JPH048095A - Television signal converter - Google Patents

Abstract

PURPOSE:To make hardware small in size and to simplify the configuration by converting a luminance signal and a chrominance signal of an HDTV signal into a digital signal directly, expanding the time base in the timing of a frequency being four times the chrominance subcarrier of an NTSC signal and applying orthogonal biphase modulation to the signal and outputting the result as the NTSC signal. CONSTITUTION:A picture element signal being a valid pattern of the NTSC system is extracted by a control circuit 18 by using a luminance signal Y of an HDTV signal and a signal quantized from color difference signals PR, PB. The signal is converted into a signal of valid picture element number when the signal is sampled at a frequency 4fSC being four times the chrominance subcarrier of the NTSC signal. The time base is expanded by a time base expansion circuit 22 so that the signal is generated in a timing of the frequency 4fSC. Then orthogonal biphase modulation is applied to the color difference signal, the result is restored into an analog signal at a D/A converter 20 by using the frequency 4fSC and NTSC encoding is applied directly. Thus, the hardware is reduced, the configuration is simplified and no adjustment is required for the NTSC encoder.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an apparatus for converting a color television signal into a color television signal of another system, specifically a high-definition television signal of a high-definition system. This invention relates to a television signal converter that down-converts a standard television signal to an NTSC standard television signal.

(Prior Art) A converter as shown in Fig. 3 is used as a conversion device for down-converting a high-definition television signal (hereinafter referred to as HDTV signal) to a standard NTSC television signal (hereinafter referred to as NTSC signal). something is proposed. FIG. 3 shows a block diagram of the circuit configuration.

A luminance signal Y and color difference signals pR and PR of the IDTV signal are input from input terminals 100, 101, and 102, and these signals are converted into R (red) and G by an inverse matrix circuit 103.
It is converted into color signals of three primary colors: (green) and B (blue). The converted R1G and B color signals are A/'D(
After being converted into a digital signal by analog/digital) converters 104, 105, 106, the aspect ratio h)16 is converted by each aspect ratio conversion circuit 107, 108, 109.
・Converts from 9 to 4=3. Next, each scanning line conversion circuit 111, 112, 113 converts the number of horizontal scanning lines from 1125 to 525, and then each field frequency conversion circuit 114, 115, 116 converts the field frequency to 60Hz. It is converted from 59.94Hz to 59.94Hz.

And each D/A (digital/analog) converter 11
After being converted back to an analog signal at 8°119.120, each low pass filter (LPF) 121°122.12
3, and is input to the NTSC encoder 124.

On the other hand, the brightness "jy '/ of the HDTV signal inputted from the input terminal 100 is also inputted to the sync separation circuit 110, where it is sync-separated, and then converted into NTS by the sync conversion circuit 117.
The above NTS
The signal is input to the C encoder 124.

Then, the NTSC encoder 124 receives the input R,
Synchronized with the G and H color signals (No. 3 is encoded using the NTSC method, and the NTSC signal is output from the output terminal 125.

FIG. 4 is a block diagram showing the detailed configuration of the NTSC encoder 124.

The manually inputted R, G, and B color signals enter the matrix circuit 126, where they are sent to the NTSC luminance signal Y and the color signals 1. Q is generated. And the luminance signal Y is the delay line 1
27 to the adder circuit 134, and the color signal I is inputted to the adder circuit 134 through the delay line 128 and the I signal low-pass filter 129.
After being modulated by the signal modulator 131, the color signal Q is input to the adder circuit 134.
0 and is modulated by the Q signal modulator 132.
34.

