WO1999063688A1 - Traffic verification system - Google Patents
Traffic verification system Download PDFInfo
- Publication number
- WO1999063688A1 WO1999063688A1 PCT/AU1999/000439 AU9900439W WO9963688A1 WO 1999063688 A1 WO1999063688 A1 WO 1999063688A1 AU 9900439 W AU9900439 W AU 9900439W WO 9963688 A1 WO9963688 A1 WO 9963688A1
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- WO
- WIPO (PCT)
- Prior art keywords
- signal
- audio signal
- data
- band
- data signal
- Prior art date
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04H—BROADCAST COMMUNICATION
- H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
- H04H20/28—Arrangements for simultaneous broadcast of plural pieces of information
- H04H20/30—Arrangements for simultaneous broadcast of plural pieces of information by a single channel
- H04H20/31—Arrangements for simultaneous broadcast of plural pieces of information by a single channel using in-band signals, e.g. subsonic or cue signal
Definitions
- This invention relates to the automatic identification of audio signals, particularly broadcast audio signals.
- audio signal encompasses both analog and digital signals.
- the data signal will preferably include a carrier signal modulated to enclose data using minimum shift frequency shift keying (MSK).
- MSK minimum shift frequency shift keying
- the notch frequency will be at approximately 3kHz.
- the data signal will, in a preferred embodiment, be present over substantially the entire timespan of the audio segment comprising the audio signal.
- the data may include two six-digit numbers presented in binary form as a 40-bit field and will preferably represent an identification tag.
- an encoder for encoding a data signal onto an audio signal including: filter means for removing a band of frequencies centred at a predetermined notch frequency from said audio signal; shaping means for spectrally shaping said data signal such that it takes on the precise shape and magnitude of the envelope of the audio signal at said removed band of frequencies; inserting means for inserting said shaped data signal into said audio signal within the removed frequency band centred at said notch frequency; and data input means for receiving data to be encoded into said audio signal.
- a decoder for decoding an encoded audio signal encoded by the encoder of the invention, the decoder including: a receiver input for receiving said encoded audio signal; receiver filter means for extracting a band of frequencies containing said code from said encoded audio signal; means for removing the envelope modulation applied to said data signal; and receiver demodulation means for demodulating said data signal.
- the present invention thereby provides a method and apparatus for inserting and detecting a data signal into an audio signal such that the data signal is virtually inaudible by a listener of the audio signal, yet is robust enough to survive severe audio processing.
- Figure 1 is a block diagram of the encoder used in the tagging stage of the method of the present invention.
- Figures 2A-2D show spectral diagrams of signals at various points in the encoder of Figure 1.
- Figure 3 shows a graphical representation of an identification data frame in a preferred form of the invention.
- Figure 4 is a block diagram of the decoder used in the identification stage of the method of the present invention.
- Figure 5 is a block diagram of the bit accumulator used in the logging stage of the method of the present invention.
- Figure 6 shows the relationship between the frequency responses of the notch filter used in the encoder and the bandpass filter used in the decoder of the present invention.
- Figure 7a shows a voltage versus frequency characteristic of a traditional MSK demodulator.
- Figure 7b shows a voltage versus frequency characteristic of an MSK demodulator used in the present invention.
- the method consists of encoding an audio signal with an identification data signal by the use of encoder 100 as shown in Figure 1.
- Stereo audio input is sampled at 48kHz and the left and right channels separately processed as shown in Figure 1.
- the spectral diagram of the left audio signal appearing at point "a" is shown in Figure 2A.
- the left channel is split into two signals, with one signal passing through bandpass filter 105 to provide a signal 400Hz wide, centred at 3kHz.
- bandpass filter 105 (at point "c") is represented by the spectral diagram shown in Figure 2C.
- the other signal at point “a” is fed into delay line 110 which delays the signal to match the delay caused by bandpass filter 105.
- Both signals are then fed into element 115, the effect of which is to remove from the original left audio signal at point "a” the band of frequencies appearing at point "c”.
- the output of element 1 15 (at point "b") is shown in Figure 2B.
- the signal at point "c” is also fed into envelope detector 120 which is a square law detector.
- envelope detector 120 which is a square law detector.
