JPH0346478A - Television signal converter - Google Patents

Abstract

PURPOSE:To improve the picture quality of an output of a simple MUSE down- converter by controlling a selector based on control information included in a high definition television signal and introducing selectively an input alternately for each field. CONSTITUTION:A MUSE signal is fed to an input terminal 101, digitized by an A/D converter 102 and inputted to an in-field interpolation circuit 103 and a synchronization reproduction and control signal decoding circuit 104. The interpolation processing is applied and the result is inputted to an in-field scanning line conversion section 105, in which the conversion to an interlace signal is processed. An output signal from a D/A converter 116 is fed to one input of a selector 112 via a delay circuit 111 and fed directly to the other input of the selector 112. An output of the delay circuit 111 and a direct signal are introduced at the selector 112 alternately switchingly for each field by an inter- field offset subsample phase signal from the synchronization reproduction and control signal decoding circuit 104.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) This invention is applicable to MUSE system, IDTV system, EDTV system, etc.
The present invention relates to a television signal conversion device that associates signals such as systems.

(Conventional technology) Advances in digital ICs, especially faster and larger memories,
Digital processing circuits for video signals are becoming popular as prices fall. Additionally, television receivers are required to have larger screens and higher definition.

Based on these demands, a completely new television system, MUSE (Multiple Sub-
NyqurstSampling Encoding)
A method has been developed. This method requires approximately five times the signal bandwidth of conventional television signals, so in order to be able to transmit the signal bandwidth for one broadcasting satellite channel,
Signal band compression is performed. This method performs band compression by performing offset subsampling on a high-definition television signal between fields and frames.

Therefore, a MUSE decoder equipped with a large capacity memory such as a frame memory is required on the receiving side.

FIG. 3 shows an example of the configuration of a MUSE decoder.

An input terminal 501 is supplied with a MUSE signal.

This signal is digitized by an A/D converter 502 using a clock having a sampling frequency of 16.2 Mt (z).

The output signal of the A/D converter 502 is sent to the frame memory 50.
4, the signal is supplied to a motion detection circuit 503, a selector 507, a field interpolation filter 505, and a synchronous reproduction and control signal decoding circuit 506.

A synchronization reproduction and control signal decoding circuit 506 reproduces a synchronization signal from the FvI USE signal and also decodes a control signal multiplexed and transmitted during the blanking period of the image signal. The control signal is
Interframe offset subsampling (hereinafter referred to as Fr03S) essential for decoding the MUSE signal
, interfield offset subsample phase (hereinafter referred to as Fi
(denoted as O3S) signals, etc.

A case will be described in which a still IL image portion is processed.

In the selector 507, according to the Fr03S signal obtained from the decoding circuit 506, the digitized MUSE
A switching selection is made between the signal and the signal delayed by one frame period in the frame memory 504, and 32.4Ml
It is output as an output signal of 1z.

This is called interframe interpolation.

The interframe interpolation output signal is input to a sampling frequency conversion circuit 510 via a low-pass filter (hereinafter referred to as LPF circuit) 508 having a cutoff frequency of 12 MHz, where the sampling rate is changed from 32.4 MHz to 48.6 MHz.
M) converted to Iz.

This signal is subsampled and outputted in a subsampling circuit 511 according to the FiO3S signal from the decoding circuit 506, and is supplied to a field memory 512, an IH delay memory 513, and an adder 515.

Adder 515 adds the output of IH delay memory 513 and the direct signal from sub-sampling circuit 511, takes an average value, outputs it, and supplies it to selector 516.

The selector 51B switches between the output from the adder 515 and the output from the field memory 512 according to the FiOSS signal from the decoding circuit 506, and outputs the original 48.
Obtain a signal with a rate of 6M1lz. This process is called in-field press.

Next, in the case of moving images, since temporal processing cannot be applied, the field interpolation circuit 505 interpolates and outputs the data according to the data within the field, and outputs it as a signal at a data rate of 32.4 MHz. In the interpolation process, F
Phase compensation for interframe offset subsampling is performed by using the r05S signal. Next, this output signal is converted into a 48.6 MHz signal by the sampling frequency conversion circuit 509 and inputted to the mixing circuit 517. This mixing circuit 517 mixes the output signal from the selector 518 and the output signal from the sampling frequency conversion circuit 509 at a mixing ratio according to the motion detection signal and outputs the mixture. This output No. 13 is input to a digital-to-analog converter (hereinafter referred to as a D/A converter), and is output as an analog signal.

