JP3166387B2 - Demultiplexer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a demultiplexer, and more particularly, to data of a plurality of frames in which data of a plurality of channels has been subjected to error correction coding and scrambled, is time-division multiplexed and input. It relates to a demultiplexer.

[0002]

2. Description of the Related Art For example, a system is provided in which audio signals can be individually listened to at a plurality of seats in a vehicle such as an aircraft through headphones or earphones, and audio signals of a large number of channels can be freely selected at each seat. In such a case, if an existing format is used as the signal transmission format, there is an advantage that components such as an IC can be shared and the cost can be reduced by mass production.

Here, considering a television sound signal transmission format of satellite broadcasting or satellite communication as a signal transmission format, one frame is composed of a two-dimensional matrix of 32 bits × 64 columns.
48 bits are transmitted in 1 msec, and the data transmission rate is
2.048 Mbps. In the case of so-called A-mode sound, the sampling frequency is 32 kHz and 14 kHz.
Four-channel data of / 10-bit quasi-instantaneous companding is transmitted using 1280 bits (32 bits × 40 columns) per frame. In the case of so-called B-mode audio, the sampling frequency is 48 kHz and 16-bit linear quantization is performed. 2
Channel data is transmitted using 1536 bits (32 bits × 48 columns) per frame.

However, in these transmission modes,
Only audio signals (audio signals) of about two or four channels can be transmitted, and it is desired to transmit audio signals of more channels for use in an audio listening system or the like in an aircraft as described above. I have.

[0005] In recent years, compression coding techniques for voice and audio signals have been remarkably developed.
For example, various high-efficiency compression encoding techniques have been put to practical use so that the quality of an audio signal is hardly degraded even when compressed to about 128 kbps. When such a high-efficiency compression-encoded signal is applied to the above-described frame format, for example, if 1536 bits are used per frame, it is possible to transmit a 12-channel audio signal.

To transmit more channels, time division multiplexing of a plurality of frames of the above frame format, for example, three frames, can be considered. At the same time.
In this case, some audio channels can be used for transmitting computer data such as TV game software.

[0007]

By the way, as described above, on the receiving side of a signal in which a data sequence of a plurality of frames (for example, three frames) is time-division multiplexed, for example, FIG.
A demultiplexer having a configuration as shown in FIG.

In FIG. 10, a signal obtained by time-division multiplexing a data string of a plurality of frames (for example, three frames) is input to an input terminal 200.
At 01, a data string of a desired frame is selected.
The data string signal of the selected frame is sent to the descrambling circuit 202 to be descrambled, and then sent to the error correction circuit 203 for error correction.
Next, it is sent to the channel selection circuit 204, and a plurality of channels (for example, 12 channels) in the one frame
2 channels are selected from among the
05a and 205b.

As described above, the two output terminals 205a, 205
The reason why two-channel audio signals are simultaneously extracted from 5b is that two-channel audio signals, such as stereo left and right channels and main audio and sub audio, are often combined into one set.

Here, in the configuration shown in FIG. 10, any two channels in the same frame can be arbitrarily selected.
One channel cannot be selected arbitrarily. However, such a desire to select any two channels over two frames is, for example, that one channel unit of monaural sound and two channel units of stereo sound are mixed, and one channel of one frame is mixed. This occurs when a stereo audio signal is transmitted between the audio signal and one channel of another frame, or when it is desired to select audio of two national languages that straddle two frames of an audio signal multiplexed in multiple languages of several languages or more. Things.

The present invention has been made in view of such circumstances, and a frame is composed of data of a plurality of channels, and a signal obtained by time-division multiplexing a data sequence of a plurality of frames is input. It is an object of the present invention to provide a demultiplexer capable of selecting an arbitrary channel over two frames in a case where two frames are used.

[0012]

According to the demultiplexer of the present invention, a plurality of channels of data are subjected to error correction coding and scrambling to form a frame, and a data sequence of a plurality of frames is time-division multiplexed. Receiving the input signal and selecting a data sequence of at least two of the plurality of frames, and a data descrambler for descrambling the data sequence of each frame selected by the frame selecting device. Scramble processing means, error correction processing means for error-correcting each output signal from the descrambling processing means, and data strings of a plurality of channels in each frame to which each output signal from the error correction processing means is input respectively Channel selection to select the data string of each one of the channels By having a stage, it is to solve the problems described above.