On the other hand, the input synchronization signal is sent to the synchronization signal generator 135 and 3.
The synchronization signal generator 135 outputs the burst modulator y<rus and a composite synchronization signal, and the output of the oscillator 136 is sent to the burst modulator 133 and the 57゛ phase shifter 137. be done. After being modulated by the burst modulator 133, the Hurst frac pulse is input to the adder circuit 134, and the composite synchronization signal is also input to the adder circuit 134. The output of the oscillator 136 is also sent to a 190° phase shifter 138, and the outputs of these phase shifters 137 and 138 are used to control each of the modulators 131.
．． 132 is controlled. Then, an NTSC composite color signal E is outputted from the adder circuit 134 into which the above-mentioned signals are manually input.

[Problem to be solved by the invention]

However, in the above-mentioned television signal conversion device, the luminance signal Y and the color difference signals pR, P of the HDTV signal are
R is converted into an R3GBO color signal using an inverse matrix circuit, then quantized, and then converted into an analog signal after performing aspect ratio conversion, scanning line number conversion, and field frequency conversion, and then NTSC encoded. There are problems in that the amount of software is huge, the configuration is complicated, and there are many adjustment points.

For example, in the case of scanning line number conversion, the number of scanning lines of HDTV (No. 3) is 1125, and the number of scanning lines of NTSC is 525, so the number of scanning lines of NTSC signal is more than 15 of the scanning lines of HDTV No. 43. 7 tree scanning lines will be created, and if linear interpolation is used, the line memory capacity will be 148 (H is one horizontal scanning period) of the HDTV signal, and the R
, G, and B signals, three identical circuits or three systems are required. Furthermore, the NTSC encoder has a configuration as shown in FIG. 4, and requires a considerable amount of hardware to perform stable encoding, and since it is performed using analog signals, there are many adjustments to be made.

The present invention was developed in view of these problems, and aims to provide a television signal converter that has small hardware, has a simple configuration (ft'), and can perform NTSC encoding without adjustment. It is said that

[Means to solve the problem]

The television signal conversion device of the present invention includes an A/D converter that converts the brightness signal and color difference signal of a high-definition television signal into digital signals, and an NTSC system from which the converted brightness signal and color difference signal are converted. extraction means for extracting an effective screen pixel signal of a standard television signal;
converting means for converting the extracted pixel signal into an image signal of an effective screen when sampled at a frequency four times as high as the color subcarrier of the standard television signal; a time axis expansion means for expanding the time axis so that the image signal occurs at the timing of the frequency; a modulation means for performing orthogonal two-phase modulation of the image signal; and a D/A converter for converting the modulated image signal into an analog signal. It is equipped with the following.

[Effect]

The television signal converter of the present invention has an HD
The brightness signal and color difference signal of the TV signal or the color signal of R2O,B are directly converted into digital signals without being converted, and this quantized signal power becomes the effective screen of 1 to N T S C4; A partial pixel is extracted, and the time axis is expanded so that the image signal is generated at a timing that is four times the frequency of the color subcarrier of the NTSC signal. Then, the generated image signal is subjected to orthogonal two-phase modulation, returned to an analog signal, and then output as an NTSC signal.

〔Example〕

FIG. 1 is a block diagram showing the circuit configuration of a television signal converter according to an embodiment of the present invention. In the figure,
11, 12.13 are input terminals into which the brightness signal Y and color difference signals PR and PB of the HDTV signal are input, 15.16.17
18 is an A/D (analog/digital) converter that quantizes and converts the input luminance signal Y and color difference signals pR, pB into digital signals, and 18 is an effective screen of the NTSC signal from the converted luminance signal and color difference signal. A control circuit (extraction means) for extracting pixel signals controls the starting point of horizontal pixels. 21 is a synchronization separation circuit that separates a synchronization signal from the input luminance signal (Y), 22°, 23.24 is a time axis expansion circuit that expands the time axis, and 25, 26, and 27 are converters for converting the number of pixels in the horizontal direction. The horizontal pixel number conversion circuit (conversion means) converts the extracted pixel signal into an image signal of the effective screen when sunblinked at a frequency of 4fsc, which is four times the color subcarrier of the NTSC signal, and then expands the time axis. Circuit 22゜23.2
4 extends the time axis so that the converted image signal is generated at the timing of the frequency 4fsc. 28 is N
29, 30.31 is a scanning line number conversion circuit that converts the number of scanning lines; 32.33 is a circuit that multiplies the color difference signal by a coefficient to match the amplitude; coefficient circuit, 34.3
5 is an adder, 36.37 is a subtracter, and 38.39 is a signal changeover switch that switches the signals from the adder 34.35 and the subtracter 36.37 according to the signal from the synchronous burst generation circuit 28. 3435, subtractor 36.
37 and signal changeover switches 38 and 39 constitute a modulation means 42 for orthogonal two-phase modulation of the above-mentioned image signal. 40 is a D/A (digital/analog) converter for converting the modulated image signal into an analog signal, and 41 is an output terminal for the synthesized NTSC signal.