- the envelope information of the signal at point "c” is thereby extracted.
- the signal consists of a base band component and another product centred at 6kHz, each component being bandlimited to twice the filter bandwidth.
- This signal is then fed into element 125 where the 6kHz centred component is removed by an FIR lowpass filter and the baseband signal is passed through a square root function to recover the envelope.
- the signal at point "b” is further delayed by delay line 130 to match the delays to the signal at point "c" caused by elements 120 and 125.
- An identification data signal enters the system at point “e” and is modulated using minimum shift frequency shift keying (MSK) centred at 3kHz by MSK generator 150.
- MSK minimum shift frequency shift keying
- This MSK modulated identification signal is then input to modulator 135, which amplitude modulates the data signal in accordance with the signal at the output of element 125.
- This modulating signal is essentially the envelope information of the band of frequencies removed from the original left audio signal.
- the amplitude modulated MSK data signal is then summed at summer . 140 with the delayed output at point "b".
- the output of summer 140 (at point "d") is shown in Figure 2D, and consists of the original audio input at point "a" with an identification data signal shaped to conform with the envelope of the audio signal and inserted in the notch centred at 3kHz. This provides an audio signal with an identification tag that is robust enough to be retrievable at reception after going through heavy audio processing subsequent to its transmission. The data is also virtually inaudible to the listener.
- the tagged audio signal is then broadcast in the normal manner, whether it be from a radio station or an audio signal for a television transmission.
- the identification data signal used above is derived in the following way.
- the identification tag consists of two 6-digit numbers. One of these numbers represents the location at which the recording was made, while the other number identifies the individual recording produced at the location. Of course, in practice, these two numbers could represent any type of data, including an identification mark, a control signal, general information, or a combination of the above.
- the data used to tag the audio cut as described above is modulated using minimum-shift frequency shift keying. This method has the benefits of being constant envelope and has substantially lower sidelobes than other phase-modulation techniques.
- the data rate chosen is 100 bits per second. This requires a frequency shift of +/-25Hz and the major lobe of the data spectrum is 150Hz wide.
- the decoder (described below) filter (220 in Figure 4), has a passband 200Hz wide and guardband extending an additional 50Hz either side.
- the notch filter (made up of bandpass filter 105, delay line 110 and subtracting element 115) has a stop band 300Hz wide (which spans the decoder filter's guardband) and a, transition region extending out 200Hz either side of 3kHz.
- the overall transmission frequency response should extend to approximately 4kHz.
- the data tag is preferably inserted at 3kHz. This improves the inaudibility of the data signal in the audio signal since the human ear is reasonably insensitive to phase changes, particularly at higher frequencies. A balance must be found between achieving inaudibility and robustness of the data tag. Inserting the tag at higher frequencies will improve the inaudibility, but will have deleterious effects on the robustness. Inserting the data tag at 3kHz has been found to satisfy both criteria.
- a receiver At a remote location, a receiver will detect the tagged audio signal and the decoding stage begins.
- the received signal is received by decoder 200 shown in Figure 4, and the left and right audio signals are combined at summer element 205.
- the output of summer 205 is sampled in stereo at 32kHz but is immediately converted to mono and lowpass filtered by filter 210 which passes signals between 0 to 4kHz to allow the sampling rate to be reduced to 8kHz at the output of decimator 215.
- the signal is then passed through FIR bandpass filter 220 (2.9 - 3.1 kHz) to separate the amplitude modulated MSK identification data signal (the "tag") from the rest of the audio signal.
- the filtered signal is then amplitude-limited to remove the envelope modulation that was applied in the encoder to mask the data. This is preferably done by multiplying the filtered signal by the inverse of the signal envelope.
- the resulting constant envelope MSK signal is then converted down to baseband using a quadrature 3kHz local oscillator (made up by 100Hz oscillator 260 and x30 frequency multiplier 230) and mixer 225.
- the signal is then demodulated with a delay-line FM demodulator (10 ms delay line 245 and mixer 250).
- the signal After demodulation the signal is filtered by lowpass filter 255 to eliminate noise above 100Hz and then passed to a lossy accumulator register and clock recovery routines (not shown).