Here, as the signal transmission format, for example, a signal format conforming to an audio signal transmission format of a satellite broadcast or a television broadcast signal of a satellite communication can be used. This is a two-dimensional matrix of 32 bits × 64 columns. Constitute one frame. In this one frame, at least the frame synchronization signal and one of the high-efficiency compression encoded data are included.
Two channels and a so-called BCH code are arranged.
It is conceivable to time-division multiplex and transmit the frames.

[0014]

The above-mentioned frame selection circuit selects any two frames (including the same frame), and the above-mentioned channel selection circuit selects each arbitrary channel in each frame. Channel can be selected.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a block circuit diagram showing a basic configuration of a demultiplexer according to a first embodiment of the present invention.

In FIG. 1, an input terminal 100 has
A data signal in which a plurality of frames of data of a predetermined frame format are time-division multiplexed is supplied. In this predetermined frame format, data of a plurality of channels is subjected to error correction encoding such as so-called BCH encoding and scrambled to form a frame. The data of the plurality of channels may be, for example, audio signal data or computer data such as TV game software.

The data signal supplied to the input terminal 100 is sent to a frame selection circuit 101, and the frame selection circuit 101 corresponds to two of the time-division multiplexed data strings of a plurality of frames. Select and output each data string. This frame selection circuit 101
Are sent to the descrambling circuits 102a and 102b, respectively, and are subjected to descrambling. These descramble circuits 1
Output signals 02a and 102b are sent to error correction processing circuits 103a and 103b, such as so-called BCH decoders, for error correction processing. Output signals from these error correction processing circuits 103a and 103b are supplied to channel selection circuits 104a and 104b, respectively.
b. The channel selection circuit 104a selects one of the data streams of a plurality of channels in one frame of the output from the error correction processing circuit 103a and sends it to the output terminal 105a, and the channel selection circuit 104b performs the error correction processing. An output terminal 10 selects a data stream of one channel from data streams of a plurality of channels in one frame of an output from the circuit 103b.
Send to 5b.

According to the first embodiment having such a configuration,
Any two frames (including the same frame) can be selected by the frame selection circuit 101, and the channel selection circuit 10
Since any channel in each frame can be selected at 4a and 104b, a desired channel can be selected over two frames. For example, even when stereo sound is transmitted by mixing one channel unit monaural sound and two channel unit stereo sound, and one frame of one frame and one channel of another frame are transmitted, Can be taken out. Therefore, when one channel of one frame and one channel of another frame, which are used in monaural, become unnecessary, the conventional demultiplexer uses these vacant channels to output only monaural sound. While transmission could not be performed, according to the first embodiment, a stereo signal can be transmitted on two channels, and the degree of freedom is increased.

Next, a more specific second embodiment of the demultiplexer according to the present invention will be described with reference to FIG. In the second embodiment shown in FIG. 2, the selector 1 is a frame selecting means, for example, the data rate data DT _A and the frequency of 6Mbps is supplied with the clock CK of 6 MHz. The input data DT _A is,
For example, three data in a frame format (data rate of 2 Mbps) as shown in FIG. 3 are time-division multiplexed. The frame format shown in FIG. 3 is a format conforming to, for example, the frame configuration of an audio signal of a satellite broadcast or a television broadcast signal of satellite communication, and one frame is represented by a matrix of 32 bits × 64 columns. The data rate in this format is exactly 2.048 Mbps, and the input data DT _A obtained by time-division multiplexing three frames in this format.
Is exactly 6.144 Mbps.

The frame format 3 shown in FIG.
In the 2 × 64 matrix, the first 16 bits of the first column are used as a frame synchronization signal, the remaining 16 bits are used as a control code (control code), and the second column is unused (undefined). Using the next 48 columns from the third column to the 50th column, an audio signal of 12 channels (128 bits per channel) is transmitted 32 bits at a time from the first channel (A-CH1) to the twelfth channel (A-CH).
12) is arranged cyclically four times. These 12-channel audio signals may be 6 pairs of stereo left and right channels (from A-CH1L, A-CH1R to A-CH6L, A-CH6R). Also, the fifth and sixth channels of audio (A-CH5, A-CH5)
-CH6) and the eleventh and twelfth channels (A-CH1).
1, A-CH 12) may be, for example, a game channel for sending game software or the like. In this game channel, 16 channels of 32 bits are provided per frame from G-CH1 to G-CH16. In actual use, these channels are grouped by 2 channels, and the channel of 64 bits per frame is set to 8 channels. The next 51st column is used for control data, and the remaining 13 columns from the 52nd to 64th columns are error correction codes, for example, so-called BCH codes. This BCH code is the first column of the frame (first column)
(63,5)
0) BCH code.