FIG. 2 is a block diagram showing the detailed configuration of each circuit in FIG. 1. FIG. 2(a) shows the scanning line number conversion circuit 29, 30.3
In the figure, 51 is a line memory, 52 is an adder, 53 is a 1/2 coefficient circuit for multiplying by a coefficient of 1/2, 54 is a thinning circuit, and 55 is a time axis expansion circuit. Figure 2 (b
) and (c) are examples of the Y signal horizontal pixel number conversion circuit 25, in which 56 is a 1-pixel delay circuit, 57 is an adder 58 is a 1/2 coefficient circuit, 59 is a thinning circuit, and 60 is a low frequency The pass filter 61 is a thinning circuit.

In the converter configured as described above, input terminal 1
The luminance signal Y and the color difference signals PR and PR of the HDTV signal inputted from the A/D converters 15, 16 .
At step 17, each signal is converted into a digital signal and inputted to time axis expansion circuits 22, 23 and 24. Time axis expansion circuit 2
2, 23° 24 expands the time axis by 4/3 for each line in accordance with a control signal from a control circuit 18, which will be described later. Further, the horizontal pixel number conversion circuits 25, 26, and 27 adjust the number of pixels in the horizontal direction to the effective number of pixels when the above-mentioned NTSC signal is sunblinked at a frequency of 4 fsc. Here, if the sunblink frequency of the A/D converter 15 of the luminance signal Y is 74.25 MHz (BTA studio standard), the number of effective pixels in the horizontal direction is 1920 pixels (BTA studio standard), and the time axis expansion circuit 22 So the time axis is 4/3
Since the number of pixels is doubled, the number of effective pixels input to the horizontal conversion circuit 25 is 1920 x −=1440. Also, N.T.
The effective number of pixels in the horizontal direction of the luminance signal Y of the SC signal is 4f
If you perform sunblink at the timing of the sc frequency 7
Since the number of pixels is 60 (assuming the horizontal effective scanning rate is 0.84), it is sufficient to generate one pixel using two pixels. At this time, Y
A block diagram of the signal horizontal pixel number conversion circuit 25 is shown in Figure 2 (
As shown in b), the configuration is such that two pixels are averaged to one pixel (if you want to strictly limit the band, refer to the same figure (C
).

On the other hand, for the color difference signals pR and pB, the A/D converter 16
．． 17 sunblink frequency is 1/2/3 of the luminance signal Y
7.125M) 12 (BTA studio standard),
The number of effective pixels is 960 pixels (BTA studio standard). Therefore, if the time axis is multiplied by 4/3, the number of effective pixels is 7.
It becomes 20 pixels. However, the bandwidth of the color difference signal of the HDTV signal is approximately 15MHz at maximum, and the time axis expansion circuit 2
3.24 and the scanning line number conversion circuit 30.31, the equivalent band becomes 15 X 'X and ~5.6 MHz, and N
Cross color appears during TSC decoat. Therefore, in the case of a color difference signal, the band of the color difference signal PR is limited to 1/4 (1.5 MHz in NTSC terms) and the band of the color difference signal PB is limited to 1/11 (0.5 MHz in NTSC terms) using a low-pass filter. At this time, there is no need to thin out the pixels since they are already 760 pixels or less. Therefore, the horizontal pixel number conversion circuits 26 and 27 for the color difference signal are composed of low-pass filters. In addition, A/D converter 16.1
4 of the NTSC signal depending on the sampling frequency of 7.
There may be cases where the number of horizontal effective samples is considerably larger than an integer multiple of 760 when performing sample blinking at frequencies f and c, but in that case, the number of samples may be converted using an interpolation filter.

