JP2005020763A - Passenger entertainment system for commercial aircraft or other vehicles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the passenger entertainment system for a commercial aircraft and other vehicles in which a large channel capacity and a low power consumption are realized and a status that is practically immune to a quantization noise, a background noise and a crosstalk etc. is maintained. <P>SOLUTION: A plurality of digital audio signal sources (12) are provided for generating a plurality of compressed digital audio signals. The compressed digital audio signals are provided to a multiplexer (14) which multiplexes those signal in time domain and generates a single composite digital audio data signal. The composite digital audio data signal is provided to a demultiplexer (18) which is capable of selecting a desired channel from the composite digital audio data signal. A selected channel is provided to a decompression circuit (20) where it is expanded to generate a decompressed digital output signal. The decompressed digital output signal is then provided to a digital-to-analog converter (22) and converted to an analog audio signal. The analog audio signal is provided to an audio transducer (24). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The field of the invention is onboard entertainment systems for large commercial aircraft and other passenger vehicles.

 This patent is a continuation-in-part of SN (US Patent Application) 08 / 066,302 filed May 20, 1993.

  Recently, considerable attention has been given to the design and implementation of cabin entertainment and communication systems for use in large commercial aircraft. Examples of such systems are disclosed in the following patents: US Pat. No. 3,795,771 entitled “Passenger Entertainment / Passenger Service and Self-Test System”; “Wireless Audio Passenger Entertainment System (WAPES)” US Pat. No. 4,428,078 entitled “Method and apparatus for performing passenger-related and occupant-related functions in an aircraft” US Pat. No. 4,774,514; “Aircraft service system including central control system for occupant call lights and passenger reading lights” U.S. Pat. No. 4,835,604; entitled "Passenger Service and Entertainment System for Supplying Frequency-Multiplexed Video, Audio and Video Game Software Signals to Passenger Seat Terminals"; U.S. Pat. No. 4,866,515; US Pat. No. 5,123,015 entitled “Multiplexer”.

As shown in FIG. 1, a conventional (ie, prior art) passenger entertainment system 1 disclosed in the aforementioned patent generally has the following means: a plurality of audio signal sources 2 (eg, compact disc player and audio) A tape player); a plurality of analog-digital (A / D) converters 3 for converting an analog signal generated by an audio signal source into a digital format; a multiplexer 4 for time-domain multiplexing (synthesis) of the converted digital signals; A signal distribution network 5 for sending to a plurality of remote locations; at least one demultiplexer 6 for demultiplexing the combined signal and selecting one or more channels from the combined signal; a plurality of digitals for converting the selected channel to an analog format・ Analog (D / A) converter 7: Convert analog signal into sound wave A plurality of audio transducer 8 for conversion;
It is.
U.S. Pat.No. 3,795,771 U.S. Pat.No. 4,428,078 U.S. Pat.No. 4,774,514 U.S. Pat.No. 4,835,604 U.S. Pat.No. 4,866,515 U.S. Pat.No. 5,123,015

  As will be readily appreciated by those skilled in the art, conventional compact disc players can provide digital signal outputs, but these digital signal outputs are easily used in conventional passenger entertainment systems. Can not. One of the main reasons is that, since a compact disc player generally includes its own internal oscillator (oscillator), when using a plurality of conventional compact disc players, the respective digital outputs are out of synchronization. For this reason, it becomes considerably difficult to combine a plurality of digital outputs. Another main reason why the digital output of a conventional compact disc player is not utilized is that the conventional compact disc player provides a digital signal output with a 16-bit sample size and a 44 kHz sampling rate. This makes it difficult to distribute multiple channels (eg, 50 or more channels) through an audio signal distribution network without exceeding a desired power consumption level and without generating a significant bit error rate. For example, if a conventional compact disc player output with a 16-bit sample size and a 44 kHz sampling rate must be used in a 72-channel system, a transfer rate exceeding 50 megabits per second is required. However, conventional systems that can achieve 50 megabits per second transfer require significantly more power than is desirable in an aircraft environment. In addition, such systems require complex circuitry, generate large amounts of heat, and occupy more space than is desirable in an aircraft environment.

  Also, as will be readily appreciated by those skilled in the art, cable attenuation and distortion increase as data transfer rates increase. Such an increase in cable attenuation and distortion makes transmission considerably more difficult and in particular increases the bit error rate.

  As a means of reducing the data transfer rate and, as a result, greatly eliminating the complexity in data transmission, the conventional passenger entertainment system utilizes the analog output signal S1 supplied by the conventional compact disc player 2, A digital (A / D) converter 3 is used to convert the analog output signal S1 into a digital format. In this scheme, the sample size and sampling rate of the converted signal can be selected so that the transfer rate required to distribute multiple channels can be minimized. This method provides the desired transfer rate, but at the expense of audio fidelity and sound quality.

  More specifically, since the sample size and sampling rate of the converted signal are reduced, the resolution of the digital display of the original analog audio signal is reduced and considerable signal degradation occurs due to quantization errors. This signal degradation effectively limits the range in which the sample size and sampling rate can be reduced. Also, as will be readily appreciated by those skilled in the art, in the aircraft environment, considerable background noise enters the system when the signal is distributed in an analog format. In addition, the most common type of noise in the aircraft environment is that generated by aircraft power distribution systems, with a frequency of approximately 400 Hz. In the following, this type of noise is referred to as “400 Hz background noise”. Because of this 400 Hz background noise, it is difficult for an aircraft to convert an analog audio source signal to a digital format without including significant background noise in the resulting digital signal unless sufficient shielding is utilized.

  However, as described above, in order to achieve a satisfactory data transfer rate and a satisfactory power consumption level, the analog output signal of a conventional compact disc player is used, and the analog output signal is converted into a digital signal with a sufficiently low sample size and sampling rate. The need to convert to a format seems to be generally accepted by manufacturers of traditional passenger entertainment systems. For this reason, the presence of significant amounts of quantization noise, 400 Hz background noise, signal crosstalk, etc. is always inherent in all conventional passenger entertainment systems and audio distribution systems.

  The present invention is directed to an improved passenger entertainment system that employs an improved audio signal distribution system and method for commercial aircraft and other vehicles.

  By adopting the system and method of the present invention, high channel capacity and low power consumption are obtained, and a state that is substantially unaffected by quantization noise, background noise, crosstalk, etc. is maintained.

  Preferably, the passenger entertainment system according to the present invention comprises a plurality of “true” digital signal sources (eg a plurality of dedicated compact disc players capable of supplying compressed digital audio signal output), a multiplexer. , Signal distribution circuitry, at least one demultiplexer, one decompression circuit, at least one digital-to-analog converter and at least one audio transducer.

  The digital audio signal source receives a clock and an enable signal from the multiplexer and in response provides a plurality of compressed digital audio signals to the multiplexer. The multiplexer multiplexes the digital audio source signals, generates a composite digital audio signal, and sends the composite digital audio signal to the distribution network. The distribution network sends the digital composite signal to at least one remote location where the demultiplexer is located.

  The demultiplexer selects one or more desired channels (or signals) from the composite signal and provides the selected channels to the decompression circuit. Each decompression circuit decompresses the transmitted channel and as a result supplies each decompressed digital audio signal to a digital-to-analog converter. Each digital audio converter converts the incoming decompressed digital audio signal into an analog audio signal, which is then fed to an audio transducer located, for example, in a passenger headset. Finally, each audio transducer generates sound waves in response to the sent analog audio signal.

  Preferably, the passenger entertainment system of the present invention includes a plurality of analog video signal sources, a plurality of analog audio signal sources, a passenger address system, and a plurality of overhead video projectors in addition to the digital audio signal distribution system described above. A modular signal distribution network capable of transmitting all audio and video signals to a plurality of remote seat locations via a single coaxial cable, a plurality of in-seat video displays; Such embodiments are described in detail below in the section entitled “Detailed Description”.

  As is apparent from the above description, it is an object of the present invention to improve a passenger entertainment system using an improved digital audio signal distribution system and method for use in commercial aircraft and other vehicles.

  It is another object of the present invention to improve a passenger entertainment system using an improved integrated video and audio signal distribution system for use in commercial aircraft and other vehicles.

  It is yet another object of the present invention to provide a passenger entertainment system that can distribute integrated video and compressed digital audio signals over a single coaxial cable.

  It is yet another object of the present invention to provide a method for efficiently transmitting digital signal compression coefficients through a digital signal distribution network such as used in commercial aircraft and other vehicles.

  As will be readily appreciated by those skilled in the art, the passenger entertainment system according to the present invention converts transmitted digital audio data into a compressed digital format until the data reaches a remote seat position. Since it is maintained, it is not affected at all by quantization noise, background noise, crosstalk and the like. In contrast, traditional passenger entertainment systems that need to provide all audio data in an analog format and then convert it to a digital format has an inherent tendency to pick up 400 Hz background noise, and a significant signal Deterioration occurs. Specifically, any signal that exists in analog format in the noisy environment of a commercial aircraft is subject to distortion and degradation due to 400 Hz background noise. If the audio source signal is placed in an analog format that can be distorted before it is converted to a digital format, any signal obtained after analog-to-digital conversion is not the original audio signal, but the distorted audio. Signal. For this reason, users of conventional passenger entertainment systems must be equipped with significant shielding or significant decontamination (noise reduction) circuitry at the input and output signal lines. Without such equipment, the transmitted audio signal must accept a considerable amount of noise.

