Wireless digital transmission system for speakers

CA 02249071 1998-09-23 WIRELESS SYSTEM WITH DIGITAL TRANSMISSION FOR LOUDSPEAKERS The present invention relates to a wireless system with digital transmission for loudspeakers.

Wireless speaker systems are known in which an analog audio signal is converted into a frequency modulated signal, this frequency modulated signal being transmitted over the AC power supply lines of a home network.

The signal received by the home network is then converted back to an audio signal after extraction of the modulated frequency signal.

Such a teaching is in particular disclosed by US Pat. No. 4,829,570.

This patent further contemplates the use of a compression device to allow compression of the analog signals delivered by a compact disc player, the wide dynamic range of which requires a very large bandwidth to allow frequency modulation transmission. .

Wideband and large deviations pose many problems which are solved herein by the use of a compressor circuit to reduce the total dynamic range of the audio signal.

This document already allows us to become aware 2o of a first difficulty which is the limitation of stereophonic systems in particular using frequency modulation and operating with analog systems such as variable frequency oscillators.

When we want to switch from simple stereophonic quality to stereophonic quality of the “Digital CD” type, the quantity of information to be transmitted is such that we are very quickly limited in frequency modulation by the passband.

Finally, this type of system taught by US Pat. No. 4,829,570 is acceptable for use for private purposes on the domestic network of a personal home but can be difficult to set up in a building or even less in communities or establishments. commercial CA 02249071 1998-09-23 2 sets.

In fact, the music broadcast on the power supply network will be picked up at the same time by all the speakers installed and connected to the network.

This poses a problem of copyright regulation and it is therefore desirable to provide a device which makes it possible to avoid widespread distribution.

Finally, such a device requires, in order to have the two stereophonic channels, to provide a first carrier frequency for the first channel and a second carrier frequency for the second channel.

These frequencies will have to be selected according to very precise conditions, which will also limit the possibilities of the bandwidth.

A first object of the invention is to provide a wireless digital transmission system for loudspeakers which allows the broadcasting of stereo signals of compact digital disc quality and / or remote control.

This first goal is achieved by the fact that the digital transmission wireless speaker system comprises:

means for compressing the file representative of the digital audio signal of "Compact disc" type, a transmission device comprising means for transforming this compressed signal into a serial signal circulating in packets intended for a phase quadrature modulator circuit and means for transmitting the signals leaving the quadrature phase modulator circuit to the domestic electricity supply network;

a reception device comprising means for connecting to this domestic network and for extracting from the electricity supply signal by a phase quadrature demodulator the information packets conveying the digital audio signal in order to transform it into a parallelized digital signal sent to a decompression circuit;

- Means of transforming the decompressed digital signals into an analog signal intended to supply a loudspeaker after adequate amplification.

CA 02249071 1998-09-23 3 A second aim is to allow the transmission of several musical signals to different loudspeakers.

This object is achieved by the fact that the serialization means comprise means of inserting a destination address into the packets of serialized signals;

and in that the reception means comprise means for comparing the address appearing in the received packet with the address specific to the reception device to which the loudspeaker is connected.

According to another particular feature, the serialization device comprises means of multiplexing several frames of digital files representative of a different audio signal intended for different addresses.

Another object of the invention is to provide a system which makes it possible to ensure that copyright cannot be defrauded.

This third object is achieved by the fact that the transmission circuits comprise an encryption circuit and the connected reception device comprises a decryption circuit using a secret key stored in the memory of the deserialization circuit.

According to another feature, the information of the digital signal is serialized according to a protocol comprising a first part constituting the protocol information, a second part constituting the address of the recipient, a third part constituting the digital signal or the multiplexed digital signals, and a fourth part constituting the end of protocol information.

According to another particularity, the protocol comprises a fifth part constituting the control information of the loudspeakers.

According to another particularity, the protocol comprises a sixth part constituting at least one encryption key.

According to another particular feature, the system comprises means for including control commands allowing the individual adjustment of each loudspeaker, in the serial signal circulating in packets.

According to another particular feature, the system CA 02249071 1998-09-23 4 comprises means for converting an analog signal into a digital signal, arranged upstream of the means for compressing the file representative of the audio signal, when the audio signal to be transmitted is analog type.

Other characteristics and advantages of the present invention will emerge more clearly on reading the description below given with reference to the appended drawings in which:

- Figure 1 shows a schematic view of the electronic circuit for implementing the invention;

FIG. 2 represents a schematic view of an audiovisual system of the "jukebox" type in which the device of the invention can be used.

The invention will now be described in conjunction with FIG. 1 in which the reference (13) designates the two conductors of a domestic electrical energy supply network of a building or of a room intended to accommodate a public or a community such as for example a bar, a department store, a sports arena, etc ....

To this power supply network is connected a transmission device (10) comprising the primary winding of a first transformer (108) which delivers through its secondary winding through a diode rectifier circuit a power supply signal to a supply circuit (100) which extracts, from the AC signal of the rectified mains, the signals necessary for supplying the various circuits of the device.

