JPH1098733A - Video signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expand and encode an image signal which is compressed having character information superposed, to remove noises such as ringing, block distortion and to actualize pixel interpolation without destroying the character information of a source image. SOLUTION: With a character information identification signal showing the timing where character information is superposed on a video signal, the output of an interpolator 302, the output of a 1st delay unit 101, and a zero level showing a no-signal state are switched to output a luminance signal, and similarly the output of the interpolator 302, the output of a 2nd delay unit 102, and the zero level indicating the no-signal state are switched with the character information identification signal to output a color difference signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention expands and decodes a compressed image signal, interpolates pixels without destroying character information superimposed on the expanded image signal, and generates noise such as ringing and block distortion. The present invention relates to a video signal processing device for removing the image signal.

[0002]

2. Description of the Related Art A conventional video signal processing apparatus will be described below.

In the United States, since July 1993, it has been legally required that all television receivers of type 13 or larger have a built-in closed caption decoder capable of decoding character multiplex broadcasting (also referred to as closed caption) in which character (caption) information is superimposed. Was Already, in March 1980, US broadcasters have started closed caption broadcasting, but the purpose of this broadcasting is to display text on the screen simultaneously with television images to assist the hearing impaired. With the expansion of closed caption broadcasting, a video signal in which the caption signal is superimposed is often recorded and reproduced on storage (package) media such as video software and video discs using English subtitles. In the closed caption format defined by the U.S. National Captioning Institute (NCI), a field in which caption information is superimposed on the 21st scan line of a video signal (line 21, which is the scan line on which the first video signal after a vertical synchronization period is present). Although the first mode and the field 2 mode to be superimposed on the 284th scanning line have been defined, only the field 1 mode is currently used in the United States.

On the other hand, in recent years, MPEG (Moving Picture Exp
erts Group, an international standard for media-integrated video compression),
Standardization using various image compression techniques such as JPEG (Joint Photographic Experts Group, an international standard for color still image compression) is underway. The image compression technique is intended to reduce the amount of information by removing redundant portions from an image signal having a huge amount of information, and to make the image signal easy to be handled by all devices. The image compression technology is roughly classified into a lossless coding method and a lossy coding method. The lossless encoding method is a method in which information can be stored in the process of compression and decompression and the original image can be completely reproduced, and the irreversible encoding method is an encoding method in which the original image cannot be completely reproduced. Since the irreversible compression method basically discards information, some problems appear when the compressed image signal is expanded and decoded. Generally speaking, the more discarded information, that is, the higher the compression ratio, the more adverse noise occurs. For example, ringing around a high-frequency image signal or block distortion in which a fast-moving portion looks like a block on an image reproduction monitor is a device. A device that removes or reduces noise such as ringing and block distortion is a noise remover. .

[0005] As one of the compression methods, there is a case where information is discarded from an original image in advance, that is, pixels are thinned out and then compressed. When a compressed image signal compressed in this way is expanded, it is thinned out after expansion decoding. It is necessary to interpolate only those pixels using an interpolator to convert the number of pixels to the number of pixels of the screen size of the standard television signal.

Then, the standard television system, N
NTSC for TSC and PAL television signals
/ PAL encoder, and outputs a luminance signal and a carrier chrominance signal or a composite television signal obtained by mixing the two.

As described above, a video signal processing apparatus performs decompression and decoding of an image signal obtained by thinning out pixels of a television signal on which a caption signal is superimposed and compressing the image signal, and performs noise removal, pixel interpolation, and NTSC / PAL encoding.

FIG. 3 is a block diagram showing the configuration of a conventional video signal processing apparatus, and FIG. 4 is, for example, MPEG1 (MPEG1).
SIF (Source
Input Format, original image input format)
In the case of the SC system (30 frames / sec, 352 × 240 pixels / frame), FIG.
Indicates a color difference signal. There are two types of color difference signals, RY and BY, having the same image size. The SIF is a standard television signal (30 frames / second, 858 × 525 pixels, but the number of effective pixels with a video signal is 704 × 480 pixels / frame), and the pixels are halved in the horizontal and vertical directions respectively. is there.