- the clock recovery phase-locks a 100Hz bit clock to the zero-crossings of the demodulated signal using zero crossing detector 265.
- a 3kHz signal is derived from this clock (oscillator 260) and is used as the local oscillator for the quadrature mixer mentioned above. This, ensures that the local oscillator is synchronised with the 3kHz carrier used in the encoder.
- the demodulated signal is sampled at sampling gate 270 using the recovered bit clock, and the output of sampling gate 270 is fed into bit accumulator 300 shown in Figure 5.
- the sampled bits from the abovedescribed stage are passed sequentially to 73 lossy accumulators shown by the equivalent circuit of the bit accumulator 300, including commutating lowpass filter 310, 73-bit output shift register 320 and 32-bit CRC register 330.
- the commutating filter 310 averages out random noise while allowing repetitive data bits to build up.
- Frame synchronisation is achieved by using a signal frame sync bit which lies midway between the high and low data levels. This is detected by frame sync detector 340.
- the output of the commutating filter is periodically transferred to the output shift register 320 and CRC register. If the output shift register contains one and only one start bit, and if the other 72 bits pass the cyclic redundancy check, a valid frame is reported for logging.
- the time constants in the clock recovery phase-locked-loop and the bit accumulator register are of the order of two seconds, providing good averaging during gaps between words while achieving reasonably fast initial acquisition.
- a report of the data collected can be generated and automatically sent to a central location where the information is sorted and customised reports produced.
- the retrieved data can be formatted in plain text and MS ACCESS database format. Custom reports and analysis can be written in ACCESS or VBA to perform almost any reporting function.
- the device of the invention can log audio data for periods of any length (depending on configuration and model type) in a low-bandwidth (3.5kHz) format. For example for periods of between 14 and 42 days. If additional disk storage is used, up to 180 days may be logged.
- An actual logged audio segment can be requested by the collecting/reporting site (CRS).
- the remote device then sends the low-bit rate coded audio data to the CRS for playback elsewhere.
- the "downloaded" audio can be played back on a suitably- equipped PC workstation.
- a particular advantage of the present invention lies in the ability to actively interrogate the data logger to locate and replay a particular audio segment recorded at a particular time. For example, if one wants to hear what commercial was broadcast from station X at 1 :30 am on Tuesday 9th of March 1999, then these parameters can be input to the system to replay the precise audio segment transmitted at the desired time.
- TVS Traffic Verification System
- a remote TVS unit can also be directed to change reception frequency to log an alternative station at different times of the day by using a suitable digitally controlled receiver.
- the method and device of the present invention provides a means of accurately and reliably automatically identifying an audio signal by tagging the audio signal with identification data which is robust enough to survive heavy audio processing and is virtually inaudible to the ear of the listener.
- identification data which is robust enough to survive heavy audio processing and is virtually inaudible to the ear of the listener.
- a tagged audio signal is received by decoder 200 which separates the data signal from the audio signal using bandpass filter 220.
- the passband of this filter must be wide enough to pass the major lobe of the data spectrum plus any allowance for carrier frequency offset. There will also be a small but finite transition region either side of the passband before maximum stopband attenuation is reached.
- the bandwidth of the notch filter (made up of elements 105, 110 and 115 in Figure 1 ) in the encoder 100 must extend to the edges of the stopband in the decoder as shown in Figure 6. To minimise the audible effect of the notch, the notch bandwidth would . intuitively be as small as possible.
- notch bandwidth must cover the width of the stopband of the filter 220 in decoder 200, there is a lower limit imposed upon the notch bandwidth. Best results would therefore be expected to be achieved by the use of a notch filter with very steep sides, however, this was found not to be the case.
- a steep-sided notch filter has a relatively long impulse response which is likely to be sufficiently long to be audible as a ringing effect.
- a balance must be found between having a notch filter whose bandwidth is broad enough so as to minimise ringing effects, but not so broad as to become audible because of the elimination of too large a slice of audio frequency components.
- the notch filter Due to the limitations of current DSP technology, it is not possible to implement the notch filter directly as an FIR digital filter at a sampling rate of 48kHz (and in stereo). It is therefore necessary to reduce the sampling rate (for example to 12kHz), bandpass filter the signal, and then interpolate the signal back up to a 48kHz sampling rate.
