JPH05153424A - High-definition television signal processor - Google Patents

Abstract

PURPOSE:To easily detect the signal level of a frame pulse and to simplify the configuration by using only the signal level of the frame pulse of a 1st line of a band compressing signal. CONSTITUTION:The initial adjustment is implemented, e.g. at the time of the factory shipping of products. An adjustment BS tuner is connected to an input terminal IN and a MUSE signal A is inputted from the BS tuner. The frame pulse FP1 of a 1st line in this case is inputted to a comparator circuit 9 as a frame pulse signal VE through a latch 7 and a D/A converter 8. Thus, a reference voltage source 10 is adjusted manually and a reference level signal Vref is set so that a proper amplitude level is obtained by an A/D converter 4 with a level control signal G outputted from the comparator circuit 9. Even when the signal level of the frame pulse FP1 of the MUSE signal A inputted successively is fluctuated, the fluctuation component is detected by the comparator circuit 9, the level control signal G representing the difference is imparted to a control amplifier 2, in which automatic adjustment is implemented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is applicable to high definition or H
The present invention relates to a signal processing device suitable for a receiver for high definition television broadcasting such as DTV (High-Definition Television),
More specifically, MUSE (Multiple Sub-Nyquist Samplin
g Encoding) ALC (automatic level control) circuit of frame pulse (video frame synchronization signal) in a decoder.

[0002]

2. Description of the Related Art In recent years, high-definition broadcasting has been developed as TV (television) broadcasting of high-definition images. High-definition broadcasting has a large screen aspect ratio of 16: 9 on the TV receiver and 112 scanning lines.
It is a system for transmitting high-definition TV signals such as five lines, and its transmission standard is significantly different from the conventional NTSC system.

A high-definition signal is a BS (Broadcasting) signal.
Satellite: Broadcasting satellite) is used to transmit to each customer, but the transmission band of the high-definition signal is 5 of the current TV broadcasting.
BS1 with high definition signal that requires more than double
It is not possible to transmit with the bandwidth of the channel.

Therefore, as a signal band compression method for enabling transmission of high-definition signals by BS, MUS is used.
E method has been developed and is widely known ("Development of MUSE method" NHK Technical Research Vol. 39, No. 2, Se
r. No. 172, 1987 reprint, "Hi-Vision Satellite Transmission System-MUSE-", Television Society Journal, Vol. Four
2, No. 5, 1988 etc.). The MUSE method is 8.1 MH with multiple sub-sampling of high-definition signals.
This is a method of analog transmission after compression in the z transmission band.
This band-compressed signal is called a "MUSE signal". The MUSE signal transmitted from the broadcasting system is received by the BS tuner and then decoded by the MUSE decoder into the original high-definition signal.
The signal is down-converted to the standard television signal and displayed on the display screen.

An important point in such a MUSE transmission system is strict or accurate control of the amplitude level of the input signal of the MUSE decoder. That is, this is because the MUSE transmission system is a system premised on performing non-linear processing such as non-linear emphasis and completely restoring the transmission signal using complementary characteristics between the MUSE encoder and the MUSE decoder. Therefore, the level control of the input signal of the MUSE decoder is
It must be done accurately because of the effect on the image quality.

The level error of the transmitted MUSE signal is also caused by the difference in the signal level of the output stage of the BS tuner placed before the MUSE decoder. That is, the level of the output signal amplitude of the connected BS tuner is slightly different depending on the model and the like, and each has a certain tolerance. Therefore, in order to reproduce a high quality image, the output signal level of the connected BS tuner and the MUS
The input signal level of the E decoder must be matched.

Due to such a request, the MUS has been generally used in the past.
The input stage of the E decoder is provided with an ALC circuit for automatically absorbing and adjusting the difference (or fluctuation) in the signal level of the input MUSE signal.

An example of a conventional ALC circuit is shown in FIG.
As shown in, signal levels a (quantization level 239/256) and b (quantization level 16/256) of the frame pulses FP ₁ and FP ₂ existing in the first and second lines of the input MUSE signal. To calculate a level error between the signal levels a and b and the input level of the A / D converter on the MUSE decoder side, and control the reference voltage of the A / D converter by the calculated error signal. These are known (for example, see Japanese Patent Laid-Open No. 1-226284).

[0009]

The conventional ALC circuit described above uses two reference voltages as reference voltages of the A / D converter, and the reference voltages are arranged so as to change symmetrically with respect to the reference potential. It uses a control circuit.

However, according to such a configuration,
A circuit for detecting the frame pulses FP ₁ and FP ₂ of the first line and the second line, which are in opposite phase to each other, may be complicated. Further, since the reference voltage of the A / D converter is controlled, the reference voltage itself of the A / D converter changes due to the malfunction of the ALC circuit, and the A / D conversion operation in the proper dynamic range is not performed. , It may cause discoloration of the reproduced image.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a high definition television signal processing device which can easily detect the signal level of a frame pulse and can simplify the structure.

