JPH07135620A - Second generation EDTV signal decoding device - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention provides NTSC and second-generation EDTV (E
It is an object of the present invention to provide a decoding device for an EDTV2 signal in which an inconvenient image is not displayed when switching to DTV2). [Configuration] When the EDTV 2 and the NTSC are switched and the output of the identification signal detection circuit 13 is changed, the frequency counter 15 generates a pulsed signal in the m field period. During the m fields, the video signal switching circuit 16 forcibly sets the output of the video signal to zero, and the contents of the subtitle memory 8 are rewritten by switching the memory selection circuit 14 while the screen is darkened. According to the present invention, even if the EDTV 2 and the NTSC use different image memories, it is possible to prevent an inconvenient image from being output at the time of switching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a second generation EDTV signal decoding device mounted on a television capable of receiving a second aspect EDTV (hereinafter referred to as EDTV2) signal compatible with wide aspect.

[0002]

2. Description of the Related Art In the case of current television receivers, there is a device for switching the normal mode / zoom mode of screen output as shown in FIG. 2, which has a function of zooming the screen by a scanning line conversion system. To have. 2 will be described below.

Luminance signal (Y), color difference signal (RY, B-
Y) is converted into a digital signal by the A / D conversion circuit 19 and input to the scanning line interpolation circuit 20. The scanning line interpolation circuit 20 performs a motion adaptive scanning line interpolation process to convert an input signal into a double-density video signal. Here, 21 is a frame memory. The scanning line conversion (vertical enlargement) circuit 22 is provided when the scanning line-interpolated video signal is a letterbox signal.
Scanning line conversion processing for converting 360 scanning lines to 480 is performed to compensate for the definition of the image. Reference numeral 23 is a memory used for time-axis conversion of the video signal. The scanning line conversion circuit 22 is passed through when the video signal is in the normal mode. The 26 video signal selection circuit selects either the through signal or the output of the scanning line conversion circuit 22.

Next, the caption processing circuit 24 extracts the caption portion from the video signal, and adds the caption portion to the video signal by the synthesizing circuit 27 at the desired insertion position of the caption. Here, 25 is a memory for storing a subtitle area. The video signal subjected to the scanning line interpolation, the scanning line conversion (vertical enlargement), and the caption processing as described above is finally converted into an analog signal by the D / A conversion circuit 28 and output as a video.

[0005]

When the circuit shown in FIG. 2 is used in the EDTV2 decoder for development and sharing, the EDTV2
If the memory 25 for unnecessary subtitle processing is used for image processing of the EDTV2 signal, a memory having a smaller capacity can be efficiently used. However, this alone
While switching between the V2 mode and the NTSC mode and rewriting the contents of the memory, an inconvenient image is output on the screen.

In view of the above points, the present invention has as its object the provision of an EDTV2 signal decoding device designed to darken the screen while rewriting the contents of the memory during switching.

[0007]

SUMMARY OF THE INVENTION The present invention comprises an identification signal detection circuit for discriminating between an EDTV2 mode and an NTSC mode,
An EDTV2 signal decoding device having a video signal switching circuit for darkening the screen for several field periods before switching the signal system between the EDTV2 mode signal and the NTSC mode signal when the identification signal detection output changes It has made it possible to solve the above problems.

[0008]

According to the present invention, with the above-described structure, when the EDTV2 mode and the NTSC mode are switched, the output of the video signal is forcibly set to zero, thereby suppressing an inconvenient image output when the image memory is rewritten. You can

[0009]

EXAMPLE FIG. 1 shows an example of the present invention. 1 is an A / D conversion circuit for converting an analog signal into a digital signal, 2 is 3
3D Y / C separation circuit for 3D Y / C separation, 3 scanning line interpolation circuit for performing motion adaptive scanning line interpolation processing, 4 frame memory for scanning line interpolation, 5 video in EDTV2 mode A scanning line conversion (vertical enlargement) circuit for increasing the number of scanning lines of the signal, 6 is a scanning line conversion memory used for time-axis conversion of the video signal, 7 is a subtitle portion, and the subtitle signal is extracted at an arbitrary subtitle insertion position A subtitle processing circuit for adding to the video signal, 8 a subtitle memory for storing a subtitle area of the video, 9 a video signal selection circuit for selecting a video converted by scanning line or a normal video, 10 a video signal for the subtitle signal Reference numeral 11 is a D / A conversion circuit for converting a digital signal into an analog signal.