  Finally, as will be readily appreciated by those skilled in the art, a digital signal source capable of supplying a compressed digital audio signal to a signal distribution network via a multiplexer is used to later convert such a signal. By the method of decompression, the passenger entertainment system of the present invention can achieve a signal reproduction state far superior to that which can be achieved by utilizing the characteristics of the A / D conversion method of the preceding system. Specifically, prior art systems (including the content disclosed in the aforementioned patents) convert an analog audio signal supplied by a conventional compact disc player into a digital signal, eg, 8 bit size and 20-30 kHz sampling rate. Since the signal resolution is sacrificed when converting to a digital signal, signal fidelity or quality is considerably sacrificed. In contrast, if a digital signal with a 16-bit sample size and a 37.8 kHz sample size is compressed according to the present invention to produce a digital signal with the same sampling rate as the 4-bit sample size, there will be signal degradation. Is also very small. In other words, the digital signal compression rate is close to reducing the amount of data sent through the signal distribution circuit at a ratio of 4 to 1 without causing noticeable degradation of sound quality.

  In order to highlight various embodiments and breakthrough aspects of the present invention, a number of sub-items are provided in the following description. Further, where a particular structure appears in several drawings, the structure has been indicated using the same reference numerals in each drawing.

Digital Audio Signal Distribution System Referring to the drawings, FIG. 2 is a block diagram illustrating the basic components of a digital audio signal distribution system 10 according to one embodiment of the present invention.

  As shown, the digital audio signal distribution system 10 includes a plurality of "true" digital signal sources 12, a multiplexer 14, a signal distribution network 16, a plurality of demultiplexers 18, a plurality of decompression circuits 20, a plurality of It has a digital / analog converter 22 and a plurality of audio transducers 24.

  Each digital audio signal source 12 is, for example, a compact disc player, model No. manufactured and sold by Matsushita Electric Industrial Co., Ltd. in Osaka, Japan. Can have RD-AX7091. Further, preferably here, each digital audio signal source 12 receives a plurality of clocks and usable signals from multiplexer 14, and in response to such signals, a compressed digital audio with a 4-bit sample size and a 37.8 kHz sampling rate. A signal output can be generated. More specifically, prior to storage on a compact disc (or other digital media), digital audio data is converted from a 16-bit format to a 4-bit compact disc interactive (CD) using adaptive delta pulse code modulation (ADPCM). -I) Compressed to level B format. ADPM compression and CD-I level B format are known in the relevant field and will not be described in detail here.

  Preferably, each of the six digital signal sources 12 supplies 8 channels (4 stereo or 8 mono) of compressed digital audio data to the multiplexer 14. The compressed digital audio channel (s) are received from the digital audio signal source 12, and the compressed digital audio signal received by the multiplexer 14 is multiplexed (synthesized) in the time domain to form a single composite audio signal. Preferably, the transfer rate of the composite audio signal is 19.3536 MHz. Multiplexer 14 sends the composite audio signal to signal distribution network 16, which sends the composite audio signal to a plurality of remote locations such as passenger seats. One or more demultiplexers 18 are located at remote locations. Each demultiplexer 18 selects one or more desired channels from the composite signal under the control of a digital passenger control unit (DPCU) 134 (shown in FIG. 3) and decompresses each selected channel into a decompression circuit 20. To supply. Each decompression circuit 20 decompresses the channel (signal) sent thereto, and supplies the decompressed digital signal to a digital / analog (D / A) converter 22 as a result. Each of the digital-to-analog converters 22 converts the signal sent thereto into an analog audio signal, which is sent to the audio transducer 24. Finally, each audio transducer converts the analog audio signal sent thereto into sound waves.

  As described above, since the passenger entertainment system 10 according to the present invention performs digital-analog conversion only once for each selected channel, it is not affected at all by background noise, crosstalk and the like. Also, the one-time digital-to-analog signal conversion performed by the system 10 according to the present invention is necessary to convert the selected uncompressed digital audio signal into a form that can be used by the audio transducer. In addition, a “true” digital audio signal source 12 that can supply compressed digital audio signals to signal distribution network 16 via multiplexer 14 and later decompress these signals can be used to provide the passenger entertainment of the present invention. System 10 can obtain much better resolution than can be achieved using the characteristics of the A / D conversion method of the prior art system. More specifically, when the prior art system converts an analog audio signal supplied by a conventional compact disc player into a digital signal, eg, a digital signal with an 8-bit sample size and 20-30 KHz sampling rate, the signal resolution (Reproduction fidelity or sound quality) is sacrificed considerably. In contrast, a digital audio signal with a 16-bit sample size and a 37.8 kHz sampling rate is compressed, for example, signal degradation occurs when generating a digital signal with the same sampling rate as 4 bits, but very little Degree. In short, the digital signal compression rate reduces the amount of data sent through the signal distribution circuit without causing noticeable deterioration in sound quality at a ratio close to 4: 1.

Overview of Passenger Entertainment System Referring to FIG. 3, a preferred embodiment of a passenger entertainment system 100 according to a preferred embodiment of the present invention comprises a plurality of true digital audio signal sources 102, a plurality of video signal sources 104, It may include a mix of audio, video and control signal sources including one or more analog audio signal sources 106, a cabin management terminal 108 and a cabin intercommunication data system (CIDS) 110. Such audio, video and control signal sources 102-110 are connected to each other and to a plurality of remotely located audio headsets 114, in-seat video monitors 116 and overhead video monitors 118 via a combined audio and video signal distribution system. It is connected to the. The composite audio / video signal distribution system has the following components: video system control unit (VSCU) 120; passenger entertainment system controller (PESC) 122; video modulation unit (VMU) 124; multiple area distribution boxes (ADBs) 126; multiple floor block boxes (FDBs) 128; multiple seat electronics boxes (SEBs) 130; multiple tapping units (TUs) 132; multiple passenger control units (DPCUs), multiple in-seat video cassette players (IVCPs) 136; a plurality of video cassette player controllers (VCPCs) 138. Many of the signal sources 102-110 and signal distribution system components 120-138 described above are described in more detail below. However, the following general description may be helpful in fully understanding the structure and function of the passenger entertainment system 100 improved in accordance with the present invention.

  As described above in the section entitled “Digital Audio Signal Distribution System”, preferably, each of the plurality of digital audio signal sources is a single compact disc player manufactured and sold by Matsushita Electric Industrial Co., Ltd., Osaka, Japan. Model No. Has RD-AX7091. Also, each of the digital audio signal sources 102 is preferably capable of providing a compressed digital audio signal output having a 4-bit sample size having 8 channels (4 stereo or 8 mono) and a 37.8 kHz sampling rate. Furthermore, in accordance with a preferred embodiment of the present invention, a digital output signal having 8 channels in a compact disc interaction (CD-I) level B format can be generated and the supplied control signals (ie, clock and enable signal). All compact disc players (CDP), digital audio tape players (DAT) and other digital audio signal sources 102 that can be synchronized to the frame format used by the system can be used.

  Each of the compressed digital audio signals generated by the digital audio signal source 102 is sent to a separate input (not shown) of the video system control unit (VSCU) 120. The structure and function of the video system control unit 120 is described in detail in the section entitled “Structure and function of VSCU” below. However, at this point, a multiplexer (not shown) located within the video system control unit 120 multiplexes the compressed digital audio signal sent to it in the time domain to produce a composite pulse code modulation (PCM) data signal. Must be understood to occur. The composite PCM data signal is then sent to the filter / combiner 312 (shown in FIG. 5) for synthesis with the composite RF video signal received from the video modulation unit (VMU) 124, and the resulting composite PCM / RF video signal. Are sent to a passenger entertainment system controller (PESC) 122.

  Preferably, the passenger entertainment system controller (PESC) 122 performs a second multiplexing operation that adds an additional 24 entertainment channels and 6 passenger address channels to the composite PCM / RF video signal. More specifically, the passenger entertainment system controller (PESC) 122 separates the composite PCM data / RF video signal into separate PCM data and RF video components. Additional data channels are added to the PCM data portion of the separated signal, and then the PCM data and RF video portion of the composite signal are recombined and further transmitted.

  The composite PCM / RF video signal is then sent from a passenger entertainment system controller (PESC) 122 to a plurality of area distribution boxes (ADBs) 126. Area distribution boxes (ADBs) 126 are arranged in a daisy chain configuration, and are preferably equipped with up to eight area distribution boxes along the daisy chain. However, it will be readily understood by those skilled in the art, for example, depending on the type of coaxial cable (not shown) used to connect Area Distribution Boxes (ADBs) 126. Can be equipped with an area distribution box 126. Each area distribution box 126 taps off a small portion of the composite PCM / RF video signal (provides a branch line). The tapped composite PCM / RF video signal is then divided and split so that the tapped composite PCM / RF video signal can be distributed to a plurality of floor blocking boxes (FDBs) 128. It will be appreciated that a separate signal is supplied to each floor blocking box (FDB) 128.

  Each floor blocking box (FDB) 128 operates as a signal splitter utilized by the two daisy chains of seat electronics boxes (SEBs) 130. Preferably, each floor block box 128 here supports up to 30 seat electronics boxes (SEBs) 130 by placing up to 15 seat electronics boxes (SEBs) 130 in a particular daisy chain. However, it will also be noted here that the number and specific configuration of seat electronics boxes (SEBs) 130 may vary from system to system.

  Each seat electronics (SEB) 130 has a directional tap 702, a band division filter 704, a demultiplexer 706, a decompression circuit 708, a plurality of videos depending on the function (audio or video) provided at a predetermined passenger seat position. Processing circuits 714 and 716 (all shown in FIG. 9) can be included. The directional tap 702 taps off a small portion of the composite PCM / RF video signal used in the seat electronics box (SEB) 130, and this composite PCM / RF video signal is then sent to the next seat electronics box in a given daisy chain. It works to convey to (SEB) 130 with a small amount of loss. Band splitting filter 704 separates the tapped composite PCM / RF video signal into its separate PCM data and RF video components. The RF video component is sent to each tuner 714 of the video processing circuit, and the PCM data signal is sent to a demultiplexer (IVAS gate array) 706 via a linear analog amplifier 730 and an amplitude comparator 732.