In parallel, on the primary of this first transformer (108) is connected a second transformer (109) whose secondary winding is supplied through a transistor by a phase quadrature modulation circuit (101).

This circuit (101) is supplied with voltage by the circuit (100) and receives from a microcontroller (102) streams of data packets (P1, P2) representing digital information serialized according to a protocol (P) shown below.

This protocol (P) comprises a first part (IP) constituting the protocol information, a second part (AD) constituting the address of the recipient CA 02249071 1998-09-23 or the addresses of each of the recipients, a possible third part (IC) constituting the loudspeaker control information, a possible fourth part (CE) constituting an encryption key or several keys, each for an address, a fifth part (SNA) constituting the digital audio signal or multiplexed audio signals, each signal being associated with one of the addresses of the recipient and finally, a sixth part (IFP) constituting the end-of-protocol information.

The signals are phase quadrature modulated by the io circuit (101) on a carrier, located between 200 and 300 kHz, and are superimposed on the AC mains signal through the transformer (109).

The digital audio signals coming from the audio source, after compression, represent a digital rate of 128 kilobits per second and are processed by the microcontroller (102) to be sent in successive packets according to the protocol (EP) explained above.

The program of the microcontroller (102) can be arranged to perform the multiplexing of several audio sources allowing, for example, to send a piece of classical music to a first speaker while sending at the same time a piece 2o of jazz music to a second speaker, each with a specific address and its own decryption key.

In this case, the device (10) sends one or more frames to a user identified by a card or a box (11) connected to the loudspeaker.

The transmission device (10) and the reception device (s) (11) are only connected to one another through the electrical conductors of the domestic electrical supply network.

Finally, the operating program of the microcontroller (102) will, when receiving commands sent by a remote control unit (12), for example emitting a wave signal to a sensor (1020), to include the commands thus generated by this box (12) in the package, so as to constitute the control information for the speaker CA 02249071 1998-09-23 6.

This control information allows individual adjustment of each speaker by adjusting the right channel, left channel, bass, treble, volume, etc. ...

When you want to protect audio information conveyed on the home network, so as to allow the collection of copyright and prevent the same musical piece from being listened to by people who have not paid the copyright, an encryption circuit (103) placed between the compression circuit (104) and the microcontroller (102) will be added to the device.

In the case where the source of the musical signals is not of the “Digital” type, an analog-to-digital converter (106) is added to the device, receiving at its input the output signals of an analog amplifier (107), which receives analog audio signals.

The reception device (11) is constituted as above by a first transformer (118) allowing, using a rectifier circuit, to supply a supply circuit (110) intended to generate the supply signals necessary for the device. operation of the various circuits of the reception device (11).

A second transformer (119) connected to the primary of the first, using a decoupling capacitor, supplies a quadrature-phase demodulator (111), which supplies the protocol signals and the protocol packets on its serial output. to a microcontroller (112) which transforms these series signals into parallel signals intended for a decryption circuit (113), the output of which is connected to a decompression circuit (114).

The output of the decompression circuit (114) is itself connected to a digital to analog conversion circuit (115), the output of which is intended to supply a loudspeaker (HP).

The compression and decompression circuits by an amplifier (116) apply a level 3 "MPEG" type algorithm and the encryption (103) and decryption (113) circuit apply an "3o" type algorithm. MMPP "(MultiMedia Protection Protocol).

CA 02249071 1998-09-23 7 The memory of the microcontroller (112) of the box (11) is loaded with the identification address which makes it possible to compare its address with the address received in the packet to identify whether the digital information audio are intended for it or are intended for another speaker.

Likewise, the memory of the microcontroller is loaded during initialization or during manufacture with a decryption key.

Loading during initialization with the decryption key can be done using the fourth zone of the protocol.

The digital analog converter circuits (CAN / or DAC) of encryption compression and amplification of the transmitter device (10) can be produced, for example, by a digital signal processor marketed by MOTOROLA under the reference 563XX and commonly called "DSP (Digital Signal Processor)".

Likewise, the decryption, decompression and digital-to-analog conversion circuits of the receiver device (11) can be implemented in a digital signal processor marketed by MOTOROLA under the reference 563XX and commonly called “DSP (Digital Signal Processor)”.

It is thus possible, thanks to such a device, to allow the installation of 2o multiple loudspeakers in different premises provided that they are supplied by the same phase of the network to which the transmission device (10) will be connected.

This transmission device (10) must on the one hand be connected to an audio signal source which could be for example the digital output of a compact disc player or the digital output of a hard disk of a juke- box such as that described in FIG. 2 and corresponding to the PCT patent application FR 95 01 333 published under the number WO 96/12256 and on the other hand to the conductors of the electrical supply network of the building or the room.

The jukebox of figure 2 is constituted by a central unit (1), a microprocessor which is a high performance PC compatible system.

The choice when implementing CA 02249071 1998-09-23 8 fell on a system of the "Intel 80486 DX / 2" type which has storage means and the following characteristics:

- compatibility with the Vesa local bus, - processor cache memory: 256 kB, - high performance serial and parallel ports, - SVGA type graphics adapter to microprocessor, - SCSI / 2 type bus controller, - self-powered static RAM random access memory .

