JP2891479B2 - MUSE-525 converter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television converter, and more particularly, to a television converter.
The present invention relates to a MUSE-525 converter for converting a television signal from a MUSE system to an NTSC system or an EDTV system.

[Conventional technology]

FIG. 12 shows a block diagram of a MUSE-525 converter, which was announced at the IEICE Spring National Convention in 1988.

In the figure, an input terminal 1 receives a MUSE baseband signal. After being A / D converted by the 8-bit A / D converter 2, the de-emphasis circuit 3 and the audio data separation, PLL,
The signal is input to the control signal generation circuit 9. Output 103 of de-emphasis circuit 3 is horizontal scanning time conversion, 1125 lines → 10
The data is input to the 50-line scanning line conversion circuit 4. Horizontal scanning time conversion, 1125 lines → 1050 lines The output 104 of the scanning line conversion circuit 4 is a field interpolation, vertical LPF, 1050 which is a luminance signal processing circuit.
The 525-line interlace conversion circuit 6 and the field interpolation, TCI decoding, and 525-line interlace conversion circuit 7, which are processing circuits for the color signal system, are input. An output 106 of the luminance signal processing circuit 6 is input to one input of the inverse matrix circuit 8 via an 8-bit D / A converter 13a. on the other hand,
Outputs (color difference outputs) 108 and 109 of the color signal processing circuit 7 are input to the other inputs of the inverse matrix circuit 8 via 8-bit D / A converters 13b and 13c, respectively. Outputs 112, 113, and 114 of the inverse matrix circuit 8 are signals converted into R, G, and B, respectively, and output via output terminals 10, 11, and 12 to a subsequent circuit.

 Next, the operation will be described.

In order to convert the MUSE signal into 525 signals, a method of performing the same interpolation as the MUSE decoder, a method of performing only the field interpolation, and a method of not performing the interpolation at all can be considered. Considering the scale of the device, a device that performs MUSE interpolation is not suitable, and a MUSE signal that does not perform interpolation at all has a large amount of aliasing distortion, resulting in insufficient image quality. Therefore, in this apparatus, only the field interpolation is performed. This signal has a horizontal band of about 12.2 MHz. In addition, the edge portion slightly flickers due to aliasing distortion caused by inter-frame offset subsampling. However, the aliasing component of MUSE is 0
Because it does not exist at ~ 4MHz, the wrapping after conversion is NTSC
It is not as prominent as the system cross color.

In order to convert a Hi-Vision signal into 525 signals, conversion of the aspect ratio and conversion of the number of scanning lines must be performed. FIG. 13 shows various conversion methods. This method is practical in terms of the roundness and the number of scanning lines, and the method described here was adopted. This method is a high-definition 11
Extract 254 to 1050 aspect ratio 4: 3 images,
In addition, there is a feature that the filter in the vertical direction is simplified by the conversion to be reduced to 525 lines.

In the configuration of the MUSE-525 converter shown in FIG. 12, field interpolation is performed by 525 to avoid high-speed signal processing.
It was done in this system. In addition, the configuration of the filter also serves as both a pre-filter for thinning out to 525 lines and a field interpolation filter, thereby reducing the circuit scale.

[Problems to be solved by the invention]

Since the conventional MUSE-525 converter unit is configured as described above, the horizontal band in the still image area is only 4.2 MHz equivalent to that of the current TV in 525-line conversion. The bandwidth needs to be further expanded.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and is a MUSE that can expand the horizontal band theoretically to about 7 MHz in a still image area in terms of 525 lines with a relatively simple circuit. The purpose is to obtain -525 converter devices.

[Means for solving the problem]

