JPH0355986A - Muse 525-line converter - Google Patents

Abstract

PURPOSE:To obtain a picture with high horizontal resolution by adding a sampling frequency conversion circuit to a MUSE-525 line converter so as to expand a horizontal reproduction band in a still picture area. CONSTITUTION:A filter whose gain is 1 at f=0 and whose gain is 0 at f=5.67, 11.34, 17.01[MHz] is realized by a 13-tap transversal filter, receives a MUSE base band signal of a still picture whose time axis is converted at a 525-line system horizontal scanning time, applies 6 kinds of interpolation filter processing, applies inter-field offset sampling at fs=17.01[MHz] and the result is given to a 2-dimension LPF. The filter acts like restoring a signal reflected to a vertical high frequency portion to a horizontal high frequency portion band with the inter-field offset sampling of the MUSE encoder. Then the filter expands the horizontal reproduction band up to 4.2-5.67MHz in the still picture area equivalent to the 525-line system conversion.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a television system converter, and in particular to an M
The present invention relates to a MUSE525 converter that converts television signals from the USE system to the NTSC or EDTV system.

[Conventional technology]

Figure 12 shows the configuration of the MUSE-525 converter presented at the 1986 IEICE Spring National Conference. In the figure, the MUSE baseband signal is input to input terminal 1. After being A/D converted by an 8-bit A/D converter 2, a de-emphasis circuit 3 and audio data separation. The signal is input to the PLL and control signal generation circuit 9. The output 103 of the de-emphasis circuit 3 is input to a horizontal scanning time conversion circuit 4, which converts 1125 lines to 1050 lines. Horizontal scanning time conversion, 1125 lines → 1050 lines The output 104 of the scanning line conversion circuit 4 is a luminance signal system processing circuit, field interpolation, vertical LPF, 1050 lines → 52 lines.
The signal is inputted to a 5-line interlace conversion circuit 6 and a color signal processing circuit for intra-field interpolation, TCI decoding, and 525-line interlace conversion circuit 7, respectively. The output 106 of the luminance signal system processing circuit 6 is an 8-bit D/A converter 13a.
is inputted to one input of the inverse matrix circuit 8 via. On the other hand, the output of the color signal processing circuit 7 (color difference output)
108 and 109 are 8-bit D/A converters 13b and 1, respectively.
3c to other inputs of the inverse matrix circuit 8. Outputs 112, 113 of inverse matrix circuit 8
, 114 are signals converted to R, G, and B, respectively, and are output to the subsequent circuit via output terminals 10, 11, and 12. Next, the operation will be explained.

To convert from MUSE signal to 525 signals, use MUS
Possible methods include a method that performs the same interpolation as the E decoder, a method that performs only intra-field interpolation, and a method that does not perform interpolation at all. Considering the scale of the device, a device that performs MUSEo interpolation is not suitable, and a MUSE signal that does not perform any interpolation will have a lot of aliasing distortion and the resulting image quality will be insufficient. Therefore, this device uses a method that only performs intra-field interpolation.

This signal has a horizontal band of approximately 12.2 MHz. Additionally, edge portions flicker to some extent due to aliasing distortion caused by inter-frame offset subsampling.

However, since the aliasing of MUSE does not exist in the range from 0 to 4 MHz, the aliasing after conversion is not as noticeable as the cross color of the NTSC system. In order to convert a high-visigon signal to a 525-line signal, it is necessary to convert the aspect ratio and the number of scanning lines. Figure 13 shows various conversion methods. Roundness.
In terms of scanning line number conversion, methods ``■'' and ``■'' are practical, and method ``■'' was adopted here. This method extracts a 1050-line image with an aspect ratio of 4:3 from a high-visibility 1125-line image and thins it down to 525 lines, making it easy to filter in the vertical direction. In the structure of the MUSE-525 converter shown in Fig. 12, intra-field interpolation is performed using a 525-wire system as a measure to avoid high-speed signal processing. In addition, the filter structure was designed to serve as both a Buri filter for thinning out to 525 filters and an intra-field interpolation filter, thereby reducing the circuit scale. [Problems to be Solved by the Invention] Since the conventional MUSE-525 converter device is configured as described above, in the still image area, the horizontal band is 4.2 MHZ, which is equivalent to the current TV, when converted to 525 lines. There is no choice but
As the resolution of monitors continues to increase, it is necessary to further widen the horizontal bandwidth. This invention was made to solve the problems of the conventional ones as described above, and uses a relatively simple circuit to theoretically reduce the horizontal band to about 7 questions 2 when converted to a 525-line system in the still image area.
The purpose of this study is to obtain a MtJSE-5 converter device that can expand the band up to 25. [Means for Solving the Problems] The MUSE-5 25 converter device according to the present invention has a sampling frequency conversion circuit added between a 1125 line → 1050 line conversion circuit and an intra-field interpolation circuit. It is.

