JP2809738B2 - Video signal converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention converts a high-definition television signal having a larger number of scanning lines and an aspect ratio than a standard television signal into a standard television signal. To a video signal conversion device.

(Prior Art) TC as a high-definition television signal having a larger number of scanning lines and an aspect ratio than a standard television signal, and two color difference signals being line-sequential by a dot interlace method.
Some are encoded in the I method.

FIG. 8 shows a television signal converter for converting the high-definition television signal into a standard television signal.

A high-definition television signal is input to an analog-to-digital (hereinafter referred to as A / D) converter 11 via an input terminal 10,
It is converted to a digital signal. The input pattern of the luminance signal is dot-interlaced, for example, as shown in FIG. The solid line is the scanning line of the first field, and the position of the mark is the sub-sample phase position of the luminance signal. The dotted line is the second field, and the position of the triangle is the sub-sample phase position of the luminance signal. This signal is input to the input processing device 12, where processing such as de-emphasis processing is performed. The output signal of the input processing device 12 is input to the time axis conversion device 13. The time axis conversion device 13 is, for example, 11
25 lines / 60Hz, 1 horizontal scanning time of 2: 1 signal is 525 lines / 60Hz,
Since this is converted into one horizontal scanning time of a 1: 1 signal, this processing is performed commonly for the luminance signal and the color difference signal. Further, this output signal is supplied to a field interpolation and scanning line number conversion device 14.
, An interpolation process using the upper, lower, left and right data is performed, and the number of scanning lines is converted from 1125 to 525.

Here, the luminance signal Y and the chrominance signal C are further separated and input to the luminance signal D / A converter 16 to be converted into an analog signal. On the other hand, the color difference signal C is
The data is input to 17 and TCI decoding and time axis expansion are performed. That is, the chrominance signal is time-axis-compressed (for example, compressed to 1/4) and multiplexed during the horizontal blanking period of the luminance signal, and the (RY) signal and the (BY) signal are line-sequential. Decode this because it is

The color difference signal C is time-expanded by a factor of 4 by the expansion device 17a, and the TCI decoder 17b uses the upper and lower lines of the (RY) signal and the (BY) signal that are not present in the current line. Interpolated and the two color difference signals are synchronized.
The (RY) signal and the (BY) signal are respectively D / A
The signals are input to the converters 18a and 18b and are converted into analog signals.

According to the above method, as shown in FIG.
Lines / 60Hz, the aspect ratio is, for example, 16: 9.
Conversion to a standard television signal of 60 Hz and an aspect ratio of 4: 3 can be easily realized. Reference numeral 51 denotes a display screen, and a hatched portion is a truncated line.

(Problems to be Solved by the Invention) According to the above-mentioned conventional converter, the upper, lower, left and right sides are cut out from a high-definition television signal of 1125 lines / 60 Hz and an aspect ratio of 16: 9 as shown in FIG. The standard television signal is converted to 525 lines / 60Hz and the aspect ratio is 4: 3. Therefore, according to this method, if important information is generally present in the peripheral portion of the screen, this is lost. Also, if important information is added to the center of the screen on the transmission side in consideration of this conversion and transmitted, a viewer watching a high-definition television signal may feel very unnatural. Further, converting a movie or the like by this method may cause a copyright problem.

Furthermore, the effective horizontal scanning rate according to the HDTV studio standard is about 87.3%. The horizontal effective scanning rate according to the NTSC system is 82.8%. Here, when converting a signal transmitted by the MUSE system with a horizontal effective scanning rate of 77.9% to an NTSC system signal, if a true circular image conforming to the HDTV studio standard is to be accommodated in the NTSC horizontal effective scanning period, about Appears as a 10% landscape circle. So, conversely, NTSC
If the entire MUSE signal is contracted and converted so that it becomes a perfect circle when converted to the method, a horizontal blanking period appears on the display screen.

Therefore, the present invention does not lose important information of a high-definition television signal, can convert it to a standard television signal with a minimum hardware scale, and furthermore, even when displayed on a display. It is an object of the present invention to provide a video signal conversion device capable of performing signal processing so that the ratio between the horizontal and vertical lengths of images on a sending side and an image receiving side does not greatly change.