The MUSE-525 converter according to the present invention has an A / D converter that receives a MUSE baseband signal as an input, converts an analog signal to a digital signal, an output signal of the A / D converter as an input, and converts an input signal into an A / D signal. A de-emphasis circuit for converting to a linear phase signal, an output signal of the A / D converter as an input, an audio data separation circuit for separating and decoding only an audio signal, and an output signal of the A / D converter. A PLL circuit for inputting and separating only the synchronization signal data and generating a clock; a control signal generating circuit for receiving and outputting only the output signal of the A / D converter and separating and decoding only the control signal data; and the de-emphasis Using the output signal of the circuit as input, convert horizontal scanning time of MUSE system to horizontal scanning time of NTSC system, and extract horizontal scanning time from 1125 scanning lines only 1050 lines and horizontal scanning time conversion 1125 lines → 1050 lines scanning A conversion circuit, an input filter for the horizontal scanning time conversion and the output signal of the 1125 → 1050 scanning line conversion circuit, and an interpolation filter for converting without aliasing when converting the sampling frequency; and A sampling frequency conversion circuit having an output signal as an input signal and a switch circuit that switches at a period of a sampling frequency to be converted, and an output signal of the sampling frequency conversion circuit as an input, which is vertically subjected to inter-field offset sampling as MUSE encoder processing. A field interpolation filter for returning the signal folded back to the high frequency band to the horizontal high frequency band, and an output signal of the field interpolation filter as input, which is used when converting from 1050 interlaces to 525 interlaces. A vertical LPF for conversion without aliasing distortion and an output signal of the vertical LPF And 1050 → 525 interlace conversion circuit which converts the 525 interlace from Taresu, the 1
050 lines → D / A converter for luminance signal which receives the output signal of the 525 interlace conversion circuit as input and converts digital data to analog signal, and the horizontal scanning time conversion and 1125 lines → 1
The output signal of the 050 scanning line conversion circuit is used as an input signal, and a field interpolation filter for preventing aliasing distortion due to untransmitted pixels and 525 line interlace conversion, and an output signal of the field interpolation filter A TCI decoding circuit which separates a time-division multiplexed luminance signal and color difference signal into color difference signals as input, and expands a time-axis-compressed color difference signal by time-base expansion and restores the original; An output signal is input, and a 525 interlace conversion circuit that converts the line-sequential color difference signal into 525 interlaces for both RY and BY signals, and an output signal of the 525 interlace conversion circuit is input. For two RY signals for converting digital data into an analog signal, BY
D / A converter for signal, D / A converter for Y signal and R
It is provided with an inverse matrix circuit that receives output signals of the D / A converters for the -Y signal and the BY signal and converts them into R, G, B signals.

[Action]

In the present invention, the horizontal band can be expanded up to about 7 MHz in terms of a 525-line system by the above-described configuration (however, the offset sub-sampling between frames,
Image quality degradation due to aliasing distortion due to inter-field offset subsampling and interlace is ignored).

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a MUSE-525 converter according to an embodiment of the present invention. In the drawing, an input terminal 1 receives a MUSE baseband signal. The input signal 101 is an 8-bit A / D
The output 103 of the de-emphasis circuit 3 input to the de-emphasis circuit 3 and the audio data separation / PLL / control signal generation circuit 9 via the converter 2 is used for horizontal scanning time conversion, 11
25 lines → 1050 lines are input to the scanning line conversion circuit 4. Horizontal scanning time conversion, 1125 lines → 1050 lines The output 104 of the scanning line conversion circuit 4 is a sampling frequency conversion circuit 5 which is a luminance signal processing system.
Are input to a field interpolation, TCI decoding, and 525-line interlace conversion circuit 7 which is a color signal processing system. Output 10 of sampling frequency conversion circuit 5 which is a luminance signal processing system
5 is input to the field interpolation, vertical LPF, 1050 lines → 525 lines interlace conversion circuit 6. Field interpolation, vertical
The output 106 of the LPF, 1050 lines → 525 lines interlace conversion circuit 6 is input to one input of the inverse matrix circuit 8 via the 8-bit D / A conversion circuit 13a. On the other hand, field interpolation, YCI decoding, and outputs (color difference outputs) 108 and 109 of the 525-line interlace conversion circuit 7, which are color signal processing systems, are each 8-bit D / A.
The signals are input to the other inputs (two systems) of the inverse matrix circuit 8 via the converters 13b and 13c. Outputs 112, 113, and 114 of the inverse matrix circuit 8 output R, G, and B signals whose horizontal bands have been expanded.

This embodiment (FIG. 1) is an apparatus in which a sampling frequency conversion circuit 5 is added to the circuit of the conventional example (FIG. 12). Therefore, the circuit after the sampling frequency conversion is processed at the sampling frequency converted by the sampling frequency.

Hereinafter, the sampling frequency conversion circuit will be described.

The signal input to the sampling frequency conversion circuit 5 is the output signal of the horizontal scanning time conversion and 1125 lines → 1050 lines scanning line conversion circuit 4 shown in FIG. As described in the above-mentioned conventional example, in order to convert the MUSE baseband signal into the 525-line standard system, it is necessary to correct a difference in scanning time due to a difference in the number of lines and an aspect ratio. Therefore, the MUSE baseband signal is 480 pixels per scanning line and the sampling frequency is 16.
2 MHz. To convert this to the 525-line standard, 1
360 pixels per scanning line, sampling frequency 11.34MHZ
need to be z.

