JPH11266452A - Composite television signal transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the occurrence of erroneous correction and impossible signal decoding in a TV receiver by arranging signals in an effective scan period and signals on a prescribed line in a vertical retrace period into the same signal order as a transmission part in a reception part to restore an original composite TV signal. SOLUTION: Multiple data (i) is given to a multiple data separator 13. The output of a compressed data buffer 14 is given to a picture decoder 16 and is decoded to become a decoded video signal (j) and is given to one contact of a switch SW1 and a line decoder 17. A non-compressed data buffer 15 whose enable terminal a signal corresponding to the timing of the vertical retrace period of the decoded video signal (j) is given to outputs various signals inserted in the vertical retrace period. These signals and the decoded video signal (j) are switched by a switching signal (k) to become a digital composite TV signal 1, and it is given to a DA converter 19 through a component composite converter 18 to become a composite TV signal a'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television signal transmission system for transmitting a composite television signal using a digital line.

[0002]

2. Description of the Related Art Broadcast waves (VHF band and UHF band radio waves) have been used for the purpose of eliminating difficult viewing areas and expanding service areas.
Has been put to practical use, after being received in a place with good reception conditions, relayed and transmitted to a destination by modulation using a microwave band such as SHF, and delivered again to ordinary homes as broadcast waves. . Hereinafter, an example of the relay system will be described with reference to FIG. The broadcast radio wave x radiated from the broadcast antenna 100 is received and viewed by the television receiver 200 in a general home where the antenna can be seen.
However, in order to make it possible to receive even a distant television receiver 200 ′ in which the broadcast signal x does not directly reach San-in or the broadcast radio wave x, A
The television signal received at the relay station on the mountain is transmitted to the relay station on the mountain B using the microwave y, and transmitted again from the relay station on the mountain B as the broadcast radio wave x ′. The above is an example of an analog-based relay system that has been conventionally used. However, conventionally, since all transmission systems are of the analog type, the broadcast radio wave is affected by external noise, fading, or ghost, and the quality of the received image is degraded. It is difficult to make these corrections because their effects accumulate according to the number of relay stages.

In recent years, digitalization of systems has been promoted for the purpose of effective use of radio wave resources (frequency bands) and stable operation of systems. In wireless transmission, in particular, the development of digital modulation schemes has been actively pursued, and the frequency band of one analog line is digitally modulated, and a video signal coded with high efficiency is multiplexed and transmitted on this line, thereby enabling transmission of two or more channels. It is becoming possible. Also, with the advancement of error correction technology, an error-free environment can be easily constructed. Further, with regard to high-efficiency coding, a high-efficiency coding method for video signals and audio signals conforming to the international standard for moving image compression (such as the MPEG2 method) has been put to practical use. As described above, by integrating the digital transmission technology and the high-efficiency encoding technology of the video signal, a high-quality long-distance transmission system that cannot be realized by the analog system can be realized.

By the way, at present, when a terrestrial broadcast wave is received and demodulated into a composite television signal, an effective video signal is obtained.
In addition to (images in the range visible on the screen), various signals as shown below are inserted in the vertical blanking period (portion not visible on the screen). -VITS (Vertical Interval Test Signal): Analog signal for maintaining line quality such as color bars-Character multiplexed signal: 5.73 Mbps (color subcarrier 8)
GCR signal (Ghost Canceller Reference): Reference signal of analog waveform for ghost cancellation • I and Q signals (program monitoring and switching signals) • Others, extended data service, closed caption, V chip ( However, the above-mentioned MPEG2 method is a standard for efficiently compressing only the video signal in the effective scanning line period, and is used in the vertical blanking period of the composite television signal. The included signals as described above are not subject to compression. Further, the compression method of MPEG2 employs a basic algorithm called block coding, which collectively processes eight pixels in each of horizontal and vertical directions. For this reason, if the same compression processing as that of the image signal is performed on the reference signal inserted in the vertical blanking period, there is a drawback that the data amount increases since there is no correlation for each line. Furthermore, since a reference signal such as a GCR is distorted by compression, a problem occurs that the reference signal cannot be used as a decoded reference signal.

