JP4158701B2 - Video transmission system - Google Patents

Description

  The present invention provides a video transmission system for transmitting real-time digital video on a balanced transmission path.

  2. Description of the Related Art Conventionally, in an interphone system that images a visitor with an imaging camera provided in an entrance unit, an imaging camera using an analog transmission method such as baseband or FM modulation using a cable constituting an inexpensive balanced transmission line such as an interphone line. It was common to transmit the video signal from to the main unit in the room.

  However, in recent years, digitization has progressed in image pickup devices and monitor devices used in image pickup cameras, and most of the input / output interfaces used can be switched to digital RGB signals or YUV signals, or one of them. Yes.

In this situation, when the analog transmission method is used, the digital RGB signal or YUV signal of the video is once converted into an analog NTSC (Nata1 T1vision Standard Committee: EIA RS-170A standard <also called composite signal>) signal. Since then, video transmission has been performed.
Similarly, on the receiving side, the NTSC signal is converted into a digital RGB signal or a YUV signal through A / D conversion and the like, and then output to the monitor device.

  Therefore, when the analog transmission method is used, the cost is increased to convert the digital video signal to analog, and in addition, the digital signal from the image sensor is converted into an analog signal for transmission, which increases quantization distortion and transmission. There was a problem that the video quality deteriorated due to road attenuation or the like.

  In addition, when the FM modulation method is adopted for transmission of the video signal, it is necessary to perform FM modulation / demodulation processing in addition to this, which is a further factor in increasing the cost.

On the other hand, in order to solve these problems, attempts have been made to digitally transmit video.
(For example, Patent Document 1)
JP2003-244686A (see FIG. 1)

  The transmission method described in the above-mentioned Patent Document 1 is an Ethernet (R) method, and since a necessary transmission band is wide, it is necessary to use a twisted pair wire more than a CAT5 cable as a transmission line. Above, intercom systems that use multiple pairs of wires and as a result use conventional intercom lines (for example, a pair of interphones between an entrance unit and a parent unit in a room) There is a problem in that it is not compatible with the system, and cannot be replaced.

  The present invention has been made in view of the above points, and the object of the present invention is to be able to use an inexpensive pair wire used in an intercom system or the like, and to make a digital video signal with a simple configuration. An object is to provide a video transmission system capable of transmission.

In order to achieve the above object, according to the first aspect of the present invention, there is provided image pickup means for picking up an image. An imaging circuit that outputs a digital RGB signal or a digital YUV signal composed of a luminance signal, a color difference signal, a horizontal / vertical synchronization signal, and a digital video signal composed of a digital RGB signal or a digital YUV signal from the imaging circuit video input circuit capturing said signal conversion circuit for converting the digital video signal into an IQ signal conforming to the digital modulation, digital modulation circuit for digital modulation by M-ary modulation and IQ signal converted by the signal conversion circuit, the digital modulation The video data signal digitally modulated by the circuit is connected to a balanced transmission line such as a pair line or intercom line. Digital video transmission apparatus having a transmission circuit for transmitting in use available bandwidth, receiving circuit for receiving the video data signal transmitted via the balanced transmission line, digital demodulating the IQ signal from the video data signal Demodulation circuit, signal conversion circuit for converting the demodulated IQ signal from the digital demodulation circuit into a digital video signal in the form of a digital RGB signal or digital YUV signal, and an image for sending the converted digital video signal to the display circuit for display wherein a digital video receiver, Ri consists to the balanced transmission line and the display circuit, the vertical and horizontal synchronizing signals, that also serves as the preamble signal for clock synchronized playback of the digital modulated signal with an output circuit And

According to the first aspect of the present invention, since the digital modulation is multi-level modulation, the necessary transmission band may be narrowed. Therefore, like a pair line or an interphone line used in a conventional analog transmission type interphone system. Even if a balanced transmission line with a narrow transmission band is used, video can be transmitted in real time, so that only the digital video transmission device and digital video reception device can be changed without changing the wiring of the existing intercom system. Therefore, since it can be replaced with the conventional product and further digitally modulated and transmitted, there is no deterioration in video quality even with long distance transmission, and the digital video signal from the imaging circuit is digitally modulated and demodulated as it is, Quantization noise does not occur, video quality does not deteriorate, and digital signals including horizontal and vertical sync signals of video signals Since the modulated video data signal is transmitted, it is possible to reproduce the video synchronization signal on the digital video receiver side, and the digital video input / output interface is configured according to the interface configuration of the imaging circuit and the display circuit. Therefore, it can be manufactured at low cost. Also, by using the horizontal / vertical synchronization signal of the digital video signal also as the preamble signal, the bandwidth required for transmission can be reduced, and as a result, compared to the case where a pair of lines are used for transmission of the synchronization signal. The number of pairs required for signal transmission can be reduced by one.

