JPH06181583A - Transmitter for digital video signal - Google Patents

Abstract

PURPOSE:To restore HD-signals and to save a transmission data amount by utilizing (transmitting STD-signals after down conversion. CONSTITUTION:The HD signals are supplied to a sub sampling circuit 1, the HD-signals are thinned out by the sub sampling circuit 1 and the output signals of the sub sampling circuit 1 are supplied to an HD/STD conversion circuit 3. At the conversion circuit 3, the picture data of the STD-signals are formed. The HDsignals from a picture processing circuit 2 and the STD-signals from the conversion circuit 3 are transmitted. At a reverse conversion circuit 5 on a reception side, HD data can be restored by using the received STD-signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video signal transmission apparatus for converting a standard video signal having a high resolution (for example, a high-definition signal) into a standard video signal having a lower resolution (for example, an NTSC system).

[0002]

2. Description of the Related Art A system having a higher resolution than existing television systems such as the NTSC system (525 lines / 60 fields) and the PAL system (625/50) has been proposed. For example, the 1125/60 system (also referred to as a high-definition system) and the 1250/50 system (also referred to as an HD-MAC system) are typical high resolution television systems. When transmitting this high resolution video signal (hereinafter, referred to as HD signal), so-called down conversion may be performed in which the video signal is converted into a video signal similar to the existing standard resolution system.

When the transmission band of the digital VTR is insufficient for recording / reproducing HD signals, down conversion is necessary when reproducing a high resolution video signal by an existing monitor. H for down conversion
A sub-sampling technique for thinning out pixels of the D signal is used. In addition, it is necessary to convert the number of lines.

[0004]

As one of systems for down conversion, one pixel of a standard resolution signal (hereinafter referred to as STD signal) is created from several pixels of an HD signal, and an image of the HD signal is generated. It is conceivable that subsampling is performed for processing. If all the pixels are used as the data of the HD signal of several pixels, there is a problem that the STD image data cannot be used in the processing after the transmission.

At the time of down-conversion, it is necessary to convert the number of lines. For example, when the number of lines is halved for each field, there is a problem that a difference in resolution occurs between fields in the image of the STD signal after conversion.

Therefore, an object of the present invention is to provide a digital video signal transmission apparatus capable of reducing the number of transmission data.

Another object of the present invention is to provide a transmission apparatus for a digital video signal in which a difference in resolution between fields is prevented when converting the number of lines.

[0008]

According to the present invention, a second standard video signal having a higher resolution than the first standard video signal is supplied, and after digitizing this signal, the first standard video signal is output from this signal. In a transmission device for forming a digital video signal having a signal resolution and transmitting the digital video signal,
A digital video signal based on the second standard video signal is supplied, and a sub-sampling circuit for periodically thinning out the image data thereof and a digital video signal based on the first standard video signal are formed from the output of the sub-sampling circuit. And a transmission device for transmitting a part of the output of the sub-sampling circuit and the output of the conversion circuit.

The present invention is provided with a second standard video signal having a higher resolution than the first standard video signal, digitizing this signal, and then having the vertical resolution of the first standard video signal from this signal. In a transmission device which forms a digital video signal and transmits the digital video signal, when a digital video signal based on the second standard video signal is supplied and one of the field signals is input, a plurality of line signals are input. And the second asymmetry is obtained by inverting the first asymmetry coefficient for a plurality of line signals when the other field signal is input. A transmission device for a digital video signal, comprising a conversion circuit configured to be multiplied by a coefficient and combined, and a transmission device for transmitting the output of the conversion circuit.

[0010]

The HD signal is sub-sampled at the time of down conversion, and the STD signal is formed from the data after the sub-sampling. As a result, the amount of transmission data can be reduced. Further, when the number of lines is halved, the spatial distance between lines can be made constant, and the resolution can be made equal between fields.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the entire system of one embodiment. The input image (digital HD signal) is supplied to the sub-sampling circuit 1. The number of pixels of the HD signal is halved by the sub-sampling circuit 1.

