JPH0654276A - Television signal input switching circuit - Google Patents

Abstract

PURPOSE:To automatically select the output of a MUSE/NTSC down converter. CONSTITUTION:A video output is extracted from the MUSE/NTSC down converter output inputted from a first private input terminal 12. A horizontal synchronizing signal is taken out by a synchronizing signal separating circuit 20, and the number of horizontal synchronizing signals forms is counted by a horizontal synchronizing signal counter 22. When the counted value of this counter satisfies a prescribed condition, a video signal discriminating circuit 24 discriminates the existence of an analog video signal in the MUSE/NTSC down converter video output and outputs a signal in the high level to a selecting circuit 26. The selecting circuit 26 selects the MUSE/NTSC down converter output in response to the signal in the high level from the video signal discriminating circuit 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television signal input switching circuit, and more particularly to a VTR capable of supporting high-definition broadcasting by connecting or incorporating a BS tuner and connecting a MUSE / NTSC down converter. The present invention relates to a television signal input switching circuit used in a television receiver or the like.

[0002]

2. Description of the Related Art Conventionally, some VTRs and television receivers to which a BS tuner is connected or built-in have an input terminal dedicated to a scramble decoder.
In this case, if the BS tuner channel is set to the scramble broadcast channel, the input from the scramble decoder dedicated input terminal is automatically selected. On the other hand, a VTR to which a conventional BS tuner is connected or built-in
A television receiver, a television receiver, or the like has only a line input terminal as an input terminal for connecting a MUSE / NTSC down converter.

[0003]

Therefore, when trying to receive a high-definition broadcast by switching the channel of the BS tuner, the user has to manually select and switch the line input to which the MUSE / NTSC down converter is connected. There was a problem that it did not happen.

Therefore, the main object of the present invention is B
Simply select the channel of the S tuner and the MU will automatically
A television signal input switching circuit capable of selecting a television signal input from an SE / NTSC down converter.

[0005]

SUMMARY OF THE INVENTION The present invention is based on MUSE /
A dedicated input terminal for inputting a signal from the NTSC down converter, a signal detecting means for detecting that a signal is inputted from the dedicated input terminal, and a signal from the dedicated input terminal is selected according to the output from the signal detecting means. It is a television signal input switching circuit having an input selecting means for outputting.

[0006]

Function: The MUSE / NTSC down converter is connected to the dedicated input terminal of the MUSE / NTSC down converter. Then, the signal detecting means detects the high-definition signal input from the MUSE / NTSC down converter dedicated input terminal. An analog video signal output from a MUSE / NTSC down converter, for example, is used to detect the high-definition signal. This analog video signal is output from the MUSE / NTSC down converter when receiving high-definition broadcasting, but is not output when not receiving high-definition broadcasting. And, for example, MU
If the horizontal synchronizing signal of the analog video signal from the SE / NTSC down converter is counted and it is determined that the high-definition broadcast is being received when the count number exceeds a certain value, the determination becomes more reliable. . The input selection means, depending on the detection output of the signal detection means, MUSE / NT
The input from the SC down converter is selected and output.
In other cases, other input signals such as the output of the scramble decoder and the normal output of the BS tuner are selected and output.

[0007]

According to the present invention, the input from the MUSE / NTSC down converter is automatically selected only by setting the channel of the BS tuner to the high-definition broadcasting channel. No need for manual operation, eliminating the hassle.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a television signal input switching circuit 10 of this embodiment is incorporated in a VTR or a television receiver to which a BS tuner can be connected or built in, and a channel setting of the BS tuner is set. Depending on the MUS
The output of the E / NTSC down converter, the output of the scramble decoder, or the normal output of the BS tuner is automatically switched appropriately.

For this reason, the television signal input switching circuit 10 has a first dedicated input terminal 12 to which the output of the MUSE / NTSC down converter is input, a second dedicated input terminal 14 to which the output of the scramble decoder is input, and B.
It includes a BS tuner input terminal 16 to which the normal output of the S tuner is input. M input from the first dedicated input terminal 12
The output from the USE / NTSC down converter is input to the buffer 18, where the MUSE / NTSC down converter video output is extracted. This MUSE / NTS
Whether or not the channel of the selected BS tuner is set to the high-definition broadcasting channel is detected by the C down converter video output, that is, the presence or absence of the analog video signal. When receiving high-definition broadcasting, MUSE / N
An analog video signal is included in the TSC down converter output. Therefore, it can be determined whether or not the high-definition broadcast is being received depending on the presence or absence of the analog video signal.