FIG. 4 diagrammatically shows the processing progress of the MUSE signal.

For example, if the MUSE signal is to transmit a still image portion where the image changes in a stepwise manner, as shown in FIG. 4(F), the MUSE signal will be transmitted as shown in FIG. The bandwidth is compressed and transmitted. That is, offset subsampling is performed between frames, and offset subsampling is performed between fields. Solid lines are odd fields and dashed lines are even fields. Then, the signals shown in (A) and (B) in the figure are transmitted alternately for each frame. The sampling rate is 16.
2MIIz.

The decoder performs interpolation between frames (C
), the signal is converted to 32°4MHz. The part that performs this conversion is the selector 507 part. This signal is passed to a sampling frequency converter 510,
48.6 MHz signal ((D) in the same figure) f: converted,
Next, the sub-sample circuit 511 converts the signal into the signal shown in FIG. Then, in the selector 51B, the signal of the part marked with an "X" is interpolated between fields, and is output as a signal shown in FIG.

Frequency conversion is performed as in the signal in Figure 4 (D), and then subsampling is performed between fields as shown in Figure 4 (E), as can be seen by paying attention to the shaded pixels in Figure 4. This is because by performing interpolation, phase compensation is performed by interfield offset subsampling. In other words, this is to eliminate the phase shift of information between fields.

As mentioned above, the MUSE decoder is an extremely complex circuit, requires a large amount of memory, and is expensive. Furthermore, since the signals of the MUSE system are completely different from the signals of the current system, the images cannot be displayed on normal existing television receivers.

Therefore, a MUSE down converter is being developed that simply converts the MUSE system signal into the current television system.

FIG. 5 shows a conventional simple MUSE down converter.

A MUSE signal is supplied to an input terminal 701, and is digitized by an A/D converter 702 at a clock rate of 16.2 MIIz. The output of the A/D converter 702 is input to a field interpolation circuit 703 and a synchronous reproduction and control signal decoding circuit 704.

The intra-field interpolation circuit 703 performs interpolation processing using only the signal shown in FIG. 4(A) and interpolation processing using only the signal shown in FIG. 4(B). Therefore, signals in the states shown in FIGS. 4(G) and 4(H) are obtained and are input to the intra-field scanning line converter 705.

Here, processing is performed to convert a 1125-line 2:l interlaced signal into a 525-line 2:(interlaced signal. This signal is converted into an analog signal by a D/A converter 706, and then NTSC The encoder 707 converts it into an NTSC signal and outputs it to the output terminal 70g.This signal can be displayed on current television receivers.The NTSC encoder 707 also outputs the S
An output terminal 709 for a terminal input luminance signal is also provided.

(Problems to be Solved by the Invention) As mentioned above, the circuit of the MUSE decoder (Fig. 3) is very complicated and expensive, so a simple MUSE down converter as shown in Fig. 5 was developed. has been done.

However, the simple MUSE down converter has the following problems.

That is, for example, when a video signal with luminance in which white and black change in a stepwise manner within a field as shown in FIG. 6(A) is processed, the signals in FIG. 4(A) and (B) are processed. The X-marked portions are simply interpolated spatially between fields while following the respective interframe offset subsampling phases. For this reason, as can be seen from the diagonally shaded pixels in Fig. 4 (G) and (H), a shift occurs between the odd and even fields (Fig. 6 (B) and (C)), and as a result, As shown in Figure 6 (CD), the vertical edges become jagged. This is because the white and black areas on odd and even lines are different, as shown in FIG. 6(E).

This jaggedness tends to be very noticeable because the structure of the interlaced signal is 525 lines.

As described above, the conventional simple MUSE down converter has the problem of causing jagged edges as shown in FIG.