In FIG. 3, an image signal compressed by an image decoder 301 is expanded and decoded, and a luminance signal and a color difference signal, which are expanded image signals of the SIF format image size, are output. This is interpolated by the interpolator 302 into a pixel size of a standard television signal and converted. The luminance signal is vertically interpolated to twice the number of pixels and the number of scanning lines (the number of lines) is set to 240.
From the line to 480 lines, the color difference signal is vertically interpolated to quadruple the number of pixels and converted from 120 lines to 480 lines. Further, pixel interpolation is performed in the horizontal direction, the luminance signal is changed from 352 pixels to 704 pixels in one line, and the color difference signal is
Conversion is performed from 76 pixels to 352 pixels, respectively. For example, interpolation in the vertical direction is embodied by weighting and adding two pixels before and after in the vertical direction. The same applies to the horizontal interpolation. The interpolated luminance signal and color difference signal are converted into a television signal by the NTSC / PAL encoder 303, and a luminance signal and a carrier color signal or a composite television signal obtained by mixing the two is output.

[0010]

However, the above-mentioned conventional configuration has the following problems. As described above, in the field 1 mode, the caption signal is superimposed on the line 21 of the video signal. However, when the interpolator 302 interpolates pixels in the vertical direction, the video signal is not present on the line 22 after the line 21. Or if there is noise, the caption signal on line 21 will be destroyed after vertical pixel interpolation, resulting in closed captioning.
Decoder cannot decode caption information. Further, in a standard television signal, one frame is composed of two fields and is interlaced (interlaced).
In the IF, the video signal of the second field, which is the second field, is discarded because only the first field, which is the first field, is discarded to thin out half the pixels in the vertical direction. Field is first
Field repetition. That is, a caption signal which is not originally included in the original picture which is a standard television signal is superimposed on the 283 lines where the first video signal after the vertical synchronization period of the second field is present, and the caption decoder erroneously decodes this caption signal. Doing so may cause malfunctions. Also, the color difference signal has noise and the like. If the luminance signal and the color difference signal are mixed by the NTSC / PAL encoder after interpolation and converted into a composite television signal, the noise of the color difference signal is superimposed on the caption signal of the luminance signal. Also, there is a possibility that the caption information cannot be decoded by the closed caption decoder.

As described above, there is a problem that the caption signal is destroyed by the interpolator and cannot be accurately decoded by the closed caption decoder.

The present invention solves the above-mentioned conventional problems. A video signal that can be accurately interpolated by a closed caption decoder by interpolating pixels without destroying the caption signal by an interpolator and can be easily embodied. It is an object to provide a processing device.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, a decoded video signal is subjected to processing such as interpolation with a text information identification signal indicating the timing of superimposing text information on the video signal. It has a configuration for appropriately switching between a video signal and no signal.

Thus, a desired processing can be performed without destroying the caption signal, the caption signal can be accurately decoded, and a video signal processing apparatus which is easy to realize can be obtained.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A video signal processing apparatus according to the present invention comprises an interpolator for interpolating pixels of a luminance signal and a chrominance signal output from an image decoder, and a delay unit for delaying the luminance signal output from the image decoder for a predetermined time. A first delay unit and a luminance signal output from the interpolator, a luminance signal output from the first delay unit, and a zero level representing a no-signal state are switched by a character information identification signal indicating a timing of superimposing character information on a video signal. A first switch unit, a second delay unit for delaying a color difference signal output from the image decoder for a predetermined time, a color difference signal output from the interpolator based on a character information identification signal, and a color difference signal output from the second delay unit To switch between zero level and zero level indicating no signal state
Switch means.