  The invention of claim 2 is characterized in that, in the invention of claim 1, a single carrier system is used as a digital modulation system used in the digital modulation circuit.

  According to the invention of claim 2, the configuration of the digital modulation circuit is simplified by using the single carrier method.

  The invention of claim 3 is characterized in that, in the invention of claim 1, a multicarrier system is used as a digital modulation system used in the digital modulation circuit.

  According to the invention of claim 3, the transmission band of the balanced transmission line such as the interphone line and the pair line can be utilized to the maximum, so that the screen size of the video can be increased and the definition can be made higher, and the necessary band Therefore, it is possible to superimpose and transmit other signals on the same line. Therefore, in the case of an interphone, it is possible to superimpose and transmit voice and control signals in the necessary transmission band. In addition, it is possible to easily prevent the transmission of video data signals by masking frequencies that are likely to generate noise or frequencies that are likely to affect other systems. Even in transmission paths with large differences, each carrier has a narrow band, making equalization for attenuation easy. As a result, signal errors are less likely to occur, and primary modulation is also possible. By using multi-level PSK, the digital modulation circuit can be simply configured for each carrier in the same manner as in the invention of claim 2, and the transmission speed of each carrier is relatively low by transmitting using many carriers. It is good, and it is excellent in noise resistance and can reduce the occurrence of errors.

In the invention of claim 4, in the invention of any one of claims 1 to 3 , two kinds of signals are prepared as the preamble signal so that each of the vertical and horizontal synchronization signals of the digital video signal can be identified, The two types of preamble signals are distinguished by the difference in length of the preamble length.

According to the invention of claim 4 , it is possible to distinguish the horizontal / vertical synchronizing signal of the digital video signal composed of the digital RGB signal or the digital YUV signal.

In the invention of claim 5, in the invention of any one of claims 1 to 3 , two kinds of signals are prepared as the preamble signal so that each of the vertical and horizontal synchronizing signals of the digital video signal can be identified. The types of preamble signals are characterized by being identified by differences in preamble signal patterns.

According to the fifth aspect of the present invention, it is possible to distinguish between the horizontal and vertical synchronizing signals of the digital video signal with a simple configuration, and it is not necessary to increase the preamble signal length, so that it is not necessary to reduce the transmission band.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects of the present invention, the transmission speed including the digital data portion consisting of the preamble signal and the video data of the digitally modulated signal is the transmission speed of the RGB signal or YUV signal. In the video receiver, after the digital demodulation, the period of the vertical / horizontal synchronization signal is a period without the digital part. It is characterized by playing.

According to the sixth aspect of the invention, since a period without digital data is used for error detection, digital data errors can be detected, and the reliability of data transmission can be improved.

According to a seventh aspect of the present invention, in the digital video receiver according to any one of the first to sixth aspects of the present invention, the digital video receiver includes a memory circuit that stores at least two scanning lines or more of scanning line data. When an error is included, the previous scan line data is read from the memory circuit and used in place of the error scan line data.

According to the seventh aspect of the present invention, it is possible to suppress the disturbance of the image by using the data of the previous scanning line stored in the memory circuit.

According to an invention of claim 8, in the invention of any one of claims 1 to 7 , the digital video receiving device is provided with a memory circuit for storing data for at least one field or one screen, and the next one field or one When an error is included in the scanning line received during the reception period of the screen, the data of the corresponding scanning line is read from the data of one field or one screen stored in the memory circuit, and the error scanning line is read. It is used in place of data.

According to the eighth aspect of the present invention, it is possible to suppress image disturbance even when there is an error in one or a plurality of scanning lines in one received field or one screen.