SUMMARY OF THE INVENTION An object of the present invention is to provide a television signal converter that can improve the image quality of the output of a simple MUSE down converter using simple means.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes an analog-to-digital converter into which a high-definition television signal band-compressed by offset subsampling is input, and an output signal from the analog-to-digital converter. a converting means for converting the supplied signal into a signal having the same number of scanning lines as the current television signal by interpolating the signal; a digital-to-analog converter for converting the output of the converting means from digital to analog; selector means for supplying the output of the receiver to one input via a delay circuit for obtaining phase compensation between fields and directly to the other input; and control included in the high-definition television signal. and means for controlling the selector means based on information to alternately select and derive inputs for each field.

(Function) The above means eliminates misalignment between fields and improves the image quality of the resulting image.

(Example) Embodiments of the invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. A MUSE signal is supplied to the input terminal 101, and the A/D converter 102 converts the MUSE signal to 1.
Digitized with a clock rate of 8.2 MHz. The output of the A/D converter 102 is connected to a field interpolation circuit 103 and a synchronous reproduction and control signal viewing circuit 10.
4 is input. The intra-field interpolation circuit 103 performs interpolation processing using only the signals shown in FIG. 4(A) and interpolation processing using only the signals shown in FIG.
) Interpolation processing is performed using only the signals of ). Therefore, signals in the states shown in FIGS. 4(G) and 4(H) are obtained and are input to the intra-field scanning line converter 105. Here, processing is performed to convert a 1125-line 2:(interlace signal) into a 525-line 2:1 interlace signal.

This signal is converted into an analog signal by the D/A converter 10B.

Here, the output signal of the D/A converter 106 is transmitted to the delay circuit II.
It is supplied to one of the selectors 112 via I, and directly to the other of the selectors 112.

The selector 112 alternately switches and derives the output of the delay circuit 111 and the direct signal for each field using the interfield offset subsample phase signal from the synchronous reproduction control signal decoding circuit 104.

Here, the delay circuit 111 has td shown in FIG.
In the case of the MUSE decoder shown in Fig. 3, the time tds for tcz: is tdll-1/48.6x 10' (see).
-20.6 (nscc), but in the case of the MUSE down converter, it is necessary to take into account the number of scanning lines, 525, and the aspect ratio and circularity of the screen.

Therefore, for example, if you want to display a high-definition television signal with a wide aspect ratio as shown in Figure 2 (A) by cutting off the left and right sides of the screen and displaying it as shown in Figure 2 (B), use tdm TDenX (11251525). X f(1B/9)Ha4/3)l x (ttHa2)■64.1 (nsec
) is appropriate. In addition, when displaying the entire screen of a high-definition television signal by making the top and bottom of the screen black or gray as shown in FIG. 2 (C), t d - tdm
11/12) 48.1 (nscc) is appropriate. In this way, the delay time of the delay circuit 111 may be switched depending on the mode.

The signal output from the selector H2 is converted into an NTSC signal by an NTSC encoder (not shown).

This signal is a signal that can be displayed on current television receivers.

As mentioned above, by adjusting the time for each field, the displayed screen will not have jagged edges as shown in Figure 6, and will have a natural image as shown in Figure 6 (A). can be obtained.

[Effects of the Invention] As explained above, the present invention can improve the image quality of the output of the simple MUSE down converter by simple means.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the operation of the circuit in FIG. 1, and FIG.
The figure is an explanatory diagram of the configuration of the MUSE decoder, and Figure 4 is the MUSE decoder.
An explanatory diagram shown to explain the signal processing progress of the decoder, Fig. 5 is an explanatory diagram of the configuration of a conventional simple MUSE down converter, and Fig. 6 is an explanatory diagram to explain the problems of the conventional simple MUSE down converter. FIG. 102... A/D converter, 103... Intra-field interpolation circuit, 104... Synchronous reproduction control signal decoding circuit, 105... Intra-field scanning line converter, 108
...D/A converter, 111...Delay circuit, 112.
··selector.

Claims (1)

[Claims] An analog-to-digital converter into which a high-definition television signal band-compressed by offset subsampling is input, and an output signal from the analog-to-digital converter is supplied, and this signal is subjected to intra-field interpolation processing. a converting means for converting the signal into the same number of scanning lines as the current television signal; a digital-to-analog converter for converting the output of the converting means from digital to analog; a selector means supplied to one input via a delay circuit and directly supplied to the other input; controlling the selector means based on control information contained in the high definition television signal; 1. A television signal conversion device comprising means for alternately selecting and deriving inputs for each field.