JP2000316141A - Device and method for scanning line number conversion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of folded distortion in a vertical direction by equally converting resolutions and the number of scanning lines of inputted video signal of plural forms and resolutions and the number of scanning lines of the number of scanning lines of an NTSC, a PAL, an SECAM and the like and converting the video signals into forms such as the NTSC, the PAL, the SECAM or the like. SOLUTION: An input signal digitized by an A/D 4 has a high band element in a vertical direction of a video eliminated by a vertical direction LPF 5, and folding distortion in the vertical direction to be generated in converting the number of scanning lines is prevented. The input signal whose high band element in the vertical direction to the video is eliminated is inputted to a scanning line number conversion part 6 and converted into the same number of scanning lines as a conventional system. After conversion of the number of scanning lines, a digital video signal output 9 has the number of operation lines and an operation clock converted by the scanning line number conversion part 6 and it is made to be a signal input in the same form as the one a video encoder 12 deals with.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to NTSC, PA
The present invention relates to an HDTV broadcast receiver having a video output terminal such as L or SECAM.

[0002]

2. Description of the Related Art At present, MUSE broadcasts have been put into practical use as HDTV broadcasts, and set-top boxes for viewing MUSE broadcasts on a general NTSC broadcast television receiver and recording on a high-definition television. MUSE system in the form of an output terminal for
An MN converter for converting to the SC system has been put to practical use. The MN converter is a kind of a scanning line number conversion device.

[0003]

On the other hand, digital HDTV broadcasting such as DTV in the United States and BS digital in Japan is being put to practical use. In digital broadcasting, HDTV broadcasting or SDTV broadcasting of two or three channels may be used depending on time of day.
Also in HDTV broadcasting, broadcasting of a system with a different number of scanning lines is performed. Therefore, digital HDTV broadcast receivers have 10
It is required to support a plurality of broadcast formats such as 80i, 720p, 480p, and 480i. As a result, digital HDTV reception set-top boxes and digital HDT
A problem arises in that a system that converts the number of scanning lines and outputs a video signal such as NTSC, such as a recording output terminal of a V-compatible television, must also support a plurality of broadcast formats.

[0004]

According to the present invention, as a method for solving the above-mentioned problems, a horizontal synchronizing frequency and an operating clock frequency are set so that an input section of a video signal of a scanning line number conversion apparatus can cope with a plurality of broadcasting formats. And the like, and by making the scanning line number conversion algorithm of the scanning line number conversion unit variable according to the broadcast format, conversion from a plurality of broadcast formats to a video signal such as NTSC is enabled.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A basic embodiment of the present invention is as follows.
By making the horizontal synchronization frequency, the operating clock frequency, and the like variable, a video signal input unit corresponding to a plurality of formats having a resolution equal to or higher than the conventional resolution such as NTSC, PAL, and SECAM and the number of scanning lines; By having a plurality of line number conversion algorithms, the resolution and the number of scanning lines of a plurality of input video signals can be adjusted to NTSC, PA
L, SECAM and other resolutions, a scanning line number conversion unit that converts the number of scanning lines equivalently, and a video encoder unit that converts the video signal converted by the scanning line number conversion unit into a format such as NTSC, PAL, SECAM, etc. A scanning line number conversion device is configured. With this configuration, a set-top box for viewing a digital HDTV broadcast having a plurality of broadcast formats on a conventional television receiver or a video for recording on a video tape recorder compatible with a conventional broadcast system is provided. A digital HDTV broadcast-compatible television having an output terminal can be realized.

In addition to the basic embodiment of the present invention, a configuration in which a vertical low-pass filter is provided between a video signal input section and a scanning line number conversion section is conceivable. With such a configuration, it is possible to prevent vertical aliasing generated at the time of scanning line conversion.

In addition to the basic embodiment of the present invention, a matrix section for converting a mixing ratio of each of RGB signals included in a luminance signal and a color difference signal is provided between a video signal input section and a video encoder section. Configurations are possible. With such a configuration, the mixing ratio of the luminance signal and the color difference signal in the received video signal and the RGB signals of the luminance signal and the color difference signal specified by the standard in the signal format output from the video encoder unit is Even in different cases, the difference can be absorbed.