[0012]

In order to solve the above problems, the present invention provides a signal of a frame pulse of a first line (or a second line) of a band-compressed signal in which a signal level fluctuation of a frame pulse is transmitted. This level 1
The determination is made based on the relative level between the frame pulse signal level of the line (or the second line) and the signal level of the frame pulse of another frame that is subsequently input.

That is, according to the present invention, a band-compressed signal of a transmitted high-definition television signal is converted into a digital signal by an A / D converter, and the high-definition television is converted based on the converted digital signal. In a high-definition television signal processing device for decoding into a John signal, a signal level which holds the signal level of the first video frame synchronization signal in the band compression signal input to the A / D converter as a reference value is adjustable. The level setting means is compared with the reference value and the video frame synchronization signal obtained from the output signal of the A / D converter to detect a variation in the signal level of the video frame synchronization signal, and the variation detection signal is output. Level fluctuation detecting means and a fluctuation amount of the signal level of the video frame synchronization signal based on the fluctuation detection signal. A automatic level control means for controlling the input signal level of the A / D converter to extinguish, configured with a.

[0014]

According to the present invention, the level setting means can adjust the reference value of the signal level to an arbitrary value, and at the time of this adjustment, the reference value is set to the first video frame synchronization signal, for example, the horizontal scanning period number. It is set to the signal level of the frame synchronization signal of the first line (or the second line).

During the signal processing operation of the high definition television signal processing device, the level fluctuation detecting means extracts the video frame synchronizing signal contained in the output signal of the A / D converter, and the extracted video frame synchronizing signal. And the reference value signal set as described above are compared with each other, the level fluctuation amount which is the difference between them is detected, and the fluctuation detection signal is output to the automatic level control means. The automatic level control means controls the input signal level of the A / D converter in order to cancel the fluctuation by the inputted fluctuation detection signal.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments according to the present invention will be described with reference to the drawings. [I] Circuit Configuration FIG. 1 shows an embodiment of a high definition television signal processing apparatus according to the present invention. In FIG. 1, the input terminal IN is BS
Connected to the output terminal of the tuner (not shown), 8.1M
The MUSE signal A band-compressed to Hz is input. The input MUSE signal A has unnecessary high frequency components cut by the LPF 1 of 8.1 MHz, and the filter output signal B thereof is sent to the control amplifier 2.

The control amplifier 2 is a variable voltage control amplifier (VC
The control amplifier output signal C having an appropriate amplitude level is output to the clamp circuit 3 based on a level control signal G from a comparison circuit 9 described later.

The clamp circuit 3 MUs by the clamp pulse H as the clamp level information of the horizontal line numbers 563 and 1125 supplied from the MUSE decoder 6.
The horizontal synchronizing signal (HD) period of the SE signal A is a clapp level, that is, 128 gradations (128/2) out of all 256 gradations.
56) is a circuit for regenerating the corresponding DC component by clamping it to 56), and the clamp output signal D is the A / D converter 4
Given to.

The A / D converter 4 is a PLL (not shown).
The sampling frequency is 16.2 depending on the pulse signal from the circuit.
The clamp output signal D which is a MUSE signal is sampled with MHz and 8-bit precision, the MUSE signal is converted into digital data, and the corresponding digital MUSE signal E is output.

A high-definition television signal processing device is A /
The digital MUSE signal E from the D converter 4 is latched by the clock signal of 16.2 MHz which is the same as the sampling frequency and output to the MUSE decoder 6. The digital MUSE signal E output from the latch 5 is simultaneously given to the latch 7.

As shown in FIG. 3, the latch 7 latches the data of the first frame pulse FP ₁ of the first line from the digital MUSE signal E as shown in FIG.
Output to the D / A converter 8.

The D / A converter 8 converts the input first frame pulse FP ₁ into an analog signal and sends the converted frame pulse level signal V _E to the comparison circuit 9. The comparison circuit 9 is a comparison circuit using an operational amplifier or the like, and includes a frame pulse level signal V _E and a reference level signal V _E.
Compare with _ref . The reference level signal V _ref is provided by the reference voltage source 10.

The reference voltage source 10 is, for example, a circuit that divides a constant voltage from an appropriate constant voltage source to generate a reference level signal V _ref , and uses a variable resistor or the like as a voltage divider to arbitrarily generate the generated voltage. It is possible to adjust the reference level signal V _ref .

The level control signal G generated by the comparison operation of the frame pulse level signal V _E and the reference level signal V _ref in the comparison circuit 9 is supplied to the control voltage input terminal of the control amplifier 2.