Twelve channels of audio (or eight channels of audio and eight channels of computer data such as TV game software) as shown in FIG.
With respect to the data (2.048 Mbps) having the frame configuration of FIG.
Data signals such as those containing a 8-channel 2-channel and the computer data (6.144 Mbps) is input data DT _A supplied to the selector 1. The selector 1 can arbitrarily select and take out two of the three time-division multiplexed frames, and has, for example, a configuration as shown in FIG.

In the specific circuit configuration of the frame selection selector shown in FIG.
_A denotes four flip-flops 11 and 1 operating on the bit clock CK of the time-division multiplexed data (6.144 Mbps).
2, 13, and 14 are supplied to the series circuit. FIG. 5 shows the bit clock CK (6.144 MHz), the input data DT _A ,
And the output data DT _B from the flip-flops 11, 12, 13 and 14 show DT _C, DT _D, the DT _E respectively. In FIG. 5, each data DT _A , DT
_B, DT _C, DT _D, reference numeral A in DT _E, B, C is for distinguishing three frames the time-division multiplexing.

Output data D from flip-flop 12
T _C is sent to the data input terminal D of the flip-flop 15L. Each data _{DT A, DT B, DT C} , DT
_D, DT _E is sent to the selector (switching selection circuit) 16, taken out is one data selected according to the selection control signal SEL, is sent to the flip-flop 15R.
The bit clock CK is supplied to clock input terminals of the flip-flops 15L and 15R. The bit clock CK (6.144 MHz) is used by the 1/3 frequency divider 1
7 and is divided into a frequency of 1/3 (2.048 MHz), taken _out as an output clock CK _out , and
Each enable terminal E of the flip-flops 15L and 15R
N. These flip-flops 1
Output signals from 5L and 15R are taken out as output data DT _Lout and DT _Rout , respectively.

Here, as shown in FIG. 6, the 1/3 frequency dividing circuit 17 changes the pulse phase (or falling timing) of the output clock CK _out in response to the shift control signal SFT, and this changes the flip-flop 15L. , 15R
, The selected frame is shifted one frame at a time. That is, the pulse of 1/3 min the output clock from the frequency divider 17 is supplied to the flip-flop 15L CK _out is obtained at the timing of the frame A of the data DT _C, frame A is selected in the output data DT _Lout In this state, when the shift pulse SP ₁ of the shift control signal SFT is supplied, the output clock CK from the ３ frequency divider 17 is output.
delay the next falling pulse CP ₁ of _out is (phase 120 ° worth of 1/3 frequency-divided output) one clock period of the bit clock CK (6.144 MHz) of the multiplexed data only, during which the flip-flop 15L is enabled since a state, the next frame B be be selected withdrawn from time t _1. Similarly, the next frame C is selected from the time t ₂ by the output clock pulse CP ₂ corresponding to the _second shift pulse SP ₂ , and further, the third shift pulse SP ₂
Again original frame A from the output clock pulse CP ₃ by the time t ₃ when depending on ₃ is selected. Thus, each time the shift pulse of the shift control signal SFT is supplied, the selected frame is cyclically shifted in the order of A, B, and C.

[0025] Note the output data DT _Rout from the flip-flop 15R are frame selection with the same frame shifted relative data selected by the selector 16 from among the data DT _A to DT _E is taken out is made Things. For example, when the selector 16 is a data DT _A selection is sent to the flip-flop 15R, the output data DT _Rout becomes the data of 2 frames ahead of the relationship with the output data DT _Lout from the flip-flop 15L, the output data When DT _Lout is the data sequence of frame A, output data DT _Rout is the data sequence of frame C.