In the basic embodiment of the present invention, it is conceivable to provide a function of converting the aspect ratio of a video signal when converting the number of scanning lines of a video signal input by a scanning line number conversion unit. . By providing this function, processing such as providing letterboxes above and below the received video, or cutting off the left and right edges of the received video,
A received video having an aspect ratio of 16: 9 is converted to an aspect ratio of 4: 3.
Can be viewed on conventional television receivers.

In a basic embodiment of the present invention, an input section of a video signal is constituted by an A / D converter,
A configuration in which a signal is input to a D converter through a low-pass filter that prevents aliasing distortion, and an input video signal is sampled at a sampling frequency according to the number of effective pixels in one horizontal period after being converted by a scanning line number conversion unit. Can be considered. Originally, the number of scanning lines is converted, and the signal output from the video encoder has only a narrower bandwidth than the original HDTV video signal. Therefore, by adopting this configuration, the bandwidth of the input HDTV signal is handled as it is. In addition, the video signal input unit and the scanning line number conversion unit can be operated with a low frequency clock.

In the basic embodiment of the present invention, it is conceivable that the input section of the video signal is made a digital input, and is constituted by a digital low-pass filter for preventing aliasing and a sampling frequency converter. Originally, a digital HDTV broadcast receiver handles a signal digitally until immediately before decoding and outputting a received signal. Therefore, by using a digital input for an input portion of a video signal, signal degradation due to noise or the like can be prevented. In addition, by providing a digital low-pass filter for preventing aliasing distortion and a sampling frequency converter in the input section of the video signal, the scanning line number conversion section can be operated with a clock of a minimum required minimum frequency.

In the basic embodiment of the present invention, the video signal converted by the scanning line number conversion unit is output as a digital signal before being converted into a format such as NTSC, PAL, or SECAM by a video encoder. Conceivable. With such a configuration, NTSC, PAL, SEC
It becomes easy to incorporate a device that performs signal processing such as image quality correction before conversion into a format such as AM.

In addition to the basic embodiment of the present invention, the HD
Apart from the TV video signal input section, NTSC, PAL, S
It has a digital video signal input of the same resolution as ECAM (hereinafter referred to as SDTV digital video signal input), and has a selector between the scanning line number conversion unit and the video encoder unit. Signal and the above S
A configuration in which a signal from a DTV digital video input is switched and a signal is transmitted to a video encoder unit is conceivable. At present, digital signal processing is frequently used also in signal processing of a conventional television broadcast system. Therefore, by adopting such a configuration, a set having both a digital HDTV broadcast reception function and a conventional television broadcast reception function is provided. Switching between digital HDTV broadcasting and conventional broadcasting can be easily performed in a top box or a television receiver. In addition, by having the digital output of the signal after the conversion of the number of scanning lines according to claim 7, it becomes easy to incorporate a device for performing signal processing such as image quality correction before converting to a format such as NTSC, PAL, or SECAM. .

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention. FIG. 1 shows claims 1, 2, 3,
It is an embodiment of claim 4, claim 5, claim 7, or claim 8.

A digital HDTV broadcast signal which has been received, decoded and converted into an analog signal is inputted from an HDTV analog video signal input 1 and after a high frequency component causing aliasing distortion is removed by an aliasing prevention low-pass filter 2. , A / D converter 4. The sampling frequency in the A / D converter 4 is determined by a clock generated by the A / D converter clock generator 3. The clock frequency generated by the A / D converter clock generator 3 is determined by the following procedure.

First, the number of effective pixels per scanning line after the conversion of the number of scanning lines is divided by the ratio of a period other than blanking in one scanning line before the conversion of the number of scanning lines, and the result is closest to the result. Find an integer value. The value obtained by multiplying the obtained integer value by the horizontal synchronization frequency before the conversion of the number of scanning lines is the frequency of the clock generated by the A / D converter clock generator 3. H
Since the signal input from the DTV analog video signal input 1 has a plurality of formats, the frequency of the clock generated by the A / D converter clock generator 3 is variable according to the signal format before scanning line conversion.

The input signal digitized by the A / D converter 4 is subjected to a vertical low-pass filter 5 to remove vertical high-frequency components of the image. The A / D converter 4 has a line memory for one or more scanning lines, and removes a high-frequency component in the vertical direction of the video signal by performing calculations between different scanning lines. By removing the high frequency component in the vertical direction of the video signal, it is possible to prevent aliasing distortion in the vertical direction that occurs when the number of scanning lines is converted.