According to a ninth aspect of the present invention, in the seventh or eighth aspect of the present invention, the data length of a transmission data unit when transmitting the video data signal is a length obtained by dividing one scanning line into a plurality of lengths.

According to the ninth aspect of the present invention, even if an error occurs in the transmission data unit, the influence of the error may be a small range with respect to the screen size, and even if the error cannot be recovered, the influence on the screen can be reduced .

Since the present invention can use an intercom line used in a conventional analog transmission system interphone, it can replace the conventional product by changing only the video transmitting device and the video receiving device without changing the wiring. It is also possible to perform digital modulation and transmit, so there is no degradation in video quality even over long distance transmission, and the digital signal from the imaging circuit is digitally modulated and demodulated as it is, so quantization noise does not occur, Since video quality does not deteriorate and digital modulation is multilevel modulation, video can be transmitted in real time even on balanced transmission lines with narrow transmission bands such as interphone lines and pair lines, and video signals Since video data signals that have been digitally modulated, including horizontal and vertical sync signals, are transmitted, video sync signals can also be played back on the video receiver side. Imaging circuit digital video output interface, and by constituting in accordance with the interface configuration of the display device, it becomes possible to reduce the circuit blocks, there is an effect that the manufacturing cost can be inexpensive. Also, by using the horizontal / vertical synchronization signal of the digital video signal also as the preamble signal, the bandwidth required for transmission can be reduced, and as a result, compared to the case where a pair of lines are used for transmission of the synchronization signal. The number of pairs required for signal transmission can be reduced by one.

  Embodiments of the present invention will be described below.

(Embodiment 1)
FIG. 1 shows a system configuration of the present embodiment. In this embodiment, a digital video transmission device 1 is provided in an entrance unit 20 of an interphone, and a digital video reception device 2 is a master unit (hereinafter referred to as a parent unit). By using a transmission system with a narrow transmission band, which will be described later, the two devices 1 and 2 are connected by a one-pair cable 3 as a balanced transmission path.

The image pickup circuit 4 of the digital video transmission apparatus 1 is a digital RGB signal (or luminance signal) composed of, for example, a red signal, a green signal, a blue signal, and a horizontal / vertical synchronization signal obtained from a video signal captured by a color imaging camera (not shown). In the case of a digital RGB signal, the digital RGB signal is converted into a YUV signal by the RGB-YUV conversion circuit 6 via the video input circuit 5. The signal is converted, converted into an IQ signal suitable for the digital modulation signal by the signal conversion circuit 7, and digitally modulated by the digital modulation circuit 8. Here, each color data is composed of, for example, 8-bit data. When a signal digitally modulated by the transmission circuit 9 is transmitted as a video data signal, in the case of a digital RGB signal, the screen size is QVGA (320 × 240) size. Assuming that 30 frames per second and each color of the digital RGB signal is 8-bit data, the amount of video data per second is 320 × 240 × 30 × 8 × 3 = 55.296 Mbps.

  On the other hand, when transmitting with a YUV signal, since the human eye is more sensitive to brightness than color, there is little influence even if the color difference is compressed and transmitted, so luminance: 8 bits, color difference: 8 bits (4 bits) Similarly, when transmitted at × 2), the video data for one second is 320 × 240 × 30 × 8 × 2 = 36.864 Mbps. In this case, when the digital YUV signal is the output of the imaging circuit 4, the RGB-YUV conversion circuit 6 is unnecessary. In addition, since there is not much difference in the appearance of the screen between the RGB signal and the YUV signal, when using an intercom line with a narrow transmission band, it is more efficient to transmit the YUV signal, and the data on the large screen than the RGB signal. If the screen size is the same, transmission in a narrower band is possible.

  Since the digital video signal has a transmission data amount ranging from 37 to 55 Mbps as described above, in this embodiment using the cable 3 such as an intercom line that can use only a transmission band up to 20 to 30 MHz, the modulation method of the digital modulation circuit 8 is used. The digital multi-level modulation method is adopted. As this multilevel modulation scheme, for example, in the case of a single carrier, multilevel modulation of QPSK <4 phase shift keying> (2 bits / symbol) or 8PSK <8 phase modulation> (3 bits / symbol) or more is adopted. Of course, QPSK or 8PSK may be primary modulation and SS (spread spectrum) modulation may be employed.