The MUSE encoder performs a sampling frequency conversion from 48.6 to 32.4 MHz. That is, 32.4
Although it is necessary to perform a sampling frequency conversion of 48.6 MHz, this is a sampling frequency conversion after interpolation, and a sampling frequency conversion of 16.2 to 24.3 MHz before interpolation. Therefore, the sampling frequency conversion according to the present invention is before interpolation, and is 11.34 → 525 conversion.
Convert the sampling frequency to 17.01MHz.

According to the sampling theorem as shown in the following equation (1), the original signal can be restored by using sample values and is represented as follows.

g (t) = Σg (iT) S (t−iT) (1) As shown in FIGS. 2, 3, and 4, the sampling frequency f before conversion is used.
The sample values at s = 11.34 MHz are Q ₀ , Q ₁ , Q ₂ , ..., Q ₁₀ , Q
_11, Q _12, and ... and, the sampling frequency of the converted f's
= Sample values at _{17.01MHz P 0, P 1, P} 2, ... , and P _'0,
P ' ₁ , P' ₂ , ... _{Q 0, Q 1, P 0} , P 1 from ..., ... and _{P '0, P' 1,} Q 0 to convert ... to, Q _1, Q _2, ... and g
(0), g (T), g (2T),... (Where T = 1 / 17.01M), and substitute this into equation (1) to obtain g (t).
The time t of P ₀ , P ₁ ,... And P ′ ₀ , P ′ ₁ ,. However, when the sampling frequency to be converted is an integer ratio, Pi and P′i, Qj have a specific phase relationship, which can be further simplified.

That is, in principle, it is considered that this conversion should be performed by interpolating Pi using the least common multiple of 34.02 MHz between 11.34 MHz and 17.01 MHz. However, as shown in FIG. I want to convert the baseband signal to the form of offset sampling between fields.
It is necessary to interpolate Pi at a frequency of 68.04 MHz. This one
Offset sampling between fields at 7.01MHz and Qj
It is assumed that. As shown in FIGS. 3 and 4, the sampling function at T = 1 / 2.68 MHz is sampled at 68.04 MHz, and S ₀ , S ₁ , S ₂ ,. Qj is divided as follows from the phase relationship of

Therefore, in order to convert from Qj to Pi, Pi ', the six types of interpolation filters shown in the above equation (2) may be arranged as shown in FIG.

In the above, correct conversion can be performed if the number of terms in the sum is infinite, but in reality it is finite. On the other hand, considering the interpolation filter in the frequency domain, the MUSE as shown in FIG.
This is an LPF for removing harmonic components generated by the band compression processing of the system and removing components folded back to the baseband by resampling at fs = 17.01 MHz. Since it operates at 68.04 MHz in principle, f = 5.67 n (MHz)
It is necessary to sufficiently suppress the characteristics at (n = 0, 1, 2,..., 6).

Therefore, for example, as shown in FIG.
A filter having a gain of 0 at 1, f = 5.67, 11.34, 17.01 [MHz] can be realized by a 13-tap transversal filter. FIG. 8 shows tap coefficients of the six interpolation filters.

Next, the reason for expanding the horizontal band in a still image will be described. By using the MUSE baseband signal of the still image converted into the time axis during the horizontal scanning time of the 525 lines shown in FIG. 6 as an input signal and performing six kinds of interpolation filter processes having the characteristics of FIG. As shown in FIG. 9, M = 5.67, 11.34, 17.01,2
The spectrum existing at 2.68, 28.35 [MHz] disappears.
Then, when the inter-field offset sampling is performed at fs = 17.01 [MHz], the vertical high frequency component shown by the hatched portion in FIG. 10 is folded back to the horizontal frequency M = 12.15 to 20 [MHz]. Since this is sufficiently band-limited by the pre-filter of the MUSE encoder, it can be faithfully reproduced. But MU
Since the SE-525 converter presupposes field interpolation, it is necessary to allow a time-folding component in a still image area.

Therefore, when expanding the horizontal band in the actual image,
In the still image area, there is a possibility that the aliasing distortion in the time direction, such as flicker, may increase. MU in the video area
Due to the moving picture pre-filter of the SE encoder, the horizontal reproduction band is a MUSE system, and the maximum horizontal band is 5.67 [MHz] when converted to 16.2 [MHz] or 525 lines.