[Effect]

In the MUSE-525 converter of this invention, by adding a sampling frequency conversion circuit, the horizontal band can be expanded to a maximum of about 7 MHz in terms of 525 lines (however, interframe offset subsampling, interfield offset subsampling and image quality deterioration due to aliasing distortion due to interlacing is ignored).

〔Example〕

An embodiment of this invention will be explained below with reference to the drawings. FIG. 1 shows a MUSE-525 converter according to an embodiment of the present invention. In the figure, input terminal 1 has a MUSE
The base hand signal is input. The input signal 101 is an output 10 of the de-emphasis circuit 3 which is inputted to the de-emphasis circuit 3 and the audio data separation, PLL and control signal generation circuit 9 via the 8-bit A/D converter 2.
3 is input to the horizontal scanning time conversion circuit 4, which converts 1125 lines to 1050 lines. Horizontal scan time conversion, 1125
Book → 1050 lines The output 104 of the scanning line conversion circuit 4 is sent to the sampling frequency conversion circuit 5, which is a luminance signal processing system, and the field interpolation, TCI decoding, and chrominance signal processing system, which is a luminance signal processing system.
25 lines are input to the interlace conversion circuit 7. Output 10 of the sampling frequency conversion circuit 5 which is a luminance signal processing system
5 is intra-field interpolation. Vertical LPF, 1050 pieces → 52
Five lines are input to the interlace conversion circuit 6. Intra-field interpolation. Vertical LPF, 1050 lines → 525 lines Output 106 of interlace conversion circuit 6 is 8-bit D/A conversion circuit 1
3a to one input of the inverse matrix circuit 8. On the other hand, intra-field interpolation is a color signal processing system. The outputs (color difference outputs) 108 and 109 of the TCI decoding and 525-line interlace conversion circuit 7 are each 8-bit D/A.
Transducer 13b. It is input to other inputs (two systems) of the inverse matrix circuit 8 via 13e. Outputs 112, 113, and 114 of the inverse matrix circuit 8 are R, G, and B signals whose horizontal bands have been expanded.

The present 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 sampling frequency conversion is processed using the converted sampling frequency. The sampling frequency conversion circuit will be explained below. The signal input to the sampling frequency conversion circuit 5 is the first
Horizontal scan time conversion shown in the figure! This is the output signal of the 1125 lines → 1050 lines scanning line conversion circuit 4. As mentioned in the conventional example above, converting the MUSE baseband signal to the 525-line standard system requires the number of lines. It is necessary to correct differences in scanning time due to differences in aspect ratio. Therefore, MUSE
The baseband signal has 408 pixels per scanning line and the sampling frequency is 16.2 MHz. This is 525
To convert to this standard system, it is necessary to use 360 pixels per scanning line and a sampling frequency of 11.34 MHz. Also, MUSE encoder has 48.6-32.4 M
Performs Hz sampling frequency conversion. In other words, the decoder needs to perform sampling frequency conversion from 32.4 to 48.6 MHz, but this is the sampling frequency conversion after interpolation, and before interpolation it is 16 MHz.
．． The sampling frequency is converted from 2 to 24.3 MHz. Therefore, the sampling frequency conversion according to the present invention is before interpolation, and is converted from 11.34 to 17 in the 525-line system.
．． 01 MHz sampling frequency conversion.

According to the sampling theorem, as shown in equation (1) below, the original signal can be restored using sampled values, and is expressed as follows.

g(t)-Σg (iT)S (t-iT)...
(1) As shown in Figure 2.3.4, the sample value at the sampling frequency f s = 11.34 MHz before conversion is Q0 1 Ql l Qz + . . I Q
IOI QllI Q+z, ..., and the sampling frequency after conversion f's = 17. OI Ml
Let the sample value at lz be P. ,P,,P. ,...and P
'. ,P'',,P'.,...Qo .Q..
... to Po. P+. ...and P'. , P′. 、・
To convert Q-, QI, Qt,... to g(0
), g(T). g (2T),... (where T = 1
/17. OIM) and substitute it into equation (1) to get g
(t), and add p. , p. ,... and P'.

