KR940001836B1 - Digital video system - Google Patents

Abstract

The optical signal transmitter transmits an NTSC television signal. The optial transmitter comprises a transmitter (100) for transmitting a digital optical signal, a receiver (200) for reconstructing the NTSC television signal from a digital optical signal transmitted from the transmitter, and a relay (19) for relaying the digital optical signal transmitted from the transmitter to the receiver. A synchronous signal and front porch in the NTSC television signal are replaced by a preset data. The preset data is reformed to make the digital optical signal. The preset data received by the receiver is reconstructed to the horizontal synchronous signal and front porch.

Description

Optical transmission

1 is a block diagram schematically showing an optical transmission device according to the present invention.

2 shows a data frame corresponding to a video signal according to the invention;

* Explanation of symbols for main parts of the drawings

1: Audio code unit 2: Video code and unit

3: Clock Generation Unit 4: Sign Memory Unit

5: code control unit 6: multiplexing unit

7: all-optical conversion unit 9: video line equalizer

10: voice line equalizer 11: photoelectric conversion unit

12: demultiplex unit 13: decoding memory unit

14: serial-to-parallel conversion unit 19: repeater

100: transmitter 200: receiver

The present invention relates to an optical transmission device, and more particularly, to an improved optical transmission system capable of digitally transmitting NTSC TV signals.

In general, the optical transmission device not only enables a high transmission quality and a long distance transmission by adopting a digital transmission method, but also enables wideband signal transmission by using an optical transmission path. 6Mbps, 45Mbps and 90Mbps are commercially available in Korea, and 565Mbps optical transmission devices are being developed.

Although the commercially available 90Mbps optical transmission device has a wide transmission bandwidth, it is impossible to digitally transmit TV signals by the 90Mbps optical transmission device because it does not reach the wide bandwidth of 100Mbps or more necessary for digital transmission of NTSC type TV signals. It was.

Accordingly, an object of the present invention is to provide an optical transmission device capable of transmitting TV signals as a domestic commercial optical transmission device.

When the optical transmission device according to the present invention converts and transmits the NTSC composite color TV signal to a digital signal, it transmits only the actual image information without omitting the digital transmission of the synchronization signal portion of the TV signal converted to the digital signal, the synchronization instead of the synchronization signal The amount of data to be transmitted is reduced by adding a representative value of several preset bits that can represent a signal. Meanwhile, the receiver reproduces the original NTSC composite color TV signal by restoring the synchronization signal to the representative value added instead of the horizontal synchronization signal.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of an optical transmission apparatus according to the present invention. The optical transmission apparatus converts and transmits an NTSC composite color TV signal into a digital signal and receives a video channel and an audio channel. 100 and a repeater 19 which inputs a signal from the transmitter 100 and reproduces the original NTSC composite color TV signal and an audio signal to the receiver 200 and a relay 19 that relays the signal from the transmitter 100 to the receiver 200. It is composed of

The transmitter 100 includes an image line equalizer 9, an audio signal equalizer 10, an image encoding unit 2, an audio encoding unit 1, a code memory unit 4, a clock generation unit 3, and code control. And a unit 5, a multiplexing unit 6, an all-optical conversion unit 7 and a monitoring panel 8.

The receiver 200 includes a photoelectric conversion unit 11, a demultiplexing unit 12, a decoding memory unit 13, a serial / parallel conversion unit 14, a readout control unit 15, an image decoding unit 16, and audio decoding. It consists of a unit 17 and a monitoring panel 18.

The operation of the digital video light transmission system according to the present invention is as follows. First, an NTSC composite color TV signal is input to the video line equalizer 9. One frame (picture) of an image displayed by an NTSC composite color TV signal is composed of two fields (odd and even fields). In addition, each field is composed of a plurality of horizontal lines, and the odd and even fields are alternately interlaced to produce one screen. As shown in FIG. 2A, each horizontal line consists of 84% of an active video signal and 16% of horizontal blanking. The 16% horizontal retrace consists of 2% front porch, 8% horizontal sync signal and 6% back porch. Typically, the back porch carries a color burst signal. The color burst signal is a kind of synchronization signal used to match the color carrier generated on the receiving side with the color carrier on the transmitting side. It is sent more than 8 cycles immediately after the horizontal synchronizing signal. Meanwhile, a vertical blanking signal is included between the fields in order to scan one field and then scan another field. The vertical retrace consists of an equalizing pulse and a vertical synchronization signal (not shown). The equalization pulse is a narrow pulse-shaped signal placed before and after the vertical synchronization signal to equalize the start of the odd and excellent scans.

The video line equalizer 9 compensates for deterioration, such as frequency characteristics, generated when the video signal passes through the transmission path. The signal output from the video line equalizer 9 is input to the video code unit 2. In the video encoding unit 2, a video signal is sampled and encoded into 9 bits. The audio signal is also encoded by the audio code unit 1 via the audio line equalizer 10.

The encoded video and audio signals are input to the code memory unit 4, respectively. In the code memory unit 4, the data of the front porch and the horizontal synchronization signal portion in the horizontal retrace section are omitted from the coded image, and a line state signal indicating this portion is added. In this way, the encoded video signal, audio signal, and line state signal are multiplexed by the multiplexer unit 6, and then stored in the buffer of the delay. Also, the multiplexed signal is serialized and then converted into a head portion to fit the data transmission frame structure. Is added. The output signal of the multiplexer unit 6 is transmitted via the optical cable as a digital signal which is optically changed by the all-optical conversion unit 7.