[Constitution of the Invention] (Means for Solving the Problems) The present invention relates to a high-definition television system which has a larger number of scanning lines than a standard television signal and in which two color difference signals are line-sequentially encoded by a time axis compression method. A conversion device for converting a television signal into a standard television signal, comprising: input signal processing means for performing a certain signal processing such as interpolation processing on the high-definition television signal; and at least one output signal of the input signal processing means. 1st delay horizontal scanning time
And a color signal of the output signal of the input signal processing means and the output signal of the first delay means is selected from the output signal of the input signal processing means and the output signal of the first delay means. Signal selecting means for selecting and outputting the output signal of the input signal processing means for the luminance signal, and controlling the signal selecting means to provide n (n ≧ n)
1) A control signal generating means for outputting a control signal for causing the signal selecting means to select a color difference signal from the delay means for each horizontal scanning time, and the number of scanning lines of an output signal from the signal selecting means is set to a standard television. When the output signal from the signal selecting means is temporarily stored in the field memory in order to change the number of scanning lines of the signal by thinning, the writing timing is controlled, and the color signal period and the luminance signal are also applied to the signal of the writing line Between the periods, a write inhibit period of a predetermined period is provided, and in order to maintain a similar horizontal and vertical balance between an image based on an output signal from the signal selecting means and an image based on a signal read from the field memory, The frequency of the read clock is made lower than the frequency of the write clock to the memory, and m = n−8k ((k = 2,3,4), 1 of the input side of the signal
(The number of horizontal samples, m is the number of samples in the period in which the color and luminance are adjusted) and the number of scanning lines and time axis conversion means.

(Operation) By the above means, the line-sequential relationship of the color difference signals can be maintained by the control signal generating means and the signal selecting means even if the scanning line conversion processing device thins the lines, and the thinning is performed by the thinning. It is possible to compress important information without losing it by the scanning line conversion processing, and to process the luminance signal and the chrominance signal in common. Further, by controlling the writing and reading of the field memory, the image can be displayed without causing a large difference between the aspect ratio of the image based on the high-definition television signal and the aspect ratio of the converted image.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In this embodiment, the aspect ratio differs with a larger number of scanning lines than a standard television signal (for example, an NTSC television signal), and two color difference signals (for example, a (RY) signal and a (B- Y) signals) are line sequential,
A description will be given of an example of converting a high-definition television signal (for example, a MUSE television signal) encoded by the TCI method into a standard television signal. Also,
The display state after the conversion is as shown in FIG. 5 (A).

A high-definition television signal is input to the A / D
The signal is supplied to the converter 11 and converted into a digital signal. The sampling clock Φ1 here is, for example, Φ1 = 16.2 MHz.
It is.

The digitized signal is input to the input processing device 12 at the next stage, where processing such as non-linear expansion and de-emphasis processing is performed. The output signal of the input processing device 12 is input to the aliasing removal / interpolation processing device 20.

In the aliasing removal / interpolation processing device 20, the input pattern of the luminance signal is dot-interlaced, for example, as shown in FIG. The solid line is the scanning line of one field, and the position of the mark is the sub-sample phase position of the luminance signal. The dotted line is the second field, and the position of the triangle is the sub-sample phase position of the luminance signal. This signal is subjected to an interpolation process using the data in the field, and is converted into a signal as shown in FIG.
At the same time, aliasing components are removed by dot interlacing using a digital filter.

Next, the output signal of the aliasing removal / interpolation processing device 20 is
It is input to the pre-processing device 21.

The signal input to the preprocessing device 21 is input to the unit delay elements 212 and 213 via the unit delay element 211.

The output signal of the unit delay element 212 is supplied to the selector 215 via the unit delay element 214. On the other hand, the unit delay element 213
Are output to the selector 215 via the unit delay element 217 after being delayed by one horizontal scanning period in the line memory 216. The selector 215 is controlled by a control signal CN1 from the synchronization control device 29, and continuously selects, for example, every three horizontal scanning periods among the signals from the line memory 216, each color difference signal of three horizontal scanning periods, The luminance signal can be selected from the unit delay element 214 (the timing chart is shown in FIG. 2). The output of the selector 215 is output via the unit delay element 218.

FIG. 2 is a timing chart showing the operation of the preprocessor 21 in a signal conversion mode for converting a high definition television signal into a standard television signal.