  The demultiplexer 706 selects one or more desired channels from the composite PCM data signal under the control of a plurality of digital passenger control units (DPCUs) 134 and outputs a decompression circuit 708 (the ADPCM gate array shown in FIG. 9). ) Send each channel selected. Further, each decompression circuit 708 decompresses the channel sent here and supplies the decompressed digital audio signal to a pair of digital-analog (D / A) converters 710 as a result. The digital / analog converter 710 converts the decompressed digital audio signal into an analog signal. The resulting analog audio signal is amplified by amplifier 712 and sent, for example, to a transducer (not shown) located in passenger headphones 114.

  The RF video portion of the split signal is sent to a plurality of video processing circuits via a signal splitter 734. Each of these circuits has a tuner 714 and a tuner control circuit 716 (all shown in FIG. 9). The signal splitter 734 functions to separate the individual tuners 714 from each other, and the tuner control circuit 716 is controlled via a microprocessing unit (MPU) 718 and one of a plurality of digital passenger control units (DPCU) 134. . Each tuner 714 is controlled by an associated video control circuit 716 that receives control signals from the microprocessing unit 718, and each tuner 714 can select a desired video channel from the composite RF video signal. After a particular video channel is selected, the video processing circuit sends this channel to the seat display unit (SDU) for display.

  In-seat video cassette players (IVCPs) 136 are controlled by a video cassette player controller (VCPC) and serve as an additional source of video signals for display by seat display units (SDUs) 116. Preferably, the in-seat video cassette players (IVCPs) 136 are, for example, part numbers manufactured and sold by Matsushita Electric Industrial Co., Ltd. in Osaka, Japan. Can have RD-AV1203. In-seat video cassette players (IVCPs) 136 are controlled in a conventional manner by video cassette player controllers (VCPCs) 138 and, when operable, analog audio and video signals passed through the seat electronics box (SEB), Supply to a seat display unit (SDU) 116 and a passenger headset (not shown).

VMU Structure and Function Referring to FIG. 4, the video modulation unit (VMU) 124 preferably receives a plurality of analog video signals generated by the video signal source 104 at separate balanced input ports 202. Each of the analog video signals sent to the video modulation unit (VMU) 124 is supplied to an amplitude modulator 204 located in the video modulation unit 124, which is connected to each of the video signals supplied at the selected carrier frequency. Modulate. Amplitude modulation is well known in the prior art and will not be described in detail here. Preferably, however, each supplied video signal is modulated at a selected carrier frequency between 235 MHz and 300 MHz. In addition, each modulator 204 is electronically coupled to and controlled by a microprocessing unit (MPU) 205. The microprocessing unit (MPU) 205 serves as means for changing the operating parameters of the modulation unit 204, and thus serves as means for selecting a desired carrier frequency by a program. More specifically, a microprocessing unit (MPU) 205 is located in a video system control unit (VSCU) 120 via an RS-232 interface 207 (shown in FIG. 5), a central processing unit (CPU). Communicating with 316, the microprocessor 205 sets the carrier frequency in response to a signal received from the video system control unit (VSCU) 120. Here, each carrier frequency (135 MHz to 300 MHz) is preferably set to a default value, and if there is no other value, another value is indicated. The default frequencies for this preferred embodiment are shown in Table 1.

  However, it should be noted that the above frequencies here preferably only include the carrier frequency and are not intended to limit the scope of the invention to the specific frequencies described above. Further, as described above, it is desirable to be able to program the carrier frequency utilized by the passenger entertainment system 100 of the present invention, for example, if interference occurs at a particular frequency, it is stored in the memory of the cabin management terminal 108. This frequency can be changed by entering a new carrier frequency in the existing database. Also, if a particular video input signal is not available (ie, if a particular video source 104 becomes inoperable), the carrier frequency 204 of a particular modulator 204 can be changed. For example, if a particular video recording is broadcast on channel 1 and the video source 104 sent to channel 1 fails, the video recording can be played back by another video source 104 and the modulator connected to this source is as described above. The signal sent here can be modulated up to 151.25 MHz (channel 1 carrier frequency).

  After modulation, each video signal is sent to a separate input 206 of a plurality of primary combiner circuits 208. Each primary combiner circuit 208 combines the three video input signals and shapes the combined video signal, and each resulting combined signal is sent to one input of the secondary combiner circuit 210. The signal generated by the secondary combiner circuit 210 is referred to herein as a composite RF video signal.

Prior to distribution throughout the passenger entertainment system 100, the composite RF video signal is passed through a low pass filter 212, amplified by an amplifier 214, and split by a four-way splitter 216. Thus, the composite RF video signal is preferably provided here to four separate output terminals 218 of a video modulation unit (VMU) 124.

  Referring to FIG. 3, a video modulation unit (VMU) 124 is connected to a plurality of tapping units (TUs) 132, and the tapping units (TUs) are connected to a plurality of video projectors or video monitors 118. Each tapping unit (TU) 132 is, for example, a TU model No. manufactured and sold by Matsushita Electric Industrial Co., Ltd. in Osaka, Japan. Can have RD-AA5101. Further, each tapping unit 132 can have a video tuner (shown in FIG. 4 (a)) that selects the desired channel from the composite RF video signal, so that each tapping unit 132 (all displays the same channel). Up to three separate video monitors or projectors 118 can be driven. The tapping unit 132 receives the composite RF video signal from the video modulation unit 124, which is controlled by a central processing unit (CPU) 316 (shown in FIG. 5) located in the video system control unit (VSCU) 120. Is done. More specifically, a central processing unit (CPU) 316 located in the video system control unit (VSCU) 120 controls channel selection by the tapping unit 132 and functions of the video monitor or projector 118.

Structure and Function of Tapping Unit Referring also to FIG. 4 (a), each tapping unit 132 has a directional tap 220, a tuner 222, a tuner control unit (224), and three video signal amplifiers 226. ing. The directional tuff 222 taps off a small portion of the composite RF video signal generated by the video modulation unit 124 and passes the remaining portion of the composite RF video signal to the next tapping unit 132 along the predetermined daisy chain with little signal loss. Function to send by. The tuner control circuit 224 is connected to a central processing unit 316 disposed in the video system control unit (VSCU) 120, and controls the tuner 222 in response to signals received therefrom.

  In response to the signal received from tuner control circuit 224, tuner 222 selects the desired channel for viewing video monitor 118 and sends the selected channel to amplifier 226.

Structure and Function of VSCU Referring now to FIG. 5, preferably the video system control unit (VSCU) 120 of the present invention is a central control of the audio and video portions of the passenger entertainment system 100 according to the present invention. Giving function. In addition, a video system control unit (VSCU) 120 receives database and program selection information from a cabin management terminal (CMT) 108, and based on this information, a video signal source 104, a digital audio signal source 102, a video modulation unit (VMU) 124. A control signal is given to a plurality of tapping units (TUs) 132.

  In addition to providing a central control function for the passenger entertainment system 100 according to the preferred embodiment of the present invention, the video system control unit (VSCU) 120 is responsible for all video source audio signals and digital audio generated by the video signal source 104. All compressed digital audio signals supplied by the signal source 102 are received and multiplexed. The signal generated upon completion of the multiplexing operation performed by the video system control unit (VSCU) 120 is referred to herein as a composite PCM data signal.

  The video system control unit (VSCU) 120 includes a passenger entertainment system controller (PESC) 122, a plurality of area distribution boxes (ADBs) 126, a plurality of floor block boxes (FDBs) 128, and a plurality of seat electronics boxes (SEBs) 130. Distributes composite PCM data signals to multiple remote locations.

  Preferably, the video system control unit (VSCU) 120 comprises a mix of a plurality of compact disc players (CDPs) 102 to 48 compressed digital audio channels (8 channels per player) and a video cassette player 104. Up to 48 analog audio channels (4 channels per player) and analog audio playback device 106 (12 channels per player), a total of up to 72 channels can be received. More specifically, the video system control unit (VSCU) 120 is configured to accommodate 3 blocks of input channels each having 24 channels, so that a particular block of input channels is of only one type. Channels (ie, compressed digital audio channels or analog audio channels).

  Thus, preferably, the video system control unit is adapted to support 24 analog audio channels and 48 compressed digital audio channels, or 48 analog audio channels and 24 compressed digital audio channels, for a total of up to 72 channels. Can be configured.

  The analog audio channels received from the audio playback device 106 and the video source 104 are converted to a 16-bit sample size digital format using an analog-to-digital converter 302, and the resulting digital signal is then converted to 4 by adaptive delta pulse code modulation. Compressed to bit sample size format. Preferably, the analog-to-digital conversion process is performed by one of up to 48 MASH (multi-stage noise shaping) analog-to-digital converters 302 (24 per analog audio board 301). Each MASH analog-to-digital converter 302 receives a single analog input signal, converts this signal to a digital format, and converts the resulting digital signal to another converted digital signal (ie, another MASH analog-to-digital converter 302). And a single digital output signal having two channels. The MHSH transform is well known in the prior art and will not be described in detail here. Further, preferably, the MASH converter is a NAS DAC chip part number sold by Matsushita Electric Industrial Co., Ltd. in Osaka, Japan. Can have MH646A. After the MASH analog-to-digital signal conversion process is complete, the resulting digital signal, each having two channels, is sent to separate input terminals 304 of multiple ADPCM gate arrays 306. Here, preferably three ADPCM gate arrays 306 are utilized, each coupled to eight separate MASH analog-to-digital converters 306. Four digital signals, each having two channels, are received by each ADPCM gate array 306, compressed by adaptive delta pulse code modulation, and then multiplexed to form a single compressed digital output signal having eight channels. The resulting three compressed digital output signals are then routed from the ADPCM gate array 306 to separate inputs 308 of the integrated video audio system (IVAS) gate array 310.

