KR970002972B1 - Transmitting apparatus of digital cable broadcasting system - Google Patents

Abstract

A transmission apparatus of a digital cablecast system is disclosed. The transmission apparatus of the digital cablecast system comprises: a system clock generator(5) for generating a system clock by extracting a color subcarrier from a composite video signal; an video signal analog/digital converter(4) for converting the composite video signal to a digital signal in response to the system clock; an audio signal analog/digital converter(6) for sampling an audio signal in reponse to an audio sampling clock and converting the audio signal to the digital signal; a digital video signal compressor(7) for compressing the dital video signal by a differential pulse code modulation(DPCM); and a digital signal3(DS3) multiplexer(9) for transmitting the audio sampling clock to the audio signal analog/digital converter(6) and transmitting a DS3 frame. Thereby, the transmission apparatus of the digital cablecast system may reduce a transmission noise and perform the cablecast service of high quality.

Description

Transmission device of digital cable broadcasting system

1 is a block diagram of a transmission device of a digital cable broadcasting system according to the present invention.

2 is an explanatory diagram of a digital representation of an NTSC composite video signal.

3 is an explanatory diagram of a digital representation of a TV audio signal.

4 is an explanatory diagram of a voice multiple control signal.

5 is a block diagram of a DPCM encoder.

6 is an explanatory diagram of a prediction method.

7 is an input / output characteristic diagram of a club (CLIP) part.

8 is an input / output characteristic diagram of a quantizer and an inverse quantizer.

9 is an explanatory diagram for explaining a DS3 frame configuration method of a TV signal.

10A to 10C are exemplary diagrams for mapping methods of TV audio samples and mapping of audio samples.

11 is an explanatory diagram for a mapping method of a compressed video signal.

12 is an explanatory diagram for explaining a method of operating a stuffing control signal.

* Explanation of symbols for main parts of the drawings

l: NTSC composite video signal 2: 2 channel audio signal

3: audio multiple control signal 4: video signal analog / digital converter

5: System Clock Generator 6: Audio Signal Analog / Digital Converter

7: Digital Video Signal Band Compressor 8: Audio Sampling Clock

9: DS3 Multiplexer 10: DS3 Data and Transmit Clock

11: DS3 signal transmission unit 12: DS3 line signal

13 DS3 Synchronous Clock 14 Quantizer

15: inverse quantizer 16: clip (CLIP) unit,

17: Predictor 18: Leak part

The present invention transmits a digital cable broadcasting system for enabling digital cable broadcasting of a Korean-style NTSC (Nation Te1evision System Committee) TV (Digital Signa1 3) (Digital Signa1 3) (transmission rate: 44.736Mbps) that is a North American digital hierarchy. Relates to a device.

In the conventional CATV, the analog system using a coaxial line is the mainstream. In the case of the CATV, the service quality is low due to transmission noise.

In order to overcome this problem, the present invention solves the problem of transmission noise and performs high quality TV (TV) broadcasting service by expressing Korean NTSC TV as digital, performing band compression, and transmitting it to DS3 level. The purpose is to provide a transmission device of a digital cable broadcasting system.

The present invention has been made in order to achieve the above object, the system clock generator for generating a system clock by extracting the color subcarrier from the composite video signal input from the outside; A video signal analog / digital converter for converting the composite video signal input from the outside into a digital sampled according to the system clock of the system clock generator; An audio signal analog / digital converter that converts an audio signal input from the outside according to an audio sampling clock and converts it to digital using a complement, and receives a digital video signal from the video signal analog / digital converter and differential pulse code modulation (DPCM) A digital video signal band compressor for band-compressing the amount of information of the digital video signal according to the method; And receiving a digital audio signal from the audio signal analog / digital converter, the digital audio signal, a compressed video signal from the digital video signal bandpass compressor, an audio multiple control signal from the outside, and a DS3 (digital signal 3) synchronization clock. It includes a DS3 multiplexer that outputs an audio sampling clock to an audio signal analog / digital converter and configures and outputs a DS3 frame.

Hereinafter, with reference to the accompanying drawings will be described an embodiment according to the present invention;

1 is a block diagram of a digital cable broadcasting system transmitting apparatus according to the present invention, in which 1 is a baseband NTSC composite video signal, 2 is a 2 channel TV (TV) audio signal, and 3 is a TTL (Tr).

ansister-Transister Logic circuit) Voice multiple control signal represented by logic and composed of mono / multi (MN / ML), stereo / dual language (ST / DL), 4 is a video signal analog / digital converter, 5 is a system clock generator, 6 is an audio signal analog / digital converter, 7 is a digital video signal bandwidth compressor, 8 is an audio sampling clock, 9 is a DS3 multiplexer, 10 is DS3 data and transmit clock represented by pseudo Emulator Coupled Logic (ECL) logic. 11 denotes a DS3 signal transmitter, 12 denotes a DS3 line signal for remote transmission, and l3 denotes a DS3 synchronous clock of 44.736 MHz.

