JP2808884B2 - Television signal converter - Google Patents

Description

The present invention relates to a high-definition television signal, MUSE (Muit).
An input of an ipul Sub-Nyquist Sampling (National Television) signal which is the current standard television signal is input.
The present invention relates to a television signal conversion device having a function of converting an audio signal into a signal, and suppressing audio output when horizontal synchronization of a high-definition television signal (MUSE signal) cannot be detected.

2. Description of the Related Art In recent years, as a high-definition television transmission method, a television signal having a transmission method different from the NTSC signal, which is a conventional television signal, such as a MUSE signal in which one image is sampled in four fields and transmitted, has been developed and used. It has become. Accordingly, it has become necessary to convert a MUSE signal into an NTSC signal and reproduce it on a conventional television receiver.

FIG. 5 shows a schematic block diagram of a conventional television signal converter. In FIG. 5, 1 is an external BS.
(Broadcasting Satellite) An A / D converter for converting a MUSE signal, which is an analog signal input from a tuner (not shown) through a terminal A, to a digital signal.
A video signal processing circuit for converting the output of the / D converter 1 into an NTSC signal. Terminal B is an NTSC signal from the video signal processing circuit 2.
A terminal 3 for connecting a signal output to an external monitor (not shown) has an audio signal processing circuit 3 for demodulating an audio signal separated by the video signal processing circuit 2, and an output 4 from the audio signal processing circuit 3. The terminal C is a terminal for connecting the audio signal from the mute circuit 4 to an external amplifier (not shown).

Next, the operation of the conventional television signal converter configured as described above will be described. In FIG. 5, a MUSE signal input from an external BS tuner is input terminal A.
The video signal is converted into a digital signal by the A / D converter 1 and converted into an NTSC signal by the video signal processing circuit 2,
Output to an external monitor through terminal B. At the same time, the audio signal separated by the video signal processing circuit 2 is demodulated by the audio signal processing circuit 3 and output to the mute circuit 4. In the mute circuit 4, the operation of muting the audio signal is switched by the mute signal output from the audio signal processing circuit 3, and the audio signal from the mute circuit 4 is output to the external amplifier through the terminal C.

However, in the above-described conventional television signal converter, the audio signal synchronization detection of the audio signal processing circuit 2 for the high-definition television signal (MUSE signal) is performed for each frame (vertical synchronization period). Moreover, since it is necessary to protect the synchronization to cope with the deterioration of the C / N ratio of the high-definition television signal (MUSE signal), the output timing of the mute signal is delayed, and the high-definition television signal (MUSE signal) There is a problem that a shock noise appears in the audio output when the signal is switched to a non-signal state.

The present invention solves the above-mentioned conventional problem. When a MUSE signal is input with a simple configuration and converted into an NTSC signal, when horizontal synchronization of a high-definition television signal (MUSE signal) cannot be detected. It is another object of the present invention to provide a television signal conversion device having a function of suppressing audio output.

Means for Solving the Problems In order to achieve the above object, a television signal converter according to the present invention has an A / D converter that inputs a high-definition television signal (MUSE signal) and converts it into a digital signal, A video signal processing circuit for converting a television signal (MUSE signal) into a current standard television signal (NTSC signal), an audio signal processing circuit for reproducing an audio signal, and a mute circuit for suppressing the audio signal; As means for detecting an HD (horizontal synchronization signal), an HD (horizontal synchronization signal) detection circuit is provided.

According to the television signal conversion device of the present invention, when the high-definition television signal (MUSE signal) is switched and becomes no signal, or when the signal becomes a signal other than the high-definition television signal (MUSE signal), the horizontal synchronization is performed. Can not be detected, the sound output can be suppressed, and the occurrence of sound shock noise can be prevented.

Embodiment 1 FIG. 1 shows a configuration of a television signal converter according to a first embodiment of the present invention. In FIG.
Parts common to those in the conventional example shown in FIG. 5 are denoted by the same reference numerals, and detailed description is omitted. From the signal output by the timing pulse output during the HD period from the video signal processing circuit 2
HD detection means for detecting HD (horizontal synchronization signal).

 Next, the operation of the above embodiment will be described.

FIG. 2 shows the HD signal (horizontal synchronization signal) in the MUSE signal which is a high-definition television signal and the HD signal from the video signal processing circuit 2.
FIG. 2A is a waveform diagram showing the timing of the timing pulse output during the period. FIG. 2A shows the relationship between the HD signal waveform when the MUSE signal is input from the terminal A and the timing pulse from the video signal processing circuit 2. 2B shows the relationship between the HD signal waveform and the timing pulse from the video signal processing circuit 2 when the MUSE signal is not input from the terminal A. As described above, when the MUSE signal is not input during the period of the timing pulse output from the video signal processing circuit 2 during the HD period, as shown in FIG.
, A mute signal is output to the mute circuit 4 and the sound power is suppressed.