  In addition, an integrated video audio system (IVAS) gate array 310 combines the compressed digital audio signal generated by the digital audio signal source 102 with the compressed digital output signal generated by the ADPCM gate array 310 to form a composite PCM data signal. The function of the IVAS gate array 306 is described in detail below. However, at this point, the integrated video audio system (IVAS) gate array 310 receives the compressed digital audio signal received from the digital audio signal source 102 and the ADPCM gate array 310, multiplexes the converted and compressed signal in the time domain. It can be appreciated that a composite pulse code modulation (PCM) gate signal is formed. The Integrated Video Audio System (IVAS) gate array 310 then sends the composite PCM data signal to the filter / combiner 312 which combines it with the composite RF video signal provided by the video modulation unit (VMU) 124. . The filter / combiner 312 filter (not shown) reduces the amplitude of the composite PCM data signal and modulates the resulting waveform to produce an analog waveform whose frequency and other characteristics are similar. ) Form a signal. In this way, composite PCM data signals can be converted into passive analog signal processing components (ie, directional taps, splitters, etc.), as well as linear analog signals placed in area distribution boxes (ADBs) 126 and floor block boxes (FDBs) 128. It is converted into a form that can be passed through the amplifier. The filter / combiner 312 combiner (not shown) combines the filtered composite PCM data signal with the composite RF video signal to form a composite PCM / RF video signal. The resulting composite PCM / RF video signal is then sent to the Passenger Entertainment System Controller (PESC) 122 for further processing and finally distribution to remote seat positions.

  As further shown in FIG. 5, the video system control unit (VSCU) 120 can preferably have nine subsystem boards including: two analog signal conversion boards 301; one central processing unit (CPU) board 303; one ARINC interface board 305; one local area network (LAN) board 307; one digital audio board 309; one tuner board 311; One power board (not shown); one motherboard 313;

  For convenience, dashed lines are used here to show what circuit components are on a given subsystem board.

  Each audio signal conversion board 301 has 24 audio signal input ports 302, 24 MASH analog-to-digital converters 314, and 3 ADPCM gate arrays 306. The audio signal input port 314 receives analog audio signals from the plurality of video sources 104 and the audio playback device 106 and then sends these signals to the MASH Aronag to digital converter 302. Each of the MASH analog-to-digital converters 302 converts a single incoming analog audio signal into a digital audio signal, and the resulting pair of digital audio signals is multiplexed to provide 2 channels and 16-bit sample size and 37.8 kHz sampling rate A single digital audio signal is formed. Each of the converted audio signals having two channels is then sent to one input terminal 304 of three ADPCM gate arrays 306. In the ADPCM gate array 306, this signal is compressed and combined with the other three converted audio signals to form a compressed digital output signal having 8 channels. Each of the three ADPCM gate arrays 306 generates a separate compressed digital output signal, and then each of the three compressed digital output signals is sent to the digital audio board 309, where it is an integrated video audio system (IVAS) gate. An array 310 is arranged.

  Integrated video audio system (IVAS) gate array 310 located on digital audio board 309 receives compressed digital audio signals from digital audio signal source 102 and ADPCM gate array 306, multiplexes these signals, and combines the composite PCM data described above. Form a signal. The composite PCM data signal is then fed to the motherboard filter / combiner 312.

  As described in more detail below, the integrated video audio system (IVAS) gate array 310 of the digital audio board 309 also functions as a channel selector or demultiplexer. More specifically, an integrated video audio system (IVAS) gate array 310 can be used to select a preview audio channel to listen at the cabin management terminal 108. In this mode, in response to control signals generated by the central processing unit (CPU) 316, the integrated video audio system (IVAS) gate array 310 can select the desired audio channel (mono 1 or stereo 2) from the composite PCM data signal. Select. Selected audio channels with compressed digital audio data are sent to ADOCM gate array 318, decompressed to 16-bit format, and then paired with a MASH digital-to-analog converter 320 (MASH sold by Matsushita Electric Industrial Co., Ltd., Osaka, Japan) DAC chip model No. MN6475A is desirable), demultiplexed (demultiplexed), and converted to analog format. The resulting analog preview channel is then sent to the gain control circuit 322 and finally sent to the cabin management terminal 108 where it is heard, for example, by an audio transducer located in a stereo headset (not shown).

  The tuner board has a tuner control circuit 324 and a tuner circuit 326. Tuner circuit 326 receives a composite RF video signal generated by video modulation unit (VMU) 124 and can select a preview video channel from the composite RF video signal in response to a control signal generated by central processing unit 316. More specifically, tuner control 324 receives control signals from central processing unit (CPU) 316 and in response adjusts tuner 326 operating parameters and selects the desired RF video channel. As can be seen from Table 1, the carrier frequency of the channel to be previewed is preferably set to 139.25 MHz or 295.25 MHz, so that the tuner 326 also uses 139.25 MHz or 295.25 MHz to be used as the preview carrier frequency. Set to select. Finally, the selected RF video channel is demodulated by tuner 236 and sent to cabin management terminal 108 for viewing. In this manner, the channel can be previewed before being distributed throughout the passenger entertainment system 100. On the other hand, if it is desired to monitor only the video channel, the carrier channel of this video channel can be selected by the tuner 326 in the manner described above, and the channel to be monitored is sent to the cabin management terminal 108 for viewing. The CPU board is a central processing unit 316 (preferably a Type 68000 series microprocessor manufactured by Motorola, Inc., Phoenix, Arizona), a crystal control oscillator 328 with a crystal frequency of 19.66 MHz, a frequency divider circuit 330, multiple memories A component 332 and a microprocessor monitoring circuit 334; Central processing unit 316 performs several functions including initialization, subsystem control, and subsystem communication management. Chip initialization is executed by writing a program command to a peripheral chip that controls the operation mode of the chip. As part of performing the initialization function, the central processing unit 316 must receive a system configuration database from the cabin management terminal (CMT) 108.

  Communication between the central processing unit (CPU) 316 and other peripheral devices (or subsystems) is performed as follows. A central processing unit (CPU) 316 communicates with a cabin management terminal (CMT) via a local area network (LAN) 319 to obtain configuration information and execution commands used to control video system functions. The central processing unit (CPU) 316 controls the frequency of the modulator 204 located therein and operates the diagnostic function via the RS-232 interface 338 to the microprocessor 205 of the video modulation unit (VMU) 124. Communicate with. The central processing unit (CPU) 316 communicates with the cabin intercommunication data system (CIDS) 110 via one of the ARINC-429 interfaces 336. A central processing unit (CPU) 316 controls the selected video signal source 104 via an RS-232 interface 338 that corresponds to the selected video signal source 104. More specifically, upon receiving a command from the cabin management terminal (CMT) 108 to control a specific function of the video signal source 104, the central processing unit (CPU) 316 receives the RS-232 corresponding to the video signal source 104. This command is executed by communicating with the corresponding video signal source 104 via the interface 338. Communication between the central processing unit (CPU) 316 and the digital audio signal source 102 is performed in a similar manner. Finally, communication between the central processing unit (CPU) 316 and the video display units (VDUs) 118 and tapping units (TUs) 132 is performed via the RS-485 interface 340.

  A memory component 332 connected to the central processing unit 316 is a pair of RAM memories for data storage (128 KX 8 each), a pair of EPROMs for program storage (512 K X 8 each), and built-in test equipment (BITE) It has a pair of EEPROMs (64K x 8 each) for storage of information, configuration data and downloadable databases.

  The microprocessor monitoring circuit 334 has a reset line (not shown) of the central processing unit 316, and the main function of the monitoring circuit 334 is to ensure continuous system performance. More specifically, if the central processing unit 316 is caught in an infinite loop, the monitoring circuit 334 detects this condition and resets the central processing unit 316. Furthermore, the monitoring unit 334 can detect potential power interruptions and power abnormalities. Thus, if a power interruption or anomaly is detected, the monitoring circuit 334 sends a signal to the central processing unit 316, so that the central processing unit 316 initiates the shutdown process in sequence, that is, backs up critical data. can do.

  The ARINC interface board 305 has four ARINC-429 ports 336, 19 RS-232 ports 338, and three RS-232 ports 338. An RS-232 port 338 provides communication between the central processing unit 316 and the digital audio signal source 102, video source 104, and video modulation unit (VMU) 124. RS-485 port 340 communicates between central processing unit 316 and tapping units (TUs) 132, and ARINC-429 port 336 communicates between central processing unit 316 and cabin intercommunication data system (CIDS) 110.

Structure and function of PESC Referring now to FIG. 6, preferably a passenger entertainment system controller (PESC) 122 includes two analog signal conversion boards 401 and 403, a motherboard 405, a CPU board 407, a local An area network (LAN) board 409, a power supply board (not shown), and an ARINC interface board 411 are included. As with the video system controller unit (VSCU) 120, dashed lines are used to indicate which circuit components are located on which board.