FIG. 2A shows an output video signal of the unit delay element 214, which is supplied to one input unit of the selector 215. FIG. 11B shows a video signal output from the unit delay element 216 via the line memory 216, and is supplied to the other input section of the selector 215. There is a shift of one horizontal scanning period between the two video signals.

The control signal CN1 has a period in which it is at a low level corresponding to the color difference signal position at the timing shown in FIG. 9C, and in this period, the selector 215 selects a signal on the unit delay element 216 side. Accordingly, in the video signal output from the selector 215, as shown in FIG. 2 (D), the color difference signals of the three horizontal scanning periods continuously from the unit delay element 216 exist every three horizontal scanning periods. However, there is a luminance signal selected from the unit delay element 214 side.

A processing signal (FIG. 2 (D)) from the preprocessing device 21 is supplied to the unit delay element 301 of the scanning line number / time axis conversion device 30. The number-of-scanning-lines / time-axis conversion device 30 performs the conversion of the number of scanning lines and the conversion of the time axis using the field memory 302 to which the output of the unit delay element 301 is supplied. That is, as shown in FIG. 5 (A), data compression is performed in the horizontal and vertical directions so that a high-definition television signal having an aspect ratio of 16: 9 can be displayed on a display having an aspect ratio of 4: 3 without loss of information. Part.

After the output of the field memory 302 passes through the unit delay element 303, the luminance signal output control device 32 and the chrominance signal output control device 33
Supplied to

First, the normal operation when the number of scanning lines and the time axis of the high definition television signal are converted (compressed) in the number of scanning lines / time axis conversion device 30 will be described.

Assuming that the number of scanning lines of a high-definition television signal in the vertical direction is, for example, 1032, the number of scanning lines is thinned out at a ratio of one to three when viewed in frame units, and is reduced to 1/3, that is, 344 scanning lines. Decimate the signal and convert the rest to 688 lines.

To this end, as shown in FIG. 2 (E), the control signal CN3 from the synchronization control device 29 causes the field memory 302 of the input video signal to be output once every three horizontal scanning periods.
It is only necessary to prohibit the writing to. As a result, the number of effective scanning lines is converted from 1032 lines to 688 lines. This writing process is performed simultaneously without distinguishing the luminance signal and the color difference signal. The clock for this writing process is Φ2, and Φ2
2 = 32.4 Mhz. This is because interpolation data is added in the aliasing removal / interpolation processing device 20 as shown in FIG.

The signal written in the field memory 302 in this manner is read at a clock rate of, for example, 936fH = 29.48 MHz, and is derived through the unit delay element 303. As a result, one horizontal scanning period of a high-definition television signal corresponds to the number of scanning lines.
The time axis is converted in one horizontal scanning period of a 525-line, 1: 1 interlace ratio signal (FIG. 2 (F)). Here, since the upper and lower 80 lines do not form an effective screen, there is no problem even if they are truncated at the time of memory reading.

This output signal is input to a luminance output processing device 32, where processing such as extraction of a luminance signal portion and addition of a blanking signal is performed in accordance with the specifications on the output side, and is converted into an analog video signal by a D / A converter 34. It is converted and derived to an output terminal. 2 (F) is also input to the color signal processing device 33. Here, a color difference signal is extracted. First, a color difference signal is written to the line memory and then read out with a clock having a period four times as long as the write clock. As a result, the color difference signal which has been compressed by a factor of 1/4 and which has been present in a part of one horizontal scanning period is restored to the original time (525 scanning lines, 1: 1
It is expanded during one horizontal scanning period of the interlace signal).

Further, since the (RY) signal and the (BY) signal are line-sequential as shown in FIG. 6, it is necessary to convert the color difference signal into sequential scanning. That is, for example, in the line No. 2 in FIG. 6, only the (BY) signal exists,
The (RY) signal is interpolated and synthesized using the data of the upper and lower lines NO.1 and NO.3. In line No.3,
The (RY) signal is used as it is for this line,
The (BY) signal is interpolated using signals existing in the upper and lower lines.

The color difference signal obtained in this manner is subjected to processing such as addition of a blanking signal in the same manner as the luminance signal, corrected to a signal conforming to the specifications on the output side, and output, and the D / A converter 35 converts the analog signal into an analog signal. After that, the signal is derived to an output terminal.