Thus, the NTSC / NTSC signal is output by the character information identification signal for identifying the scanning periods of the lines 21, 22, 22, 283, and 284 and the other scanning periods.
By selectively switching the luminance signal and chrominance signal of the PAL encoder input to the output of the interpolator, the output of the delay unit, and zero level representing the no-signal state, the pixel interpolation is performed without destroying the caption signal, and the closed caption decoder performs the pixel interpolation. This has the effect that the caption signal can be decoded accurately.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 1 is a block diagram showing a configuration of a video signal processing device according to Embodiment 1 of the present invention. However, the same components as those of the conventional video signal processing device shown in FIG. 3 are denoted by the same reference numerals, and the description of the operation is omitted.

The luminance signal output from the image decoder 301 is
The first delay unit 101 delays by the same time as the delay time delayed by the processing of the interpolator 302. Similarly, the color difference signal is delayed by the second delay unit 102 by the same time as the delay time of delay by the interpolator 302.

For example, in the field 1 mode in which a caption signal is superimposed on the line 21, "01" is used in the scanning period of the line 21, "10" is used in the scanning period of the line 283, and "11" is used in the scanning period of the lines 22 and 284. In other periods, the character information identification signal becomes "00", so that "01" is the output of the interpolator 302 for "00" and "10" is the output of the first delay unit 101 for "11". The luminance signal is switched by the first switch means 103 to a zero level indicating a no-signal state. When the character information identification signal is “00”, the output of the interpolator 302 is “11”,
When the output of the delay unit 102 is "01" and "10", the second switch means 104 is set to a zero level indicating a no-signal state.
Use to switch the color difference signal.

Switch means 103 and switch means 104
The luminance signal and color difference signal switched in
The encoder 303 converts the signal into a television signal, and outputs a luminance signal and a carrier chrominance signal, or a composite television signal obtained by mixing the two.

(Embodiment 2) FIG. 2 is a block diagram showing a configuration of a video signal processing apparatus according to Embodiment 2 of the present invention. However, the same components as those of the conventional video signal processing device shown in FIG. 3 and the video signal processing device according to the first embodiment of FIG. 1 are denoted by the same reference numerals, and the description of the operation is omitted.

As described above, the higher the compression ratio, the more noise such as ringing and block distortion is generated.
The noise of one output luminance signal and color difference signal is removed by a noise remover 201.
However, if the noise is removed by a two-dimensional (vertical and horizontal direction) smoothing filter, the caption signal is destroyed by the noise remover 201 as in the interpolator 302. Therefore, the luminance signal and the color difference signal output from the image decoder 301 are delayed by the first delay unit 202 and the second delay unit 203 by the same time as the delay time delayed by the noise remover 201 and the interpolator 302. Then, according to the same character information identification signal as in the first embodiment, the output of the interpolator 302 is "00" and the first is "11" and "11".
When the output of the delay unit 202 is "10", the first switch means 103 switches and outputs the luminance signal to a zero level indicating a no-signal state. Similarly, the character information identification signal is "00".
When the output of the interpolator 302 is "11", the second delay 2
In the case of "01" and "10" at the output of 03, the second switch means 104 switches and outputs the color difference signal to a zero level indicating a no-signal state.

