JP2630872B2 - Television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television signal converter for converting a television signal into a second television signal having a different aspect ratio. In particular, MUSE (Multiple Sub-Nyquist-Sam) having an aspect ratio of 16: 9.
pling Encoding) The signal is converted to NTS with an aspect ratio of 4: 3.
The present invention relates to a television receiver provided with a MUSE / NTSC converter for converting into a C signal.

[0002]

2. Description of the Related Art Hi-vision, which is the next-generation high-definition television, is being broadcast in satellite broadcasting. This Hi-Vision signal is band-compressed by a band compression technique called the MUSE method. The compressed signal (hereinafter, referred to as a MUSE signal) is being broadcast.

[0003] However, since the MUSE broadcast is not compatible with the current television broadcast, it cannot be received by the current television receiver.

[0004] In order to watch the MUSE broadcast on a normal NTSC television receiver, there is a MUSE / NTSC converter 100 as shown in FIG. This MUSE / NTSC converter 100 converts a MUSE signal into an NTSC signal. In addition, this MUSE / NTS
The operation of the C converter is described on pages 31 to 45 of the magazine "Television Technology October 1989" published by Electronic Technology Publishing Co., Ltd.

[0005] The aspect ratio of a Hi-Vision signal is 16: 9 as shown in FIG. 4A. And NTS
The aspect ratio of the C television signal is 4: 3. For this reason, when displaying the current Hi-Vision image on an NTSC television receiver, a mode in which the screen on the side of the Hi-Vision screen is cut off as shown in FIG. There is a mode in which a ranking area b (visible blanking area) is provided (hereinafter, referred to as a wide mode). The blanking area b is usually set to a low (black) luminance level.

Generally, the wide mode shown in FIG. 4C is often used. This is because there is an advantage that the composition intended at the time of program creation on the transmission side in HDTV is also stored on the reception side.

Further, in the current NTSC television receiver, the level of the back porch is used as the luminance reference level. However, black level variation was observed,
When a so-called bright screen having a high average luminance level (hereinafter referred to as APL) of an image is used, a dark portion in the screen floats black due to a gray side, and when a low screen has a low APL, a black-side gradation is reproduced. An impossible black sink occurs.

In order to solve the problem, as shown in FIG. 2, an automatic black level correction circuit (for example, an I.S.
C: CX20125).

A specific description will be given with reference to the drawings. The pin in FIG. 2 has a luminance signal before black level correction, the pin has a first pulse which is at a high level during a retrace period, and the pin has a second positive polarity signal obtained by delaying a composite synchronization signal by a composite synchronization signal.
A pulse is input, and a luminance signal after black level correction is output to the pin.

The pedestal level of the back porch of the luminance signal input to the pin is clamped by the AND output of the first and second pulses in the pedestal clamp circuit 6a.

The luminance signal is amplified by an amplifier circuit 6b, and a blanking circuit 6c for changing a signal other than the luminance signal to near a white level in order to accurately peak-hold the luminance signal by the first pulse. Through
Black peak hold circuit 6 for holding a black peak of a luminance signal
is input to d.

Then, one of the outputs of the black peak hold circuit 6d passes through the limiter circuit 6e and becomes a voltage corresponding to the black level most, so that the pedestal clamp circuit 6a
Is compared with the voltage obtained by the comparison circuit 6f. An error signal is detected by this comparison, and the gain of the black signal obtained by slicing the luminance signal by the black detection circuit 6g at about half the luminance level is used as the gain control circuit 6h.
To change.

The above operation performs black extension of the luminance signal.

APL is detected by the APL detection circuit 6j from the luminance signal subjected to the black extension, and the APL is detected.
A DC rate correction pulse proportional to PL is generated. This DC transmission rate correction pulse is applied to the back porch of the luminance signal by the transmission rate correction circuit 6k.

However, the first pulse is input to the APL detection circuit 6j as a control signal. When the first pulse is at a high level, the APL detection circuit 6j
Is set to not work. Similarly, the first pulse is also input to the blanking circuit 6c as a control signal, and is set so as not to affect the black peak hold circuit 6d when the first pulse is at a high level. .

Accordingly, the pin outputs a luminance signal which is black-extended and whose transmission rate is corrected. That is, a signal obtained by correcting the black level of the luminance signal is obtained by the black level correction circuit 6.

Therefore, the black level used in the next stage from the circuit 6 changes by the transmission rate pulse.

Therefore, it is possible to prevent black sunken or black floating.

[0019]

However, when a MUSE signal having an aspect ratio of 16: 9 is reproduced in a wide mode using a converter on a television receiver having an aspect ratio of 4: 3, when a black level correction circuit is used, When the APL detection circuit operates in the upper and lower blanking areas with a low luminance level, the APL becomes low, and the transmission rate correction pulse does not have an appropriate value, so that it is impossible to perform an appropriate black level correction.