The input signal from which the high-frequency component in the vertical direction of the image has been removed by the vertical low-pass filter 5 is input to the number-of-scanning-lines conversion section 6 and converted into the same number of scanning lines as the conventional system such as NTSC, PAL, SECAM or the like. Is done. Since the signal input from the HDTV analog video signal input 1 has a plurality of formats, the scanning line number conversion unit 6 has a plurality of conversion algorithms according to the format. When converting the number of scanning lines, the number of effective scanning lines after conversion should be smaller than the number of effective scanning lines in the format after conversion such as NTSC, PAL, SECAM, etc. By inserting a box to make up, a video having an aspect ratio of 16: 9 can be viewed with a correct roundness on a conventional television having an aspect ratio of 4: 3 in a format in which letter boxes are inserted above and below. In addition, the scanning line number conversion unit 6 adjusts the operation clock frequency with the video encoder 12,
Clock conversion is performed so that a signal input by the clock generated by the D converter clock generator 3 is output by the clock generated by the video encoder clock generator 7.
At the time of clock conversion, of the effective signal period in one horizontal scanning period, a period corresponding to both ends of the screen is cut off, the remaining effective signals are complemented, and the screen is expanded in the horizontal direction, so that the aspect ratio is 16 : 9 video can be viewed on a conventional television having an aspect ratio of 4: 3 at the correct roundness in a format in which the left and right are cut off.

The signal obtained by converting the number of scanning lines and the operation clock in the number-of-scanning-lines conversion section 6 is input to an RGB mixing ratio conversion matrix 8. The mixing ratio of the RGB signals of the luminance signal and the color difference signal input from the HDTV analog video signal input 1 is equal to the R of the luminance signal and the color difference signal handled by the video encoder 12.
When the mixing ratio is different from the mixing ratio of each of the RGB signals, the RGB mixing ratio conversion matrix 8 converts the input signal into a video encoder 12.
The conversion is performed so as to be the same as the mixing ratio of the RGB signals of the luminance signal and the color difference signal handled in the above.

Digital video signal output 9 after scanning line number conversion
Are converted in the number of scanning lines and the operation clock by the number-of-scanning-lines conversion unit 6, and the luminance signal,
The mixing ratio of each of the RGB signals of the color difference signal is the video encoder 1
A signal converted to be the same as the format handled in 2 is output. The SDTV digital video signal input 10 is a signal input of the same format as the format handled by the video encoder 12.

The video signal selector 11 switches between the output of the RGB mixing ratio conversion matrix 8 and the input from the SDTV digital video signal input 10,
Send to The video signal selector 11 controls the digital HDT
Switching between V-broadcasting and conventional television broadcasting can be easily performed. In addition, after the number of scanning lines is converted, the digital video signal output 9 and the video signal selector 11 convert the number of scanning lines to NT.
It is easy to perform image quality correction before converting to a video signal such as SC, PAL, or SECAM.

The signal selected by the video signal selector 11 is converted by the video encoder 12 into NTSC, PAL, SEC
It is converted to a video signal such as AM and output from a video signal output 13.

(Embodiment 2) FIG. 2 shows a second embodiment of the present invention. FIG. 2 shows the first and sixth embodiments.

The received and decoded digital HDTV broadcast signal is input from the HDTV digital video signal
After being input in synchronization with the clock input from the DTV digital video signal clock input 15 and removing the high frequency components that cause aliasing distortion due to the sampling frequency conversion by the aliasing distortion prevention digital low-pass filter 16, the sampling frequency converter 17 And the sampling frequency is converted. The converted sampling frequency is determined by a clock generated by the scanning line number conversion clock generator 18. The procedure for determining the frequency of the clock generated by the scan line number conversion clock generator 18 is as follows.
This is the same as the case of the A / D converter clock generator 3 in the first embodiment.

The signal whose sampling frequency has been converted by the sampling frequency converter 17 is sent to the scanning line number converter 6.
Is input to Subsequent processing is the same as in the first embodiment, and a description thereof will not be repeated.