  Corresponding to the digital video transmitting apparatus 1 described above, the digital video receiving apparatus 2 provided in the living room master unit 21 includes a receiving circuit 10 that receives a transmitted video data signal, and an IQ signal from the received video data signal. A digital demodulation circuit 11 corresponding to the modulation method, a signal conversion circuit 12 for converting the IQ signal demodulated by the digital demodulation circuit 11 into a YUV signal, and a YUV for converting the YUV signal into a digital RGB signal. A RGB conversion circuit 13 and a video output circuit 14 that takes in the converted digital RGB signal and outputs it to a display circuit 15 including a liquid crystal display or the like.

  By the way, in the present embodiment, the digitally modulated video data signal is transmitted from the transmission circuit 9 of the digital video transmission device 1 in a packet format.

  That is, as shown in FIG. 2, each packet includes video data D, preamble signal A corresponding to horizontal synchronization arranged before video data D, preamble signal B corresponding to vertical synchronization, and rear of video data D. In the receiving circuit 10 of the digital video receiver 2 using the preamble signals A and B, the digital modulation signal clock is reproduced and the horizontal / vertical synchronization signal of the video signal is reproduced. Playback is in progress.

  The horizontal / vertical synchronization signal is preferably reproduced after reception, but may be reproduced by any circuit block of the digital video receiver 2 (since it is sufficient that the synchronization signal is finally output to the display circuit). .

  The error detection signal C after the video data D may be, for example, a CRC code, or a parity if it has a simple configuration. Further, it may be a signal having not only error detection but also an error correction function.

  The preamble signals A and B may have a pattern as shown in FIG. 3, for example. In order to facilitate the synchronous reproduction of the digital modulation signal, the signal pattern may be a repetitive pattern of 0101.

  In the case of adopting, for example, the OFDM system, which is a multi-carrier system to be described later, it may be possible to enhance the preamble signal against noise or noise by making one signal period of the preamble longer than the data part. .

  FIG. 4 also shows a state in which digitally modulated video data D is transmitted in a packet format from the digital video transmitter 1 as in FIG.

In this case, as shown in FIG. 5, the preamble signals A and B have the same length and different signal patterns. In addition, the digital modulation signal data is transmitted continuously (without a break). That is, as shown in FIG. 2, it does not have to be completely divided into packets. )
In the present embodiment configured as described above, by adopting the multi-level modulation method, the cable 3 made of an intercom line with a narrow transmission band can be used as a balanced transmission path, and the replacement with an existing intercom system is possible. It becomes possible.

Of course, if there is no problem in cost, it is also possible to use a CPEV line (2 or 3 pairs), a CAT5 cable (4 pairs) used for LAN, a CAT6 cable, or the like.
(Embodiment 2)
This embodiment uses a multicarrier system (OFDM system or the like) for digital modulation and transmission of video data signals. As shown in FIG. 6, the signal conversion circuit 7 of the video transmission apparatus 1 converts it into a plurality of IQ signal formats. The difference from the first embodiment is that the signal is input to the digital modulation circuit 8 adopting the multicarrier system. Of course, the digital demodulator circuit 11 on the digital video receiver 2 side corresponds to multi-carrier modulation, and demodulates a plurality of IQ signals from the video data signal received by the receiver circuit 10. The video data signal is transmitted in the packet format as in the first embodiment.

  Thus, even in the present embodiment, the cable 3 between the transmission circuit 9 of the digital video transmission device 1 and the reception circuit 10 of the digital video reception device 2 has an interphone with a narrow transmission band as in the first embodiment. A cable consisting of a pair of paired wires such as a wire is employed.

  Of course, if there is no problem in cost, it is also possible to use a CPEV line (2 or 3 pairs), a CAT5 cable (4 pairs) used for LAN, a CAT6 cable, or the like.

  In addition, since the other structure is the same as Embodiment 1, in FIG. 6, the same code | symbol is attached | subjected to the same component as the component of FIG. 1, and description is abbreviate | omitted.

(Embodiment 3)
The present embodiment is an embodiment in which a countermeasure is taken when a reception error occurs in the configuration of the second embodiment. As shown in FIG. 7, the receiver 10 and the digital demodulator 11 of the digital video receiver 2 The second embodiment is different from the second embodiment in that a memory circuit 16 is provided therebetween. The memory circuit 16 does not necessarily have to be at this position. The read / write processing for the memory circuit 16 is performed by a signal processing unit (not shown).

