Systems and methods of remotely enabling sound enhancement techniques

A system and method of remotely enabling sound enhancement techniques is disclosed. In an embodiment, a watermark is embedded in an encoded multi-channel audio stream to remotely enable an enhancement decoder portion of a multi-channel audio decoder.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and system for controlling audio enhancement techniques to decode enhanced audio. In particular, the invention relates to using an enhanced audio signal to remotely control an audio decoder.

2. Description of the Related Art

Digital watermarking is a process for modifying physical or electronic media to embed a machine-readable code into the media. The media may be modified such that the embedded code is imperceptible or nearly imperceptible to the user. Most commonly, digital watermarking is applied to media signals such as images, audio signals, and video signals.

Digital watermarking systems typically have two primary components: an encoder that embeds the watermark in the host media signal, and a decoder that detects and reads the embedded watermark from a signal suspected of containing a watermark. The encoder embeds a watermark by altering the host media signal. The decoder analyzes a suspect signal to detect whether a watermark is present. In applications where the watermark encodes information, the decoder extracts this information from the detected watermark.

When the host media is an audio signal, watermarking embeds auxiliary data in a host audio signal. One feature of some audio watermarking techniques is that the embedded signal is substantially imperceptible to a listener of the host signal.

SUMMARY OF THE INVENTION

There exist many audio-enhancing techniques to spatially enhance a stereo image with respect to a listener when the enhanced audio is played through a speaker system. In one such example, a matrix system encodes a three or more channels or audio signals down to a two channel stereo signal. Examples of matrix encoding techniques include, but are not limited to, Left Center, Right, Surround (LCRS), 5.1, 6.1, 7.1, and the like. In an embodiment, a recorder records the encoded stereo signal and a playback device plays the encoded stereo signal.

In another embodiment, a transmitter transmits the encoded stereo signal and a receiver receives the encoded stereo signal. The receiver or playback device decodes the encoded two-channel stereo signal into the at least three channels to allow placement of specific sounds at any one of three or more predetermined locations.

Since matrix encoding can not often be reliably detected from the audio itself, a watermark can be incorporated into the matrix-encoded audio. In an embodiment of the invention, a watermark encoder embeds a watermark in a multi-channel audio signal. A matrix encoder then encodes the multi-channel audio signal as a two-channel audio signal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For a more detailed understanding of the invention, reference is first made toFIG. 1.FIG. 1illustrates an embodiment of a system100for using a watermark embedded in a multi-channel audio signal to remotely control a matrix decoder.

At an encoding portion102, a watermark encoder104embeds a watermark in multi-channel audio110from a multi-channel audio source106. The watermark comprises a control message to activate an enhancement decoder of an audio decoder126at a decoding portion120.

In an embodiment, the watermark encoder104embeds a watermark in at least one channel of the multi-channel audio110. In another embodiment, the watermark encoder104embeds a watermark in a portion of the channels of the multi-channel audio signal110. In a further embodiment, the watermark encoder104embeds a watermark in each channel of the multi-channel audio110. The multi-channel audio format can be either digital or analog.

The system100is compatible with watermarking technologies that use audio channels to carry data without interfering with the audio channel's original purpose. A watermark is a pattern of data that can be detected. In one embodiment, a watermark includes adding a pattern of tones, a pattern of bits, or often information that is not easily noticeable.

The watermark encoder104embeds a watermark in the multi-channel audio110using a key. The key is a set of parameters that define the watermarking process and is used in a decoder to decode the watermark message. The watermark encoder104may provide the watermark in the multi-channel audio signal110using various known watermarking principles, such as, for example bitplane techniques, transform techniques, format based techniques, and the like. For example, the watermark encoder104can use commercially available watermarking technology provided by Verance Corporation. An example of watermarking technology is disclosed in U.S. Pat. No. 6,737,957, by Petrovic et al. and assigned to Verance Corporation, which is herein incorporated herein in its entirety by reference.

Typical bit rates of watermark messages are low, ranging from less than a bit per second to a few tens of bits per second. In an embodiment, the watermark encoder104encodes the watermark at least once every three seconds. In another embodiment, the bit rate is less than 10 bits per second. In a further embodiment, the bit rate is greater than 10 bits per second.

The watermark encoder104produces a composite audio signal112, which comprises the multi-source audio110with the watermark embedded in one, all, or a portion of the audio channels.