[0005]

As described above, according to the prior art, when a composite television signal is transmitted to a distant place using a digital line, various auxiliary signals included in a vertical blanking period are processed by the same algorithm as a video signal. Cannot be compressed and transmitted. Furthermore, it is not clear what type of signal will be inserted during the vertical retrace interval due to future technological advances. For this reason, a method of efficiently transmitting only a specific signal (for example, character data) is not always optimal for analog signal transmission, and may not be accepted by future systems. The present invention eliminates the disadvantage that, when digitally transmitting a composite television signal, various types of signals during the vertical blanking period are compressed, waveform distortion and the like are added, and a television receiver cannot perform erroneous correction or signal decoding. It is another object of the present invention to construct a highly reliable digital composite television signal transmission system.

[0006]

According to the present invention, in order to attain the above object, the transmitting side digitizes predetermined line information inserted during a vertical blanking period without compression and converts it into a component signal. Buffering temporarily, adding a timestamp as a reference of the time axis at the time of reproduction in the same manner as the compressed data of the video / audio, multiplexing the data into a bundle of data streams, and transmitting the data. The corresponding video / audio / uncompressed data is separated from the bundle of data streams and rearranged and restored on the same time axis. As a result, it is possible to provide a digital transmission system capable of reproducing a signal almost equivalent to a composite television signal obtained when receiving a broadcast wave even at a remote place.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of an embodiment of the present invention will be described below in detail with reference to FIG. First, the transmitting side will be described. The description of the processing of the audio signal is omitted here. The composite television signal a is provided to an AD converter 1 and a clock generator 2. The composite television signal a digitized by the AD converter 1 passes through a YC separator 3 and a composite component converter 4,
It is converted to a digital video signal b. Clock c (4fsc: 14.3MHz) and clock d (13.5MHz) used at this time
Are generated by the clock generator 2 based on the composite television signal a. The digital video signal b is provided to the image encoder 5 and the non-compression processing circuit 6. The compressed image output data e subjected to the compression processing by the image encoder 5 is temporarily stored in the transmission-side compressed data buffer 7 and then supplied to the data multiplexer 8. Further, by giving the system clock f generated by the image encoder 5 to the time stamp generator 9, a time stamp g is generated and given to the data multiplexer 8. On the other hand, the digital video signal b supplied to the non-compression processing circuit 6 is supplied to the gate circuit 10 and the transmission side line decoder 11.

Here, the transmission-side line decoder 11 applies an image valid period (525/60) to a predetermined line in a vertical blanking period (first field: 14 to 21 lines, second field: 277 to 284 lines). A gate signal h corresponding to 720 samples is generated and supplied to the gate circuit 10. As a result, the gate circuit 10 gates various signals inserted into a predetermined line during the vertical blanking period, and the output of the gate circuit 10 is temporarily stored in the transmission-side uncompressed data buffer 12 and then is subjected to data multiplexing. To the vessel 8. Then, the data multiplexer 8 gives a time stamp g as a reference on the time axis to the compressed data from the transmission-side compressed data buffer 7 and the uncompressed data from the transmission-side uncompressed data buffer 12. The important thing here is that
The time stamp for compressed data is given in consideration of the principle processing delay time required for encoding / decoding. The reason for this is that uncompressed data arrives at the data multiplexer 8 with almost no processing delay, whereas compressed data is delayed by a few frames depending on the compression algorithm. Thus, the multiplexed data i is output from the data multiplexer 8. Although a detailed description is omitted here, the multiplexed data i is transmitted to the destination via a digital modulator, a microwave transmission line, or a wired transmission line thereafter. The output of the digital demodulator at the destination is
As a result of the error correction, the multiplexed data i becomes the same as that at the time of transmission.

