JPH0244826A - Digital signal transmission equipment - Google Patents

Abstract

PURPOSE:To simplify equipment constitution by compressing a digital signal so as to record and reproduce it and interpolating lacked data so as to transmit interpolated compression data. CONSTITUTION:The output of an error correction circuit 28 is directly impressed on an interpolation circuit 32, and data which cannot be corrected in the error correction circuit 28 is interpolated. The interpolation circuit 32 complements data required by inter-frame or inter-frame interpolation. Since the interpolation circuit 32 executes interpolation and adds the error correction code for transmission to a signal and transmits it to a transmission line 40 without expansion- processing the signal reproduced from a magnetic tape 22 as a recording medium, the signal is given from a recording and reproducing system to a transmission circuit in a communication system in the form of a compression signal. Thus, the constitution of the equipment is simplified for an amount that compression and expansion is unnecessarily executed, and the deterioration of a signal quality can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital signal transmission device equipped with a digital recording/reproducing system.

[Conventional technology]

In recent years, digital tape recorders that digitize and record various signals such as video and audio have been actively developed and put into practical use.
Digitalization of transmission media has been actively researched, and some of it has been put into practical use.

However, when recording or transmitting video signals such as standard television signals in digital form, the amount of data becomes enormous, so it is common practice to use the statistical properties and visual characteristics of image information. Bandwidth compression technology is used to reduce the amount of data to a fraction of the size. Furthermore, since data errors occur due to noise in recording/reproducing systems and communication lines, error correction codes are used to detect and correct these errors. Furthermore, if a large amount of noise is mixed in, it may not be possible to correct it with error correction codes, but in the case of images, spatial or temporal correlation such as vertical correlation can be used. can fill in the missing parts of the data. This process is called interpolation.

Although these technologies are common to recording/reproducing systems and communication systems, different systems are often adopted in reality.

This is because the quality of the recording/reproducing system is significantly different from that of the communication @line, such as there are far more continuous burst-like errors. To explain in detail, the recording/reproducing system and the communication system each use their own compression method and error correction code, and the communication system (transmission circuit) from the recording/reproducing system to the communication system (transmission circuit)
At the time of passing the signal to the computer, the signal was converted back to a digital or analog video signal. Furthermore, if the encoding sampling rate is different between the recording/reproducing system and the communication system, it is necessary to first restore the signal to an analog signal or to interpose an interface circuit.

[Problem to be solved by the invention]

In this way, in the past, the recording and reproducing system and the communication system perform their own compression and decompression processing, and when a digital recording and reproducing system is incorporated into a digital transmission system, the system becomes larger and more expensive. Therefore, there is a risk that image quality will deteriorate due to repeated compression/expansion processing. That is, if the band compression method for recording and the band compression method for transmission are different, there is a high possibility that image quality will deteriorate. For example, subsampling may be performed using field offset method on one hand and line offset method on the other hand.
This is the case when the setting values of the quantizer for differential quantization are different.

Therefore, an object of the present invention is to provide a digital signal transmission device that does not cause the above-mentioned signal deterioration.

[Means to solve the problem]

A digital signal transmission device according to the present invention includes a band compression means for compressing a digital signal and outputting a compressed signal, a recording and reproducing means for recording and reproducing the compressed signal, and an interpolator for interpolating missing data in the recording and reproducing means. and a transmitting means for transmitting the compressed data interpolated by the interpolating means.

[Effect]

With the above means, the interpolation means performs interpolation without expanding the compressed signal, so recording, reproduction and transmission can be performed without repeating compression and expansion. Therefore, unnecessarily compressed
Since no expansion is performed, the configuration of the device is simplified, and deterioration of the signal crystal quality can also be prevented.

〔Example〕

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

FIG. 1 shows a block diagram of an embodiment of the present invention. In FIG. 1, an analog video signal is input to an input terminal 10, and the signal is digitized by an A/D converter 12. The band compression circuit 14 band-compresses the output data (digital video signal) of the A/D converter 12 by subsampling, differential encoding, etc., and reduces the amount of data to a fraction. The error correction code addition circuit 16 adds an error correction code to the output data of the band compression circuit 14, and the modulation circuit 18 digitally modulates the data using, for example, a scrambled NRZ method, and the output is recorded on a magnetic tape 22 by a magnetic head 20. Ru.

A recorded signal on the magnetic tape 22 is reproduced by a magnetic head 24 and demodulated by a demodulation circuit 26.

The error correction circuit 28 performs error correction according to the error correction code added by the error correction code addition circuit 16. The output of error correction circuit 28 is a compressed video signal. In the conventional example,
The output of the error correction circuit 28 is expanded by the expansion circuit, but in this embodiment, the output of the error correction circuit 28 is expanded by the interpolation circuit 3.
2 to interpolate data that could not be completely corrected by the error correction circuit 28. The interpolation circuit 32 supplements the necessary data by, for example, intra-frame or inter-frame interpolation.

When performing interpolation on a compressed signal, it may not be easy depending on the compression method, but there are cases where it is very easy to perform interpolation, such as line interpolation on a differential quantized signal. You can choose a combination of methods.