A matrix encoder108receives the composite audio signal112from the watermark encoder104. The matrix encoder108encodes and enhances the composite audio signal112into a two-channel audio signal114comprising the watermark. The matrix encoder108may use various signal processing techniques, such as, for example, compression, coding, error-correction, modulation, filtering, frequency shifting, time delay, integration, differentiation, summing, subtracting, and the like, as are known to one of skill in the art of audio signal processing. In an embodiment, the matrix encoder108is a surround sound encoder. In a further embodiment, the matrix encoder108is a Circle Surround encoder.

A transmitter116receives the two-channel audio signal114for broadcasting the two-channel audio signal114as an audio transmission136via an antenna118. Although the embodiment illustrated inFIG. 1shows the transmitter116and the antenna118, any type of broadcast scheme can be used, including AM, FM, broadband, cable, optical fiber, computer network, analog transmission, digital transmission, land line, and the like.

In another embodiment, the two-channel audio signal114is stored on digital media, such as, for example a compact disc (CD), a digital video disc (DVD), a super audio CD, a solid state memory device, such as EEPROM, EPROM, PROM, ROM, RAM, or the like. In another embodiment, the two-channel audio signal114is stored on analog media, such as, for example, a magnetic tape, or the like.

At the decoding portion120of the system100, a receiver122receives the audio transmission136via an antenna124. The receiver122and antenna124transform the audio transmission136into a two-channel audio signal128corresponding to the two-channel audio signal114.

In other embodiments, the receiver122may be a receiver designed for other broadcast schemes, such as a receiver for AM, FM, broadband, cable, optical fiber, computer network, analog transmission, digital transmission, and the like.

In another embodiment, the receiver122is a playback device for receiving the two-channel audio signal128from the storage device storing the two-channel audio signal114. Examples of storage devices include CD's, DVD's, solid state memory, magnetic tape, and the like.

The decoding portion120further comprises a watermark detector138. The watermark detector138receives the two-channel audio signal128. Using the key and conventional watermark detection algorithms, the watermark detector138detects and decodes the watermark embedded in the two-channel audio signal128. The watermark comprises information pertaining to the encoded and enhanced audio of the two-channel audio signal128. In an embodiment, the watermark message identifies the encoded and enhanced audio as a surround sound encoded audio stream. In a further embodiment, the watermark message identifies the encoded and enhanced audio as a Circle Surround encoded audio stream. Further, the watermark detector138enables a control signal132.

The decoding portion120further comprises the matrix decoder126. In an embodiment, the matrix decoder126further comprises an enhancement decoder portion. The matrix decoder126may use various signal processing techniques, such as, for example, decompression, coding, error-correction, de-modulation, filtering, frequency shifting, time delay, integration, differentiation, summing, subtracting, and the like, as are known to one of skill in the art of audio signal processing to decode the two-channel audio signal128.

The matrix decoder126receives the two-channel audio signal128and the control signal132. The control signal132activates the enhancement decoder portion of the matrix decoder126in the correct mode to correctly decode the encoded and enhanced two-channel audio signal128. The matrix decoder126decodes the two-channel audio signal128to produce a decoded audio output134. In an embodiment, the matrix decoder126is a surround sound matrix decoder. In a further embodiment, the matrix decoder126is a Circle Surround matrix decoder.

The decoding portion120further comprises an indicator130. The indicator130receives the control signal132. The control signal132activates the indicator130to indicate that the receiver122is receiving an encoded and enhanced audio signal, which the enhancement decoder portion of the matrix decoder126is capable of decoding. Typically, the indicator130comprises a visual indicator, such as, for example, a lamp, a light emitting diode (LED), a liquid crystal display (LCD), or the like. In an embodiment, the indicator130indicates that the receiver122is receiving a surround sound encoded audio stream. In a further embodiment, the indicator130indicates that the receiver122is receiving a Circle Surround encoded audio stream.

In an embodiment where the audio transmission136is audio without an embedded watermark, the watermark detector138receives the two-channel encoded audio signal128, and determines that the watermark is absent. In the absence of a watermark for a predetermined period of time, the watermark detector138generates the control signal132indicating that the audio is not enhanced audio. The control signal132deactivates the enhancement decoder portion of the matrix decoder126and deactivates the enhanced audio indicator130.

In an embodiment, the predetermined period of time is approximately 3 seconds. In another embodiment, the predetermined period of time is less than 10 milliseconds. In a further embodiment, the predetermined period of time is more than 3 seconds. In a yet further embodiment, the predetermined period of time is between approximately 10 milliseconds and 3 seconds.

The predetermined amount of time depends on the application. For example, once a song on a CD has started to play, the watermark does not need to be repeated throughout the song, as it is likely that the audio encoding technique used to enhance the audio was used throughout the entire song. In this example, the watermark may be absent for tens of seconds.