The digital signal thus changed is transmitted to the receiver 200 through the repeater 19. The receiver operates in the reverse order of the transmitter. The photo-converted digital signal input to the receiver 200 is converted into an electrical signal in the photoelectric conversion unit 11, and the demultiplexing unit 11 transmits a transmission frame to generate a data write / read clock from the photoelectrically converted signal. After the line start signal is extracted in the interval of, it is provided to the serial-to-parallel conversion unit 14.

In the serial-to-parallel conversion unit 12, the front porch and the horizontal synchronization signal omitted by the transmitter are reproduced. Data that is registered at the sampling frequency on the basis of parallel data received from the serial-to-parallel conversion unit 14 and control signals received from the read control unit 15, which are equivalent to the code memory unit 4 of the decoding memory unit 13 and the transmitter. And convert it back to the serial-to-parallel conversion unit 14. The data at this time includes the back porch and the actual video signal, and values representing the audio information of the channel, the print perch and the horizontal synchronization signal. These data are provided to the image encoding unit 16 via the serial-to-parallel conversion unit 14. The image encoding unit 16 generates a synchronization signal pattern by receiving the representative value and the line state information of the synchronization section and provides the same to the display unit (not shown). In the voice decoding unit 17, the voice of the signal output from the code memory unit 14 is decoded and divided into channels 1 and 2, and then provided to a speaker (not shown). Here, the monitor panels 8 and 18, which are not described, collect the alarms in the power source and the system, and perform an indication thereon. The clock generation unit 3 also generates a sampling clock and detects the registered signal of the TV signal. The code control unit 5 controls the code memory unit 4 and the multiplexer unit 6 via the clock generation unit 3.

Adjusting the storage and input / output transmission speed of video and audio data encoded as described above, and data reduction (protective storage unit 4 for performing front porch and horizontal synchronization signals in the horizontal return line, and video and audio data to be decoded) The data recovery performed by the decoding memory unit 14 for storing the data, adjusting the input / output speed, and restoring the reduced data will be described in detail with reference to FIG.

First, referring to FIG. 2, the TV signal includes a synchronization section T ₁ and a video data section T ₂ of a horizontal line.

In order to construct the image data in the data stream transmitted at the transmission system (for example, T3C class (90.764 Mbps), it is necessary to have a promised frame structure. The frame length can be arbitrarily determined, but the image data is determined according to the TV signal line frequency. Since it has a repeated form, the frame structure is configured in accordance with the length of the image information corresponding to one line of the TV signal, which is advantageous in terms of an error control code.

For this reason, in the present invention, when the frame is configured to have such a structure in the frame, the line frequency of the TV signal is 15.734264 kHz, so the number of bits that one frame can have is the number of bits per frame = 90.764 ÷ 0.01573464 = 5768.55708. Preferably, the transmission speed can be adjusted by transmitting the frame length in two types of 5768 bits or 5769 bits, but the frame structure is set to have a length of 5766 bits to 5769 bits for the convenience of hardware design (Fig. 2b).

Here, the head portion B1 includes a flag indicating the start of the frame, parity and control bits, and the audio bits (48 bits) (B2) are sampled at 63 times, in which two channels of audio signals are four times the TV line frequency, and 12 per sample. PCM code that has been A / D converted to bits.

The next bit section B4 is, for example, 5562 bits of data for the entire image section, which is the T ₂ section of FIG. 2a. The interval B5 can optionally be used for communication for data and video as required.

The section B3 is a section representing a synchronization pattern, and the section T ₁ is selected from the code memory unit 4 ( _first ) in a signal obtained by A / D conversion of the entire section T7 _Z (T ₂ ) by the transmitter. Instead of removing it from the figure, insert only a predetermined bit, e.g. 9 bits (optionally 6 bits), indicating the state of the section corresponding to this (e.g. horizontal sync signal C1, front porch C2, etc.) By reducing the data length. On the other hand, the data is recovered by inserting the actual data value in accordance with the synchronization pattern in the receiving section. That is, since the level of the value of the synchronization signal is constant, samples may be continuously recorded only with the representative value of the synchronization signal.

That is, as described above, since the front porch and the horizontal synchronization portion T _{1 of the} horizontal retrace section and the equalization pulse and the vertical synchronous signal of the vertical retrace section are not shown, the transmission unit 100 is constant for each main or field. In the present invention, only the actual video information may be transmitted, and the TV signal may be restored by replacing the representative value (this information may be transmitted for each field or frame in the transmitter 100).

In this way, data reduction of about 15 to 16% can be achieved, and as a result, a TV signal can be processed as a 90Mbps optical transmission device.

Claims (1)

Transmitter 100 converts NTSC TV signal including horizontal synchronous signal and front porch into digital optical signal, and transmits the digital optical signal from the transmitter 100 to recover NTSC TV signal. A relay means 19 connected between the receiver 200 and the transmitter 100 and the receiver 200 to provide a communication path from the transmitter 100 to the receiver 200 for the digital optical signal. In the optical transmission device comprising: means for configuring the digital transmission signal by the transmitter 100 by replacing the horizontal synchronization signal and the front porch of the digital signal A / D conversion of the NTSC TV signal with a predetermined data value The horizontal synchronization signal and the front porch of the digital signal received from the digital signal received by the receiver 200 according to the data value Optical transmission apparatus comprises a means for recovery.