The video signal (image signal) whose horizontal pixel number has been converted by the horizontal pixel number conversion circuits 25, 26, and 27 is subjected to scanning line number conversion by the scanning line number conversion circuits 29, 30, and 31. At this time, the scanning line number conversion circuits 29, 30, and 31 are configured as shown in FIG. There is. This input video signal is delayed by one line of the HDTV signal in the line memory 51 and applied to the adder 52 . Then, in the adder 52, the input video signal is added to the video signal of the previous line applied from the line memory 51, and this signal is multiplied by 1/2 in the 1/2 coefficient circuit 53, and the average of the upper and lower lines is calculated. Waru. next,
The decimation circuit 54 decimates each line, and the time axis expansion circuit 55 expands the time axis to a period corresponding to one line of the NTSC signal.

Further, the luminance signal Y whose number of scanning lines has been converted by the scanning line conversion circuit 29 is applied to the adder 34 .

On the other hand, the color difference signals pR and pB are processed by the scanning line number conversion circuit 30.3.
After the number of scanning lines is converted in step 1, coefficients are multiplied in coefficient circuits 32 and 33. These coefficient circuits 32 and 33 are HD
The amplitude of the color difference signal PR9pB of the TV signal is the color signal 1 of the NTSC signal. This is to match the amplitude of Q.

The color difference signal multiplied by the coefficient in the coefficient circuits 32 and 33 is added to the luminance signal in an adder 34 and 35, and subtracted from the luminance signal in a subtracter 36 and 37. Here, the luminance signal output from the scanning line number conversion circuit 29 is
′, the color difference signal output from the coefficient circuit 32 is Io, and the color difference signal output from the coefficient circuit 33 is Q′, then the signals applied to terminals a, b, c, and d of the signal changeover switch 38 are Y, respectively. '+I',Y'+Q',Y'I'
, Y'-Q'. And signal changeover switch 3
8 switches the above four types of signals in the above order at a frequency timing of 4 fsc. Therefore, the signal changeover switch 38
The signals output from are Y11, Y+Q, Y-1, Y-
Q, Y+I, Y+Q.

..., and orthogonal two-phase modulation is performed at the frequency fsc.

On the other hand, the luminance signal Y input from the input terminal 11 is also applied to the synchronization separation circuit 21. This synchronization separation circuit 21 separates the synchronization signal multiplexed on the luminance signal Y, and applies this synchronization signal to the control circuit 18 and the synchronization burst generation circuit 28 for the NTSC signal. Then, the control circuit 18 determines whether the image signal is valid in the horizontal direction according to the input synchronization signal, and the time axis expansion circuit 22
．． A control signal is applied at 23.24. By kneading, the horizontal cutout portion is determined.

Further, the NTSC signal synchronization burst generation circuit 28 generates an NTSC signal according to the synchronization signal inputted from the synchronization separation circuit 21.
A synchronizing signal of the C signal and a color burst signal are generated and applied to the terminal f of the signal changeover switch 39 described above. Then, a control signal is sent to the signal changeover switch 39 so that the signal of the terminal f is selected by the switch 39 for the part other than the effective image signal part (synchronization and color burst part), and the signal of the terminal e is selected for the part of the effective image signal. Therefore, the signal changeover switch 39 outputs an NTSC digital video signal to which a synchronization signal and a color burst signal are added.Then, the D/A converter 40 outputs the NTSC digital video signal. is converted into an analog signal at a frequency of 4fsc, and outputted from the output terminal 41 as an NTSC video signal.