Reference numeral 12 is an auxiliary signal decoding circuit for decoding the auxiliary signals in the upper and lower non-picture portions of the EDTV2 mode signal, and 13
Is an identification signal detection circuit that generates different identification signals in the EDTV2 mode and in the NTSC mode, and 14 is a memory selection circuit that selects whether the subtitle memory 8 is used for subtitles or for decoding a non-image portion. , 15 is EDT
It is a frequency counter that produces a pulsed signal for a certain period when the V2 mode and the NTSC mode are switched. Reference numeral 17 is a weak electric field determination circuit for determining whether or not the video input signal is a weak electric field, and 18 is a video signal selection circuit for forcibly dropping the output of the video signal to the ground. Has been done.

The operation of the embodiment shown in FIG. 1 configured as above will be described below. The operations of the A / D conversion circuit 1, the scanning line interpolation circuit 3, the scanning line conversion circuit 5, the caption processing circuit 7, and the D / A conversion circuit 11 are as described in the section of the conventional technique shown in FIG. Therefore, other parts will be described here.

Of the EDTV 2 mode signals, the video signal is 3
The signals of the upper and lower non-image parts are input to the dimension Y / C separation circuit 2 and the auxiliary signal decoding circuit 12. This auxiliary signal decoding circuit includes an interpolation line auxiliary signal (hereinafter, referred to as a VT signal) and a vertical high frequency auxiliary signal (hereinafter,
(Denoted as VH signal) is extracted, and these auxiliary signals are used for respective processing in the scanning line interpolation circuit 3 and the scanning line conversion circuit 5.

The frequency counter 15 has a number of fields necessary for rewriting the contents of the subtitle memory 8 when the discrimination signal output from the discrimination signal detection circuit 13 is switched (hereinafter referred to as m fields in this embodiment). A pulse-like signal that is H output only for a period is output. Memory selection circuit 1
4 is NTSC according to the output of the identification signal detection circuit 13.
The contents can be selected so that they can be used for subtitle processing in the mode and for decoding auxiliary signals in the upper and lower non-picture areas in the EDTV2 mode.

Therefore, an inconvenient image is output by inputting the output signal of the frequency counter 15 to the image signal switching circuit 16 and forcibly dropping the image output to the ground for the m field period to darken the screen. Is preventing. When the weak electric field detection circuit 17 determines that the input signal is a weak electric field, the video signal selection circuit 18 is forcibly connected to the signal line to prevent unnecessary video switching due to malfunction of the identification signal detection circuit 13. It's suppressed.

Thus, the EDTV according to the embodiment of FIG.
When switching between the 2 mode and the NTSC mode, it is possible to prevent an inconvenient image from being output even if the contents of the image memory are rewritten.

In the present embodiment shown in FIG. 1, the identification reference of the identification signal detection circuit 13 is the VT signal 9 and the VH signal 1.
Although it depends on the presence / absence of 0, it is not limited to the EDTV 2 and a letterbox signal may be used as a criterion. Further, the video signal selection circuit 18 is the weak electric field detection circuit 1.
It is controlled by the output of No. 7, but it may be considered that the VTR signal is always connected to the signal line.

[0017]

As described above, according to the present invention, E
Even if some of the image memories are used differently between the DTV2 mode and the NTSC mode, the screen is darkened for a few field periods at the time of switching, thereby producing an inconvenient image output that occurs when the image memory is rewritten. It can be prevented from being marked, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an EDTV2 signal decoding device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an example of a conventional scanning line conversion device of a television receiver.

[Explanation of symbols]

 1 A / D conversion circuit 2 3 dimensional Y / C separation circuit 3 Scan line interpolation circuit 4 Frame memory 5 Scan line conversion circuit 6 Scan line conversion memory 7 Subtitle processing circuit 8 Subtitle memory 9, 18 Video signal selection circuit 10 Compositing Circuit 11 D / A conversion circuit 12 Auxiliary signal decoding circuit 13 Identification signal detection circuit 14 Memory selection circuit 15 Frequency counter 16 Video signal switching circuit 17 Weak electric field discrimination circuit

Claims (2)

[Claims] 1. An identification signal detection circuit for discriminating between a second generation EDTV mode and an NTSC mode, and a video signal for switching the signal to darken the display screen for several field periods when the output signal of the identification signal detection circuit changes. A second generation EDTV signal decoding device having a switching circuit. 2. The video signal switching circuit includes a weak electric field discriminating circuit for discriminating whether or not the input video signal is a weak electric field.
The second generation E according to claim 1, further comprising a video signal selection circuit for switching the video signal to ground.
DTV signal decoding device.