Returning to FIG. 2, for example, a desired two frames in the time-division multiplexed signal are selected by a frame selecting selector 1 having a configuration as shown in FIG. , Each sent to 2R,
Descramble processing and deinterleave processing are performed. Output signals from the descrambling circuits 2L and 2R are sent to BCH decoders 3L and 3R, respectively, and subjected to error correction processing based on the BCH code in the frame unit. RAMs 4L and 4R for error correction processing are connected to these BCH decoders 3L and 3R, respectively.

The audio demultiplexer 6L selects data of one audio channel from a plurality of channels (12 audio channels, or 8 audio channels and 8 data channels) in one frame from the BCH decoder 3L, and outputs an audio output signal. A
_Dout is output, and one data channel is selected by the data demultiplexer 7 to output a computer data output signal _CDout . The audio demultiplexer 6R selects data of one audio channel from a plurality of channels (12 audio channels) in one frame from the BCH decoder 3R and outputs an audio output signal AD _Rout .

Here, the output from the BCH decoder 3L is sent to the channel control circuit 5, where the current frame (any of the frames A, B and C) is discriminated, and the shift control signal until the target frame is reached. The SFT is sent to the selector 1 (the 1/3 frequency dividing circuit 17 in FIG. 4). The input bit clock CK is sent to the system clock generating circuit 8, and the system clock signal from the system clock generating circuit 8 is sent to the selector 1 and the like. An interface circuit 9 is connected to the system clock generating circuit 8 so that, for example, a clock for identifying left and right stereo channels and a word synchronizing signal are extracted.

With the above configuration, any two frames (including the same frame) can be selected from a signal obtained by time-division multiplexing three frames, and a desired channel of each frame can be selected. This makes it possible to obtain a stereo signal in which the left and right channels are arranged over two frames, for example, and the degree of freedom is increased.

Next, as an application example of the embodiment of the demultiplexer according to the present invention, a system in which a desired channel can be freely selected from a plurality of channels at each seat in a vehicle such as an aircraft and listened through headphones or the like. Will be described in detail with reference to the drawings.

FIG. 7 is a block diagram showing a schematic configuration of a signal transmission system to which a demultiplexer as one embodiment of the present invention is applied.

In FIG. 7, a transmission signal source 110 includes a video signal reproducing device 111 such as a so-called VTR (video tape recorder) or a video disk player.
An audio signal reproducing device 112 such as a so-called CD (compact disk) player or a tape recorder;
A computer data output device 113 such as V-game software is provided. A so-called PA (Passenger) having an in-flight broadcasting function using a microphone, etc.
Address) control device 116 is provided.

Of the output signals from these devices, audio or audio signals from the video signal reproducing device 111 and the audio signal reproducing device 112 and computer data from the computer data output device 113 are transmitted to the audio signal transmitting device 120. Have been. The video signal from the video signal reproducing device 111 is sent to another video signal transmitting device (not shown), and the audio signal from the PA control device 116 is directly sent to a speaker (not shown) provided on the wall or ceiling inside the device. (For example, as an analog audio signal) and the audio signal transmitting device 12
Also sent to 0.

The audio signal transmitting device 120 includes, for example, up to four audio signal transmitting units 121A and 121A.
1B, 121C, and 121D. One audio signal transmission unit 121 multiplexes, for example, an audio signal of 32 channels and a data signal of 8 channels (or an audio signal of 36 channels). The signal is modulated into an RF signal and output.
An RF mixing circuit that inputs and mixes an RF output signal from another audio signal transmission unit is provided in the RF modulation unit 122. Specifically, each of the audio signal transmission units 121A, 121B, 121C, 121D
RF signals of different carrier frequencies are frequency-multiplexed and output every time. In this case, the video signal reproducing device 111
The video signals of a plurality of channels may also be modulated at different carrier frequencies by an RF modulator (not shown), frequency-multiplexed with the RF modulation signal of the audio signal, and transmitted through a single coaxial cable.

The frequency-multiplexed RF signal is sent to an RF splitter 131 of a zone management unit 130 provided for each zone for zone division in the airplane, and an RF splitter 13 is provided.
1 to the zone management unit of the next zone via the RF amplifier 132. The RF signal input to the RF splitter 131 is split and transmitted for each column, which is a division area for dividing the zone. A plurality of seat units 140 are connected in series in one column.
The F signal is sent to the next seat unit 140 via the RF splitter 141 and the RF amplifier 142.