[0025]

FIG. 3 to FIG. 12 show examples of the method of converting the number of scanning lines in the first embodiment and the second embodiment. 3 to 12, white circles indicate scanning lines before conversion and black circles indicate scanning lines after conversion. The conversion of the number of scanning lines is performed by multiplying the scanning lines before conversion by a certain coefficient and adding the scanning lines after multiplying the coefficients. The values shown to the right of the black circles in FIGS. 3 to 12 are coefficients for multiplying the scan line before conversion. The coefficients shown in FIGS. 3 to 12 are examples, and the interval between the centers of gravity of the scanning lines after the conversion of the number of scanning lines becomes substantially constant within the range of the calculation accuracy of the multiplier used, and
The coefficient may be determined so that the odd-numbered field scanning line and the even-numbered field scanning line after conversion are different from each other.

FIG. 3 shows a first embodiment relating to a scanning line number conversion method. When converting an input signal of the 1080i format into an NTSC signal, the scanning line 1 of the input signal is used.
Scanning lines are synthesized at a rate of 5 to 7 lines. When the number of scanning lines is converted at this ratio, the number of effective scanning lines after conversion is 504 per frame.
The four scanning lines are masked and converted into a video signal. In this algorithm, the ratio of the effective scanning lines to the total number of scanning lines before and after the conversion of the number of scanning lines is the same, so that the memory required for the conversion of the number of scanning lines can be minimized.

FIG. 4 shows a second embodiment relating to the scanning line number conversion method. When converting an input signal of the 720p format into an NTSC signal, the scanning line 20 of the input signal is used.
The scanning lines are synthesized at a rate of seven out of seven lines. When the number of scanning lines is converted at this ratio, the number of effective scanning lines after conversion is 504 per frame.
The scanning lines are masked and converted into video signals. In this algorithm, the ratio of the effective scanning lines to the total number of scanning lines before and after the conversion of the number of scanning lines is the same, so that the memory required for the conversion of the number of scanning lines can be minimized.

FIG. 5 shows a third embodiment of the method for converting the number of scanning lines. When converting an input signal of 1080i format into an NTSC signal, the scanning line 9 of the input signal is used.
Scan lines are synthesized at a ratio of four to four. In this algorithm, all the effective scanning lines before the conversion of the number of scanning lines become the effective scanning lines after the conversion, so that the received video can be viewed without being cut more than necessary.

FIG. 6 shows a fourth embodiment relating to the scanning line number conversion method. When converting an input signal of the 720p format into an NTSC signal, scanning lines are synthesized at a rate of three out of three scanning lines of the input signal. In this algorithm, all the effective scanning lines before the conversion of the number of scanning lines become the effective scanning lines after the conversion, so that the received video can be viewed without being cut more than necessary.

FIG. 7 shows a fifth embodiment relating to the scanning line number conversion method. 1080i format input signal is NTSC
When converting to a signal, scan lines are synthesized at a rate of one out of three scan lines of the input signal, and letter box scan lines are separately synthesized above and below the screen to form a letter box video. Generate. In this algorithm,
A received image having an aspect ratio of 16: 9 can be viewed on a conventional television having an aspect ratio of 4: 3 with a correct roundness by inserting letter boxes at the top and bottom of the screen.

FIG. 8 shows a sixth embodiment relating to the scanning line number conversion method. When converting an input signal of 720p format into an NTSC signal, scan lines are synthesized at a rate of one out of four scan lines of the input signal, and letter box scan lines are separately synthesized at the top and bottom of the screen. To generate a letterbox format video. In FIG. 8, scanning lines are synthesized from two scanning lines before conversion, and two scanning lines before conversion are discarded. This is because one scanning line is synthesized from four scanning lines before conversion. Of the coefficients to be multiplied by the scan line before conversion
It can be assumed that the coefficient of the book is zero. According to this algorithm, a received image having an aspect ratio of 16: 9 can be viewed at a correct roundness on a conventional television having an aspect ratio of 4: 3 with letterboxes inserted above and below the screen.