The problem is that, for example,
The problem is solved by passing through a two-dimensional LPF having the characteristics shown in FIG.
This filter has the function of returning the signal folded back to the vertical high band by the offset sampling between fields of the MUSE encoder in the still image region to the band of the horizontal high band.
Therefore, in this filter, the horizontal reproduction band is expanded from 4.2 to 5.67 MHz in the still image area in terms of 525 lines.

Finally, FIG. 11 shows an embodiment of an actual circuit of the sampling frequency conversion circuit shown in FIG.

In the figure, 14 is an input terminal, 17 is an output terminal, 10a to 19g
Is a constant multiplier, 20a and 20b are one-sample delay circuits, 21a to 21
e is an adder, and 16b to 16d are SW circuits.

In the above embodiment, MUSE-525 (interlace)
Although the converter has been described, the MUSE standard receiving adapter system, which was announced at the Technical Report of the Institute of Television Engineers of Japan on September 20, 1984, may have the same effect as the above embodiment.

The same effect can be obtained with the MUSE-525 in-interlace converter device.

〔The invention's effect〕

As described above, according to the MUSE-525 converter according to the present invention, an A / D converter that receives a MUSE baseband signal as input, and converts an analog signal into a digital signal,
A de-emphasis circuit that receives an output signal of the A / D converter and converts the input signal into a signal having a linear phase;
Using the output signal of the converter as input, separating only the audio signal,
An audio data separation circuit for decoding, the output signal of the A / D converter is input, and only the synchronization signal data is separated, a PLL circuit for generating a clock, and the output signal of the A / D converter are input, A control signal generating circuit that separates and decodes only control signal data, and an output signal of the de-emphasis circuit as inputs, converts a horizontal scanning time of a MUSE system to a horizontal scanning time of an NTSC system, and scans 1125
Horizontal scanning time conversion and 1125 lines to extract only 1050 lines out of the lines → 1050 lines scanning line conversion circuit and horizontal scanning time conversion and 1125 lines
An interpolation filter for converting the sampling frequency into an input signal with the output signal of the scanning line conversion circuit of 1050 lines as input, and a sampling frequency to be converted with the output signal of the interpolation filter as an input signal. A sampling frequency conversion circuit having a switch circuit that switches at a period of, and an output signal of the sampling frequency conversion circuit as an input. A field interpolation filter for returning to the band of the band portion, and a vertical LPF for converting the output signal of the field interpolation filter as an input and converting from 1050 interlaces to 525 interlaces without aliasing distortion
With the output signal of the vertical LPF as an input, a 1050 line → 525 interlace conversion circuit for converting 1050 line interlaces to 525 line interlaces, and an output signal of the 1050 line → 525 interlace conversion circuit as inputs, A luminance signal D / A converter for converting digital data into an analog signal, and the output signal of the horizontal scanning time conversion and 1125 lines → 1050 lines conversion circuit are input signals, and pixels and 525 lines not transmitted are transmitted. A field interpolation filter for preventing aliasing distortion due to race transformation, and an output signal of the field interpolation filter are input, and a time-division multiplexed luminance signal and color difference signal are separated into only color difference signals. A TCI decoding circuit for extending the time-axis-compressed color difference signal by time-base expansion and returning it to its original state, and receiving the output signal of the TCI decode circuit as input and converting line-sequential color difference signals into RY and B signals A 525 interlace conversion circuit for converting both Y signals into 525 interlaces, and two RY signals for inputting the output signals of the 525 interlace conversion circuits and converting digital data into analog signals. A D / A converter for Y signal;
D / A converter for signal, D / A for RY signal, D / A for BY signal
The output signal of the converter is provided as an input, and an inverse matrix circuit for converting the input signal into R, G, B signals is provided, so that the horizontal reproduction band is expanded in the still image area, and an effect of obtaining an image with high horizontal resolution is obtained. is there.