In one seat unit 140, for example, 3
Circuits for the seats are provided collectively, and the RF signal split by the RF splitter 141 is split into three RF signals by the RF splitter 144, and the three RF receivers 145
A, 145B, and 145C, respectively. The RF receiving section 145 extracts an RF signal in one band of the frequency-multiplexed signal, performs RF demodulation, extracts a signal of a desired channel from the demodulated signal, and outputs the signal. The signals output from each of the RF receivers 145A, 145B, and 145C are transmitted to a passenger-side control unit 146A,
46B and 146C, respectively. The passengers of each seat can connect to the control units 146A, 146B, and 146C with the headphones 147A, 147B, and 147C, respectively, and arbitrarily select and listen to an audio signal of a desired channel.

Next, the audio signal transmitting unit 121 on the audio signal transmitting side will be described with reference to FIG. The audio signal transmission unit 121 shown in FIG. 8 receives, for example, an audio signal of 32 channels and a data signal of 8 channels and has a frequency band of 6 channels.
It is converted into a signal of MHz and output. The audio signal transmission unit 121 is also called an audio multiplexer unit or AMUX because the audio signal is multiplexed and output.

[0038] The audio signal transmitting unit 121, and 32-channel audio signal AU ₁ ~AU ₃₂ is for example supplied in the form of a so-called balanced inputs,
Each signal is converted by the buffer amplifier 21 from a balanced input form to an unbalanced form signal. Buffer amplifier 2
The audio signals of 32 channels from 1 are grouped for every two channels (for example, stereo left and right channels), sent to an A / D converter 22 and converted into digital signals, sent to a signal compression circuit 23 and compressed respectively. It is encoded. In the signal compression circuit 23, for example, a high-efficiency compression encoding process that adaptively controls the bit allocation for each band divided in the frequency axis direction using a human auditory characteristic according to an input signal, or a so-called so-called AD
(Adaptive difference) PCM encoding processing and the like are performed.

The computer data DT _{1 to} DT ₈ such as 8-channel TV game software are input in a balanced manner according to, for example, the format of a so-called EIA-422 interface, and converted into unbalanced signals by the buffer amplifier 21, respectively. 24.

Here, as the signal compression circuit 23, a first compression mode for performing a high-efficiency encoding process which takes a long processing time using the above-mentioned human auditory characteristics or the like but has good reproduction sound quality, and an ADPCM or the like. A circuit capable of switching and selecting the second compression mode having a relatively short processing time is used,
When listening to audio signals such as music for each seat, switch to the first compression mode. When forcibly switching to the PA channel at the time of announcement of a message or the like from the captain, switch to the second compression mode. It is preferable to switch. This is because the first compression mode is preferable because high sound quality is desired when listening to music or the like. During an announcement or the like, the sound from the speakers provided on the wall or ceiling of the aircraft and the sound from the headphones are used. This is because the second compression mode in which the time difference between them is small is more preferable. The selection of the switching of the compression mode is performed by a control signal from the controller 30. As a specific example of the first compression mode, a so-called ATRAC (Adaptive T) adopted in signal compression of a so-called MD (mini disc) is used.
Ransform Acoustic Coding) method or so-called dcc
So-called PASC (Precision Adaptive Sub-b) used for signal compression of digital compact cassettes
and Coding) method.

The output signals for the above-mentioned 32 channels from the signal compression circuit 23 are grouped into 12 channels (6 pairs of 2 channels) in order from the signal corresponding to the AU ₁ of the original input audio signal, and the multiplexer. 25
A and 25B respectively, and the remaining AU _{25 to} AU
Eight channels corresponding to ₃₂ sent to the output signal and the output signal are grouped together by the multiplexer 25C from the digital data interface circuit 24 corresponding to the data (DT ₁ to DT ₈₎ of the eight channels (four pairs min) Can be The digital data interface circuit 2
4, the clock signal is taken out to the outside via a buffer amplifier.