FIGS. 9 and 10 show a seventh embodiment relating to the scanning line number conversion method. 480p format input signal is NT
When converting to an SC signal, the scanning lines are combined at a rate of one out of two scanning lines of the input signal, and the required number of scanning lines are combined. FIG. 9 shows an example in which one scanning line is synthesized from two scanning lines before conversion, and FIG. 10 shows an example in which every other scanning line is extracted before conversion. The scanning lines are combined at a rate of one, and the difference can be regarded as a difference in coefficient by which the scanning line before conversion is multiplied.
In this algorithm, the ratio of the effective scanning lines to the total number of scanning lines before and after the conversion of the number of scanning lines is the same, so that the memory required for the conversion of the number of scanning lines can be minimized. Since all previous effective scanning lines are converted effective scanning lines, the received video can be viewed without being cut more than necessary.

FIG. 11 shows an eighth embodiment relating to the scanning line number conversion method. When converting an input signal of the 480p format into an NTSC signal, the scanning line 8 of the input signal is used.
Scanning lines are combined at a rate of three from the book, and letterbox scanning lines are separately combined at the top and bottom of the screen to generate a letterbox video. According to this algorithm, a received image having an aspect ratio of 16: 9 can be viewed at a correct roundness on a conventional television having an aspect ratio of 4: 3 with letterboxes inserted above and below the screen.

FIG. 12 shows a ninth embodiment relating to the scanning line number conversion method. When converting an input signal of the 480i format into an NTSC signal, the scanning line 4 of the input signal is used.
Scanning lines are combined at a rate of three from the book, and letterbox scanning lines are separately combined at the top and bottom of the screen to generate a letterbox video. According to this algorithm, a received image having an aspect ratio of 16: 9 can be viewed at a correct roundness on a conventional television having an aspect ratio of 4: 3 with letterboxes inserted above and below the screen.

[0035]

According to the present invention, a scanning line number conversion apparatus for converting a plurality of types of HDTV signals into video signals which can be viewed on a conventional television can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a scanning line number conversion device according to a first embodiment of the present invention;

FIG. 2 is a block diagram of a scanning line number conversion device according to a second embodiment of the present invention;

FIG. 3 is an explanatory diagram of a method of synthesizing seven to fifteen scanning lines when inputting 1080i.

FIG. 4 is an explanatory diagram of a method of synthesizing 7 scanning lines from 20 scanning lines when 720p is input.

FIG. 5 is an explanatory diagram of a method of combining four scanning lines from nine when 1080i is input;

FIG. 6 is an explanatory diagram of a method of combining one scanning line from three scanning lines when 720p is input.

FIG. 7 is an explanatory diagram of a method of combining one scanning line from three scanning lines at the time of 1080i input.

FIG. 8 is an explanatory diagram of a method of combining one scanning line from four scanning lines when 720p is input.

FIG. 9 is an explanatory diagram of a method of combining one scanning line from two scanning lines when 480p is input.

FIG. 10 is an explanatory diagram of a method of combining one scanning line from two scanning lines when 480p is input.

FIG. 11 is an explanatory diagram of a method for combining three scanning lines from eight scanning lines when 480p is input.

FIG. 12 is an explanatory diagram of a method of combining three scanning lines from four scanning lines when inputting 480i.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 HDTV analog video signal input 2 anti-aliasing low-pass filter 3 A / D converter clock generator 4 A / D converter 5 vertical low-pass filter 6 number of scanning lines conversion unit 7 video encoder clock generator 8 RGB mixing ratio conversion matrix 9 scanning Digital video signal output after line number conversion 10 SDTV digital video signal input 11 Video signal selector 12 Video encoder 13 Video signal output 14 HDTV digital video signal input 15 HDTV digital video signal clock input 16 Anti-aliasing digital low-pass filter 17 Sampling frequency converter 18 Scan line number conversion clock generator

Claims (17)