[Ii] Circuit Operation Next, the operation will be described. First, the initial adjustment will be described. Initial adjustment is performed, for example, when the product is shipped from the factory. A BS tuner for adjustment is connected to the input terminal IN, and the MUSE signal A is input from the BS tuner. At this time, the frame pulse FP ₁ of the first line is the latch 7, D
Frame pulse level signal V via the A / A converter 8
Since it is input to the comparison circuit 9 as _E , the reference voltage source 10
Is manually adjusted and the reference level signal V _ref is set by the level control signal G output from the comparison circuit 9 so that the A / D converter 4 has an appropriate amplitude level. By the above operation, the reference level signal V _ref is set to the signal level of the first frame pulse FP ₁ of the first line as shown in FIG.

Next, the operation of the high definition television signal processing apparatus at the time of receiving the MUSE signal A will be described. In the high-definition television signal processing device initialized as described above, the MUSE signals A that are sequentially input are fed to the LPF.
1 → Control amplifier 2 → Clamp circuit 3 → A / D converter 4 → Latch 5
The SE signal E is supplied to the MUSE decoder 6. MUSE
The decoder 6 restores the original high-definition signal by decoding the digital MUSE signal E and supplies it to the high-definition display device or the MUSE / NTSC down converter. At this time, the frame pulse FP of the MUSE signal A is caused by some cause, for example, the influence of the radio environment.
_If the signal level of ₁ fluctuates, the fluctuation is detected by the comparison circuit 9. Variation is the difference between the frame pulse level signal V _E and the reference level signal V _{re f,} the level control signal G indicating the difference control amplifier 2
Given to. The control amplifier 2 controls the gain so that the level control signal G becomes zero, and outputs the control amplifier output signal C having an appropriate level. The fluctuation of the frame pulse FP may decrease or increase, and the control amplifier 2 adjusts the gain according to each case.

In this way, a feedback loop is formed which starts from the output of the latch 5 and returns to the latch 7 → D / A converter 8 → comparison circuit 9 → control amplifier 2. In the comparison circuit 9, the frame pulse level signal V _E
And the reference level signal V _ref are compared with each other, and the function of initializing the reference level signal V _ref by the reference voltage source 10 exists in one loop. Therefore, adjustment at the time of shipment and automatic level at the time of actual operation are performed. Control can be realized in one loop. And since it is not necessary to incorporate a complicated ALC circuit in the MUSE-IC as in the conventional case, the MU
It is possible to simplify the SE-IC and the high-definition television signal processing device itself. Also, the frame pulse F
Since the detection of the level change of P only needs to be performed based on the frame pulse FP ₁ of the first line, the simplification of the detection operation can be achieved as well as the simplification of the circuit configuration. Further, unlike the conventional case, since the reference voltage of the A / D converter is not adjusted, the clamp level can always be set to the correct level, and the image discoloration may occur due to the fluctuation of the clamp level. Absent.

In this embodiment, the A / D converter 4
Since the input signal level is controlled by the control amplifier 2, it is resistant to malfunction due to disturbance noise.
Also, considering that the signal polarities are opposite, the HD line that is the target of frame pulse detection may be the second line, that is, the second frame pulse FP ₂ .

[0029]

As described above, according to the present invention, if the signal level of the frame pulse of either the first line or the second line is initially set as the reference value, the set reference value is set in actual operation. Since the input signal (not the reference voltage) of the A / D converter is controlled by the comparison operation with, the circuit configuration can be simplified and the clamp level does not fluctuate. It becomes possible to automatically adjust to the signal of.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of a conventional control level.

FIG. 3 is an explanatory diagram of a control level according to the present invention.

[Explanation of symbols]

1 ... LPF 2 ... Control amplifier 3 ... Clamp circuit 4 ... A / D converter 5 ... Latch 6 ... MUSE decoder 7 ... Latch 8 ... D / A converter 9 ... Comparison circuit 10 ... Reference voltage source A ... MUSE signal B ... Filter output signal C ... control amplifier output signal D ... clamp output signal E ... digital MUSE signal F ... television signal G ... level control signal H ... clamp pulse V _E ... frame pulse level signal V _ref ... reference level signal FP ₁ ... first frame Pulse FP ₂ ... 2nd frame pulse

Claims (2)

[Claims] 1. A band-compressed signal of a transmitted high-definition television signal is converted into a digital signal by an A / D converter, and is decoded into the high-definition television signal based on the converted digital signal. A high-definition television signal processing device, comprising: a level setting means capable of adjusting a signal level for holding a signal level of a first video frame synchronization signal in the band compression signal input to the A / D converter as a reference value. A level fluctuation detection that compares the reference value with a video frame synchronization signal obtained from the output signal of the A / D converter, detects a fluctuation in the signal level of the video frame synchronization signal, and outputs the fluctuation detection signal. Means for canceling the fluctuation of the signal level of the video frame synchronization signal based on the fluctuation detection signal. A high-definition television signal processing device comprising: an automatic level control means for controlling an input signal level of a D converter. 2. The high definition television signal processing apparatus according to claim 1, wherein the first video frame synchronization signal is a video frame synchronization signal of the first line in the horizontal scanning period. Signal processing device.