Here, in the above embodiment, the luminance signal Y and color difference signals p, , p of the HDTV signal are not converted into R, G, B color signals,
It is directly converted to an NTSC signal. That is, the luminance signal Y and color difference signals Pp, , P of the HDTV signal
From the quantized signal of B, pixels within a predetermined range on the screen,
In other words, the signal of the pixel of the part that becomes the effective screen of the NTSC system is extracted, and this is converted into a signal of the effective number of pixels when sampled at a frequency of 4fsc, which is four times the color subcarrier of the NTSC signal, and this signal is , c, the time axis is expanded so that it occurs at the timing of the frequency. and,
The color difference signal is subjected to orthogonal two-phase modulation by calculation, and after being returned to an analog signal at a frequency of 4 fsc, NTSC encoding is directly performed. Because of this, the hardware is small and
The configuration is simplified and NTSC encoding is not adjusted. Specifically, the color difference signal PR1 is
Since the sampling frequency of PB is usually 1/2 or less, hardware (particularly memory capacity) can be reduced to about 1/2 by directly converting the format of the Y, PR, and PB signals. In addition, scanning line number conversion is also possible between HDTV signals and NT signals.
Taking advantage of the fact that the ratio of the number of scanning lines of an SC signal is 11251525, which is close to 2, it is possible to
By generating one scanning line of the SC signal, it is possible to further reduce the amount of hardware. Similarly to the vertical pixel conversion, hardware can be reduced by generating one pixel from two pixels. Furthermore, D/
By performing A conversion at a frequency four times the color subcarrier fSC of the NTSC signal and performing digital quadrature two-phase modulation,
At the same time as reducing hardware, it is possible to stabilize N-chosc encoding without any adjustment.

Furthermore, as mentioned above, if the sunblink frequency of the A/D converter is set to a value around 74.25MHz, the luminance signal will be configured to generate one pixel in the NTSC system from two horizontal pixels, so sub-sunfull The configuration is further simplified when applied to a system using Since one line of the NTSC system is generated using two scanning lines, it can be similarly simplified when applied to a system using a color difference line sequential system.

〔Effect of the invention〕

As described above, according to the present invention, the brightness signal and color difference signal of an HDTV signal can be directly converted to an NTSC signal without converting into R, G, and B color signals, and the hardware is small and the configuration is simple. In addition, the effect of NTSC encoding or no adjustment can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of a television signal converter according to an embodiment of the present invention, and FIGS. 2(a) and (b)
), (c) are block diagrams showing the detailed configuration of each circuit in FIG. 1, FIG. 3 is a block diagram showing the circuit configuration of a conventional example, and FIG.
This figure is a block diagram showing the detailed configuration of the NTSC encoder in FIG. 3. 15, 16. 17-...-A/D converter 18
-... Control circuit (extraction means) 21...
...Synchronization separation circuit 6.37...Subtractor 8.39...Signal changeover switch 0...-D
/ A converter 2... Conversion means

Claims (1)

[Claims] An A/D converter converts the brightness signal and color difference signal of a high-definition television signal into digital signals, and converts the converted brightness signal and color difference signal into effective screen pixels of a standard NTSC television signal. an extraction means for extracting a signal; a conversion means for converting the extracted pixel signal into an image signal of an effective screen when sampled at a frequency four times the color subcarrier of the standard television signal; and a converted image signal. a time axis expansion means for expanding the time axis so that the image signal is generated at a timing of four times the frequency of the color subcarrier, and a modulation means for performing orthogonal two-phase modulation of the image signal;
1. A television signal conversion device comprising: a D/A converter that converts a modulated image signal into an analog signal.