The output of the interpolation circuit 32 is then applied to a processing system for transmission. That is, the error correction code addition circuit 36 adds an error correction code for transmission, and the modulation circuit 38 performs modulation for transmission.

The output of the modulation circuit 38 is sent out on the transmission line 40. The transmission path 40 is, for example, an optical fiber or a communication satellite. The signal passing through the transmission filter 40 is demodulated by the demodulation circuit 42 of the receiving device, and the error correction circuit 44 is demodulated by the error correction code adding circuit 36.
Error correction is performed using the error correction code added in , and the expansion circuit 46 performs expansion processing corresponding to the band compression circuit 14 to restore the digital video signal. The interpolation circuit 48 interpolates the portion that could not be corrected even with the error correction code provided by the error correction code adding circuit 36. D/A converter 50
converts the output data of the interpolation circuit 48 into analog form and outputs it to the output terminal 52.

In the embodiment of FIG. 1, a magnetic tape 22 is used as a recording medium.
The interpolation circuit 32 performs interpolation on the reproduced signal without performing expansion processing, adds an error correction code for transmission, and sends it out to the transmission path 40. The signal is passed to the circuit in the form of a compressed signal,
Therefore, image quality deterioration due to repeated compression/expansion processing is eliminated.

FIG. 2 shows a block diagram of another embodiment of the present invention.

The same components as in FIG. 1 are given the same reference numerals. In this embodiment, on the transmitting side, a detour path 60 and a changeover switch 62 are used to enable a detour around the recording and reproducing system of the magnetic tape 22 (ie, the circuits 16 to 32). On the receiving side, the output of the error correction circuit 44 is applied to the interpolation circuit 64 to first interpolate uncorrectable data, and the output of the interpolation circuit 64 is sent to the recording/reproducing system 65 and its detour 64.
6, and a switch 68 selects the recording/reproducing system 65 and the detour 66. The output of the switch 68 is an expansion circuit 69
is applied, and decompression processing corresponding to the band compression in the band compression circuit 14 is performed. In the recording and reproducing system 65, 70 is an error correction code addition circuit, 72 is a modulation circuit, 74 is a recording head, 76 is a magnetic tape, 78 is a reproduction head, 80 is a demodulation circuit, 82 is an error correction circuit, and 84 is an interpolation circuit. can be,
It has the same effect as the circuits 16-32. That is, when configuring the illustrated transmitting/receiving circuit having both the transmitting side and receiving side functions, the circuits 16 to 32 and the recording/reproducing system 65
functions can be shared by one recording/reproducing system.

In the embodiment of FIG. 2, when the switch 62 is connected to the a-contact side, it operates in the same way as the transmitting side of the embodiment of FIG.

When the switch 62 is connected to the b contact side, the signal at the input terminal 10 is sent out through the transmission line 40 in real time.

On the other hand, on the receiving side, the interpolation circuit 64 first interpolates the data that could not be corrected by the error correction circuit 44. When the switch 68 is connected to the b contact side, the output of the interpolation circuit 64 is expanded by the expansion circuit 69, and the D/A converter 5
Return to analog signal with 0. When connecting the switch 68 to the a contact side, the output of the interpolation circuit 64 is connected to the magnetic tape 76.
Record it once. By performing interpolation processing on the compressed video signal in this manner, there is no need to repeat compression/expansion even when the received signal is once recorded on a recording medium.

In the embodiment shown in FIG. 2, the combination of switches 62 and 68 allows four types of usage.

In addition, in FIGS. 1 and 2, the magnetic head 2024;
, 78 are shown, but of course there may be a plurality of each, or they may be used for both recording and reproduction. Furthermore, a rotating head system such as a VTR may be used. Instead of the magnetic tape 22.76, a magnetic disk, an optical disk, etc. may be used.

In the above embodiment, the digital signal is
Although the system for transmitting video signals has been described, the present invention is of course applicable to systems for transmitting other digital signals such as audio signals.

〔Effect of the invention〕

As can be easily understood from the above explanation, according to the present invention, compression/expansion is not repeated during recording/reproduction processing and transmission processing, so the device configuration can be simplified, resulting in lower cost, smaller size, and lower power consumption. Furthermore, signal quality is not unnecessarily compromised.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the invention, and FIG. 2 is a block diagram of another embodiment of the invention. 10-input terminal 14-band compression circuit 16.36.7
0-Error correction code addition circuit 18.3872-Modulation circuit 20.24.74.7L-Magnetic hesode 22,76-
Magnetic tape 26.42゜8〇-Demodulation circuit 28.44
．． 82-Error correction circuit 32.4B, 64.84---
Interpolation circuit 46 Expansion circuit 52 - Output terminal

Claims (1)

[Claims] Band compression means for compressing a digital signal and outputting a compressed signal; recording and reproducing means for recording and reproducing the compressed signal;
A digital signal transmission device comprising: interpolation means for interpolating missing data in the recording/reproducing means; and transmission means for transmitting compressed data interpolated by the interpolation means.