Next, the operation on the receiving side will be described. The multiplexed data i is supplied to the multiplexed data separator 13, and the compressed data and the time stamp for the compressed data are stored in the compressed data buffer 14 on the receiving side in accordance with the identification code added to the head of the data. Buffer 15
Are respectively given uncompressed data and a time stamp for uncompressed data. Receive side compressed data buffer 1
The output of No. 4 is supplied to the image decoder 16 and subjected to a decoding process to become a decoded video signal j. This decoded video signal j is supplied to one of the switches SW1 and the receiving-side line decoder 17. The receiving-side line decoder 17 converts the decoded video signal j into a vertical blanking period (first field: 14 to 21).
Line, 2nd field: 277-284 line)
, And a corresponding signal is supplied to the enable terminal of the receiving-side uncompressed data buffer 15. As a result, various signal data inserted in the vertical blanking period appear in the output of the receiving-side uncompressed data buffer 15. Then, the switching signal k generated by the receiving side line decoder 17 is output.
Thus, by switching between the decoded video signal j and the output of the receiving-side uncompressed data buffer 15 connected to the other side of the switch SW1, a digital decoded television signal l having the same format as the input signal on the transmitting side is obtained. Become.

Further, the digital decoded television signal l
Is applied to the DA converter 19 via the component / composite converter 18 to obtain a composite television signal a ′. After that, processing such as modulation for transmitting as broadcast radio waves is performed again, but the description is omitted here. As described above, according to the present invention, predetermined line information in a vertical blanking period is digitized without compression, converted into a component signal, temporarily buffered, and then temporarily buffered in the same manner as compressed video / audio data. Attach a time stamp as a reference of the time axis at the time of reproduction, multiplex and transmit the data stream in a bundle, separate video / audio / uncompressed data from the data stream in the bundle, It is designed to be rearranged and restored. As described above, since various signals in the vertical blanking period are not compressed, there is no problem that a television receiver cannot perform erroneous correction or signal decoding, and a highly reliable digital composite television signal transmission. A system can be built.

[0011]

As described above, according to the present invention, it is possible to efficiently transmit a compressed video signal and various reference signals and data inserted in a vertical blanking period using the same bundle of digital transmission lines. Can be. As a result, a highly reliable digital composite television signal transmission system can be constructed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of the present invention.

FIG. 2 is a block diagram showing an example of a conventional system.

[Explanation of symbols]

1: AD converter, 2: Clock generator, 3: YC separator, 4: Composite component converter, 5: Image encoder, 6: Non-compression processing circuit, 7: Transmission side compressed data buffer, 8: Data multiplexing 9: time stamp generator, 10: gate circuit, 11: transmission side line decoder, 12: transmission side uncompressed data buffer, 13: multiplexed data separator, 14: reception side compressed data buffer, 15:
Receiving side uncompressed data buffer, 16: image decoder, 1
7: receiving side line decoder, 18: component composite converter, 19: DA converter, SW1: switcher.

Claims (3)

[Claims] 1. In transmitting a composite television signal,
A circuit for compressing a signal in an effective scanning period, a circuit for decompressing a signal on a predetermined line in a vertical flyback period, and a bundle of compressed data obtained by the compression process and uncompressed data obtained by the non-compression process. A transmission unit having a circuit for multiplexing the multiplexed data and a circuit for transmitting the multiplexed data, a circuit for separating the received multiplexed data into the compressed data and the uncompressed data, and decoding the signal of the effective scanning period from the compressed data And a receiving unit having a circuit for restoring a signal of a predetermined line in the vertical blanking period from the uncompressed data, and the receiving unit includes a signal in the effective scanning period and a signal in the vertical blanking period. A composite television signal transmission system characterized by reconstructing an original composite television signal by arranging signals of a predetermined line in the same signal order as in the transmission unit. 2. The composite television signal transmission system according to claim 1, wherein a signal of an arbitrary line in a vertical retrace period is transmitted / restored using a component (base signal of a luminance signal and a chrominance signal) signal. A composite television signal transmission system characterized in that: 3. The composite television signal transmission system according to claim 1, wherein a time stamp is added to each of the compressed data and the uncompressed data so as to maintain a time relationship during reproduction. John signal transmission system.