Multiplexers 25A, 25B, 25C
Respectively handle signals conforming to the audio signal format of, for example, satellite broadcasting or television broadcasting signals of satellite communication. One transmission frame of a format conforming to this audio signal format is composed of 32 columns × 64 columns, and in one transmission frame, 128 bits of data per channel is composed of 12 channels (for example, audio 12 channels or audio 12 channels). 8 channels +
8 channels of computer data) and what is called BC
At least an H error correction code (for example, a (63, 50) BCH code) and a preamble such as a frame synchronization and a control code are included. Data is output from one multiplexer 25 at a rate of, for example, 2.048 Mbps, and output data from each of the multiplexers 25A, 25B, 25C is sent to the time division multiplexing circuit 26 and time division multiplexed, thereby obtaining 6.144 Mbps. Is output as data of the rate. The digital signal output from the time division multiplexing circuit 26 is waveform-equalized by the equalizer 27,
The signal is compressed to a frequency band of Hz and sent to the RF modulator 122.

In the RF modulator 122, the output signal from the equalizer 27 is modulated by the intermediate frequency modulator 31 to become a predetermined intermediate frequency (IF) signal, amplified by the IF amplifier 32, and multiplied by the multiplier (modulator). ) 33. A predetermined RF from a PLL (phase locked loop) circuit 34 is input to the multiplier 33.
A carrier signal of a frequency is supplied, and the frequency of the output signal of the PLL circuit 34 is controlled by a controller 30 using a CPU or the like. Multiplier 33
Is output from a BPF (Band Pass Filter) 35
Through an RF amplifier 36 to an RF combiner (synthesizer or mixer) 37. This RF combiner 37 is connected to an external RF input terminal 126 via
For example, the RF from the other audio signal transmitting unit
A signal is being supplied. By making the RF carrier frequency of the RF modulator 122 different from the carrier frequency of the external RF input signal, the RF combiner 37 can perform frequency multiplexing. RF combiner 37
Is output to an output terminal 1 via an attenuator 38.
25.

That is, the RF modulation section 122
The frequency is determined based on, for example, three program discrete signals supplied to the controller 30, by controlling the frequency division ratio or the prescaler value in the PLL circuit 34 by the controller 30. The frequency is variably controlled, and the carrier frequency of the RF modulation signal from the multiplier 33 is variably controlled. That is, RF is generated by the program discrete signal.
The carrier frequency of the signal is determined so that it does not match (is different from) the carrier frequency of the RF signal from the other audio signal transmitting unit. Also, external RF
When there is no RF signal input from the input terminal 126, the controller 30 terminates the RF output terminal 125 by, for example, grounding the external RF input terminal 126 by a termination control signal supplied to the controller 30.

Next, the audio signal transmitting unit 1
The self-diagnosis function 21 will be described. The output signal from the time-division multiplexing circuit 26 is demultiplexed by the demultiplexer 28 and sent to the controller 30 using a CPU or the like, thereby determining whether or not the multiplex processing is performed normally. The bit monitor 29 demodulates the RF signal from the RF combiner 37, and the controller 30 determines whether or not the RF signal is normal. The self-diagnosis of the demultiplexer 28 and the bit monitor 29 (judgment as to whether or not it is normal) is performed, for example, by using an error correction code (such as a BCH code) added when multiplexed by the multiplexer 25 (25A, 25B, 25C). The calculation may be performed, and the determination may be made based on the presence or absence of an error, an error amount, and the like.

For the diagnosis of the A / D converter 21, the output signal from the A / D converter 21 is
The operation may be confirmed by monitoring at 0. Signal compression circuit 2
For 3, switch to the compulsory self-diagnosis mode (test mode) to output, for example, a 1 kHz sine (sine) wave, return this to the bit monitor 29, and monitor the signal with the controller 30. The diagnosis may be made by

The self-diagnosis is performed by forcibly switching to the self-diagnosis mode when the power is turned on or at the time of maintenance as required, and the self-diagnosis using the error correction code added at the time of multiplexing is performed. The operation is performed periodically at a predetermined period even during the normal operation. When a failure occurs, for example, the failure status and the time of occurrence are written in the non-volatile memory 30M, and the history is stored.

The output level of the RF output signal from the RF modulator 122 can be controlled by the controller 30 by controlling the gain of the RF amplifier 36. The controller 30 is provided with, for example, a so-called EIA-485 interface, through which the current failure status and failure history can be monitored, and the output level of the RF signal can be controlled.

Next, in FIG. 7, the configuration of the seat unit 140 for receiving the transmitted audio signal, particularly the configuration after the RF distributor 144 will be described in detail with reference to FIG.