Any other central unit having equivalent or superior performance can be used in the invention.

This central unit controls and manages a sound control circuit (5), a telecommunications control circuit (4), an input control circuit (3), a mass storage control circuit (2), a circuit (6) for controlling the display means.

The visualization means are mainly composed of a 14 inch (35.56 cm) flat screen video monitor (62) without interlace SVGA type with high resolution and low radiation, it is this monitor which is used for the video. reproduction of images (for example, album covers of musical selections), graphics or video clips.

Mass storage means (21) using high speed and high capacity "SCSI" type hard disks are associated with the storage means already present in the microprocessor device.

These means are used for the storage of digitized and compressed audiovisual information.

A 28.8 kbps high speed telecommunications modem adapter (41) is integrated to allow connection to an audiovisual information distribution network controlled by a central server.

For the reproduction of sound information from musical selections, the system includes loudspeakers (54) receiving the 3o signal from amplifier-tuner (53) connected to an electronic circuit (5) of the "Music Synthesizer" type designed to support a large number of CA 02249071 1998-09-23 9 input sources while providing an output having a quality of "CD" (compact disc) type, such as for example, the multimedia audio adapter to microprocessor, of the "Sound Blaster" card "SBP32AWE" from Creative Labs Inc on which two memory buffers (56, 57) are added for the purpose explained later.

Likewise, the control circuit of the display means also comprises two buffer memories (66, 67) for the purpose explained later.

A thermally regulated 240 watt ventilated io power supply provides power to the system.

This power supply is protected against over-currents and over-oscillations.

The audiovisual reproduction system manages, through its input controller circuit (3), a 14 inch (35.56 cm) "Intelli Touch" touch screen (33) from Elo Touch Systems Inc., which includes a window covering panel using "advanced surface wave technology" as well as an "AT" type bus controller.

This touch screen allows, after having displayed on the video monitor (62) or the screen of a television set (61), various selection information used by customers as well as selection information used by customers, as well as information 2o management controls and controls used by the manager or owner of the system.

It is also used for maintenance purposes in combination with an external keypad (34) which can be connected to the system which has a keypad connector for this, controlled by a key lock (32) through the interface circuit ( 3).

The input circuit (3) also interfaces with the remote control system (31) consisting for example:

- an infrared remote control from Mind Path Technologies Inc., transmitter which has 15 control keys for the microprocessor system and 8 control keys for the projection device, - an infrared receiver with serial adapter from Mind Path Technologies Inc.

CA 02249071 1998-09-23 A royalty payment device (35) from National Rejectors Inc. is also connected to the input interface circuit (3). It is also possible to use any other device which allows the reception of any method of payment by coins, bills, tokens, magnetic cards with 5 chips or a combination of the means of payment.

To house the system, a steel frame or frame with customizable exterior fittings is also provided.

In addition to these elements, a wireless microphone (55) is connected to the sound controller (5), which makes it possible to transform the latter into a powerful 1o system of announcements and information intended for the public or possibly a karaoke machine.

Likewise, a wireless speaker system can be used by the system.

The remote control assembly (31) allows the manager, for example from behind the bar, to access and control various commands such as:

- the microphone on-off command, - the speaker mute command, - the sound volume control command, - the command to cancel the music selection being listened to.

Two buffers (56, 57) are associated with the sound controller circuit (5) to enable each of them to alternately store information corresponding to a quarter of a second of sound.

Likewise, two buffers (66, 67) are associated with the video controller circuit (6) each capable of alternately storing a tenth of a second of images.

Finally, a respective buffer (46, 36, 26) is associated with each of the communication controller (4), input interface (3) and storage (2) circuits.

The digitized and compressed audiovisual data is stored in the storage means (21).

This information is transmitted via the central unit (1) to the card (105) on which the elements CA 02249071 1998-09-23 11 corresponding to the circuit (10), the encryption circuit ( 103) being directly connected to the buffer circuits (56, 57) in the case where the information is already compressed, either by a first connector (1021), avoiding the encryption circuit (103), if the information is already encrypted or n 'don't need to be, or by a second connector (1031), using the encryption circuit (103), if the information is to be encrypted.

In the event that the information is not compressed, the buffers (56, 57) will be connected to a third connector (1041) so as to use the compression circuit.

Thus, by connecting the output of the transformer (108) to the mains, it is possible, by connecting the receiving circuits (11) in different places on the mains, to supply various remote loudspeakers, in addition to the loudspeakers normally provided in the mains. the jukebox system (54).

This will allow good quality sound distribution in different premises while ensuring the manager the possibility of adjusting the volumes according to the premises or according to the arrangements of the loudspeakers.

In the event that the invention is used on another device such as a compact disc player, radio for receiving specialized channels, etc., it is possible to equip the payment device with the aid of the one of the means of payment mentioned above for the jukebox application which, as for the jukebox, will only allow the reception device to operate once the fee has been paid and for the duration provided for the fee.

This duration is determined by a clock associated with the receiving device.

Other modifications within the reach of those skilled in the art also form part of the spirit of the invention.