After the sub-sampling circuit 1, an HD image processing circuit 2 and an HD-STD conversion circuit 3 are connected. The outputs of the image processing circuit 2 and the conversion circuit 3 are transmitted via the transmission line 4. On the receiving side, an inverse conversion circuit 5 is provided, and an HD output image and an STD output image are taken out from its output. The transmission path 4 is specifically a process of wireless transmission, magnetic recording / reproduction, or the like.

The sub-sampling and down-conversion processing will be described with reference to FIG. A, B, C, D are H
4 shows four adjacent pixels in the D image. In the sub-sampling circuit 1, two pixels A and B surrounded by circles among these four pixels are transmission pixels, and two pixels C and D surrounded by triangles.
Are non-transmission pixels (thinned pixels). Then, the data after the sub-sampling, that is, the pixels C and D
The value of the data of the pixel a corresponding to the STD signal is obtained from the data of 1 by the following equation.

A = α1 · A + α2 · B α1 and α2 are weighting factors.

In the inverse conversion circuit 5 on the receiving side, the received data a
B ^ can be calculated from ^ and A ^. However, although a distortion component due to quantization appears, the number of transmission bits can be considerably reduced, so that the quantization step width can be reduced. As a result, the amount of distortion in B can be reduced.

Further, in the case of (α1> α2), B multiplied by a smaller coefficient α2 may be transmitted as an HD signal. When calculating A ^ on the receiving side, A ^ = (1 / α1) · (a ^ -α2 · B ^). As can be seen from this equation, when a ^ and B ^ have the same amount of quantization distortion, A ^ is transmitted and B
It is possible to reduce the influence of the quantization distortion on A ^, as compared with the case where ^ is calculated.

The conversion circuit 3 also performs processing for reducing the number of lines to half. FIG. 3 illustrates conventional line number conversion, in which FLD1 and FLD2 mean a first field and a second field that form one frame, and each dot represents a spatial position of each line. The upper and lower two lines of the HD image are set as one set, and the average value of the pixel values of each line is S
One line of the TD image. By doing this, STD
In the image, the line interval is not constant (2d) between the first field and the second field, and is d and 3d as shown in FIG.

As one method of preventing such a phase shift, as shown in FIG. 4, a first field FLD1 uses a 3-tap filter which inputs data of three adjacent lines, and a second field FLD2. In the above, line number conversion using a 2-tap filter that inputs data of two adjacent lines is considered. However,
In this method, as a result of different tap numbers of the filters, S
In the TD image, there arises a problem that the resolution is different between the first field FLD1 and the second field FLD2.

The present invention prevents the above-mentioned phase shift and difference in resolution between fields as a result of line number conversion. 5 and 6 show an example of a line number conversion circuit to which the present invention is applied. FIG. 5 shows a configuration when processing the first field, and FIG. 6 shows a configuration when processing the second field.

In FIGS. 5 and 6, H indicates a line delay circuit. Two line delay circuits are connected in series, and the HD of the first field or the second field is connected to one end thereof.
Signal is supplied. Three pixel data of three temporally continuous lines are taken out from taps (referred to as a first tap, a second tap, and a third tap in order from the input side) derived from the series connection of the line delay circuits.

The pixel data are supplied to the coefficient multipliers and multiplied by the coefficients w1, w2 and w3. The output signals of these multipliers are supplied to the adder circuit 12. The output signal of the adder circuit 12 is supplied to the sub-sampling circuit 13. The sub-sampling circuit 13 separates necessary data. An output signal of the first field or the second field of the STD image is generated at the output terminal 14.
Here, the filter coefficient is asymmetric (that is, w1 ≠ w
3). As an example, (w1 = 1/8, w2 = 1 /
2, w3 = 3/8.

At the time of processing the first field shown in FIG. 5, the data of the first tap is multiplied by w1.
The data of the second tap is multiplied by w2, and the data of the third tap is multiplied by w3. As shown in FIG. 6, in the second field, the coefficients for the first tap and the third tap are interchanged.

By the above processing, as shown in FIG.
In the STD image, there is no phase shift of lines between fields. However, since the number of taps of the filter used is the same between the two fields, it is possible to prevent the resolutions from being different between the fields.