, P',,... can be substituted for the time t. but,
If the sampling frequency to be converted is an integer ratio, Pi, P'i, and Qj have a specific phase relationship, so it can be further simplified. That is, in principle, this conversion is performed between 11.34 MHz and 17 MHz.
．． It may be possible to interpolate Pi using the least common multiple of 01 MHz, 34.02 MHz, but as shown in Figure 2, the MUSE baseband signal, which has been horizontally time-axis converted to a 525-line system, is sampled with inter-field offset sampling. Therefore, it is necessary to interpolate Pi at the frequency of 68.04 MHz of 34.02 MHz x2. This is sampled at 17.01 MHz with an inter-field offset to obtain Qj. Figures 3 and 4
As shown in the figure, the values obtained by sampling the sampling function at 68.04MHz when T = 1/22.68MHz are So, S+, Sz,... From the phase relationship of the above characteristics, Qj can be divided as follows. Therefore, in order to convert from Qj to Pi, Pi', use the above (2)
The six types of interpolation filters shown in the formula can be arranged as shown in Figure 5. In the above, correct conversion can be achieved if the number of summation terms is infinite, but in reality it is finite.

On the other hand, when considered in the frequency domain, the interpolation filter removes the harmonics generated by the band compression processing of the MUSE method as shown in FIG. This is an LPF for removing the precepts folded back to the baseband due to resampling of OIMllz. In principle 68.04 MH
Since it operates at z, f = 5.67 ・n (MH
! ) (n=0.1, 2, -.6)
It is necessary to sufficiently suppress the characteristics of Therefore, for example, as shown in Fig. 7, the gain is 1 at 110.
．． f -5.67, 11.34.17.01 (
A filter whose gain is 0 at Mllz) can be realized by a transversal filter with 13 taps. Note that the tap coefficients of the six types of interpolation filters are shown in Figure 8. Next, we will discuss the reason for expanding the horizontal band in still images. By using the MUSE baseband signal of a still image whose time axis has been converted to the 525-line horizontal scanning time shown in FIG. 6 as an input signal, and performing six types of interpolation filter processing having the characteristics shown in FIG. 7, As shown in FIG. 9, M = 5.67, 11.34.
The spectra existing at 17.01, 22.68, and 28.35 (MHz) disappear. And f s −1
When inter-field offset sampling is performed at a frequency of 7.01 (MHz), the vertical high-frequency range shown in the shaded area in Figure 10 will be at a horizontal frequency of M = 12.15 to 20 [MHz].
It will be wrapped up until This is sufficiently band-limited by the pre-filter of the MUSE encoder, so it can be reproduced faithfully. However, since the MUSE-525 converter is based on intra-field interpolation, it is necessary to allow aliasing in the time direction in the still image area. Therefore, expanding the horizontal band in an actual image may actually increase temporal aliasing distortion such as flicker in the still image area. M also in the video area
Due to the pre-filter for video of the USE encoder, the horizontal playback band is MUSE system, 16.2 (MHz),
The maximum horizontal band is 5.67 (Ml{z) in terms of 5 2 5 lines.

This problem can be solved by passing the image through a two-dimensional LPF having the characteristics shown in FIG. 10, regardless of whether it is a still image or a moving image. In the still image area, this filter has the function of returning the signal folded back to the vertical high frequency band by interfield offset sampling of the MUSE encoder to the horizontal high frequency band. Therefore, in the still image area with this filter, 5
Horizontal playback band is 4.2-5.67MHz when converted to 25-wire system.
Expand the bandwidth to . Finally, FIG. 11 shows an example 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, and 10a
19g is a constant multiplier, 20a and 20b are 1 sample delay circuits, 21a to 21e are adders, and 16b to 16d are S
It is a W circuit.

In the above example, the MUSE-5 25-line (interlaced) converter was explained, but the MUSE-5 25-line (interlaced) converter was
A standard system adapter device for USE system reception may be used, and the same effects as those of the above embodiments can be achieved.

Furthermore, the same effect can be achieved in the MUSE-5 2 5-wire non-interlaced converter device.

