielsen Media Research, Inc.||Method for encoding an input signal|
|US6944298||May 31, 2000||Sep 13, 2005||Digimare Corporation||Steganographic encoding and decoding of auxiliary codes in media signals|
|US6968564||Apr 6, 2000||Nov 22, 2005||Nielsen Media Research, Inc.||Multi-band spectral audio encoding|
|US6987862||Jul 11, 2003||Jan 17, 2006||Digimarc Corporation||Video steganography|
|US6996237||Jul 12, 2002||Feb 7, 2006||Arbitron Inc.||Apparatus and methods for including codes in audio signals|
|US7003132||Apr 1, 2003||Feb 21, 2006||Digimarc Corporation||Embedding hidden auxiliary code signals in media|
|US7006555||Oct 27, 1999||Feb 28, 2006||Nielsen Media Research, Inc.||Spectral audio encoding|
|US7181022||Mar 25, 2003||Feb 20, 2007||Digimarc Corporation||Audio watermarking to convey auxiliary information, and media embodying same|
|US7184570 *||May 27, 2004||Feb 27, 2007||Digimarc Corporation||Methods and systems for steganographic processing|
|US7266215||Feb 21, 2002||Sep 4, 2007||Minolta Co., Ltd.||Image forming apparatus and copy management system|
|US7333957 *||Jan 6, 2003||Feb 19, 2008||Digimarc Corporation||Connected audio and other media objects|
|US7362781||Aug 7, 2001||Apr 22, 2008||Digimarc Corporation||Wireless methods and devices employing steganography|
|US7388965||Dec 5, 2003||Jun 17, 2008||Minolta Co., Ltd.||Imaging forming apparatus and copy management system|
|US7451092||Mar 5, 2004||Nov 11, 2008||Nielsen Media Research, Inc. A Delaware Corporation||Detection of signal modifications in audio streams with embedded code|
|US7463752||Apr 12, 2007||Dec 9, 2008||Konica Minolta Business Technologies, Inc.||Imaging forming apparatus and copy management system|
|US7466742||Apr 21, 2000||Dec 16, 2008||Nielsen Media Research, Inc.||Detection of entropy in connection with audio signals|
|US7505605||Apr 13, 2004||Mar 17, 2009||Digimarc Corporation||Portable devices and methods employing digital watermarking|
|US7522728 *||Jan 6, 2000||Apr 21, 2009||Digimarc Corporation||Wireless methods and devices employing steganography|
|US7536555||Jan 3, 2006||May 19, 2009||Digimarc Corporation||Methods for audio watermarking and decoding|
|US7562392||Dec 30, 1999||Jul 14, 2009||Digimarc Corporation||Methods of interacting with audio and ambient music|
|US7567686||Oct 25, 2005||Jul 28, 2009||Digimarc Corporation||Hiding and detecting messages in media signals|
|US7672477||Sep 9, 2008||Mar 2, 2010||Digimarc Corporation||Detecting hidden auxiliary code signals in media|
|US7672843||Jun 2, 2005||Mar 2, 2010||The Nielsen Company (Us), Llc||Audio signature extraction and correlation|
|US7715446||Feb 2, 2007||May 11, 2010||Digimarc Corporation||Wireless methods and devices employing plural-bit data derived from audio information|
|US7724919||Feb 23, 2007||May 25, 2010||Digimarc Corporation||Methods and systems for steganographic processing|
|US7751588||Dec 16, 2008||Jul 6, 2010||Digimarc Corporation||Error processing of steganographic message signals|
|US7756290||May 6, 2008||Jul 13, 2010||Digimarc Corporation||Detecting embedded signals in media content using coincidence metrics|
|US7945781||Mar 30, 2000||May 17, 2011||Digimarc Corporation||Method and systems for inserting watermarks in digital signals|
|US7961881||Nov 4, 2005||Jun 14, 2011||Arbitron Inc.||Apparatus and methods for including codes in audio signals|