- the notch filter is completed by subtracting the bandpass filtered signal from the original signal delayed by an amount equal to the group delay of the combined bandpass filter and sampling rate conversion filters.
- the output of the bandpass filter 105 in the encoder 100 appears in the time domain as an amplitude modulated carrier.
- Envelope detector 120 is used to extract the amplitude modulation component and this is used to modulate the MSK data signal prior to reinsertion into the audio as described above. Closer examination of the output of the filter reveals, however, that whenever the envelope goes through zero there is a 180 degree phase reversal in the "carrier". Because this phase reversal is not carried across onto the remodulated data signal, the bandwidth of that signal is substantially wider than the original signal. This can be a problem for two reasons. Firstly, the additional AM sidebands extend beyond the edges of the decoder's filter 220 and can produce incidental phase modulation of the data signal.
- An alternative demodulator is the delay line detector, whereby the MSK signal is multiplied by itself delayed by one bit period.
- the output of this detector has a voltage versus frequency characteristic shown in Figure 7b.
- the frequencies corresponding to the two data levels coincide with the positive and negative peaks of the transfer characteristic, and any high frequency noise will produce an output no larger than this, and on average the noise will be substantially lower than the recovered data.
- Further improvement is achieved by following the demodulator with a low pass filter.
- Use of the delay line demodulator allowed the encoder's remodulator to operate without filtering and resulted in minimum audibility of the data while achieving reliable data recovery in the decoder.
- a further technical problem involved the carrier recovery.
- the data dashe decoder 200 requires the generation of a 3kHz carrier in order to translate the data signal back down to baseband. While this carrier does not have to be synchronous with the encoder 100, the amount of frequency error that can be reasonably tolerated is small, preferably less than about 5Hz. In systems where the tagged audio is stored on hard disk this is not a problem as frequency accuracy will be several orders of magnitude better than this. However, if tape storage is used, either as the final replay medium or for intermediate transfer, frequency errors substantially larger than this could be expected. There are several MSK demodulation schemes found in the literature that use phase locked loops to track such carrier errors, however these all require a loop bandwidth that is much smaller than the data rate.
- Some other modulation schemes make use of an illegal transition as a frame marker, and it was decided to do a similar thing here. An extra bit was added to the frame and this was set midway between the levels representing zero and one. In terms of the MSK modulator, this is equivalent to the carrier frequency without an offset.
- the bit bins (of which there are now 73) are scanned sequentially. If there is one and only one bit at this intermediate level it is taken as the start bit and a CRC check is done on the rest of the frame. If the CRC is valid the decoded data is then logged.
- a further problem must be considered. This is the synchronisation between the video signal and the audio signal to maintain lip-sync. As the audio signal is processed, it passes through several processing blocks. Each block contributes to an overall delay in the audio signal, causing it to lose synchronisation with the video signal. This problem is addressed by simply minimising the delays of various blocks within the system between input and output. This may be done by various methods as would be known to the person skilled in the art. It has been found that an acceptable delay is in the order of 10 milliseconds. Such a delay is not readily perceived by the viewer.
- the invention has been described in the context of television or radio broadcasts, it will be understood that the invention is equally applicable to any area where an identification or authentication of an audio signal is required.
- the receiver can determine whether the audio signal received is authentic or authorised before carrying out those instructions.
- the audio signal may be tagged with an authorisation data signal.
- Such a system may be useful in military and/or aviation applications.
- the present invention could also be applied to other audio signal applications, for example, recording, where simple identification is of benefit.
- the tag In the case of applying the tag to audio recordings for compact disks for example, where sound quality is all important, the quality may be preserved by processing the signal to insert the tag in the purely digital domain. In this case, there is no analog to digital conversion and visa versa.
- the audio signal is input as a digital signal, processed digitally to insert the tag, and output as a tagged digital signal.