In another example, while the audio for a television program may be enhanced, the audio for the commercials played throughout the television program may not be enhanced. In this example, the absence of the watermark for a few milliseconds indicates that audio for a commercial, which is not enhanced audio, is being played through the speaker system and that it is desirable to disable the enhancement decoder portion of the audio decoder.

In an embodiment where the matrix encoder108is a Circle Surround matrix encoder, and the matrix decoder126is a Circle Surround matrix decoder, the audio transmission136is a Circle Surround encoded audio stream. The Circle Surround encoded audio stream136comprises the embedded watermark, which contains the information that the audio signal is Circle Surround audio. The receiver122receives the transmission136and converts the transmission136into the two-channel encoded Circle Surround audio signal128. The watermark detector138receives the two-channel encoded Circle Surround audio signal128, decodes the watermark, and generates the control signal132indicating that the audio is Circle Surround audio. The control signal132activates the Circle Surround matrix decoder126and the Circle Surround indicator130. The Circle Surround matrix decoder126de-matrixes and decodes the two-channel encoded and enhanced Circle Surround audio128. The audio output134comprises multi-channel enhanced audio.

In an embodiment where the matrix encoder108is other than a Circle Surround matrix encoder and the matrix decoder126is a Circle Surround matrix decoder, the audio transmission136is encoded audio with an embedded watermark indicating the audio is not Circle Surround encoded. The receiver122receives the transmission136and converts the transmission136into the two-channel encoded audio signal128. The watermark detector138receives the two-channel encoded audio signal128, decodes the watermark, and generates the control signal132indicating that the audio is not Circle Surround audio. The control signal130deactivates the Circle Surround mode of the matrix decoder126and deactivates the Circle Surround indicator130. In an embodiment, the Circle Surround matrix decoder126does not de-matrix the two-channel encoded audio signal128. The audio output134comprises the two-channel audio signal128. In another embodiment, the Circle Surround matrix decoder126processes the two-channel audio signal128to provide a two-channel output signal at the audio output134. In another embodiment, the Circle Surround matrix decoder126de-matrixes the audio, but does not decode the audio enhancement.

In an embodiment where the matrix encoder108is other than a Circle Surround matrix encoder and the matrix decoder126is a Circle Surround matrix decoder, the audio transmission136is encoded audio without an embedded watermark. The receiver122receives the transmission136and converts the transmission136into the two-channel encoded audio signal128. The watermark detector138receives the two-channel encoded audio signal128, and determines that the watermark is absent. In the absence of a watermark for a predetermined period of time, the watermark detector generates the control signal132indicating that the audio is not Circle Surround audio.

In an embodiment, the predetermined period of time is approximately 3 seconds. In another embodiment, the predetermined period of time is less than 10 milliseconds. In a further embodiment, the predetermined period of time is more than 3 seconds. In a yet further embodiment, the predetermined period of time is between approximately 10 milliseconds and 3 seconds.

The control signal132deactivates the Circle Surround mode of the matrix decoder126and deactivates the Circle Surround indicator130. In an embodiment, the Circle Surround matrix decoder126does not de-matrix the two-channel encoded audio signal128. The audio output134comprises the two-channel audio signal128. In another embodiment, the Circle Surround matrix decoder126processes the two-channel audio signal128to provide a two-channel output signal at the audio output134. In another embodiment, the Circle Surround matrix decoder126de-matrixes the audio, but does not decode the audio enhancement.

FIG. 2illustrates another embodiment of a system200for using a watermark embedded in a multi-channel audio signal to remotely control a matrix decoder.

At an encoding portion202, the matrix encoder108receives the multi-channel audio signal110from the multi-channel audio source106. The matrix encoder108encodes and enhances the multi-channel audio signal110into a two-channel audio signal212. The matrix encoder108may use various signal processing techniques, such as, for example, compression, coding, error-correction, modulation, filtering, frequency shifting, time delay, integration, differentiation, summing, subtracting, and the like, as are known to one of skill in the art of audio signal processing. In an embodiment, the matrix encoder108is the surround sound encoder. In a further embodiment, the matrix encoder108is the Circle Surround encoder.

The watermark encoder104receives the encoded and enhanced two-channel audio signal212from the matrix encoder108and embeds a watermark in the two-channel audio signal212. The watermark comprises a control message to activate the enhancement decoder of the matrix decoder126at the decoding portion120.