|US7961949||Oct 12, 2009||Jun 14, 2011||Digimarc Corporation||Extracting multiple identifiers from audio and video content|
|US7974439||Sep 15, 2009||Jul 5, 2011||Digimarc Corporation||Embedding hidden auxiliary information in media|
|US7987094||Feb 20, 2007||Jul 26, 2011||Digimarc Corporation||Audio encoding to convey auxiliary information, and decoding of same|
|US7987245||Nov 26, 2008||Jul 26, 2011||Digimarc Corporation||Internet linking from audio|
|US7992003||Jul 19, 2006||Aug 2, 2011||Digimarc Corporation||Methods and systems for inserting watermarks in digital signals|
|US8014563||May 25, 2010||Sep 6, 2011||Digimarc Corporation||Methods and systems for steganographic processing|
|US8027510||Jul 13, 2010||Sep 27, 2011||Digimarc Corporation||Encoding and decoding media signals|
|US8027663||Oct 19, 2007||Sep 27, 2011||Digimarc Corporation||Wireless methods and devices employing steganography|
|US8051294||May 19, 2009||Nov 1, 2011||Digimarc Corporation||Methods for audio watermarking and decoding|
|US8055012||Jul 28, 2009||Nov 8, 2011||Digimarc Corporation||Hiding and detecting messages in media signals|
|US8184849||Jul 6, 2010||May 22, 2012||Digimarc Corporation||Error processing of steganographic message signals|
|US8184851||Apr 12, 2011||May 22, 2012||Digimarc Corporation||Inserting watermarks into portions of digital signals|
|US8190713||Jul 21, 2011||May 29, 2012||Digimarc Corporation||Controlling a device based upon steganographically encoded data|
|US8204222||Sep 13, 2005||Jun 19, 2012||Digimarc Corporation||Steganographic encoding and decoding of auxiliary codes in media signals|
|US8244527||Jan 4, 2010||Aug 14, 2012||The Nielsen Company (Us), Llc||Audio signature extraction and correlation|
|US8355514||Oct 26, 2007||Jan 15, 2013||Digimarc Corporation||Audio encoding to convey auxiliary information, and media embodying same|
|US8369363||May 11, 2010||Feb 5, 2013||Digimarc Corporation||Wireless methods and devices employing plural-bit data derived from audio information|
|US8369972 *||Oct 10, 2008||Feb 5, 2013||The Nielsen Company (Us), Llc||Methods and apparatus to perform audio watermarking and watermark detection and extraction|
|US8457951||Jan 29, 2009||Jun 4, 2013||The Nielsen Company (Us), Llc||Methods and apparatus for performing variable black length watermarking of media|
|US8521850||Jul 21, 2011||Aug 27, 2013||Digimarc Corporation||Content containing a steganographically encoded process identifier|
|US9015740||May 14, 2014||Apr 21, 2015||The Nielsen Company (Us), Llc||Systems and methods to wirelessly meter audio/visual devices|
|US9124769||Jul 20, 2009||Sep 1, 2015||The Nielsen Company (Us), Llc||Methods and apparatus to verify presentation of media content|
|US9460730||Dec 28, 2012||Oct 4, 2016||The Nielsen Company (Us), Llc||Methods and apparatus to perform audio watermarking and watermark detection and extraction|
|US20020034297 *||Aug 7, 2001||Mar 21, 2002||Rhoads Geoffrey B.||Wireless methods and devices employing steganography|
|US20020135810 *||Feb 21, 2002||Sep 26, 2002||Minolta Co., Ltd.||Image forming apparatus and copy management system|
|US20030018479 *||Mar 21, 2002||Jan 23, 2003||Samsung Electronics Co., Ltd.||Electronic appliance capable of preventing malfunction in speech recognition and improving the speech recognition rate|