  The first analog signal conversion board 401 has the same components as the audio signal conversion board 301 arranged in the video system control unit (VSCU) 120. More specifically, the first analog signal conversion board 301 has 24 audio signal input ports 402, 24 analog-to-digital MASH converters 404, and 3 ASPCM gate arrays 406. Audio signal input port 402 receives analog audio signals from a plurality of audio playback devices 106 and then sends the signals to MASH analog-to-digital converter 404. The MASH analog-to-digital converter 404 converts each input analog audio signal to a digital format, and the resulting digital signal pair is multiplexed into a single digital audio with 2 channels and 16-bit sample size and 37.8 kHz sampling rate A signal is formed. Each of the converted audio signals is then sent to input terminals 408 of three ADPCM gate arrays 406. Here, this signal is compressed and combined with the other three converted signals to form an 8-channel compressed digital output signal. Each of the three ADPCM gate arrays 406 generates a separate compressed digital output signal, and then each of the three compressed digital output signals is sent to a second analog signal conversion board 403. An integrated video audio system (IVAS) gate array 410 is arranged on the board 403.

  The second analog signal conversion board 403 has several components arranged in the first analog signal conversion board 401 and the integrated video audio system (IVAS) gate array 410. Further, the second analog signal conversion board includes ten audio signal input ports 412 (a) to (f) and 414, six MASH analog-digital converters 416, one ADPCM gate array 416, an integrated video audio system. An (IVAS) gate array 410 is included.

  Preferably, the audio signal input ports 412 and 414 of the second analog signal conversion board 403 of the passenger entertainment system controller (PESC) 122 are provided with four voice operation switches (VOX) and a passenger address (PA). There are audio channels and six other PA audio channels. However, at any time, only six PA audio channels are sent to the MASH analog to digital converter 416. More specifically, the voice operation switching (VOX) circuit 420 detects the presence or absence of an audio signal at the VOX PA input terminal 414 and connects between the VOX PA input 414 and the first four PA audio channels 412 (a to d). A control signal is supplied to the 4-channel (2 to 1) multiplexer 421 that is selected in (1). Each channel of the multiplexer 421 is controlled by a separate VOX circuit 420, so when the VOX circuit 420 detects an audio signal at its input, the signal is sent to the multiplexer 421 and the PA audio input 412 is routed to the VOX PA audio input 414. The multiplexer 421 is prompted to replace it.

  Since the analog to digital MASH converter 416 and the ADPCM gate array 418 function as described above, these functions will not be described in detail here.

  The primary function of the IVAS gate array 410 of the passenger entertainment system controller (PESC) 122 is to add additional audio, control and passenger address signals to the composite PCM / RF video signal. More specifically, the IVAS gate array 410 multiplexes the PCM data portion of the composite PCM / RF video signal, the compressed signal received from the ADPCM gate arrays 406 and 418 and the CPMS / PSS data message received from the microprocessor 430 in the time domain. Therefore, the compressed signal and the CPMS / PPS data signal sent from the ADPCM gate arrays 406 and 418 are added to the composite PCM data signal. The resulting “perfect” composite PCM data signal is then sent to the filter / combiner 422 for synthesis with the RF video signal, and the “perfect” composite PCM / RF video signal is sent from the RF combiner 422 to multiple area distribution boxes (ADBs). Sent to 124. It can be seen that the filter / combiner 422 of the passenger entertainment system controller 122 functions similarly to the filter / combiner 312 located within the video system control unit 120.

  A separator 424 located on the motherboard 405 of the passenger entertainment system controller (PESC) 122 separates the composite PCM / RF video signal sent by the video system control unit (VSCU) 120 and integrates the integrated video audio system (IVAS). The gate array 410 is supplied with the PCM data portion of this signal. Separator 424 performs a separation function based on frequency, so all frequency elements below about 50 MHz are sent to PCM audio board 403, and all frequency elements above about 100 MHz are sent to RF video board 405. . The RF video portion of the separated signal is supplied to filter / combiner 422 by separator 424 for recombination with the PCM data signal.

  The CPU board 407 of the passenger entertainment system controller (PESC) 122 has the same circuit as that of the CPU board 303 arranged in the video system controller unit (VSCU) 120. More specifically, the CPU board 407 includes a microprocessor 430, a monitoring circuit 432, an oscillator 434, a frequency divider 436, and a plurality of memories 438. Such components function in the same manner as the components of the CPU board 303 of the video system control unit (VSCU) 120. However, these components are configured to correspond to the functions of the passenger entertainment system controller (PESC) 122 described above.

ADB Structure and Function Referring now to FIG. 7, preferably each area distribution box (ADB) 126 distributes power, audio, video, and service data to multiple floor block boxes (PDBs) 128. To act as a zone controller. The area distribution boxes (ADBs) 124 are arranged in a daisy chain configuration in which a maximum of eight area distribution boxes (ADBs) 124 are arranged in each daisy chain. However, as will be readily appreciated by those skilled in the art, it will be appreciated that the number of area distribution boxes (ADBs) 126 may be varied as described above. Interconnection between area distribution boxes (ADBs) 126 is made using a single coaxial cable and up to two twisted pair DATA buses (DATA1 and DATA2 buses).

  The main function of each area distribution box (ADB) 126 is to tap off a small part of the composite PCM / Rf video signal, and then to the next area distribution box (ADB) 126 arranged in a predetermined daisy chain. Sending the rest of the video signal with little signal loss. The area distribution box (ADB) then amplifies and separates the tapped portion of the composite PCM / RF video signal for further distribution within the passenger entertainment system 100. More specifically, the combined PCM / RF video signal sent to each of the area distribution boxes (ADBs) 126 is added to the first directional tap 502, and this tap 502 is connected to the reception area distribution box (ADB) 126. To use, tap off a small portion of the signal and send the remaining portion of the signal to the next Area Distribution Box (ADB) 126 located in the daisy chain (if there is another ADB). The tap output of directional tap 502 is then sent to a band separation filter 504 that separates the tapped PCM / RF video signal into PCM data and RF video portions, respectively. Then, each portion of the tapped PCM / RF video signal is sent to an amplifier 506 or 508 where the signal is amplified, so that each amplified signal is sent to a combiner 510 for recombination. The recombined PCM / RF video signal is then sent to a series of two-way splitters 513, 514 or 516 that split the PCM / RF video signal to form four PCM / RF video output signals. Finally, the PCM / RF video output signal is sent to separate floor block boxes (FDBs) 128.

  Area distribution boxes (ADBs) 126 have a plurality of control functions and execute an address assignment protocol. More specifically, control data, configuration information, database information and other messages are downloaded from the passenger entertainment system controller (PESC) 122 to the area distribution boxes (ADBs) 126 via the DATA 1 bus. The RS-485 port 520 provides an interface between the DATA1 bus and the area distribution box (ADB) 126, and the RS-485 port 520 supplies data received from the DATA1 bus to the communication controller 522. Upon receipt of the message, the communication controller 522 first confirms receipt of the received message and then decides whether to store the message downline (save and process the message data) or send it. This determination is made by comparing the address of the area distribution box (ADB) 126 determined by the discrete address input 524 to the specific area distribution box (ADB) 126 ... with the address information contained in the message. .

  Examples of message formats are shown in Figure 7 (a), with start flag 750, destination seat electronics box (SEB) number 752, PCU / SDU code 754, destination area distribution box (ADB) number 756, destination floor block box (FDB) ) Number 758, destination column address 59, source seat electronics box address 760 and PCU / SDU code 761, multiple data / control bytes 762, checksum code 764, two cyclic redundancy check bytes 766 and 768, message end flag 770. Further preferably, the communication protocol here comprises a command response protocol that is centrally controlled by an area distribution box (ADB) 126. More specifically, each area distribution box (ADB) 126 initializes all addresses of seat electronics boxes (SEBs) connected to it before starting normal communication, and seat electronics boxes (SEBs). Must start.

  Here, a communication protocol used by the area distribution box (ADBs) 126 and the seat electronics box (SEBs) 130 will be described. The polling of the seat electronics boxes (SEBs) 130 is performed sequentially by the area distribution boxes (ADBs) 126 according to addresses. Preferably, two types of poles are used here: an active pole (APOLL) and an inactive pole (IPOLL). These pole types correspond to the “activity state” of the seat electronics box (SEBs) 130. The seat electronics box (SEB) 130 is active when the area distribution box (ADB) 126 joins the box 130 to normal link communication, but the active seat electronics box (SEB) 130 is addressed to it. Can only be sent after receiving an APOLL message. The Active Seat Electronics Box (SEB) 130 can respond with several types of messages including: Acknowledgment (ACK), Byte Result (BRES), Active State (ASTA), PSS data. The seat electronics box (SEB) 130 powers up in an inactive mode and can only be activated when a command from the area distribution box (ADB) 126 is received. The seat electronics box (SEB) 130 becomes inactive when it is not allowed to participate in normal link communications.

  Further, the inactive seat electronics box (SEB) 130 can only transmit in response to IPOLL messages addressed thereto from the area distribution box (ADB) 126. After receiving such a message, the seat electronics box (SEB) 130 can only respond with an inactive state (ISTA) or a byte result (BRES).

  Referring again to FIG. 7 (b), the following process is used to assign seat electronics box (SEBs) 130 addresses in each column. The addressing process can be initiated by the passenger entertainment system controller (PESC) 122 or the area distribution box (ADB) 126 sending a programming mode (PMODE) command to the seat electronics box (SEB) 130. When the seat electronics box (SEB) 130 receives, the PMODE command opens the normally closed communication relay 736.

  In this manner, communication is possible between a single pair of predetermined area distribution boxes (ADB) 126 and seat electronics boxes (SEBs) 130. Moreover, as soon as the PMODE command is distributed via the DATA1 bus, only the seat electronics boxes (SEBs) immediately adjacent to the floor block box (FDB) 128 can communicate with the associated area distribution boxes (ADBs) 126.