〔Effect of the invention〕

As described above, according to the present invention, the conventional MUSE-52
Since a sunblink frequency conversion circuit is added to the five converters, the horizontal reproduction band is expanded in the still image area, and an image with high horizontal resolution can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a MUSE~525 converter device 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. Diagram showing the pattern, 3rd
Figure 4 shows the principle of sampling frequency conversion, Figure 5 is a simple block diagram of the sampling frequency conversion circuit, and Figure 6 shows the MUSE baseband signal after being converted into 525 horizontal scan times. Figure 7 is a diagram showing the frequency response characteristics of the sampling frequency conversion filter, Figure 8 is a diagram showing the tap coefficients of the sampling frequency conversion filter, and Figure 9 is a diagram showing the sampling frequency conversion in a still image. Figure 10 is a diagram showing a three-dimensional spectrum display after interpolation filter processing. Figure 10 is a diagram showing a three-dimensional spectrum display after interfield offset sampling processing for a still image. Figure 11 is a diagram showing an actual sampling frequency conversion circuit professional. Figure 12 is a block diagram of the conventional MUSE-525 converter device, Figure 13 is an explanatory diagram of conversion from high-definition to 525-line format, and Figure 14 (a) is the sampling pattern after two-dimensional LPF processing. Figure 14(b) is a two-dimensional LP
FIG. 3 is a diagram showing a three-dimensional spectrum display after F processing. In the figure, 1.14 is an input terminal, 2 is an A/D converter,
3 is a de-emphasis circuit, 4 is a horizontal scanning time conversion, 1
125 lines → 1050 lines scanning line conversion circuit, 5 is a sampling frequency conversion circuit, 6 is a field interpolation circuit. Vertical LPF
, 1050 → 525 line interlace conversion circuit, 7 is field interpolation, TC ■ decoding, 525 line interlace conversion circuit, 8 is inverse matrix circuit, 9 is audio data separation, PLL, control signal generation circuit, 10, 11
, 12.17 is the output terminal, 1 3 a S-1 3 c
is a D/A converter, and 15a to 15f are sampling frequency converters. conversion filter, 16a to 16d are SW circuits, 19a
~l9g is a constant multiplier, 20a and 20b are one sample delay circuits, and 21a to 21e are adders. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) An A/D converter that takes the MUSE baseband signal as input and converts it from an analog signal to a digital signal, and a digital converter that takes the output signal of the A/D converter as input and converts the input signal into a linear phase signal. an emphasis circuit; an audio data separation circuit that takes the output signal of the A/D converter as input and separates and decodes only the audio signal; and an audio data separation circuit that takes the output signal of the A/D converter as input and separates only the synchronization signal data. a PLL circuit that separates and generates a clock; a control signal generation circuit that receives the output signal of the A/D converter and separates only control signal data and decodes it; and a control signal generation circuit that receives the output signal of the de-emphasis circuit as input; M.U.
A horizontal scanning time conversion circuit that converts SE system horizontal scanning time to NTSC system horizontal scanning time and extracts only 1050 scanning lines from 1125 scanning lines; The output signal of the 1125 lines → 1050 line scanning line conversion circuit is input, and when converting the sampling frequency, an interpolation filter is used to convert the sampling frequency without aliasing distortion, and the output signal of the interpolation filter is used as the input signal, and the sampling frequency to be converted is set. 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 input;
An intra-field interpolation filter that returns the signal folded back to the vertical high-frequency band by inter-feed offset sampling, which is MUSE encoder processing, to the horizontal high-frequency band; and an input signal of the intra-field interpolation filter,
When converting from 050 lines non-interlace to 525 lines non-interlace, use a vertical LPF to convert without aliasing distortion and the output signal of the vertical LPF as input to convert from 1050 lines non-interlace to 525 lines non-interlace. Do 1
050 line → 525 line interlace conversion circuit; a luminance signal D/A converter that receives the output signal of the 1050 line → 525 line interlace conversion circuit and converts digital data into an analog signal; and the horizontal scanning time. An intra-field interpolation filter that uses the output signal of the conversion and 1125-line → 1050-line scanning line conversion circuit as an input signal and prevents aliasing distortion due to untransmitted pixels and 525-line interlaced conversion; a TCI decoding circuit which receives the output signal of the filter, separates the time-division multiplexed luminance signal and chrominance signal into only chrominance signals, and expands the time-axis compressed chrominance signal and returns it to its original state; a 525-line interlace conversion circuit that receives the output signal of the TCI decoding circuit and converts the line-sequential color difference signal into 525-line interlace for both R-Y and BY signals; and the 525-line interlace conversion circuit. two D/A converters for the RY signal and the B-Y signal, which take an output signal as an input and convert digital data into an analog signal; the D/A converter for the Y signal and the D/A converter for the RY signal; ,B-
The output signal of the D/A converter for Y signal is input, and the R, G,
A MUSE-525 converter characterized by comprising an inverse matrix circuit for converting into a B signal.