In addition, there is a problem that the brightness level of a blanking region generated vertically may change depending on the content of the image.

[0021]

SUMMARY OF THE INVENTION The present invention relates to a method for converting an input first television signal of a first system into a second television signal of a second system having a different aspect ratio. , A television signal converter for generating an image area where an image signal exists and a blanking area not appearing in the image signal, an APL detecting means for detecting an average luminance level of an image, and an output of the APL detecting means for outputting the luminance signal. And a black level correction circuit comprising a DC rate correction means for adding a DC rate correction pulse corresponding to the image signal, determines whether the image area is a blanking area that does not appear in the image signal. When the output of the determination means is a determination output indicating that the area is an image area, the APL circuit is operated, and a blank which does not appear in an image signal is provided. Is a television receiver controlled composed to stop if the determination output the APL circuit indicating the ring area.

[0022]

According to the present invention, when a high-vision signal having an aspect ratio of 16: 9 is received in a wide mode in a television receiver having an aspect ratio of 4: 3 for NTSC, an APL is provided in a blanking area having a low luminance level. The control circuit controls the detection circuit and the black peak hold circuit so that the black level correction circuit operates properly only in the image area.

[0023]

FIG. 1 is a block diagram of a television receiver according to an embodiment of the present invention. The same parts as those in the related art are denoted by the same reference numerals, and description thereof is omitted.

Reference numeral 1 denotes an A / D converter for converting an input analog MUSE signal into a digital signal.

2 is a MUSE converted into a digital signal.
MUSE / NTS for converting signals to NTSC signals
This is a C conversion processing circuit. M of the input digital signal
The USE signal is stored in the memory 2a for each screen. The MUSE signal is also input to the MUSE synchronization detection circuit 2b, and the synchronization signal obtained by the synchronization detection circuit 2b is input to the MUSE control circuit 2c as a control signal. The MUSE control circuit 2c outputs a signal for controlling writing of data of the MUSE signal to the memory 2a.

The synchronization signal of the NTSC synchronization generation circuit 2d is similarly input to the NTSC control circuit 2e.
The NTSC control circuit 2e outputs a signal for controlling reading from the memory 2a.

The MUSE synchronization detection circuit 2b and the NTSC
A synchronization signal is sent from the MUSE synchronization detection circuit 2b to the NTSC synchronization generation circuit 2d for synchronization with the synchronization generation circuit 2d.

The signal read from the memory 2a by the NTSC control circuit 2e is applied to a luminance signal filter 2f, (B-B), which applies a constant luminance level to a blanking area of the luminance signal to form a luminance signal of a digital signal.
(Y) A certain luminance level is given to a blanking area of a signal to form a (BY) digital signal (BY).
A constant luminance level is given to the signal shaping circuit 2g and the blanking area of the (RY) signal to provide the digital signal (RY).
The signal is input to a (RY) signal shaping circuit 2h. Then, as digital signals, output terminals 2
Output from 1, 22, and 23. Here, a control signal is sent from the NTSC control circuit 2e to each of the circuits 2f, 2g, 2
h.

Reference numeral 2i denotes a time expansion circuit for time-expanding the band-compressed MUSE signal.

Further, in the NTSC control circuit 2e, an area determination signal for determining a blanking area and an image area is output from a terminal 24.

Numeral 3 denotes a digital signal (that is, a luminance signal Y, two color difference signals (RY), (B-
Y)) is a group of D / A converters for converting the analog signals into analog signals.

Reference numeral 4 denotes an NTSC encoder to which a luminance signal Y and two color difference signals (RY) and (BY) are inputted, and a luminance signal Y and a chrominance signal used in an NTSC television receiver. Output C. Reference numeral 5 denotes a first pulse which receives the luminance signal Y to which the composite synchronization signal is added and goes high during the vertical and horizontal retrace periods, and a second pulse which goes high during the horizontal synchronization signal and the vertical synchronization signal periods. This is a sync separation circuit that outputs.

10A is a wide mode discriminating means for outputting a signal discriminating between the wide mode and another mode.
B is a MUSE signal discriminating means for outputting a signal discriminating between the MUSE signal and the NTSC signal.

Numeral 7 denotes a discrimination signal from the wide mode discriminating means 10A which becomes high level when receiving an image having an aspect ratio of 16: 9 and becomes low level when receiving an image having an aspect ratio of 4: 3. , MUSE signal, and a low level when an NTSC signal is received. The AND circuit performs a logical product operation by inputting a determination signal from the MUSE signal determination means.
Reference numeral 8 denotes an input terminal to which a MUSE signal is input. SW1
Is a first switching means for conducting or non-conducting an area discrimination signal between the image area and the blanking area from the NTSC control circuit 2e according to the output of the AND circuit 7. The second switching means switches between a signal luminance signal and an NTSC luminance signal.