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NZ503064A NZ503064A (en) | 1998-06-04 | 1999-06-01 | A method for the automatic identification of broadcast audio signals |
BR9906512-6A BR9906512A (en) | 1998-06-04 | 1999-06-01 | Traffic verification system |
GB0002212A GB2342265B (en) | 1998-06-04 | 1999-06-01 | Traffic verification system |
CA002301186A CA2301186C (en) | 1998-06-04 | 1999-06-01 | Traffic verification system |
AU42503/99A AU764862B2 (en) | 1998-06-04 | 1999-06-01 | Traffic verification system |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AUPP3924 | 1998-06-04 | ||
AUPP3924A AUPP392498A0 (en) | 1998-06-04 | 1998-06-04 | Traffic verification system |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1999063688A1 true WO1999063688A1 (en) | 1999-12-09 |
Family
ID=3808169
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/AU1999/000439 WO1999063688A1 (en) | 1998-06-04 | 1999-06-01 | Traffic verification system |
Country Status (8)
Country | Link |
---|---|
US (1) | US6757300B1 (en) |
AR (1) | AR019149A1 (en) |
AU (1) | AUPP392498A0 (en) |
BR (1) | BR9906512A (en) |
CA (1) | CA2301186C (en) |
GB (1) | GB2342265B (en) |
NZ (1) | NZ503064A (en) |
WO (1) | WO1999063688A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1228504A1 (en) * | 1999-05-25 | 2002-08-07 | Arbitron Inc. | Decoding of information in audio signals |
EP2549476A1 (en) * | 2011-07-21 | 2013-01-23 | Lee S. Weinblatt | Real-time audio encoding technique |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1928109B1 (en) * | 2000-11-30 | 2012-05-23 | Intrasonics S.A.R.L. | Cellular telephone for collecting audience survey data |
US7356051B2 (en) * | 2001-01-24 | 2008-04-08 | Broadcom Corporation | Digital visual interface with audio and auxiliary data cross reference to related applications |
US7212248B2 (en) * | 2002-09-09 | 2007-05-01 | The Directv Group, Inc. | Method and apparatus for lipsync measurement and correction |
DE602005008031D1 (en) * | 2004-03-29 | 2008-08-21 | Nxp Bv | METHOD OF REDUCING INTERMEDIATE SYMBOL TROUBLESHOOTING, SIGMA DELTA CONVERTERS FOR CARRYING OUT THIS PROCEDURE AND INFORMATION OBTAINED THROUGH THIS METHOD OF TRANSMITTING THE STORAGE MEDIUM |
JP4398416B2 (en) * | 2005-10-07 | 2010-01-13 | 株式会社エヌ・ティ・ティ・ドコモ | Modulation device, modulation method, demodulation device, and demodulation method |
US7948558B2 (en) * | 2006-09-29 | 2011-05-24 | The Directv Group, Inc. | Audio video timing measurement and synchronization |
US8804984B2 (en) | 2011-04-18 | 2014-08-12 | Microsoft Corporation | Spectral shaping for audio mixing |
US9065971B2 (en) * | 2012-12-19 | 2015-06-23 | Microsoft Technology Licensing, Llc | Video and audio tagging for active speaker detection |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5719937A (en) * | 1995-12-06 | 1998-02-17 | Solana Technology Develpment Corporation | Multi-media copy management system |
US5826227A (en) * | 1995-12-18 | 1998-10-20 | Lucent Technologies Inc. | Hiding a source identifier within a signal |
Family Cites Families (18)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3004104A (en) | 1954-04-29 | 1961-10-10 | Muzak Corp | Identification of sound and like signals |
US3845391A (en) | 1969-07-08 | 1974-10-29 | Audicom Corp | Communication including submerged identification signal |
US3586781A (en) | 1970-05-19 | 1971-06-22 | Technology Uk | Telecommunication apparatus |
US4395600A (en) * | 1980-11-26 | 1983-07-26 | Lundy Rene R | Auditory subliminal message system and method |
US4703476A (en) | 1983-09-16 | 1987-10-27 | Audicom Corporation | Encoding of transmitted program material |
US5025443A (en) * | 1988-02-24 | 1991-06-18 | Integrated Network Corporation | Digital data over voice communication |