|US20030174861 *||Jan 6, 2003||Sep 18, 2003||Levy Kenneth L.||Connected audio and other media objects|
|US20040105571 *||Dec 5, 2003||Jun 3, 2004||Minolta Co., Ltd.||Imaging forming apparatus and copy management system|
|US20040170381 *||Mar 5, 2004||Sep 2, 2004||Nielsen Media Research, Inc.||Detection of signal modifications in audio streams with embedded code|
|US20040181799 *||Mar 29, 2004||Sep 16, 2004||Nielsen Media Research, Inc.||Apparatus and method for measuring tuning of a digital broadcast receiver|
|US20040221161 *||May 27, 2004||Nov 4, 2004||Rhoads Geoffrey B.||Methods and systems for steganographic processing|
|US20050177361 *||Apr 6, 2005||Aug 11, 2005||Venugopal Srinivasan||Multi-band spectral audio encoding|
|US20050232411 *||Jun 2, 2005||Oct 20, 2005||Venugopal Srinivasan||Audio signature extraction and correlation|
|US20060080556 *||Oct 25, 2005||Apr 13, 2006||Rhoads Geoffrey B||Hiding and detecting messages in media signals|
|US20060109984 *||Jan 3, 2006||May 25, 2006||Rhoads Geoffrey B||Methods for audio watermarking and decoding|
|US20060222179 *||Nov 4, 2005||Oct 5, 2006||Jensen James M||Apparatus and methods for including codes in audio signals|
|US20070189533 *||Feb 2, 2007||Aug 16, 2007||Rhoads Geoffrey B||Wireless Methods And Devices Employing Steganography|
|US20070195991 *||Feb 23, 2007||Aug 23, 2007||Rhoads Geoffrey B||Methods and Systems for Steganographic Processing|
|US20070195992 *||Apr 12, 2007||Aug 23, 2007||Minolta Co., Ltd.||Imaging forming apparatus and copy management system|
|US20080125083 *||Oct 19, 2007||May 29, 2008||Rhoads Geoffrey B||Wireless Methods and Devices Employing Steganography|
|US20090067672 *||Sep 9, 2008||Mar 12, 2009||Rhoads Geoffrey B||Embedding Hidden Auxiliary Code Signals in Media|
|US20090097702 *||Dec 16, 2008||Apr 16, 2009||Rhoads Geoffrey B||Error Processing of Steganographic Message Signals|
|US20090192805 *||Jan 29, 2009||Jul 30, 2009||Alexander Topchy||Methods and apparatus for performing variable black length watermarking of media|
|US20090259325 *||Oct 10, 2008||Oct 15, 2009||Alexander Pavlovich Topchy||Methods and apparatus to perform audio watermarking and watermark detection and extraction|
|US20100195837 *||Jan 4, 2010||Aug 5, 2010||The Nielsen Company (Us), Llc||Audio signature extraction and correlation|
|US20100205445 *||Apr 15, 2010||Aug 12, 2010||Anglin Hugh W||Watermark systems and methods|
|US20100296526 *||May 11, 2010||Nov 25, 2010||Rhoads Geoffrey B||Wireless Methods and Devices Employing Plural-Bit Data Derived from Audio Information|
|USRE42627||Mar 22, 2007||Aug 16, 2011||Arbitron, Inc.||Encoding and decoding of information in audio signals|
|EP1978658A2||Mar 27, 1995||Oct 8, 2008||THE ARBITRON COMPANY, a division of CERIDIAN CORPORATION||Apparatus and methods for including codes in audio signals and decoding|
|WO1992005550A1 *||Sep 14, 1990||Apr 2, 1992||James Dale||Encoding system|
|WO2010121178A1||Apr 16, 2010||Oct 21, 2010||Arbitron, Inc.||System and method for determining broadcast dimensionality|
|U.S. Classification||341/182, 455/39, 369/47.26, 381/98, 360/60, G9B/20.2, 360/22, 360/15|
|International Classification||G01H3/00, G11B20/00|
|Cooperative Classification||G01H3/00, G11B20/00891, G11B20/00086|
|European Classification||G01H3/00, G11B20/00P14A, G11B20/00P|