FIG. 3 shows a configuration of a television signal converter according to a second embodiment of the present invention. In order to simplify the description, a case where the detection period of the HD signal is performed in three lines will be described. 3, the same parts as those of the conventional example shown in FIG. 5 are denoted by the same reference numerals, and the detailed description is omitted. 6
Is a D flip-flop for receiving the most significant bit (MSB) of the output of the A / D converter 1 and latching data with a timing pulse output from the video signal processing circuit 2 during the HD period. A D flip-flop 8 for latching output data of the D flip-flop 6 with a timing pulse output in the HD period from the video signal processing circuit 2, and 8 outputs the output data of the D flip-flop 7 from the video signal processing circuit 2. A D flip-flop 9 for latching with a timing pulse output during the HD period, 9 is an output of the D flip-flops 6 and 7
OR gate for OR, 10 for OR gate of D flip-flop 7 and D flip-flop 8, 11 for AND gate for ANDing OR gate 9 and OR gate 10, and AND gate 11
Is input to the mute circuit 4.

Next, the operation of the second embodiment will be described. Second
As shown in FIG. A, the HD waveform of the high-definition television signal is inverted for each line, and its level is converted into an 8-bit unit to be 192/256 at the maximum, 64/256 at the minimum, and A / A The most significant bit (MSB) of the D converter 1 is inverted for each line. Therefore, when a high-definition television signal is input from the terminal A, the D flip-flop 6, D flip-flop 7, and D flip-flop 7 The output of each of 8 is Hi (hereinafter abbreviated as H), Low (hereinafter abbreviated as L), H or L, H, L. At this time, the output of the AND gate 11 becomes H by the logic circuit including the OR gates 9 and 10. Also, when the outputs of the D flip-flops 6, 7, 8 are L, L, H or H, H, L, the output of the AND gate 11 becomes H. However, when the respective outputs of the D flip-flops 6, 7, 8 all match H, H, H or L, L, L, the output of the AND gate 11 becomes L. Therefore, when the output of the AND gate 11 is L,
That is, when the HD (horizontal synchronization signal) cannot be detected, the output of the AND gate 11 becomes L and is input to the mute circuit 4, and at this time, the mute circuit 4 is controlled to suppress the audio signal. .

FIG. 4 shows the configuration of a television signal converter according to a third embodiment of the present invention. In order to simplify the description, a case where the detection period of the HD signal is performed by two lines will be described. In FIG. 4, parts common to those in the second embodiment shown in FIG. 2 and the conventional example shown in FIG. 5 are denoted by the same reference numerals, and detailed description is omitted. In this embodiment, the D flip-flop 6 and the D flip-flop 8 are in parallel,
The configuration is such that data of the A / D converter 1 is input to both at the same timing. 12 is the D flip-flop 8
D flip-flop for latching output data of
13 is an inverter for inverting the timing pulse output from the video signal processing circuit 2 during the HD period and latching the D flip-flops 8 and 12, and 14 is the output of the D flip-flops 7 and 12 OR gate for OR, 15 is D flip-flop 8 and D flip-flop
An OR gate for ORing 12 and an AND gate 16 for ANDing the OR gates 9, 14, 15 are configured so that the output of the AND gate 16 is input to the mute circuit 4.

Next, the operation of the third embodiment will be described. Second
As shown in FIG. A, the HD waveform of the high-definition television signal is inverted for each line, and its level is converted into an 8-bit unit to be 192/256 at the maximum, 64/256 at the minimum, and A / A The most significant bit (MSB) of the D converter 1 is inverted for each line, and the rising and falling of the timing pulse from the video signal processing circuit 2 is inverted within one line. Therefore, when a high-definition television signal is input from the terminal A, the outputs of the D flip-flop 6, the D flip-flop 7, the D flip-flop 8, and the D flip-flop 12 are H, L, H, L or L, H, L, H, and the output of the AND gate 16 at this time becomes H. The outputs of the D flip-flop 6, the D flip-flop 7, the D flip-flop 8, and the D flip-flop 12 are output when all data such as H, H, H, H and L, L, L, L match. Otherwise, the output of the AND gate 16 becomes H as in the second embodiment. However, the outputs of the D flip-flop 6, the D flip-flop 7, the D flip-flop 8, and the D flip-flop 12 are AND when all data such as H, H, H, H and L, L, L, L match. The output of gate 16 is L
As in the second embodiment, the output of the AND gate 16 is input to the mute circuit 4, and at this time, the mute circuit 4 is controlled to suppress the audio signal.

In the second and third embodiments, the HD detection period is configured by two lines and three lines, respectively, and the audio signal is suppressed only when the data of all the D flip-flops match. However, the detection period of HD is increased, and the outputs of some D flip-flops among all D flip-flops are continuously H or L.
The effect is the same even if a logic circuit is configured so that the audio signal can be suppressed when the signal becomes.