In an embodiment, the watermark encoder104embeds a watermark in at least one of the channels of the two-channel audio signal212. The two-channel audio format can be either digital or analog. The watermark encoder104produces the watermarked two-channel audio signal114, which comprises the encoded and enhanced two-channel audio signal212and the watermark embedded in one or both of the audio channels.

The transmitter116receives the watermarked two-channel audio signal114for broadcasting the watermarked two-channel audio signal114as the audio transmission136via the antenna118.

In another embodiment, the watermarked two-channel audio signal114is stored on digital media, such as, for example a compact disc (CD), a digital video disc (DVD), a super audio CD, a solid state memory device, such as EEPROM, EPROM, PROM, ROM, RAM and the like. In another embodiment, the two-channel audio signal114is stored on analog media, such as, for example, a magnetic tape, or the like.

The decoding portion120of the system200is the same as the decoding portion120of the system100, shown inFIG. 1and described above.

As illustrated inFIGS. 1 and 2, the watermark can be inserted in the multi-channel audio110prior to encoding and enhancing the audio, or the watermark can be inserted into the encoded two-channel audio212after encoding and enhancing the audio.

FIG. 3illustrates a process of identifying and decoding an enhanced audio technique, according to an embodiment of the invention.

Beginning at block302, the watermark encoder104incorporates a watermark into the multi-channel audio110. In block304, the matrix encoder108encodes and enhances the multi-channel audio with the embedded watermark112into the watermarked two-channel audio114.

In another embodiment, illustrated inFIG. 2, the steps of embedding a watermark302, and encoding and enhancing304are performed in the reverse order. The matrix encoder108encodes and enhances the multi-channel audio110into the encoded and enhanced two-channel audio212prior to the watermark encoder104embedding a watermark in the encoded and enhanced two-channel audio212.

In an embodiment, the matrix encoder108is a surround sound matrix encoder, which encodes and enhances the multi-channel audio signal110,112into the encoded and enhanced two-channel audio signal114,212. In a further embodiment, the matrix encoder108is a Circle Surround matrix encoder, which encodes and enhances the multi-channel audio signal110,112into the encoded and enhanced two-channel audio signal114,212.

Referring toFIG. 3, in block306, the transmitter116transmits the watermarked two-channel audio transmission136to the receiver122. In another embodiment, the watermarked two-channel audio signal114can be stored on the storage device for playback at the receiver122.

In block308, the receiver122receives the watermarked two-channel audio transmission136. The receiver122and the antenna124convert the transmission136into the two-channel audio signal128. In another embodiment, the receiver122plays the stored watermarked two-channel audio signal128from the storage device.

In block310, the watermark detector138receives the watermarked two-channel audio signal128and retrieves the watermark from the signal128. The watermark detector138generates the control signal132indicative of the decoded watermark.

In block312, the control signal132activates the indicator130. The indicator130indicates that the receiver122is receiving encoded audio that can be decoded in the enhancement decoder portion of the matrix decoder126.

In block314, the control signal130activates the enhancement decoder portion of the matrix decoder126to decode the encoded two-channel audio signal128.

In block320, the activated matrix decoder126de-matrixes and decodes the encoded and enhanced two-channel audio signal128into the multi-channel enhanced output audio134.

In an embodiment, the matrix decoder126is a surround sound matrix decoder, which de-matrixes the audio and decodes the audio enhancement encoded by the surround sound matrix encoder into the multi-channel enhanced audio output134.

In a further embodiment, the matrix decoder126is a Circle Surround matrix decoder, which de-matrixes the audio and decodes the audio enhancement encoded by the Circle Surround matrix encoder into the multi-channel enhanced audio output134.

In block316, the control signal132deactivates the indicator130. In block318, the control signal130deactivates the enhancement decoder portion of the matrix decoder126.

In block320, in an embodiment, the matrix decoder126with the deactivated enhancement decoder portion outputs the encoded two-channel audio signal128as the audio output134. In another embodiment, the matrix decoder126processes the encoded two-channel audio signal to produce the audio output134. In another embodiment, the matrix decoder126de-matrixes the audio, but does not decode the audio enhancement.

The process ends at block322.

Other Embodiments

In another embodiment, the matrix encoder108encodes the multi-channel audio signal as a two-channel audio signal. The watermark encoder104then embeds the watermark in the two-channel audio signal.

In an embodiment, the transmitter116digitally transmits the two-channel audio signal to the receiver122. In another embodiment, the transmitter116transmits the two-channel audio signal as an analog signal to the receiver122. In a further embodiment, a recorder records the two-channel audio signal on digital media for playback at the audio receiver122. In yet another embodiment, a recorder records the two-channel audio signal on analog media for playback at the audio receiver122.

