Encoding and decoding an audio watermark using key sequences comprising of more than two frequency components
Embodiments of the invention are directed to systems, methods and computer program products for providing targeted location-based communications. An exemplary apparatus is configured to receive an encoded signal, decode the encoded signal such that embedded data is retrieved, send the embedded data a remote server; and receive a message based at least partially on sending the embedded data. Create a message vector based on the message comprising of a plurality of key sequences, each of which comprises more than two frequency components and is associated with a unique bit. Another exemplary apparatus is configured to provide the encoded signal by receiving data input, receiving a host signal, embedding the data input within the host signal such that an encoded signal is generated, and transmitting the encoded signal. A third exemplary apparatus is configured to provide the targeted communications by storing one or more messages associated with an entity, receiving data, selecting at least one of the one or more messages based at least partially on the data received, and sending the at least one of the one or more messages selected.
1. A system for creating an audio watermark signal by encoding a message comprising multiple bits of data, the message being encoded into a host signal in audible frequency range whereby all the bits of the message are located in a frame of the audio watermark signal and, the system comprising at least one encoding device comprising at least one encoding device comprising a processing device to:
receive data representing a message comprising a plurality of message bits to be encoded;
create a message vector based on the message, the message vector comprising a plurality of key sequences, each key sequence corresponding to a different message bit in the message, wherein each key sequence comprises more than two frequency components that represent frequencies of a frame of a host signal at which a message bit of the message corresponding to the key sequence is encoded within the frame, wherein a value associated with the key sequence represents the value of the message bit, and wherein each key sequence has an equal number of positive components and negative components, each having substantially the same amplitude;
read a frame of the host signal;
transform the frame of the host signal from time domain to frequency domain, wherein the frame comprises more than two frequency components, wherein each of the key sequences of the message vector comprises frequency components that correspond to frequency components of the frame of the host signal;
apply each of the key sequences of the message vector to the frame of the host signal, thereby resulting in an encoded frequency domain frame that represents all the bits of data of the message;
wherein applying each key sequence of the message vector to the frame comprises: multiplying each of the message vector frequency components of each key sequence by the corresponding frame frequency components that correspond to the frequency components in the respective key sequence, resulting in the encoded frequency domain frame;
transform the encoded frequency domain frame from the frequency domain to the time domain, thereby resulting in an encoded time domain frame that represents all the bits of data of the message; and
compile the audio watermark signal based at least in part on the encoded time domain frame.
2. The system of claim 1 , wherein applying at least one message vector to a plurality of components of the frame comprises:
applying a key sequence corresponding to a value of one to some of the plurality of frequency components of the frame to encode a one bit in the frame; and
applying a key sequence corresponding to a value of zero to others of the plurality of frequency components of the frame to encode a zero bit in the frame.
3. The system of claim 2 , wherein the amplitudes of the key sequence corresponding to a value of zero are the amplitudes of the key sequence corresponding to a value of one multiplied by negative one.
4. The system of claim 1 , wherein the processing device is further to:
append the frame to a previously encoded frame.
5. A system for decoding a message comprising multiple bits of data from an audio watermark signal in audible frequency range, whereby all the bits of the message are located in a frame of the audio watermark signal, the system comprising a processing device to:
receive the audio watermark signal, wherein the audio watermark signal comprises a message encoded in a frame of the audio watermark signal, wherein the message comprises a plurality of message bits, each encoded in different, more than two frequency components of the frame;
retrieve from a storage device a plurality of key sequences, wherein each key sequence corresponds to a different message bit in the message, wherein each key sequence comprises more than two frequency components that represent frequencies of the frame of the audio watermark signal at which a message bit of the message corresponding to the key sequence is encoded within the frame, and wherein each key sequence has an equal number of positive components and negative components, each having substantially the same amplitude;
read a frame from the audio watermark signal, wherein the frame comprises all the message bits of the message to be decoded;
transform the frame of the audio watermark signal containing the message from time domain to frequency domain;
convert the frame of the audio watermark signal to decibels;
apply the plurality of key sequences to the frame of the audio watermark signal to recover a plurality of recovered signals from the frame that represent all the message bits of data of the message;
wherein applying the plurality of key sequences to the frame of the audio watermark signal to recover the message comprises:
for each of the key sequences, multiplying each of the frequency components of the respective key sequence by the corresponding frame frequency components of the frame of the audio watermark signal, resulting in a recovered signal that represents a single bit of data of the message that corresponds with the key sequence, the recovered signal comprising a plurality of frequency components each having an amplitude;
for each of the recovered signals, average the amplitudes of the plurality of frequency components;
for each of the recovered signals, determine, based on the average of the amplitudes of the plurality of frequency components of the recovered signal, the bit of the message corresponding to the key sequence.
6. The system of claim 5 , wherein determining comprises:
determining whether the average amplitude of the recovered signal is greater than or less than zero;
assigning a one bit to the bit of the message corresponding to the key sequence when the average amplitude of the plurality of frequency components is greater than zero; and
assigning a zero bit to the bit of the message corresponding to the key sequence when the average amplitude of the plurality of frequency components is less than zero.
7. The system of claim 5 , wherein determining comprises:
determining that the average amplitude of the frequency components of the recovered signal is greater than a predetermined threshold based at least in part on the absolute value of the average of the amplitudes of the frequency components of the at least one key sequence; and
assigning a one bit to the bit of the message corresponding to the key sequence.
8. The system of claim 5 , wherein determining comprises:
determining that the average amplitude of the frequency components of the recovered signal is less than a predetermined threshold based at least in part on the absolute value of the average of the amplitudes of the frequency components of the at least one key sequence; and
assigning a zero bit to the bit of the message corresponding to the key sequence.