US4931871A (en) | 1988-06-14 | 1990-06-05 | Kramer Robert A | Method of and system for identification and verification of broadcasted program segments |
US5185762A (en) * | 1991-05-15 | 1993-02-09 | Scs Mobilecom, Inc. | Spread spectrum microwave overlay with notch filter |
FR2681997A1 (en) | 1991-09-30 | 1993-04-02 | Arbitron Cy | METHOD AND DEVICE FOR AUTOMATICALLY IDENTIFYING A PROGRAM COMPRISING A SOUND SIGNAL |
US5319735A (en) | 1991-12-17 | 1994-06-07 | Bolt Beranek And Newman Inc. | Embedded signalling |
US5410541A (en) * | 1992-05-04 | 1995-04-25 | Ivon International, Inc. | System for simultaneous analog and digital communications over an analog channel |
US5355161A (en) | 1993-07-28 | 1994-10-11 | Concord Media Systems | Identification system for broadcast program segments |
US5450490A (en) | 1994-03-31 | 1995-09-12 | The Arbitron Company | Apparatus and methods for including codes in audio signals and decoding |
US5774452A (en) | 1995-03-14 | 1998-06-30 | Aris Technologies, Inc. | Apparatus and method for encoding and decoding information in audio signals |
US6154484A (en) * | 1995-09-06 | 2000-11-28 | Solana Technology Development Corporation | Method and apparatus for embedding auxiliary data in a primary data signal using frequency and time domain processing |
US5822360A (en) | 1995-09-06 | 1998-10-13 | Solana Technology Development Corporation | Method and apparatus for transporting auxiliary data in audio signals |
US5937000A (en) * | 1995-09-06 | 1999-08-10 | Solana Technology Development Corporation | Method and apparatus for embedding auxiliary data in a primary data signal |
EP1002388B1 (en) | 1997-05-19 | 2006-08-09 | Verance Corporation | Apparatus and method for embedding and extracting information in analog signals using distributed signal features |
-
1998
- 1998-06-04 AU AUPP3924A patent/AUPP392498A0/en not_active Abandoned
-
1999
- 1999-06-01 BR BR9906512-6A patent/BR9906512A/en not_active IP Right Cessation
- 1999-06-01 CA CA002301186A patent/CA2301186C/en not_active Expired - Fee Related
- 1999-06-01 GB GB0002212A patent/GB2342265B/en not_active Expired - Fee Related
- 1999-06-01 WO PCT/AU1999/000439 patent/WO1999063688A1/en active IP Right Grant
- 1999-06-01 NZ NZ503064A patent/NZ503064A/en unknown
- 1999-06-03 AR ARP990102621A patent/AR019149A1/en active IP Right Grant
- 1999-06-04 US US09/326,414 patent/US6757300B1/en not_active Expired - Fee Related
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5719937A (en) * | 1995-12-06 | 1998-02-17 | Solana Technology Develpment Corporation | Multi-media copy management system |
US5826227A (en) * | 1995-12-18 | 1998-10-20 | Lucent Technologies Inc. | Hiding a source identifier within a signal |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1228504A1 (en) * | 1999-05-25 | 2002-08-07 | Arbitron Inc. | Decoding of information in audio signals |
EP1228504A4 (en) * | 1999-05-25 | 2007-02-07 | Arbitron Inc | Decoding of information in audio signals |
JP2008165258A (en) * | 1999-05-25 | 2008-07-17 | Arbitron Inc | Decoding of information in audio signal |
CZ304746B6 (en) * | 1999-05-25 | 2014-09-24 | Arbitron Inc. | System for decoding message symbol in audio signal and method of decoding such message symbol |
EP2549476A1 (en) * | 2011-07-21 | 2013-01-23 | Lee S. Weinblatt | Real-time audio encoding technique |
Also Published As
Publication number | Publication date |
---|---|
NZ503064A (en) | 2002-11-26 |
AUPP392498A0 (en) | 1998-07-02 |
AR019149A1 (en) | 2001-12-26 |
BR9906512A (en) | 2000-07-25 |
US6757300B1 (en) | 2004-06-29 |
CA2301186A1 (en) | 1999-12-09 |
CA2301186C (en) | 2009-09-22 |
GB2342265B (en) | 2002-12-31 |
GB0002212D0 (en) | 2000-03-22 |
GB2342265A (en) | 2000-04-05 |
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