  Next, a coping method when a reception error, which is a feature of this embodiment, is described with reference to FIG.

  First, the example of FIG. 8A shows a case where an error X occurs in the scanning line D in the scanning lines A. In this case, the received scanning line D is discarded, and the data of the previous scanning line C stored in the memory circuit 16 is output.

  This method focuses on the fact that the image difference between one scanning line is small, and the image is disturbed by displaying the image using the data of the previous scanning line on the screen. Is suppressed.

The example of FIG. 8B shows a case where an error X has occurred in the scanning line D. In this case, the same scanning line on the previous screen F stored in the memory circuit 16 is reproduced. D data is output. This method pays attention to the fact that the difference in video between one screen is small. By using the data of the same scanning line of the previous screen for the scanning line where the error occurred, the image is disturbed. Is suppressed. In this case, it is possible to cope with a case where an error occurs in a plurality of scanning lines due to burst noise or the like, which is a very effective method. This method requires a memory capacity for one screen.
(Embodiment 4)
In the third embodiment, the previous scan line data or the previous screen data stored in the memory circuit 16 is used when an error occurs using the memory circuit 16. As shown in FIG. 9, the packet transmitted from the digital video transmitting apparatus 1 is transmitted smaller than one scanning line. That is, one scan line is divided and transmitted in a plurality of packets. Even in the case of the present embodiment, the error recovery method shown in FIG. 8A or 8B of the third embodiment can also be applied, but an error recovery method using the memory circuit 16 should an error occur continuously. Even if the screen does not work effectively, the screen data is divided and transmitted so that the disturbance on the screen can be small.

  As shown by the dotted line on the right side of FIG. 9, the error of the scanning line D is recovered by the data of the scanning line before the memory circuit 16, but as shown by the dotted line part E, the error cannot be recovered. However, the screen (left side of FIG. 9) does not have a large line (due to error packet discard), and only a portion of the image Y is disturbed, which makes it difficult for the user to feel uncomfortable.

  In addition, since the structure of this embodiment also uses the structure of Embodiment 2, a structure and its description are abbreviate | omitted here.

(Embodiment 5)
As shown in FIG. 10, this embodiment uses a cable 3 in which a plurality of pair wires each constituting a balanced transmission path are provided in the same sheath. When transmitting digital RGB signals, each pair wire is connected to an R signal. This eliminates the need for complex signal conversion (signal distribution) by assigning to the G signal and B signal, and with a simple configuration, transmission circuits 9R, 9G, and 9B corresponding to the respective signals are provided to provide a three-pair line. The parallel transmission is performed. Of course, also on the digital video receiver 2 side, receiving circuits 10R, 10G, and 10B corresponding to the respective signals are provided. Since other configurations are the same as those of the second embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  Thus, in this embodiment, even with the use of the cable 3 in which three pairs of interphone wires having a narrow transmission band compared to a CAT5 cable used in a LAN or the like are provided in the same sheath, a larger screen or a higher definition can be obtained. A simple image can be transmitted, and only one cable is required. In addition, since the video data of the R signal, G signal, and B signal are independently transmitted in parallel through a plurality of pair lines, a large screen (for example, VGA size) and high-definition video can be transmitted. In addition, since each transmission path is independent, the circuit configuration is simplified, and the synchronization signal may be transmitted using at least one of the R signal, G signal, and B signal.

  Similarly, the digital YUV signal has the same advantage if it is transmitted in parallel using a plurality of pair lines.

  In FIG. 9, the case of three-pair wires is shown, but the number of pairs is not particularly limited, and it does not necessarily mean that they must be the same sheath.