  Further, as shown in FIG. 7 (b), the DATA1 bus line connecting the predetermined area distribution box (ADB) 126 to a pair of seat electronics boxes (SEB) daisy chains 738 and 740 is the floor shut-off box. In (FDB) 128, they are mutually reversed. Furthermore, the seat electronics boxes (SEBs) 130 are configured so that the reverse data cannot be correctly interpreted. Thus, if the area distribution box (ADB) 126 communicates with a pair of one of a pair of seat electronics boxes (SEB) columns (or daisy chains) 738, the box 126 can send a non-reversing message. However, if this data distribution box (ADB) 126 communicates with other columns 740, this box 126 must send a reverse message over the DATA1 bus. In this manner, a given area distribution box (ADB) 126 can communicate with a single seat electronics box (SEB) when assigning addresses. Once a given seat electronics box (SEB) 130 is addressed, the area distribution box (ADB) 126 activates this seat electronics box (SEB) 130 and closes its relay, so the area distribution box (ADB) Communication takes place between 126 and the next seat electronics box (ADB) 130 addressed. This process continues until all functioning seat electronics boxes (SEBs) 130 are addressed and activated. In addition, by addressing seat electronics boxes (SEBs) 130 in this manner, the non-operating seat electronics boxes (SEBs) 130 are flagged for repair and confirmation. be able to. If all seat electronics boxes (SEBs) 130 are correctly addressed, i.e. defective seat electronics boxes (SEBs) 130 are not identified, the link status is `` normal '' and the area distribution box (ADB) 126 to the passenger electronics system controller (PESC) ) 122. If an error is detected when addressing the seat electronics boxes (SEBs) 130, the area distribution box (ADB) 126 disables the transmitter (not shown), enters the inactive state, A command to close the relay 736 is sent to the seat electronics box (SEB) 130 to finish programming the defective seat electronics box (SEB) 130.

  Once the “normal” mode is confirmed, the communication protocol between the area distribution boxes (ADBs) 126 and the seat electronics boxes (SEBs) 130 proceeds as follows. Seat electronics boxes (SEBs) 130 are polled in turn by an area distribution box (ADB) 126 and are not allowed to transmit information unless polled. When polled, the seat electronics boxes (SEBs) 130 can send various responses, but at least a status message is always sent.

  More specifically, when a message is sent to the seat electronics box (SEB) 130, the seat electronics box (SEB) 130 always responds with at least an affirmative (ACK) or negative (NAK) message.

FDB Structure and Function Referring now to FIG. 8, preferably each floor blocking box (PDB) 128 includes one PCM / RF video signal splitter and two digital data signal splitters 604 and 606. Have. The PCM / RF video signal splitter 602 receives the composite PCM / RF video signal from the area distribution box (ADB) 126, splits this signal, and separates each of the resulting split PCM / RF video signals into separate seat electronics boxes (SEBs). ) Send to 130. Digital data signal splitters 604 and 606 split the DATA1 and DATA2 signals and function in a similar manner. However, after splitting, one polarity of the resulting split DATA1 signal is reversed.

SEB Structure and Function Referring now to FIG. 9, each seat electronics box (SEB) 130 includes a signal input board 701, an audio signal processing board 703, a video signal processing board 705, and a microcontroller unit (MCU) board 707. . The input board 701 includes a passive circuit that connects each seat electronics box (SEB) 130 to a floor isolation box (FDB) 128 or other seat electronics box (SEB) 130 (ie, the next SEB in the daisy chain). The composite PCM / RF video signal sent to each of the seat electronics boxes (SEBs) 130 is added to a directional tap 702 that taps off a small portion of the signal used by the receiving seat electronics box (SEB) 130 (other SEBs). Send the rest of the signal to the next seat electronics box (SEB) 130 located in the daisy chain. The tap output of the directional tap 702 is filtered by a band-splitting filter 704 before later distribution into the seat electronics box (SEB) 130. More specifically, the band division filter 704 has a high pass filter and a low pass filter (not shown).

  The RF video portion of the composite signal is sent through a high pass filter, and the PCM portion of the composite signal is sent through a low pass filter. After filtering, the PCM portion of the composite signal is sent to the audio board 703, and the RF video portion of the composite signal is sent to the video board 705. Upon arrival at the audio board 703, the PCM portion of the composite signal is sent to the analog amplifier 730, sent to the amplitude comparator 732, and applied to one input of the integrated video audio system (IVAS) gate array 706. The IVAS gate array 706 functions as a decoder and can select the desired PCM data channel from the composite PCM data signal. After one or more channels are selected by the IVAS gate array 706, the channels are sent to the ADCM gate array 708 for decompression. After decompression, the selected channel is sent to a pair of MASH digital-to-analog (D / A) converters 710. Here, the channels are separated, converted into analog audio signals, and sent to the headphone amplifier 712.

  As a particularly breakthrough aspect of the present invention, the IVAS gate array 706 of a given seat electronics box (SEB) 130 can be instructed to select a non-existing channel from the composite PCM data signal, thereby providing an ADPCM gate array The 708 can be supplied with a “zero channel” output. Since the zero channel output is an output channel containing a constant value, the amplitude does not change when converted to an analog format. Thus, no audio is generated when the zero channel is converted to an analog format and sent to the audio transducer.

  Further, when the zero channel output is processed by the ADPCM gate array 708, MASH digital to analog converter 710, and headphone amplifier 712 as described above, an analog audio signal that does not change amplitude is generated (not shown).

  This signal can be sent to the noise canceling headset. A noise-cancelling headset can be used by a passenger wearing it to completely eliminate substantially all flight noise, cabin noise, and the like. One of the compressed digital audio channels can be used as a zero channel in other embodiments. However, it is preferred here to be able to provide the maximum number of audio channels that a passenger can listen to, and having a separate zero channel reduces the number of channels available for this purpose.

  In another groundbreaking aspect, the present invention allows the passenger to select a video channel for viewing and always send the previously selected audio channel to the passenger's headset when the video channel is not accompanied by an audio channel. A passenger electronics system 100 can be constructed. More specifically, the seat electronics box (SEB) can only be switched on when the passenger selects a new audio channel directly or implicitly using the Digital Passenger Control Unit (DPCU) 134. 130 IVAS gate arrays 706 can be configured or programmed.

The RF video portion of the composite signal is sent from the board split filter 704 to the video board 705. More specifically, the RF video portion of the composite signal is sent to signal splitter 734 and then to one of up to three video signal tuners 714. Each tuner 714 is controlled by a tuner control circuit 716. It can be seen that the signal splitter 734 separates the video tuners 714 from each other. As described above, the tuner control circuit 716 is controlled via a microprocessing unit (MPU) 718 and one of a plurality of digital passenger control units (DPCUs) 134. Each of the video tuner control circuits 716 is in turn coupled to a single video tuner 714 that can select the desired video channel from the composite RF video signal. After a particular video channel is selected, the video processing circuit sends this channel to the seat display unit (SDU) for display.
A microcontroller unit (MCD) board 707 has a microcontroller 718, an RS-485 port 720 for communication with the DATA1 bus, an address assignment relay 721, and a DPCU interface 722 for communication with digital passenger control units (DPCUs) 134. Microcontroller 718 sends and receives communication data on the DATA1 bus via RS-485 port 720, communicates sequentially with digital passenger control units (DPCUs) 134 via DPCU interface 722, and seat electronics box via internal bus 724. It controls the internal operation of (SEB) 130 (ie, channel selection by IVAS gate array 706 and video processing circuit 714). Preferably, microcontroller 718 includes an 8-bit controller having 512 bytes of static RAM and an internal analog to digital converter (not shown).
As a particularly breakthrough aspect of the present invention, the microcontroller 718 of one seat electronics box (SEB) 130 communicates with the microcontroller 718 of another seat electronics box (SEB) 130 via the DATA1 bus. Can be configured. This allows the Digital Passenger Control Unit (DPCU) 134 located at the first seat position to receive video channel selection data from the first seat electronics box (SEB) used by that seat position one row ahead of the first seat position. The second seat electronics box (SEB) 130 used by the seat position can be supplied. In this way, the selected video signal from the second seat electronics box (SEB) 310 is received and the seat display unit (SDU) mounted on the back of the front seat provides an additional communication link between the two seats. Without being equipped, it can be controlled using a Digital Passenger Control Unit (DPCU) 134 located in the rear seat.

IVAS Gate Array Structure and Function The structure and function of the Integrated Video Audio System (IVAS) gate array 310, 410, and 706 will be described with reference to FIGS. However, the structure of the integrated video audio system (IVAS) gate array 310, 410, and 706 does not change throughout the passenger entertainment system 100, only the function of the integrated video audio system (IVAS) gate array 310, 410, and 706 changes. Must understand what to do. Further, the Integrated Video Audio System (IVAS) gate arrays 310, 410 and 706 have a single chip that functions in different ways depending on the location located within the passenger entertainment system 100. Thus, preferably, the same IVAS gate array chip can be used for any of the Video System Control Unit (VSCU) 120, the Passenger Entertainment System Controller (PESC) or the Seat Electronics Box (SEBs) 130. . However, the function of the chip changes depending on the position where it is arranged.

  As can be seen by referring first to FIG. 10, each IVAS gate array 310, 410 or 706 comprises a plurality of prescalers 802, test audio generator 804, Manchester decoder 806, audio formatter 808, audio buffer 810, timing control logic 812 , A communication controller 814, a PSS / CPMS buffer 816, and a Manchester decoder 818.

