JPH0730881A - Transmitter-receiver - Google Patents

Abstract

PURPOSE:To automatically correct an H sag generated in the case of transmission/reception. CONSTITUTION:When a video signal subject to scrambling is transmitted, a reference signal of a predetermined level is inserted into the video signal for a vertical blanking period. A reference signal detection circuit 2 at a reception side detects the reference signal from the received video signal and a subtractor circuit 4 subtracts the detected reference signal from the video signal. The result of subtraction is descrambled. Thus, even when an H sag takes place in the video signal, it is automatically corrected and picture quality is not deteriorated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitter / receiver, and more particularly to a transmitter / receiver having a transmitter for transmitting a scrambled video signal and a receiver for receiving and descrambles the transmitted video signal.

[0002]

2. Description of the Related Art Generally, in pay satellite broadcasting, a transmitting side scrambles and transmits a video signal, and a receiving side descrambles the received video signal. In a conventional receiver for pay satellite broadcasting, a known dispersal removing circuit is placed in front of a descramble circuit for descrambles a video signal.

[0003]

As described above, the conventional receiver for pay satellite broadcasting is provided with the dispersal removing circuit. However, when the dispersal removing performance is enhanced, H sag occurs. Easier to do.

However, in the conventional receiver for pay satellite broadcasting, the H sag generated at the time of reception has not been corrected and corrected. Therefore, when the descrambling process is performed on this video signal to replace the scanning lines, H
Since the video signal generated by the sag is switched to the left and right within the scanning line, discontinuous brightness and darkness is generated in the video signal along the scanning line direction. As a result, there is a drawback that horizontal bright and dark stripes appear on the entire screen and the image quality deteriorates.

The present invention has been made in order to solve the above-mentioned conventional drawbacks, and an object thereof is to provide a transmitting / receiving apparatus capable of automatically correcting H sag generated during transmission / reception.

[0006]

A transmitting / receiving apparatus according to the present invention comprises a transmitter for transmitting a scrambled video signal,
A transmitter / receiver having a receiver that receives and descrambles the transmitted video signal, and inserts a reference signal of a certain level into a vertical blanking period of the video signal when transmitting the video signal. And a receiver including a detector that detects the reference signal from the received video signal, and a receiver that includes subtraction means that subtracts the detected reference signal from the video signal. The result is that the result is descrambled.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a receiver which is a main part of an embodiment of a transmitting / receiving apparatus according to the present invention.
In the figure, the receiver is a scrambled video signal S
A / D converter 1 for analog / digital conversion of 1
A reference signal detecting circuit 2 for detecting a reference signal from the digitized video signal, and a memory 3 for storing the waveform of the detected reference signal.

The receiver further includes a subtraction circuit 4 for subtracting the waveform read from the memory 3 from the video signal, a descrambling processing circuit 5 for descrambling the subtraction result, and a reference signal detection circuit. 2 and a control circuit 6 for controlling the signal writing / reading timing of the memory 3.

In a transmitter (not shown) such as a broadcasting station, it is assumed that a reference signal of a constant level is inserted in the video signal in advance.

In such a configuration, the analog scrambled video signal is digitized by the A / D converter 1. The reference signal is detected by the reference signal detection circuit 2 from the digitized video signal. As shown in FIG. 2, the reference signal is a video signal inserted in the vertical blanking period and having a constant level in the horizontal video period. Since this signal is inserted in advance by the broadcasting station, is there.

Here, consider a case where H sag is generated in the video signal and the input of the reference signal detection circuit 2 is as shown in FIG. The reference signal detection circuit 2 detects the reference signal, converts it into a difference signal with the minimum value as the reference (0 level), and outputs it. Therefore, a signal corresponding to H sag is output.
Then, the output signal of the detection circuit 2 becomes as shown in FIG. The memory 3 stores the signal of FIG. 4 and does not change it until the next reference signal is detected.

The waveform stored in the memory 3 is read every time in synchronization with the horizontal video period, and is input to the subtraction circuit 4.
The subtraction circuit 4 subtracts the waveform output from the memory 3 from the received video signal.

Here, when the H sag is occurring, the video signal shown in FIG. 5 (A) is transformed as shown in FIG. 5 (B). Therefore, by subtracting the waveform shown in FIG. 4 from the waveform shown in FIG. 5B every time in synchronization with the horizontal video period, as shown in FIG. 5C. , H sag corrected video signal is obtained.

The H-sag-corrected video signal as described above is applied to the descramble processing circuit 5, and the descrambled video signal S2 is output. Therefore, even if H sag occurs in the video signal, it is automatically corrected.

In this case, since the received video signal is corrected according to the H sag that actually occurs, the correction can be surely performed.

[0017]

As described above, the present invention has an effect that the image quality of the video descrambled by pay broadcasting can be prevented from being deteriorated by subtracting and correcting the H sag.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a transceiver according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing a reference signal.

FIG. 3 is a waveform diagram showing a reference signal in which H sag has occurred.

FIG. 4 is a waveform diagram showing only the H sag component extracted from the signal of FIG.

5A is a normal video signal, and FIG. 5B is H.
FIG. 3C is a waveform diagram showing a video signal in which sag has been generated, and FIG.

[Explanation of symbols]

 1 A / D converter 2 Reference signal detection circuit 3 Memory 4 Subtraction circuit 5 Descramble processing circuit

Claims (2)

[Claims] 1. A transmission / reception device comprising a transmitter for transmitting a scrambled video signal and a receiver for receiving and descrambles the transmitted video signal, wherein the video signal is transmitted when the video signal is transmitted. A transmitter including a reference signal inserting means for inserting a reference signal of a constant level, a detecting means for detecting the reference signal from the received video signal, and a subtracting means for subtracting the detected reference signal from the video signal. And a receiver including and the result of the subtraction is descrambled. 2. The transmitter / receiver according to claim 1, wherein said reference signal inserting means inserts said reference signal within a vertical blanking period of said video signal.