The synchronization control device 29 in FIG. 1 generates the above-mentioned control signal, synchronizes the internal system clock with the input television signal according to the control signal of the high definition television signal, and outputs the same. A basic clock of the television signal is generated, and the television signal on the input side and the television signal on the output side are synchronized.

In the above description, the display mode of FIG. 5 (A) is shown. However, the present invention is not limited to this. For example, as shown in FIG. 5 (B),
It is needless to say that a display in which the upper and lower sides in the vertical direction and the left and right sides in the horizontal direction are cut can be realized.

Further, in this embodiment, when performing the interpolation processing as shown in FIG. 3, the interpolation is performed while weighting each interpolation data in the vertical direction. This is because, when the number of scanning lines is converted by thinning, the information above and below the thinned scanning lines is information of a position vertically separated,
The balance with the picture in the area where no thinning was performed will be shifted. In order to cover such a problem, vertical weighting processing is performed. Example 4
This will be described with reference to the drawings.

FIG. 4 (A) shows the arrangement position of the pixels (marked by ●) in the odd field and FIG. The X mark is the interpolated pixel. In this way, for example, the third line, the sixth line, the ninth line, etc. are weighted so that the upper and lower lines of the luminance signal of the thinned line are closer to the vertical direction (approximate the pattern of the upper and lower lines). Is performed, the picture at the time of the thinning-out processing is in a well-balanced compressed state as a whole. This can be understood by comparing the arrangement of the luminance signals in FIGS. 2 (D) and 2 (F).

According to this embodiment described above, the line-sequential relationship of the color difference signals can be maintained by the control signal generator and the signal selector even if the scanning line conversion processing device thins out the lines. In the thinning-out, when the same color difference signal exists at least between adjacent lines by the selecting means, one of the lines is thinned out. Further, it is possible to compress important information without losing it by the scanning line conversion processing by thinning, and to process the luminance signal and the chrominance signal in common.

Next, in the above-described system, the following control is performed so that the similarity in the vertical and horizontal directions between the video based on the MUSE system and the video based on the converted standard television signal is maintained. That is, the writing / reading clock of the field memory 302 is controlled as follows so that the perfect circle of the image based on the signal of the MUSE system is also the perfect circle in the image obtained in the standard television signal.

FIG. 7 is a timing chart when one line of sampling data is written into the field memory 302.

FIG. 7A shows the write clock S1, and FIG.
Represents a write enable signal S2, FIG. 4C represents a read clock S3, and FIG. 4D represents a read enable signal S4.

If the write clock is 32.4 MHz and the input signal is, for example, 960 samples, the color signal period of which is 188
The sample and the luminance signal period are 748 samples. Therefore, the write enable signal S2 controls the field memory so that only the color signal and the luminance signal are written to the field memory. Therefore, in the horizontal direction it is actually 936
Sample data is entered. This data is read with a 29.48 MHz clock during the read enable period.
The read enable signal S4 goes low only during the vertical blanking period, and inhibits reading.

As described above, a sample of only the chrominance signal and the luminance signal is input to the field memory 302 and read out with a clock having a horizontal frequency times the number of samples (936 fH), thereby obtaining a video image having no distortion in the vertical and horizontal directions. A signal can be obtained.

Next, in this embodiment, the background in which the above read clock is set will be described with more specific numerical values.

In the HDTV standard, the effective horizontal scanning rate is 1920/2200 samples = 87.3%. The effective vertical scanning rate is 1035/1125 lines = 92.0%. In the NTSC standard, the effective horizontal scanning rate is 52.656 / 63.556 μs = 82.8%. The effective vertical scanning rate is 483/525 lines. = 92.0% The ratio of the perfect circle in HDTV to the converted circle is (4/3) /
(16/9) x (525/375) x (1 / 82.8) / (1 / 87.3) = 1.1
07. When this ratio is 1, there is no distortion, but in this case, it means that a horizontal circle of 10.7% will be obtained if this ratio remains as it is.