1 is a configuration diagram of Embodiment 1. FIG. It is explanatory drawing of the signal example of the packet structure used for Embodiment 1. FIG. FIG. 3 is a diagram illustrating an example of a preamble signal in the case of the signal example of FIG. 2. It is explanatory drawing of another signal example of the packet structure used for Embodiment 1. FIG. FIG. 5 is a preamble signal example diagram of the signal example of FIG. 4. 6 is a configuration diagram of Embodiment 2. FIG. FIG. 6 is a configuration diagram of a third embodiment. (A) is explanatory drawing of an example of the error recovery method at the time of reception error occurrence of Embodiment 3, (b) is explanatory drawing of another example of the error recovery method at the time of reception error occurrence of Embodiment 3. FIG. 10 is an explanatory diagram of an error recovery method when a reception error occurs according to a fourth embodiment. FIG. 10 is a configuration diagram of a fifth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital video transmitter 2 Digital video receiver 3 Cable 4 Imaging circuit 5 Video input circuit 6 RGB-YUV conversion circuit 7 Signal conversion circuit 8 Digital modulation circuit 9 Transmission circuit 10 Reception circuit 11 Digital demodulation circuit 12 Signal conversion circuit 13 YUV- RGB conversion circuit 14 Video output circuit 15 Display circuit 20 Entrance unit 21 Office unit

Claims (9)

Including an image pickup means for taking a video, the image taken by the image pickup means is converted into a digital RGB signal or luminance signal, a color difference signal, a horizontal / vertical synchronization signal composed of a red signal, a green signal, a blue signal, and a vertical / horizontal synchronization signal. An imaging circuit that outputs a digital video signal consisting of a digital YUV signal consisting of:
A video input circuit that captures a digital video signal composed of a digital RGB signal or a digital YUV signal from the imaging circuit, a signal conversion circuit that converts the digital video signal into an IQ signal suitable for digital modulation, and the signal conversion circuit A digital modulation circuit that digitally modulates an IQ signal by multi-level modulation, and a transmission circuit that transmits a video data signal digitally modulated by the digital modulation circuit within a usable band of a balanced transmission line such as a pair line or an interphone line A digital video transmission device,
Receiving circuit, said digital demodulation circuit for demodulating the video data signal to the IQ signal, the digital RGB signals demodulated IQ signal from the digital demodulation circuit for receiving the video data signal transmitted via the balanced transmission line Or a digital video receiver having a signal conversion circuit for converting into a digital video signal in the digital YUV signal format, a video output circuit for sending the converted digital video signal to a display circuit and displaying it, and
Ri consists to the balanced transmission line and the display circuit,
A video transmission system characterized in that the vertical / horizontal synchronization signal is also used as a preamble signal for clock-synchronized reproduction of a digitally modulated signal .   The video transmission system according to claim 1, wherein a single carrier method is used as a digital modulation method used in the digital modulation circuit.   The video transmission system according to claim 1, wherein a multicarrier system is used as a digital modulation system used in the digital modulation circuit. As the preamble signal, two types of signals are prepared so that the vertical and horizontal synchronization signals of the digital video signal can be identified, and the two types of preamble signals are identified by the difference in the length of the preamble length. The video transmission system according to claim 1, wherein the video transmission system is a video transmission system. As the preamble signal, two types of signals are prepared so that each of the vertical and horizontal synchronization signals of the digital video signal can be identified, and the two types of preamble signals are identified by the difference in the signal pattern of the preamble. The video transmission system according to any one of claims 1 to 3 . The transmission speed including the digital data part composed of the preamble signal and video data of the digitally modulated signal is set so as to have a margin with respect to the transmission speed of the RGB signal or the YUV signal, and a period in which the digital data part is not present is set. assigned to the error detection signal, said rear digital demodulation in the video receiving apparatus, vertical and horizontal synchronizing signal period of one of claims 1 to 5, characterized in that play in the digital section is not a period of a video transmission system. The digital video receiving apparatus includes a memory circuit that stores at least two scanning lines or more of scanning line data. If an error is included in one received scanning line, the previous scanning line data is read from the memory circuit. 7. The video transmission system according to claim 1 , wherein the video transmission system is used by reading out the data instead of the error scanning line data . The digital video receiving apparatus includes a memory circuit that stores data for at least one field or one screen, and an error is included in the scanning line received during the reception period for the next one field or one screen. 8. The data of the corresponding scanning line is read from the data for one field or one screen stored in the memory circuit and used instead of the data of the error scanning line . The video transmission system described. 9. The video transmission system according to claim 7, wherein a data length of a transmission data unit when transmitting the video data signal is a length obtained by dividing one scanning line into a plurality of lengths .

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