  The prescaler 802 has a part of a phase lock loop circuit (not shown), and divides the frequency of a plurality of signals sent to an input (not shown) by a programmable coefficient. The phase-locked loop circuit has a phase detector, a filter circuit, and a voltage control oscillator (VCO) (none of which are shown), each dehigh is located outside the IVAS gate array, and the prescaler 802 is internal to the IVAS gate array. Is arranged. Each phase-locked loop generates a clock phase that is locked to the PCM data signal. Clock frequency is a programmable multiplier or divisor of the clock derived from the bit rate (ie, data transfer rate), ADPCM gate arrays 306, 318, 406, 418, and 708, and MASH analog digital digital and digital Provided to analog converters 302, 320, 404, 416 and 710. In this scheme, synchronization is maintained throughout the passenger electronics system 100 based on a 37.8 KHz frame transfer rate.

  The Manchester decoder 806 receives serial audio data in the clock and Manchester code from the baseband reception interface 820. The Manchester decoder 806 decodes the received serial audio data with NRZ (non-zero return) and detects a unique data pattern used for system synchronization. If the synchronization signal is detected, a pulse is generated by the Manchester decoder 806 and sent to the timing and control logic block 812. Further, the NRZ serial audio data is sent from the Manchester decoder 806 to the audio buffer 810, the Manchester encoder 818, and the CPMS buffer 816.

  A test audio generator 804 having a shift register, counter, and control logic (not shown) is used to test signal distribution within the passenger entertainment system 100. More specifically, the test voice generator 804 generates a square wave of programmable frequency that is placed in the passenger entertainment system control (PESC) 122 (not shown). It can be supplied to one input part of a digital converter. The MASH analog-to-digital converter converts the square wave to a digital format and sends this converted digital signal to the ADPCM gate array 410 as described above. The ADPCM gate array 410 compresses the converted digital signal and provides the resulting compressed signal to one input of the IVAS gate array 410, where the signal is multiplexed into the compressed PCM data signal and the entire passenger entertainment system 100. Distributed to. The test audio detection circuit (not shown) located in the seat electronics boxes (SEBs) 130 detects the presence of test audio in the PCM data signal and detects the presence of test audio in the passenger entertainment system controllers (PESC). Direct to 122.

  Audio formatter 808 has nine 32-bit audio sample shift registers (one shift register per eight audio input channels) and one 64-bit RF sample shift register (none of which are shown). The main function of the audio formatter 808 is to insert the bitstream data received from the compressed digital audio signal source 102 and ADPCM gate arrays 306, 406 and 418 into the composite PCM data signal. More specifically, the audio formatter 808 inserts audio, range and filter data into the composite PCM data signal in the frame format shown in FIG. 11 under the control of the timing and control logic block 812. A fixed relationship is provided between each input port of the audio formatter 808 and the time slot into which audio and control data is inserted.

  As shown in FIG. 11, each frame 902 of the composite PCM data signal has the following: 8 synchronization bits 904, 64 cabin passenger management system (CPMS) data bits 906; 32 range filter coefficients (R / F) bit 908; 6 channels with 24 bits of passenger address (PA) audio 910; 24 channels with 96 bits of passenger entertainment system controller (PESC) audio 912; video system controller unit (VSCU) digital audio 914 24 channels with 96 bits; 24 channels with 96 bits of video system controller unit (VSCU) digital audio 916; 24 channels with 96 bits of video system controller unit (VSCU) option digital or analog audio 918. The term “analog” as used in the foregoing text indicates that the unique signal is initially generated by an analog audio source. Thus, preferably, a maximum of 512 bits are provided per frame 902 here. However, it should be noted that the frame format varies considerably depending on the number data type sent through the signal distribution network and the number of bits per data type. Furthermore, since the frame format of the IVAS gate array can be changed by the program, it is desirable to be able to change it according to the needs of a given passenger entertainment system or aircraft environment.

  Here, with reference to FIGS. 12 (a) and 12 (b) and Table 2, the digital data can be read using CD-I using adaptive delta pulse code modulation, as will be readily understood by those skilled in the art. When compressed to Level B format, the data is not only compressed from 16-bit format to 4-bit format. An additional range filter coefficient 908 is added to the data. Thus, these coefficients become an important component of the composite PCM data signal and create difficult problems associated with frame formatting.

  More specifically, ADPCM compression generates one 4-bit range coefficient and one 4-bit filter coefficient for each channel in 28 frame audio samples. Thus, if 102 channels of ADPCM compressed digital audio (six PA channels, 24 PESC audio channels, 72 VSCU audio channels) are distributed throughout the passenger entertainment system 100, these every 28 frames. A 4-bit range coefficient and a 4-bit filter coefficient shall be supplied for each of the 102 channels. In the worst case scenario, transmission of range filter (R / F) coefficients would require a 816-bit data block dedicated to range filter coefficients and would involve each frame of compressed digital audio. In contrast, when a frame format according to the present invention is utilized, only 32 bits per frame are provided to accommodate range filter (R / F) coefficients. This actual reduction in the number of bits per frame required to accommodate the range filter (R / F) coefficients is performed by shifting the range filter coefficients across the frames shown in Table 2. .

  More specifically, as shown in FIGS. 11, 12 (a) and (b), the range filter (R / F) coefficient 908 corresponding to only four channels of compressed digital audio data is one predetermined frame. The range filter (R / F) coefficients 908 corresponding to different groups of four channels are supplied in subsequent frames. In this method, range filter (R / F) coefficients 908 corresponding to all 102 compressed digital audio channels are supplied over the process of a total of 26 frames (for example, frame Nos. 2 to 26 shown in Table 2). . In addition, here preferably the PA and audio data are staggered throughout the process of 28 frames (ie, one sample per channel per frame). More specifically, each sample of PA or audio data has 8 channels (or time slots). Thus, 28 samples of each group of 8 channels (ie, one sample per frame) are provided in each block of PA and audio data. The samples are arranged so that the first sample (sample 1) of a given 8-channel group is in a frame that includes a range filter (R / F) coefficient 908 corresponding to the first channel of this group. For example, since the range filter (R / F) coefficient 908 corresponding to the audio channel No. 1 is located in the frame No. 3, the first sample (sample No. 1) of the audio channel Nos. 1 to 8 is also used. Located in frame No.3. Similarly, since the range filter (R / F) coefficient 908 corresponding to audio channel No. 9 is located in frame No. 5, the first sample of audio channel Nos. 9 to 16 (sample No. 1) Is also located in frame No.5. Also, it is preferably confirmed here that even audio samples are arranged in odd frames and odd audio samples are arranged in even frames on the coaxial transmission cable. Referring now also to FIGS. 13 (a) and (b), this is because the digital audio data received by the audio formatter 808 during a given frame is sent simultaneously on the coaxial downlink (not shown). Because there is no. Instead, digital audio data received by the audio formatter 808 in one frame is sent on the coaxial downlink in the next frame. In addition, the range filter data 908 received by the audio formatter 808 in one frame is divided and sent to the coaxial downlink in the course of the next two frames. When digital audio data is received by the audio buffer, digital audio data from a given frame is stored in the current data register during this frame and sent to the output register during the next frame. In contrast, as soon as the registers allocated here are full (every two frames), the range filter data is read out and sent out. For this reason, the audio sampling rate of the audio formatter 808 and the audio buffer 810 is made equal to the frame transfer rate (that is, about 37.8 kHz), and the synchronization in the passenger entertainment system 100 is synchronized with this frame transfer rate. It is desirable to be maintained based on

  Since the format can vary considerably in accordance with the present invention, it is not intended to limit the present invention to the specific frame format shown in FIGS. 11, 12 (a), 12 (b), 13 (a), 13 (b), Should be understood. For example, a composite PCM data signal includes a plurality of compressed blocks having F frames per block, C digital audio channels per frame, and P compression parameters per channel per block, and any of these parameters. It will be appreciated that (especially the number C of digital audio channels provided per frame) can vary.

  However, it is preferred here to allocate N time slots per frame with respect to compression parameters (N is an integer greater than or equal to (C × P) / F) and a selection group of compression coefficients (N of the above compression coefficients). Depending on the case, either multiplexer 14 or IVAS gate array 310 or 410 will be configured to assign each group) to the selected frame in each compressed block.

  For sync signals 904 and 905, a single audio sync pattern 904 (as shown in FIG. 11) is provided in the composite PCM data signal, one in every 28 frames, and the frame sync pattern 905, which is the inverse of this pattern. Are supplied between all other frames, as shown in FIGS. 12 (a) and 12 (b).

  Referring again to FIG. 10, audio buffer 810 has four pairs of 4-bit shift registers, twelve 8-bit shift registers, and four 16-bit shift registers (none of which are shown). A pair of 4-bit shift registers is used to obtain left and right channel audio samples for each of up to four passenger seats. As each pair of samples is obtained, the contents of each pair of shift registers are sent to a single 8-bit shift register. These channels are then sent out of the 8-bit shift register as a single 8-bit signal with two multiplexed and compressed digital audio channels. The resulting signal is then sent to one input of ADPCM gate array 706. The remaining eight 8-bit shift registers are used to obtain compression factors for the left and right channels for each of up to four passenger seats. When compressed (range filter) coefficients are obtained, these coefficients are sent to a 16-bit shift register and then sent out on the same multiplexed output line as the corresponding compressed digital audio sample.