Looking at the overall operation of Figure 1 as follows. First, the NTSC composite video signal 1 is converted into an 8-bit digital video signal per sample by the analog / digital converter 4, and then band-compressed in half by the digital video signal band compressor 7 and then DS3. It is passed to the multiplexer (9). The system clock generator 5 extracts the color subcarrier from the NTSC composite video signal 1 and generates a system clock that is three times the color subcarrier, thereby converting the video signal analog / digital converter 4 and the digital video signal band compressor 7. In addition, the DS3 multiplexer 9 performs the function of providing the same.

The audio signal 2 is represented by the audio signal analog / digital converter 6 at 16 bits per sample and then transmitted to the DS3 multiplexer 9.

An audio sampling clock is generated from the DS3 multiplexer 9 and provided to the audio signal analog / digital converter 6, with a frequency of 3289 MHz, which is 2 / (85 * 32) of 44.736 MHz, which is the DS3 clock frequency.

The mono / multi (MN / ML) and stereo / dual language (ST / DL) signals, which are voice multiple control signals (3) expressed in TTL, are provided with a direct sync clock (l3) from the outside to form a DS3 frame. Pseudo) ECL type DS3 signal 10 is transmitted, or B3ZS line coding is performed through DS3 signal transmission unit 11, and then bipolar type DS3 line signal 12 is transmitted.

The details of each part are as follows.

The video signal analog-to-digital converter 4 samples the NTSC composite video signal at 107 MHz, which is three times the frequency of the color subcarrier provided from the system clock generator 5, and each sample is represented by 8 bits. As shown.

That is, the maximum bright color is represented by 255, the blanking level is represented by 73, and a linear pulse modulation (PCM) process is performed such that the synchronization front end is zero.

The audio signal 2 is represented by a 16-bit linear PCM by the audio signal analog / digital converter 6, the sampling frequency is 32.89 kHz, and is represented digitally as shown in FIG. 3 using two's complement.

The voice multiple control signal 3 is composed of two signals, mono / multi (MN / ML) and stereo / dual ear wax (ST / DL), expressed in TTL logic, as shown in FIG.

The digital video signal band compressor 7 performs a function of reducing the information amount of the video signal by 1/2 according to the DPCM (Diffrential PCM) method.

5 is a configuration diagram of a DPCM encoder, in which l4 denotes a quantizer, l5 denotes a dequantizer, 16 denotes a clip (CLIP) unit, 17 denotes a predictor, and 18 denotes a leak unit.

The operation of FIG. 5 is described in detail as follows.

First, the input digital video signal is predicted as a signal through which the output of the predictor passes through the leak unit 18, and the prediction error signal is quantized by the quantizer 14 to generate a compressed video signal and at the same time a compressed video. The signal is dequantized for the prediction of the next signal, and the output of the dequantizer 15 is summed with the output of the leak portion 10 and then passed through the clip portion 16 and stored in the predictor.

Here, the input / output characteristics of the quantizer 14 and the inverse quantizer l5 are as shown in FIG. 8, the characteristics of the cleaver 16 are as shown in FIG. 7, and the predictor 17 is shown in FIG. Works together. The leakage unit 18 operates to generate an output of (15 * R / 16 + 8) when the output of the predictor 17 is P. .

The leak unit l8 multiplies the output of the predictor 17 by a value less than 1 (l5 / 16) in order for the compressed image signal to converge quickly without the divergence operation when an error occurs during transmission. Perform the function.

The DS3 multiplexer 9 receives the compressed video signal, the digital audio signal, and the audio multiple control signal to perform a function of constructing a DS3 frame. In the present invention, the DS3 frame configuration is shown in FIG. DS3 frame consists of 8 data blocks in 85-bit unit to form one submultiframe, 7 submultiframes to form one multiframe, and one DS3 multiframe consists of 4760 bits. One DS3 multiframe has a period of 106.402 ms.

In the DS3 multiframe diagram, the first bit of the 85-bit data block is used for the DS3 frame structure. In FIG. 9, the portion indicated by '' X '' is not used in the present invention, and the "P" position is the parity bit of the previous frame. Where 'F0' or 'Tl' is the submultiframe sync bit, 'M0' or 'Ml' is the multiframe sync bit, and the 'C' bit is The stuffing control bit, which is not used in the present invention, is used as a control signal for adjusting the transmission rate of the video signal in the present invention.