As is clear from the above embodiment, the present invention adds a HD (horizontal synchronization signal) detection circuit as a means for detecting an HD (horizontal synchronization signal), so that a high-definition television (MUSE signal) can be realized. When switching to no signal or when a signal other than a high-definition television signal (MUSE signal) is detected, horizontal synchronization cannot be detected, suppressing audio output and preventing the occurrence of audio shock noise. While utilizing the characteristics of the synchronizing signal waveform of a high-definition television signal,
With a simple configuration including a flip-flop, an OR gate, and an AND gate, it is possible to realize a television signal conversion device provided with a mute means for suppressing an audio signal output when there is no high-definition television signal input. In a parallel configuration of flip-flops, a timing pulse for latching one D flip-flop and a latch signal supplied to the other D flip-flop via an inverter can be used to shorten the detection period of the horizontal synchronization signal. This is an excellent effect.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a television signal conversion device according to a first embodiment of the present invention, FIG. 2 is a waveform diagram showing the timing of an HD signal (horizontal synchronization signal) and a timing pulse from a video signal processing circuit, FIG. 3 is a schematic block diagram showing the configuration of a television signal conversion device according to a second embodiment of the present invention, and FIG. 4 is a television showing the configuration of the television signal conversion device according to the third embodiment of the present invention. FIG. 5 is a schematic block diagram of a signal conversion device, and FIG. 5 is a schematic block diagram of a conventional television signal conversion device. 1 ... A / D converter, 2 ... Video signal processing circuit, 3 ...
... Sound signal processing circuit, 4 ... Mute circuit, 5 ... HD detection means, 6,7,8,12 ... D flip-flop, 9,10,14,15
…… OR gate, 11,16 …… AND gate, 13 …… Inverter.

Claims (2)

(57) [Claims] 1. A high-definition television input as an analog signal in a television signal converter for receiving a high-definition television signal transmitted as an analog signal, converting the signal into a digital signal, and then converting the signal into a standard television signal. An A / D converter for converting a television signal into a digital signal; a video signal processing circuit for converting an output digital signal from the A / D converter into a standard television signal; and an audio signal separated by the video signal processing circuit. An audio signal processing circuit for demodulation; a mute circuit for suppressing an audio signal output from the audio signal processing circuit; and a timing pulse from the video signal processing circuit, each latched by an output digital signal of the A / D converter. A first D flip-flop to which the most significant bit of the signal is input and the first D flip-flop; A second D flip-flop to which the output of the flip-flop is input, a third D flip-flop to which the output of the second flip-flop is input, and a second D flip-flop to which the output of the second flip-flop is input. A first OR gate for ORing each output, a second OR gate for ORing each output of the second D flip-flop and the third D flip-flop, and an output of the first OR gate. Horizontal synchronizing signal detecting means comprising an AND gate for taking the AND of the output of the second OR gate. When the horizontal synchronizing signal of the high-definition television signal inverted for each line is input, The outputs of the first, second, and third D flip-flops are sequentially inverted, and the inputs of the AND gate do not match. When there is no horizontal synchronization signal input, the outputs of the first, second, and third D flip-flops do not match. Each output Controls the mute circuit according to the output from the AND gate of the horizontal synchronization signal detection means, which is configured so that the input of the AND gate does not invert, and when the horizontal synchronization signal is not detected, the mute circuit Is controlled so as to suppress audio signal output. 2. A high-definition television input as an analog signal in a television signal converter for receiving a high-definition television signal transmitted as an analog signal, converting the signal into a digital signal, and then converting the signal into a standard television signal. An A / D converter for converting a television signal into a digital signal; a video signal processing circuit for converting an output digital signal from the A / D converter into a standard television signal; and an audio signal separated by the video signal processing circuit. An audio signal processing circuit for demodulation; a mute circuit for suppressing an audio signal output from the audio signal processing circuit; and a timing pulse from the video signal processing circuit, each latched by an output digital signal of the A / D converter. A first D flip-flop to which the most significant bit of the signal is input and the first D flip-flop; A first flip-flop unit including a second D flip-flop to which an output of the flip-flop is input; and a timing pulse from the video signal processing circuit is applied as a latch signal via an inverter, and
The first flip-flop, comprising a third D flip-flop to which the most significant bit of the output digital signal of the A / D converter is input and a fourth D flip-flop to which the output of the third D flip-flop is input Second flip-flop means disposed in parallel with the flip-flop means; a first OR gate for ORing the outputs of the first D flip-flop and the second D flip-flop; A second OR gate for ORing the outputs of the flip-flop and the fourth D flip-flop; and an OR of the outputs of the second D flip-flop and the fourth D flip-flop
A third OR gate, and the first, second and third OR gates
Horizontal synchronizing signal detecting means comprising an AND gate for performing an AND operation of gates, wherein the first flip-flop means and the second flip-flop means arranged in parallel receive data from the A / D converter. The horizontal synchronization signal is input at the same timing to shorten the detection period of the horizontal synchronization signal in the horizontal synchronization signal detection means, and the presence / absence of the horizontal synchronization signal input of the high-definition television signal inverted for each line is determined by the input signal to the AND gate. The mute circuit is controlled by a detection signal output from the AND gate, and the mute circuit suppresses an audio signal output when a horizontal synchronization signal is not detected. Television signal conversion device.