Further, when a filter is used, there is a problem that blurring or ringing occurs after conversion. From this point, it is preferable not to use a filter. As shown in FIG. 8, with respect to the HD signal of the first field, the sub-sampling circuit 13 is simply passed through to output terminal 1
Lead to 4. Although not shown, regarding the second field,
Data is supplied from two adjacent lines 2
A tap filter is used.

In this way, as shown in FIG. 9, for the first field, the line which is not thinned out of the two lines is directly output. For the second field, the average value of two lines is output. Therefore, it is possible to prevent the phase shift of the line, and since the filter processing is not performed in the first field, it is possible to prevent the occurrence of image blurring and ringing.

Regarding the above-mentioned line number conversion, as shown in FIG. 1, it is not necessary to use the sub-sampled HD signal, and all the data of the HD image before being sub-sampled may be used. .

[0027]

According to the present invention, since the data after sub-sampling is used, the amount of transmission data can be reduced, and the STD image data can be used in the processing on the receiving side. . The line number conversion according to the present invention can prevent not only the phase shift of lines between fields but also the difference in resolution between fields. Furthermore, in one field with line number conversion,
Since the data is used directly, image deterioration due to filtering can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a system according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining subsampling according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of an example of conventional line number conversion.

FIG. 4 is a schematic diagram of another example of conventional line number conversion.

FIG. 5 is a first example of a line number conversion circuit according to the present invention.
It is a block diagram of composition about a field.

FIG. 6 is a block diagram of a configuration relating to a second field of another example of the line number conversion circuit according to the present invention.

FIG. 7 is a schematic diagram showing an operation of an example of a line number conversion circuit according to the present invention.

FIG. 8 is a schematic diagram showing a configuration relating to a first field of another example of the line number conversion circuit according to the present invention.

FIG. 9 is a schematic diagram showing an operation of another example of the line number conversion circuit according to the present invention.

[Explanation of symbols]

 1 Sub-sampling circuit 3 HD-STD conversion circuit

Claims (4)

[Claims] 1. A digital video which is provided with a second standard video signal having a resolution higher than that of the first standard video signal, digitizes the signal, and then has the resolution of the first standard video signal from the signal. A transmission device for forming a signal and transmitting the signal is supplied with a digital video signal based on the second standard video signal, and subsampling means for periodically thinning out image data of the digital video signal, and the subsampling means. A digital comprising conversion means for forming a digital video signal based on the first standard video signal from the output, and transmission means for transmitting a part of the output of the sub-sampling means and the output of the conversion means. Video signal transmission equipment. 2. The digital video signal transmitting apparatus according to claim 1, wherein the converting means has an arithmetic means for multiplying a plurality of pixel data output from the sub-sampling means by coefficient data and synthesizing the pixel data. The means is adapted to transmit only pixel data having a small coefficient among the outputs of the sub-sampling means. 3. A second standard video signal having a higher resolution than the first standard video signal is supplied, and after digitizing the signal, a digital signal having the vertical resolution of the first standard video signal is supplied from the signal. Form a video signal,
In a transmission device adapted to transmit this, when a digital video signal based on the second standard video signal is supplied and one of the field signals is input, the first line signal is supplied to a plurality of line signals. When the other field signal is input, the plurality of line signals are multiplied by the second asymmetric coefficient obtained by inverting the first asymmetric coefficient. An apparatus for transmitting a digital video signal, comprising: the converting means configured to do so; and a transmitting means for transmitting the output of the converting means. 4. A second standard video signal having a higher resolution than the first standard video signal is supplied, and after digitizing the signal, a digital signal having the vertical resolution of the first standard video signal is supplied from the signal. Form a video signal,
In a transmission device adapted to transmit this, when a digital video signal based on the second standard video signal is supplied and one of the field signals is input, an asymmetry coefficient is obtained for each of a plurality of line signals. A digital video having conversion means for directly outputting when the other field signal is input, and transmission means for transmitting the output of the conversion means. Signal transmission equipment.