The remaining 84 bits except the first bit of the 85-bit data block are used in 4-bit units. Among them, "ADCON", the audio control signal is composed of 4 bits (L / R, MN <ML, ST / DL, RSV), its use and meaning is described in detail in the next section. '' RSVD '' is used as a slot for 4-bit data transmission. '' STUF '' is used as a slot for speed adjustment for video signal transmission. '' VDA '' is used for 19 video transmission slots in 4 bit units, total 76 bits, `` VDB '' is used for 20 video transmission slots in 4 bit unit, '' VDC '' is 4 bits It is used as 21 video transmission slots in units, and `` VDD '' is used as 20 video slots in 4 bit units.

The '' l / R '' of '' ADCON '' determines the insertion order of the audio samples, which is shown in Figure 10A when the L / R signal is '' 1 ''. The audio slots AD transmit a sample of the audio signal L (hereinafter L-sample) from the LSB. When the L / R signal is `` 0 '', the audio slots AD of the first sub-multiframe are the audio signal R. Sample of (hereinafter R sample) will be transmitted from LSB. The transmission order of the L and R samples in one multiframe is transmitted in the same order as in FIG. 10B according to the L / R signal. FIG. 10C shows an example of audio signal transmission in a normal case. When the L / R of the nth multiframe is '' 1 '', the (n + 1) th is "0" and (n + 2). In the (th), L / R is transmitted as '' 1 '', audio samples are transmitted from the L sample in the nth frame, and the (n + 1) th frame is transmitted from the R sample.

MN / ML and ST / DL of `` ADCON '' are directly transmitted with external voice multiple control signals. Since the period of multiframe is 106.4 ms, MN / ML and ST / DL signals are sampled at 9.4 kHz, respectively. Same as that sent.

The video data is compressed to 4 bits per sample and then DS3 frame configuration is performed, in which the LSB is transmitted first as shown in FIG.

The '' STUF '' slot is used to adjust the transmission speed of video data. The operation is as follows. The generation rate of video data is 42.954545Mb / s (4 * 3 times the color subcarrier), and the data rate that can be transmitted in the DS3 frame configuration shown in Fig. 9 is 42.969116 when the STUF position is used as the video signal transmission. Mb / s, and 42.931523 Mb / s when the STUF position is not used for video signal transmission. Since the input video data rate exists between the speed when the STUF is always used and the speed when the STUF is not always used, the input signal can be properly transmitted using the STUF. The use of the STUF slot is made by using the SC control signal. When the STUF slot is used for video signal transmission, each of the three SCs is transmitted as '0' and the STUFF slot is not used for the video signal transmission. In each of the three SCs is transmitted as '' 1 ''.

As shown in FIG. 12, the SC uses three bits to determine the number of rules by using the majority rule.

The present invention described above performs a function of converting an NTSC TV (TV) signal adopting the Korean-type voice multiplexing system to digital and outputting the signal to DS3 level, thereby deteriorating quality due to noise, which is a problem of analog TV broadcasting. It has the effect of providing high quality video and audio signal and enabling digital cable broadcasting of Korean voice multi TV signal to DS3 level.

Claims (3)

A system clock generator 5 for generating a system clock by extracting a color subcarrier from a composite video signal input from the outside; A video signal analog / digital converter (4) for sampling a complex video signal input from the outside and converting the composite video signal into a digital signal according to the system clock of the system clock generator (5); An audio signal analog / digital converter 6 for sampling the audio signal input from the outside according to the audio sampling clock and converting the audio signal into digital using a complement; A digital video signal band compressor (7) which receives the digital video signal from the video signal analog / digital converter (4) and band-compresses the amount of information of the digital video signal according to a differential pulse code modulation (DPCM) scheme; And receiving a digital audio signal from the audio signal analog / digital converter 6, a compressed video signal from the digital video signal band compressor 7, an audio multiple control signal from outside, and a DS3 (Dgital Signa13) synchronization clock. And a DS3 multiplexer (9) for outputting an audio sampling clock to the audio signal analog / digital converter (6) and constructing and outputting a DS3 frame. 2. The digital video signal band compressor (7) according to claim 1, wherein the digital video signal band compressor (7) is predicted by adding up the input digital video signal after the output of the predictor (7) passes through the leak portion (18), and the prediction error signal is quantized by a quantizer. When the compressed video signal is generated and isochronized, the compressed video signal is inversely engraved for prediction of the next signal, and the output of the inverse quantizer is combined with the output of the leak portion 18 and then passed through the clip portion l6. Transmission apparatus of a digital cable broadcasting system, characterized in that configured to be stored in the predictor (17). 3. The DS3 multiplexer (9) according to claim 2, wherein the DS3 multiplexer (9) is configured to output a pair of pseudo-emitter common logic (ECL) data and a transmission clock and output a bipolar DS3 line signal. Transmission device of digital cable broadcasting system, characterized in that there is.