Reference numeral 9 denotes a logical sum circuit for performing a logical sum operation by inputting the area discrimination signal and the second pulse output from the sync separation circuit.

Next, the operation will be described separately for the case of receiving a Hi-Vision signal and the case of receiving an NTSC signal with reference to the drawings.

When the wide mode is selected at the time of receiving a high definition signal.

In this case, the aspect ratio is 16: 9, which is a MUSE signal. That is, a high level is input to the AND circuit 7 by each of the determination units 10A and 10B. Therefore, a high level is output from the AND circuit 7,
The first switching means SW1 conducts. Further, the second switching means SW2 switches to the MUSE signal side a.

Therefore, the MUSE input to the input terminal 8
The signal is input to the A / D converter 1 and converted into a digital signal.
The signal is input to the input terminal 20 of the TSC conversion processing circuit 2 and is converted into a wide mode NTSC digital signal. At this time, due to the difference in the aspect ratio, a blanking area b having a very low brightness level is provided above and below the screen as shown in FIG. 4C.
Is added. When this blanking area is indicated, a high level is output to the area determination signal output terminal 24.

The digital signal output of the NTSC standard is converted into an analog signal by the D / A converter group 3 respectively.

This analog signal is transmitted to the NTSC encoder 4
Is converted into a luminance signal and a chrominance signal.
Is input to the MUSE signal side a.

When the area determination signal is at the high level or the first pulse is at the high level, a high level signal is applied to the blanking circuit 6c and the APL detection circuit 6j of the black level correction circuit 6, and the black peak hold is performed. Circuit 6
For d, the black peak cannot be detected during that period, and the APL detection circuit 6j stops operating.

Therefore, the black level correction is prohibited outside the image area.

The case where the wide mode is not selected at the time of receiving the HDTV signal and the case of receiving the NTSC signal.

In this case, the area discrimination signal of the time axis conversion circuit 2b is always at the low level, and the area discrimination signal output terminal 2
4 always outputs a low level, and black level correction is prohibited only when the first pulse is at a high level, regardless of whether the first switching means is on or off.

Therefore, in the case of the wide mode, the APL can be detected not in the entire screen but in the image area excluding the blanking area from the entire screen.

Therefore, the low brightness level in the blanking area is not used for the APL detection circuit, and the black level correction is not performed in the blanking area, and the black level correction can be appropriately performed only on the image area.

[0048]

The present invention relates to a television receiver having a MUSE / NTSC converter, in which a television receiver having an aspect ratio of 16: 9 is provided with a blanking region above and below a 4: 3 aspect ratio, and a wide mode is provided. , The black level correction may not be performed in the upper and lower blanking areas.

[Brief description of the drawings]

FIG. 1 is a block diagram of a television receiver showing one embodiment of the present invention.

FIG. 2 is a block diagram illustrating a black level correction circuit.

FIG. 3 is a configuration diagram of a high-vision reception system.

FIG. 4 is a diagram illustrating a MUSE / NTSC conversion method.

[Explanation of symbols]

 Reference Signs List 1 A / D converter 2 MUSE / NTSC conversion processing circuit 2a Memory 2b MUSE synchronization detection circuit 2c MUSE control circuit 2d NTSC synchronization generation circuit 2e NTSC control circuit 2f Luminance signal filter 2g (BY) signal shaping circuit 2h (R- Y) Signal shaping circuit 2i Time expansion circuit 20 Input terminal 21, 22, 23, 24 Output terminal 3 D / A conversion circuit group 4 NTSC encoder 5 Synchronization separation circuit 6 Black level correction circuit 6a Pedestal clamp circuit 6b Amplification circuit 6c Blanking Circuit 6d Black peak hold circuit 6e Limiter circuit 6f Comparison circuit 6g Black detection circuit 6h Gain control circuit 6i Adder 6j APL detection circuit 6k Transmission rate correction circuit 7 Logical product circuit 8 MUSE signal input terminal 9 Logical sum circuit 100 MUSE / NTS Converter

Claims (1)

(57) [Claims] When converting an input first television signal of a first system into a second television signal of a second system having a different aspect ratio, an image signal is present due to the difference in the aspect ratio. A television signal converter for generating an image area and a blanking area not appearing in an image signal; APL detection means for detecting an average luminance level of an image; and a DC transmission rate correction pulse corresponding to an output of the APL detection means for a luminance signal And a black level correction circuit configured by a DC transmission rate correction means for adding an image signal, and a determination means for determining whether the image area is a blanking area not appearing in an image signal. If the output is a discrimination output indicating that it is an image area, the APL circuit is operated to indicate that it is a blanking area that does not appear in the image signal. Television receiver comprising control to to stop when the discrimination output the APL circuit.