In FIG. 9, the RF signal split by the RF splitter 144 shown in FIG. 1 is input to the input terminal 41, and is split by the RF splitter 144 into three RF signals.
The signals are sent to the input terminals 42A, 42B, 42C of the three RF receivers 145A, 145B, 145C, respectively. Since the internal configurations of these RF receiving units 145A, 145B, and 145C are all the same, the internal configuration is illustrated only for one RF receiving unit, for example, 145A, and the other RF receiving units are illustrated.
Illustration of the internal configuration of the receiving units 145B and 145C is omitted. In addition, the suffix A is omitted from the designation code of each unit in the RF receiving unit 145A.

The RF signal input from the input terminal 42A of the RF receiving section 145A is sent to the tuner 52 of the RF receiving and demodulating circuit section 51. The tuner 52 includes the audio signal transmission units 121A, 121B, and 12 shown in FIG.
An RF signal of one band is selected (tuned and tuned) from the RF signals frequency-multiplexed at different RF carrier frequencies for each of 1C and 121D, and converted into an IF (intermediate frequency) signal. send. The demodulation circuit 53
The signal is demodulated to output serial data at the data rate of 6.144 MHz, which is sent to the demultiplexer 54.

As described above, the serial data supplied to the demultiplexer 54 is time-division multiplexed into three (3 frames) of the audio format (format conforming to the television signal of the satellite broadcast or the satellite communication). It was done. The demultiplexer 54 extracts the data corresponding to one frame by demultiplexing the time-division multiplex, performs error correction decoding processing (for example, BCH decoding processing) for each frame, and then sets a desired audio channel or data channel. Select and take out. The error correction processing is for detecting and correcting an inversion error of data which may be generated due to the influence of noise or the like at the time of transmitting / receiving the RF signal. The selection of the desired audio channel or data channel is performed according to a command from a microprocessor (microcomputer) 43.

Here, when the above time-division multiplexing is solved to extract only one frame signal, the audio channel or data channel is selected from 12 audio channels or 8 audio channels and 8 data channels in one frame. In the demultiplexer 54 of this embodiment, two channels of audio can be arbitrarily selected from 32 channels of audio and 8 channels of data corresponding to 3 frames, or the data can be arbitrarily selected. It is configured so that one channel can be selected. This can be achieved by extracting a signal corresponding to any two frames when, for example, solving the time-division multiplexing.

The data and clock selected by the demultiplexer 54 are taken out through buffer amplifiers. The audio signals of the two channels (for example, stereo left and right channels) selected by the demultiplexer 54 are sent to a D / A converter 56 via a decompression circuit 55 or not.

The decompression processing in the decompression circuit 55 is controlled so that switching between a first decompression mode corresponding to the first compression mode and a second decompression mode corresponding to the second compression mode can be controlled. The mode switching and the volume (volume) setting are performed in accordance with an instruction from the microprocessor 43.

The D / A converter 56 receives, for example, 16-bit audio data expanded by the expansion circuit 55, outputs a 2-channel analog audio signal, and sends it to the headphone amplifier 57. Headphone amplifier 5
Reference numeral 7 denotes an amplifier for driving headphones 147 connected via the control unit 146 on the passenger side in FIG. A, and outputs signals from left and right output terminals 47A _L and 47A.
Retrieved via _R.

Next, the self-diagnosis function of such a circuit will be described. First, the microprocessor 43 sets the CP
The function diagnosis of each unit such as U, RAM, ROM and so-called watchdog timer is performed. If any of the tuning by the tuner 52, the demodulation by the demodulation circuit 53, and the error processing by the demultiplexer 54 have any trouble or failure,
The result (error detection output, etc.) is stored in the microprocessor 4
3 is read and stored in a memory or the like. This is an error correction code (such as the above-mentioned BCH code) previously added to the transmission signal.
Can be checked by reading the error flag, writing the result in a memory or the like, and controlling, for example, a so-called mute state, or a control not to cancel the mute if the current state is a mute state. You may.

At the time of audio self-diagnosis, the expansion circuit 55 outputs sine wave test data of, for example, 1 kHz, and the output from the headphone amplifier 57 is sent to the microprocessor 43 via the D / A converter 56. The microprocessor 43 has a built-in A / D
Detect with the converter and confirm that each circuit operates normally. Further, a 0 level signal is output from the expansion circuit 55,
The microprocessor 43 monitors the output from the so-called zero input detection terminal of the D / A converter 56,
It is checked whether the / A converter 56 is operating normally.