[Claims] 1. An input section for video signals corresponding to a plurality of formats having the same or higher resolution and the number of scanning lines as conventional resolutions such as NTSC, PAL, SECAM, etc., and resolutions of input video signals of a plurality of formats. , The number of scanning lines, NTS
A scanning line number conversion unit that converts the resolution to the same as the number of scanning lines such as C, PAL, and SECAM, and a video encoder unit that converts the video signal converted by the scanning line number conversion unit into a format such as NTSC, PAL, or SECAM. A scanning line number conversion device. 2. The apparatus according to claim 1, further comprising a vertical low-pass filter between the input section of the video signal and the number-of-scanning-lines conversion section, in order to prevent vertical aliasing distortion occurring at the time of scanning line conversion. Scanning line number conversion device. 3. The image processing apparatus according to claim 1, further comprising a matrix section for converting a mixing ratio of RGB signals included in the luminance signal and the color difference signal between the video signal input section and the video encoder section. Scanning line number converter. 4. The number of scanning lines according to claim 1, further comprising a function of converting the aspect ratio of the video signal when converting the number of scanning lines of the video signal input by the number-of-scanning-lines conversion unit. Conversion device. 5. An input unit for a video signal is constituted by an A / D converter. A signal passed through a low-pass filter for preventing aliasing distortion is input to the A / D converter. 2. The scanning line number conversion device according to claim 1, wherein the input video signal is sampled at a sampling frequency corresponding to the number of effective pixels in one horizontal period after being converted by the scanning line number conversion unit. 6. The number of scanning lines conversion according to claim 1, wherein the input section of the video signal is a digital input and comprises a digital low-pass filter for preventing aliasing and a sampling frequency converter. apparatus. 7. A digital signal format such as CCIR656 instead of converting and outputting the video signal converted by the scanning line number conversion unit into a format such as NTSC, PAL, SECAM or the like. 2. The scanning line number conversion device according to 1. 8. A digital video signal input having a resolution equivalent to that of NTSC, PAL, SECAM, etc., apart from a video signal input section having a resolution equal to or higher than a conventional resolution such as NTSC, PAL, SECAM, etc., and A selector is provided between the scanning line number conversion unit and the video encoder unit, and the selector switches a signal from the scanning line number conversion unit and a signal from the digital video input to send a signal to the video encoder unit. 2. The scanning line number conversion device according to claim 1, wherein: 9. The scanning line number conversion apparatus according to claim 1, wherein when converting an input signal of 1080i format into an NTSC signal, the number of scanning lines of the input signal is changed from 15 to 7 in the number of scanning lines. A scanning line number conversion method of combining and extracting a required number of scanning lines from the combined scanning lines. 10. The scanning line number conversion apparatus according to claim 1, wherein when converting an input signal of 720p format into an NTSC signal, the scanning lines are synthesized at a rate of 7 out of 20 scanning lines of the input signal. A scanning line number conversion method for extracting a required number of scanning lines from the combined scanning lines. 11. The scanning line number conversion device according to claim 1, wherein when converting an input signal of 1080i format into an NTSC signal, four input scanning lines are combined from nine input signal scanning lines. And a scanning line number conversion method for synthesizing a required number of scanning lines. 12. The scanning line number converter according to claim 1, wherein when converting an input signal of 720p format into an NTSC signal, the scanning lines are synthesized at a ratio of three scanning lines of the input signal to one scanning line. And a scanning line number conversion method for synthesizing a required number of scanning lines. 13. The scanning line number conversion apparatus according to claim 1, wherein when converting an input signal of 1080i format into an NTSC signal, the scanning lines are synthesized at a ratio of three scanning lines of the input signal to one scanning line. And a method of converting the number of scanning lines for generating a letterbox format image by separately combining letterbox scanning lines at the top and bottom of the screen. 14. The scanning line number conversion apparatus according to claim 1, wherein when converting an input signal of 720p format into an NTSC signal, scanning lines are synthesized at a ratio of four scanning lines of the input signal to one scanning line. And a method of converting the number of scanning lines for generating a letterbox format image by separately combining letterbox scanning lines at the top and bottom of the screen. 15. The scanning line conversion apparatus according to claim 1, wherein when converting an input signal of 480p format into an NTSC signal, the scanning lines are synthesized at a ratio of two scanning lines of the input signal to one. And a scanning line number conversion method for synthesizing a required number of scanning lines. 16. The apparatus according to claim 1, wherein the number of scanning lines is 480.
When converting an input signal in the form of p into an NTSC signal, scan lines are synthesized at a rate of 3 out of 8 scan lines of the input signal, and letter box scan lines are separately synthesized at the top and bottom of the screen. Scanning line number conversion method for generating a letterbox format image. 17. The apparatus according to claim 1, wherein the number of scanning lines is 480.
When converting an input signal in the form of i into an NTSC signal, scan lines are synthesized at a rate of 4 to 3 scan lines of the input signal, and letter box scan lines are separately synthesized above and below the screen. Scanning line number conversion method for generating a letterbox format image.