Although the first and second embodiments have been described above, the implementation method of the present invention has the following five redundancy. First, since the noise of the color difference signal is generally less noticeable than the luminance signal, the signal from which the noise is removed by the noise remover 201 may be only the luminance signal. At that time, the color difference signal output from the image decoder 301 is delayed by the second delay unit 203 by the time delayed by the noise remover 201 and the interpolator 302, and switched by the switch unit 104.
The second is that the timings of the signals need only match at the time of switching by the first switch means 103 and the second switch means 104. Therefore, the luminance signal is output by the image decoder 301 by the time delayed by the noise remover 201. If the color difference signal is output with a delay, the time delayed by the second delay unit 203 can be shortened accordingly. The third is the noise canceller 201
Since the input luminance signal and color difference signal are delayed and processed in the interpolator 302 in the same manner as the first delay unit 202 and the second delay unit 203, the internal signal is extracted and the first delay unit 202 is output. If the output of the second delay unit 203 is used instead of the first delay unit 202 and the second delay unit 203, the first delay unit 202 and the second delay unit 203 become unnecessary. Fourth is NTSC / PAL encoder 30
3 simply converts it to a television signal,
It is not necessary to connect to another device in the signal format of the luminance signal and the color difference signal. Fifth, since the highest priority object of the present invention is not to destroy the caption signal of line 21 in the field 1 mode, the caption signal interpolated by the pixel in the interpolator 302 is superimposed on the line 22, the line 283, and the line 284. If this can be tolerated, switching by the switch means 103 and the switch means 104 may be performed only during the line 21 period.

[0024]

As described above, according to the present invention, the input to the NTSC / PAL encoder is performed by the character information identification signal for identifying the scanning periods of the lines 21, 22, 22, 283, and 284 and the other scanning periods. Selectively switching the luminance signal and the color difference signal between the output of the interpolator, the output of the first delay device, the output of the second delay device, and zero level representing a no-signal state by the first switch device and the second switch device. As a result, pixel interpolation can be performed without destroying the caption signal, and the caption signal can be accurately decoded by the closed caption decoder. In addition, if the internal signal of the interpolator is taken out and used instead of the outputs of the first delay unit and the second delay unit, those delay units are not required, and the number of the delay units is increased compared to the conventional video signal processing apparatus when implementing. The size of the circuit
Only the switch means and the second switch means are very small, and have great industrial value.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a video signal processing device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a video signal processing device according to the second embodiment;

FIG. 3 is a block diagram showing a configuration of a conventional video signal processing device.

FIG. 4 is a diagram showing an example of an original image input format when compressing and encoding an image signal.

[Explanation of symbols]

 101, 102 Delay unit 103, 104 Switch means 201 Noise remover 301 Image decoder 302 Interpolator 303 NTSC / PAL encoder

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H04N 9/74

Claims (2)

[Claims] An image decoder for decompressing and decoding an input compressed image signal; an interpolator for interpolating pixels of a luminance signal and a color difference signal output from the image decoder; and a luminance signal output from the image decoder. A first delay unit for delaying the time, a luminance signal output from the interpolator, a luminance signal output from the first delay unit, and a non-signal based on a character information identification signal indicating a timing of superimposing the character information on the video signal. First switch means for switching between a zero level indicating a state, a second delay unit for delaying a color difference signal output from the image decoder for a predetermined time, and a color difference output from the interpolator according to the character information identification signal. A second switch for switching between a signal, a color difference signal output from the second delay unit, and a zero level indicating a no-signal state; and a luminance signal output from the first switch and the second switch. NTSC for converting a color difference signal output from the second switch means into a standard television signal of NTSC system or PAL system
/ PAL encoder and a video signal processing device. 2. An image decoder for decompressing and decoding an input compressed image signal, a noise remover for removing noise of a luminance signal and a color difference signal output from the image decoder, and a luminance signal output from the noise remover. An interpolator for interpolating pixels of a color difference signal, a first delay unit for delaying a luminance signal output from the image decoder for a predetermined time, and a character information identification signal indicating timing for superimposing character information on a video signal, First switch means for switching between a luminance signal output from an interpolator, a luminance signal output from the first delay unit, and a zero level representing a no-signal state, and a predetermined time delay of a color difference signal output from the image decoder And a color difference signal output from the interpolator, a color difference signal output from the second delay device, and a zero level indicating a no-signal state according to the character information identification signal. And a NTSC system for converting a luminance signal output from the first switch unit and a color difference signal output from the second switch unit into a standard television signal of the NTSC system or the PAL system.
/ PAL encoder and a video signal processing device.