  Control of the data selection process is controlled by timing control logic 812, which generates control signals that allow the shift register to be sent on the selected audio channel. More specifically, the timing control logic 812 can allow the shift register to receive data located in the selected channel number time slot, eg, in response to a signal received from a digital passenger control unit (DPCU) 134. To do. In order to provide channel number information, a counter is used that is reset by the timing control logic 812 of the sync signal when received. Thus, when the channel number selected by the digital passenger control unit (DPCU) 134 reaches the timing control logic 812, the data located in the corresponding time slot is sent to the shift register. Thus, in operation, a pair of first shift registers obtains audio data samples from the composite PCM data stream and sends the samples to the second register of the pair. The second shift register then sends the acquired samples to the ADPCM interface as the first shift register gets another sample from the next frame of the PCM data stream. It can be seen that in the “zero channel” mode described above, the channel number of the non-existing channel is supplied by the digital passenger control unit (DPCU) 134 to the timing control logic 812. Since the timing control logic 812 does not receive data corresponding to the selected channel, new data is not entered into the first shift register, and if data has already been entered into the first shift register, such data will not be entered. It is repeatedly sent to the second shift register and finally sent to the PDPCM gate array 708.

  Timing control logic 812 controls all synchronous operations within IVAS gate arrays 310, 410 and 708. For example, when the IVAS gate array 310, 410 or 708 functions as a demultiplexer, the control logic 812 directs the selected audio channel to the audio buffer 810 and divides the clock to ensure an appropriate timing reference for the serial interface. The timing control logic 812 also decodes the address so that appropriate registers (not shown) can be used for communication with the microcontroller 430 or 718 or the central processing unit 316.

IVCP communication controller 814 manages the communication protocol between IVAS gate array 706 (in SEB 130) and in-seat video cassette players (IVCPs) 138. The PSS / CPMS buffer 816 has a 16-bit shift register, a mod 8-bit counter, a 32-byte FIFO, a status register, a control register, a 16-bit address register, and control logic (none are shown). This hardware is designed to operate in one of two modes, depending on whether the IVAS gate array is located in a seat electronics box (SEB) or a passenger entertainment system controller (PESC) 122. Controlled.
When placed in a seat electronics box (SEB) 130, the PSS / CPMS buffer 816 is configured to perform a receive function. The message start byte 920 (shown in FIG. 11) is used to determine the start and end of the message.

  Each byte in the message start byte 920 except the first bit 921 corresponds to one data byte 924 in the CPMS field 906. When message start bit 922 is high, this channel becomes idle or a new message begins with message byte 924 corresponding to message start bit 922. When the message start byte 922 is low, message data is present. After the message is finished, the message start bit returns to the high state for the next data byte. This indicates that the message has ended and a new message is potentially starting. The control logic also compares the address field in each message with the address of the local unit. When the addresses are the same, an interrupt signal can be provided to the microcontroller 718.

  When located in the passenger entertainment system controller (PESC) 122, the PSS / CPMS buffer 816 performs the reverse of the functions performed in the seat electronics box (SEB) 130. More specifically, the PSS / CPMS buffer 816 receives messages from the microcontroller interface one byte at a time.

  Bytes are queued in FIFO. When the PSS / CPMS buffer places data in the serial bitstream (PCM data signal), the timing control logic 812 generates an envelope signal. While the envelope is in operation, the wait byte is strobed into the shift register and sent out. Further, as described above, the message start message byte is inserted before the message byte. The control logic also verifies that the first byte of the message is the first byte after the message start byte.

  Manchester encoder 818 encodes the formatted bitstream and generates a programmable synchronization pattern at the appropriate time. The Manchester encoder 818 includes a 16-bit register, a 16-bit shift register, a multiplexer, a plurality of gates, and a flip-flop (none are shown). During most downlink frames, the synchronization pattern is always loaded into the shift register. When synchronization must be transmitted, the shift register sends out synchronization at twice the bit rate. XOR gates are used to control the polarity of synchronization. The multiplexer selects between synchronization or data based on an external control signal (synchronization enable signal supplied by the timing control logic 812). The flip-flop is used to reclock the edge after encoding the data.

  The present invention is capable of various modifications and alternative embodiments, and the specific presentation and illustration are only described in detail in the drawings and specification by way of example. However, this is not intended to limit the invention to the particular systems and methods disclosed, but on the contrary, the invention is within the spirit and scope of the invention as defined by the appended claims. All possible changes, equivalent content and alternatives are included.

  The present invention is useful as an on-board entertainment system for large commercial aircraft and other passenger vehicles.

FIG. 1 is a block diagram illustrating the basic components of a conventional audio signal distribution system commonly used in commercial aircraft and other vehicles. FIG. 2 is a block diagram illustrating the basic components that make up an improved audio signal distribution system in accordance with the present invention. FIG. 3 is a block diagram illustrating the components that make up the preferred embodiment of the passenger entertainment system improved in accordance with the present invention. FIG. 4 is a block diagram illustrating the components that make up a video modulation unit (VMU) according to a preferred embodiment of the present invention. FIG. 4 (a) is a circuit diagram constituting a tapping unit according to a preferred embodiment of the present invention. FIG. 5 is a block diagram illustrating the circuitry comprising a video system control unit (VSCU) according to a preferred embodiment of the present invention. FIG. 6 is a block diagram illustrating the circuitry that makes up a passenger entertainment system controller (PESC) according to a preferred embodiment of the present invention. FIG. 7 is a block diagram of a circuit constituting an area distribution box (ADB) according to a preferred embodiment of the present invention. FIG. 7 (a) is a format diagram of a message sent via the DATA1 bus according to the preferred embodiment of the present invention. FIG. 7 (b) is a diagram illustrating how relays arranged in seat electronics boxes (SEBs) in an addressing scheme are used in accordance with an embodiment of the present invention. FIG. 8 is a block diagram of the circuitry that makes up a floor barrier box (FDB) according to a preferred embodiment of the present invention. FIG. 9 is a block diagram of the circuitry that makes up a seat electronics box (SEB) according to a preferred embodiment of the present invention. FIG. 10 is a block diagram illustrating the functional blocks that make up an integrated video audio system (IVAS) gate array in accordance with a preferred embodiment of the present invention. FIG. 11 is a frame format diagram according to a preferred embodiment of the present invention. FIG. 12 (a) is a timing diagram of synchronization signals and range filter coefficients in a frame format according to a preferred embodiment of the present invention. FIG. 12 (b) is a timing diagram of the synchronization signal and range filter coefficients in the frame format according to the preferred embodiment of the present invention. FIG. 13A is a preferred IVAS gate array diagram between input data, coaxial transmission cable data, and output data. FIG. 13B is a preferred IVAS gate array diagram between input data, coaxial transmission cable data, and output data.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Passenger entertainment system 2 Audio signal source 3 Analog / digital converter 4 Multiplexer 5 Signal distribution network 6 Demultiplexer 7 Digital / analog converter 8 Audio transducer 10 Digital audio signal distribution system 12 Digital signal source 14 Multiplexer 16 Signal distribution circuit Network 18 Demultiplexer 20 Decompression circuit 22 Digital / analog converter 24 Audio transducer

Claims (4)

A passenger entertainment system for commercial aircraft or other vehicles,
The passenger entertainment system is
A plurality of digital audio signal sources each outputting a compressed digital audio signal;
A plurality of analog audio signal sources each capable of generating an analog audio signal;
A plurality of video signal sources each capable of generating an analog video signal and an analog audio signal of the video source;
A plurality of analog-to-digital converters capable of inputting the analog audio signal and the analog audio signal of the video source and converting the input analog audio signal of the video source into a digital format;
The analog audio signal converted into the digital format is input from the analog / digital converter, and the analog audio signal converted into the digital format is compressed into a format compatible with the compressed digital audio signal generated by the digital audio signal source. Multiple digital signal compression circuits that can be
A multiplexer capable of forming a composite digital audio data signal by inputting the compressed digital audio signal generated by the digital audio signal source and the digital signal compression circuit and multiplexing the input compressed digital audio signal;
A plurality of video signal modulators to which the analog video signal generated by the video signal source is input and which can modulate the analog video signal at a plurality of different carrier frequencies;
A plurality of RF signal combiners that receive the modulated analog video signal from the video signal modulator and synthesize the input modulated analog video signal to form a composite RF video signal;
A baseband / RF signal combiner that receives the composite digital data signal and the composite RF video signal and combines the composite digital audio data signal and the composite RF video signal to form a composite RF video / digital audio data signal;
At least one RF signal separator capable of receiving the composite RF video / digital audio data signal and separating the composite RF video / digital audio data signal into its separate composite RF video data component and digital audio data component;
A demultiplexer which receives the digital audio data component of the RF video / digital audio data signal from the baseband / RF signal separator and can select a desired digital audio channel from the digital audio data component;
A digital signal decompression circuit which receives a selected digital audio channel from the demultiplexer and can decompress the selected digital audio channel from a compressed digital audio format into a decompressed digital audio format;
The selected digital audio channel expanded from the digital signal decompression circuit is input, the expanded selected digital audio channel is converted into an analog format, and the converted and expanded selected digital audio channel is sent to an audio transducer. A digital-to-analog converter capable of: inputting the RF video component of the composite RF video / digital audio data signal from the RF signal separator, selecting a desired video channel from the RF video component, and selecting a video channel for display RF tuner that can supply a video monitor;
It has. The composite digital audio data signal comprises F frames per block, C digital audio channels per frame, and a plurality of compression blocks having P compression parameters per block and P per channel; The multiplexer is configured to allocate N time slots, where N is an integer greater than or equal to (C × P) / F;
The passenger entertainment system of claim 1, wherein the multiplexer assigns a selection group having N of the compression factor to a selection frame (s) in each compression block. The passenger entertainment system according to claim 1, wherein the carrier frequency is variable from 135 MHz to 300 MHz by a program. A method of generating an analog audio signal without amplitude change used by a noise cancellation headset of a passenger entertainment system, comprising: generating a digital signal having a repetitive sample pattern;
Supplying the digital signal to a digital-to-analog converter;
Converting the digital signal into an analog format;
A method comprising the steps of:

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