[Brief description of the drawings]

FIG. 1 is a diagram showing a MUSE-525 converter according to an embodiment of the present invention, FIG. 2 (a) is a diagram showing a sampling pattern before sampling frequency conversion, and FIG. 2 (b).
Is a diagram showing a sampling pattern after conversion, FIG. 3 and FIG. 4 are diagrams showing the principle of sampling frequency conversion,
FIG. 5 is a simple block diagram of the sampling frequency conversion circuit, and FIG. 6 is a MUS after conversion into 525 horizontal scanning times.
FIG. 7 shows a three-dimensional spectrum display of an E baseband signal, FIG. 7 shows a frequency response characteristic of a sampling frequency conversion filter, FIG. 8 shows a lop coefficient of the sampling frequency conversion filter, and FIG. 9 shows a still image FIG. 10 is a diagram showing a three-dimensional spectrum display after sampling frequency conversion interpolation filter processing in FIG. 10, FIG. 10 is a diagram showing a three-dimensional spectrum display after inter-field offset sampling processing in a still image, and FIG. 11 is an actual sampling frequency conversion circuit , FIG. 12 is a block diagram of a conventional MUSE-525 converter, FIG. 13 is an explanatory diagram of conversion from Hi-Vision to a 525-line system, and FIG.
FIG. 14B is a diagram showing a sampling pattern after the PF process, and FIG. 14B is a diagram showing a three-dimensional spectrum display after the two-dimensional LPF process. In the figure, 1, 14 are input terminals, 2 is an A / D converter, 3 is a de-emphasis circuit, 4 is horizontal scanning time conversion, 1125 lines → 1
050 scanning line conversion circuit, 5 is sampling frequency conversion circuit, 6 is field interpolation, vertical LPF, 1050 → 525 interlace conversion circuit, 7 is field interpolation, TCI decoding, 525 interlace conversion circuit, 8 is an inverse matrix circuit, 9 is audio data separation, PLL, control signal generation circuit, 10, 11, 12, 17 are output terminals, 13a to 13c are D / A converters, 15
a to 15f are sampling frequency conversion filters, 16a to 16d are
SW circuits, 19a to 19g are constant multipliers, 20a and 20b are one-sample delay circuits, and 21a to 21e are adders. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. An A / D converter that receives a MUSE baseband signal as input and converts an analog signal into a digital signal, and receives an output signal of the A / D converter as input and converts an input signal into a signal having a linear phase. A de-emphasis circuit for inputting an output signal of the A / D converter, an audio data separating circuit for separating and decoding only an audio signal, and an input signal for the output signal of the A / D converter, and synchronizing signal data. And a control signal generating circuit that receives the output signal of the A / D converter, separates and decodes only control signal data, and inputs an output signal of the de-emphasis circuit. And MUSE
From the horizontal scanning time of the system to the horizontal scanning time of the NTSC system,
In addition, the horizontal scanning time conversion and 1125 lines → 1050 lines conversion circuit that extracts only 1050 lines from 1125 lines, and the output signal of the horizontal scanning time conversion and 1125 lines → 1050 lines conversion circuit are input and sampling is performed. When converting the frequency, an interpolation filter for converting without aliasing distortion,
An output signal of the interpolation filter as an input signal, a sampling frequency conversion circuit having a switch circuit that switches at a period of a sampling frequency to be converted, and an output signal of the sampling frequency conversion circuit as an input,
A field interpolation filter for returning a signal folded into a vertical high frequency band by an inter-field offset sampling as a MUSE encoder process to a horizontal high frequency band, and an output signal of the field interpolation filter as an input;
When converting from 50 interlaces to 525 interlaces, a vertical LPF for converting without aliasing distortion, and the output signal of the vertical LPF as input, and 1050 lines for converting from 1050 interlaces to 525 interlaces → 525 interlace conversion circuit, 1050 lines → D / A converter for luminance signal which receives the output signal of 525 interlace conversion circuit and converts digital data to analog signal, and 1125 lines for horizontal scanning time conversion → The output signal of the 1050 scanning line conversion circuit is used as an input signal, and pixels that are not transmitted and
A field interpolation filter for preventing aliasing distortion due to 525-line interlace conversion, and an output signal of the field interpolation filter is input, and a time-division multiplexed luminance signal and color difference signal are separated into only color difference signals. A TCI decoding circuit for extending the time-axis-compressed color difference signal on the time axis and restoring the color difference signal, and an output signal of the TCI decode circuit as an input, and converting the line-sequential color difference signal into RY and BY signals. A 525 interlace conversion circuit for converting both signals into 525 interlaces, and an output signal of the 525 interlace conversion circuit as an input,
Two Rs for converting digital data to analog signal
A D / A converter for a Y signal and a D / A converter for a BY signal; and an output signal of the D / A converter for the Y signal and the D / A converter for the RY signal and the BY signal. And an inverse matrix circuit for converting the signals into R, G, and B signals.
SE-525 converter.