In the encoder, since the luminance signal is compressed at 12:11 in order to secure the period of the TCI-encoded color information, 960 × (11/12) = 880 samples (the signal after interpolation) is actually used. Is a luminance signal. Therefore, to make this a perfect circle, 880
× 1.107% = 974.16 samples are required. However, you can't really expect more than 960 samples. Here, according to a subjective judgment, if you do not mind the distortion of the circle,
It is less than 3% vertically.

Therefore, assuming that the distortion of the circle is kept within 5% of the horizontal length, which is not noticeable, it is sufficient that 974.16 × (1.05 / 1.107) = 924 samples or more.

If an attempt is made to approach a perfect circle at the time and after the conversion of the scanning line, horizontal blanking appears on the screen. Therefore, it is necessary to take measures during the conversion. Here, the horizontal effective scanning rate of the MUSE system is (374/480) = 0.779.

Therefore, if the read clock at the time of conversion is selected to be 936fH, 974.16 / 936 = about 1.040, which is a 4% horizontally long circle.
The effective scanning rate after conversion is (960/936) x 77.9 = about 79.9%. As a result, it is possible to obtain an image of a perfect circle that does not matter without horizontal blanking appearing. In other words, the image can be converted without causing distortion in the horizontal and vertical lances of the image on the sending side.

Looking at the ratio between the HDTV clock and the clock on the conversion side, (1125/2, 480 fH): (525, 936 fH) = 50: 91. This ratio is the smallest integer ratio, which means that it is easy to synchronize HDTV and NTSC systems. Here, the number of samples of the input side signal and the converted side signal is generally m = n−8k (k = 2, 3, 4). n is the number of one horizontal sample of the signal on the input side, and m is the number of samples in the period in which the color and luminance are adjusted.

[Effects of the Invention] As described above, according to the present invention, important information of a high definition television signal can be converted into a standard television signal without losing important information and with a minimum hardware scale. Further, even when the image is projected on the display, the signal processing can be performed so that the ratio of the horizontal and vertical lengths of the image on the sending side and the image on the receiving side does not greatly change.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a signal waveform diagram shown for explaining the operation of the circuit of FIG. 1,
FIGS. 3 and 4 are explanatory diagrams of a pixel arrangement for explaining the operation of the circuit of FIG. 1, FIG. 5 is a diagram showing an image display example obtained when a video signal is converted, and FIG. FIG. 7 is an explanatory diagram of the pixel arrangement for explaining the operation of the color signal processing device of the circuit of FIG. 1, FIG. 7 is a timing chart for explaining the circuit operation of this embodiment, and FIG. FIG. 3 is a circuit diagram showing a scanning line and aspect ratio conversion device. 11 A / D converter, 12 Input processing device, 20 Folding removal / interpolation processing device, 21 Preprocessing device, 30 Number of scanning lines / time axis conversion device, 31 Field Memory, 32 ...
... Luminance signal output control device, 33 ... Color signal output control device,
34, 35 ... D / A converter.

Claims (1)

(57) [Claims] 1. A converter for converting a high-definition television signal having a larger number of scanning lines than a standard television signal and encoding two color difference signals in a line-sequential manner by a time axis compression method into a standard television signal. An input signal processing unit for performing a constant signal processing such as an interpolation process on the high-definition television signal; a first delay unit for delaying an output signal of the input signal processing unit by at least one horizontal scanning time; The color signal of the output signal of the input signal processing means and the output signal of the first delay means can be selected and output from the output signal of the input signal processing means and the output signal of the first delay means. A signal selecting means for selecting and outputting an output signal of the input signal processing means for the luminance signal; and controlling the signal selecting means to control the signal every n (n ≧ 1) horizontal scanning times. Control signal generating means for outputting a control signal for causing the signal selecting means to select a color difference signal from the delay means; and thinning out the number of scanning lines of an output signal from the signal selecting means to the number of scanning lines of a standard television signal. When the output signal from the signal selection means is temporarily stored in the field memory for conversion, the write timing is controlled,
A write inhibit period of a predetermined period is provided between the color signal period and the luminance signal period for the signal of the write line, and an image based on an output signal from the signal selection unit and an image based on a signal read from the field memory are provided. Video signal conversion means for converting the number of scanning lines and the time axis in which the frequency of the read clock is made lower than the frequency of the write clock to the field memory in order to maintain a similar balance in the horizontal and vertical directions. apparatus.