That is, the MU extracted in the buffer 18
The SE / NTSC down converter video output is input to the sync separation circuit 20, where it is sync separated and a horizontal sync signal is extracted. The horizontal sync signal extracted by the sync separation circuit 20 is input to the horizontal sync signal counter 22. The horizontal synchronization signal counter 22 counts the number of horizontal synchronization signals for 1 millisecond. The count result of the horizontal synchronizing signal counter 22 is input to the video signal discriminating circuit 24. When the number of horizontal synchronizing signals for 1 millisecond is N, the video signal discriminating circuit 24 outputs a high level signal when the horizontal synchronizing signals of 6 ≦ N ≦ 26 are detected 10 times in succession. That is, at this time, it is determined that there is a video signal at the output of the MUSE / NTSC down converter, that is, that high-definition broadcasting is being received. If you are not receiving high-definition broadcast, basically MUSE /
The video signal is not included in the output of the NTSC down converter, but the number of horizontal sync signals is detected under the above conditions.
This is to detect the video signal more surely and correctly. Therefore, for example, even if the horizontal synchronizing signal is temporarily counted, the number of horizontal synchronizing signals of 6 ≦ N ≦ 26 is 1 in 1 millisecond.
If it is not detected 0 times in succession, the video signal determination circuit 24 outputs a low level signal without determining that the video signal is a video signal. Then, the high level signal or the low level signal output from the video signal discrimination circuit 24 is input to the selection circuit 26.

On the other hand, in the scrambled broadcast, when the image of the transmitted audio PCM signal of the SHF satellite broadcast is scrambled, all the 12th control bits of the encoded audio PCM signal are "1".
It is predetermined that all the video is "0" when the video is not scrambled. Further, it is predetermined that all the 8th bits of the range bits of the encoded audio PCM signal are set to high level when the audio is scrambled, and all are set to low level when the audio is not scrambled. There is. From this, by detecting the 12th bit of the control bit and the 8th bit of the range bit of the encoded audio PCM signal, it can be determined whether or not the scramble broadcast is being received.

That is, the audio PCM signal is extracted by the buffer 28 from the scramble decoder output input from the scramble decoder dedicated input terminal 14. The voice PCM signal extracted by the buffer 28 is input to the QPSK demodulation circuit 30. In the QPSK demodulation circuit 30, the voice P
The CM signal is converted into QPSK demodulated digital data. This digital data is input to the synchronizing circuit 32, where a 16-bit synchronizing pattern is detected. Then, a PN (Pseudo Noise) code generator (not shown) built in the synchronization circuit 32 operates in synchronization with the frame by the frame synchronization pulse, and the PN code on the QPSK demodulated digital data. Is removed,
The PN code should not affect the subsequent processing. Then, the reproduction signal from the synchronization circuit 32 is input to the integration correction circuit 34.

In the integration correction circuit 34, the reproduction signal from the synchronization circuit 32 is divided into 16 frames, and the 16th frame is an audio muting signal.
A majority decision is made for each of the 12th bit of the control bit and the 8th bit of the range bit by integrating every 5 frames. Then, the 12th bit of the control bit and the 8th bit of the range bit, which have been majority-determined, are individually input to the scramble discrimination circuit 36 configured by an OR gate. The 12th bit of the control bit and the 8th bit of the range bit input to the scramble determination circuit 36 are at high level if they are scrambled, and at low level if they are not scrambled. Then, the 12th bit of the control bit and the 8th bit of the range bit are ORed by the scramble determination circuit. As a result, the scramble determination circuit 36 outputs a high level signal when both the video signal and the audio signal included in the scramble decoder output are in the scramble state, or when either one of the video signal and the audio signal is in the scramble state. However, when both the video signal and the audio signal are in the non-scrambled state, a low level signal is output. Then, the high level signal or the low level signal output from the scramble determination circuit 36 is input to the selection circuit 26.

The selection circuit 26 includes a first dedicated input terminal 1
2, the television signal from the second dedicated input terminal 14 or the BS tuner input terminal 16 is input. Then, in the selection circuit 26, when the output of the video signal discrimination circuit 24 is at a high level, MUSE / from the first dedicated input terminal 12
When the NTSC down converter output is selected and the output of the scramble determination circuit 36 is at high level, the scramble decoder output from the second dedicated input terminal 14 is selected. Then, when the outputs of the video signal processing circuit 24 and the scramble determination circuit 36 are both at the low level, the selection circuit 26 selects the normal output from the BS tuner input terminal 16.

In the embodiment shown in FIG. 1, MUSE / NTS is used.
A dedicated input terminal is provided for each of the C down converter output and the scramble decoder output to perform reception detection. However, if not particularly required, scramble broadcast reception detection using the scramble decoder dedicated input terminal is not performed. Good.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

[Explanation of symbols]

 10 ... Television signal input switching circuit 12 ... First dedicated input terminal 20 ... Sync separation circuit 22 ... Horizontal sync signal counter 24 ... Video signal discrimination circuit 26 ... Selection circuit

Claims (1)

[Claims] 1. A dedicated input terminal for inputting a signal from a MUSE / NTSC down converter, a signal detecting means for detecting input of a signal from the dedicated input terminal, and an output from the signal detecting means. A television signal input switching circuit comprising input selection means for selecting and outputting a signal from the dedicated input terminal.