The above self-diagnosis is performed by forcibly switching to the self-diagnosis mode at the time of power-on or maintenance, for example. The diagnosis based on the error detection by the demultiplexer 54 is performed at regular intervals even during normal operation. It may be performed on demand or as needed. Further, the result can be taken out through the input / output terminal 45. In addition,
The microprocessor 43 can exchange data with an external circuit via the input / output terminal 45.

The present invention is not limited to the above embodiment. For example, the frame configuration is not limited to the above embodiment, and the number of channels per frame is not limited to 12 channels. Further, in the illustrated embodiment, the configuration is represented by functional blocks, but it is needless to say that the configuration can be realized by hardware or software.

[0061]

As is apparent from the above description, according to the present invention, data of a plurality of channels is error-correction coded and scrambled to form a frame, and a data sequence of a plurality of frames is time-division multiplexed. A demultiplexer to which a signal obtained by the conversion is input, and selects a data sequence of at least two frames from the plurality of frames, and demultiplexes the data sequence of each of the selected frames. After performing the scramble processing and the error correction processing, respectively, the data string of one channel is selected from the data strings of a plurality of channels in each frame. Therefore, a desired channel is selected across two frames. be able to.

Accordingly, for example, a case where monaural audio in units of one channel and stereo audio in units of two channels are transmitted in a mixed manner, and stereo audio is transmitted in one channel of one frame and one channel of another frame However, these can be taken out, so that if one channel of one frame and one channel of another frame, each of which was used in mono, is no longer needed, a conventional demultiplexer would According to the present invention, while only monaural audio could be transmitted using each vacant channel,
A stereo signal can be transmitted on two channels, and the degree of freedom is increased.

[Brief description of the drawings]

FIG. 1 shows a first basic demultiplexer according to the invention.
FIG. 3 is a block diagram showing an embodiment.

FIG. 2 is a block diagram showing a more specific second embodiment of the demultiplexer according to the present invention.

FIG. 3 is a diagram illustrating an example of a frame format.

FIG. 4 is a block circuit diagram showing a specific configuration example of a selector 1 for frame selection in FIG. 2;

FIG. 5 is a time chart for explaining the operation of the frame selection selector of FIG. 4;

FIG. 6 is a time chart for explaining the operation of the frame selection selector of FIG. 4;

FIG. 7 is a block diagram showing a specific example of an audio signal transmission system to which the demultiplexer according to the present invention is applied.

8 is a block diagram showing a specific example of an audio signal transmission unit 121 in the audio signal transmission system shown in FIG.

9 is a block diagram showing a specific example of a seat unit side for receiving an audio signal in the audio signal transmission system shown in FIG. 7;

FIG. 10 is a block diagram showing a conventional example of a demultiplexer.

[Explanation of symbols]

1 ······· Selector (frame selecting means) 2L, 2R, 102a, 102b ····· descrambling circuit 3L, 3R ···· BCH decoder 6L, 6R ····· Audio demultiplexer 7 · ... data demultiplexer 101 ... frame selection circuit 103a, 103b ... error correction circuit 104a, 104b ... channel selection circuit 120 ... audio signal transmission device 121A- ... 121D... Audio signal sending unit 140... Seat unit 145A to 145C.

Continuation of the front page (56) References JP-A-6-2522871 (JP, A) JP-A-2-260726 (JP, A) JP-A-5-28639 (JP, A) (58) Fields studied (Int) .Cl. ⁷ , DB name) H04J 3/04 H04H 5/00 H04J 3/00

Claims (1)

(57) [Claims] 1. A frame is formed by performing error correction coding and scrambling on data of a plurality of channels,
A signal obtained by time-division multiplexing a plurality of frames of data strings is input, and frame selecting means for selecting data strings of at least two frames of the plurality of frames; A descrambling unit for descrambling the data sequence of each of the divided frames, an error correction unit for performing an error correction process on each output signal from the descrambling unit, and an output from the error correction unit. And a channel selecting means for receiving a signal and selecting a data stream of one channel among data streams of a plurality of channels in each frame.