In another embodiment, the receiver122receives the two-channel audio signal. The receiver122detects the watermark and activates the enhancement decoder portion of the matrix decoder126in response to detecting the watermark. The matrix decoder126decodes the two-channel audio signal into the multi-channel enhanced audio signal for playback through a speaker system. In an embodiment, the receiver122enables the indicator130in response to detecting the watermark.

In another embodiment, the absence of the watermark deactivates the enhancement decoder portion of the matrix decoder126and disables the indicator130. The two-channel audio signal is then available for playback through the speaker system

In an embodiment, a method of identifying a surround sound audio technique in an encoded audio stream comprises encoding with the surround sound matrix encoder108multi-channel audio into two-channel audio, and embedding a watermark in the two-channel audio, where the watermark identifies the audio as surround sound matrix encoded audio.

In another embodiment, a method of identifying a surround sound audio encoding technique in an audio stream comprises embedding a watermark in multi-channel audio, where the watermark identifies the audio as surround sound matrix encoded audio, and encoding with the surround sound matrix encoder108the multi-channel audio having the embedded watermark into two-channel audio.

In another embodiment, a method of identifying a surround sound audio technique in an encoded audio stream comprises receiving two-channel audio with an embedded watermark, where the watermark identifies a surround sound encoding process associated with the two-channel audio, detecting the watermark, activating the surround sound matrix decoder126if the watermark identifies a surround sound matrix encoding process, and decoding with the active surround sound matrix decoder the two-channel audio into multi-channel audio for playback through a speaker system.

In another embodiment, an apparatus which identifies a surround sound audio technique comprises the watermark encoder104to embed a watermark in a multi-channel audio stream, where the watermark identifies a surround sound encoding process associated with the surround sound matrix encoder108, and the surround sound matrix encoder108to encode the multi-channel audio stream with the embedded watermark into a two-channel audio stream.

In another embodiment, an apparatus which remotely enables the surround sound audio decoder126comprises the receiver122to receive an encoded two-channel audio stream with an embedded watermark, where the watermark identifies a surround sound encoding process associated with the two-channel audio stream, the watermark detector138to detect the watermark and to enable the surround sound audio decoder126if the watermark identifies the surround sound encoding process associated with the surround sound audio decoder; and the enabled surround sound audio decoder126to decode the two-channel audio stream into a multi-channel audio signal.

In another embodiment, an apparatus which remotely enables the enhanced audio decoder126comprises the watermark encoder104to embed a watermark in a multi-channel audio stream, where the watermark identifies an audio encoding process associated with the enhanced audio encoder108, and the enhanced audio encoder108to encode the multi-channel audio stream with the embedded watermark into a two-channel audio stream.

In another embodiment, an apparatus which remotely enables the enhancement decoder portion of the enhanced audio decoder126comprises the receiver122to receive an encoded two-channel audio stream with an embedded watermark, where the watermark identifies an audio encoding process associated with the two-channel audio stream, the watermark detector138to detect the watermark and to enable the enhancement decoder portion of the enhanced audio decoder126if the watermark identifies the audio encoding process associated with the enhanced audio decoder126, and the enabled enhanced audio decoder to decode the two-channel audio stream.

In another embodiment, a method of identifying a sound enhancement technique in an encoded audio stream comprises enhancing audio with an audio enhancement technique, and incorporating a watermark into the enhanced audio to produce a watermarked audio stream, wherein the watermark identifies the audio enhancement technique.

In another embodiment, a method of identifying a sound enhancement technique in an encoded audio stream comprises receiving an enhanced audio stream with an embedded watermark, where the watermark identifies an audio enhancement process associated with the enhanced audio stream, detecting the watermark, and activating the enhancement decoder portion of the enhanced audio decoder126to decode the enhanced audio stream when the detected watermark indicates the enhancement process associated with the enhanced audio decoder126.

In another embodiment, an apparatus to identify Circle Surround encoded audio comprises a means to embed a watermark in an audio stream indicating the audio stream is a Circle Surround encoded audio stream, and a Circle Surround matrix encoder108to encode the audio stream as the Circle Surround encoded audio.

In another embodiment, an apparatus to remotely enable the Circle Surround matrix decoder126comprises a receiving means to receive a Circle Surround encoded audio stream with an embedded watermark, where the watermark identifies the audio stream as the Circle Surround encoded audio stream, a means to detect the watermark and a means to activate the Circle Surround matrix decoder126to decode the Circle Surround encoded audio stream when the watermark is detected.