JPH0822090B2 - Television signal transmission system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a band compression transmission system of a television signal, and particularly to improving a moving image quality of a luminance signal in a MUSE system which is one of the transmission systems of this type. It relates to a transmission method.

(Prior Art) One of methods for band-compressing and transmitting a high-definition (high-definition television) signal is a multiple sub-sample transmission method using inter-frame and inter-field offset sub-sampling, for example, MUSE (Multiple Sub- Nyquist
There is a transmission method called Sampling Encoding) and an improved MUSE transmission method, which effectively compresses the bandwidth (about 1 /
4) Transmission is being done. For more details, refer to Reference (1), Ninomiya: MUSE, NH, a new transmission system for high-definition television.
See K Giken Monthly Report, Vol. 27, No. 7, pp. 19-30 (1984) and Japanese Patent Laid-Open No. 61-264889: Multiple Subsample Transmission System, Specification.

The present invention eventually introduces a variable density sampling method into the MUSE method. Regarding the conventional example of this variable density sampling, reference (2), Tanimoto et al .: TAT.
Bandwidth compression of high-definition television by (time axis conversion) method, Journal of Television Society, Vol.39, No.10, pp.84-90 (1985)
See JP-A-61-62286: Image signal band compression method, specification.

(Problems to be solved by the invention) In the conventional MUSE transmission method, since the moving image part is band-compressed and transmitted on the encoder side, interpolation of sample points that are not subsampled and not transmitted is field interpolation. , The resolution was degraded and the image was sometimes blurred.
This blur has been tolerated because the visual characteristics of the human eye are low in the sensitivity to moving images, especially in the resolution direction, and in reality, it is hardly noticeable even in MUSE format images. However, in a moving image with many high-frequency components, the above-mentioned defect due to field interpolation may be detected when viewing while conscious of this.

Therefore, the object of the present invention is to eliminate the above-mentioned drawbacks, to prevent deterioration of image quality even in a moving image with many high-frequency components, and to provide some functions on the encoder and decoder sides without breaking the basic form of the conventional MUSE transmission system. It is intended to provide a television signal transmission system which can achieve its purpose only by adding it.

(Means for Solving the Problems) In order to achieve this object, the television signal transmission system of the present invention is a television signal transmission system in which a component signal of a color television is band-compressed and transmitted by using multiple sub-sampling means. An encoder of the transmission method obtains a difference signal between an original image signal and a signal obtained through a moving area pre-filter on the encoder side with respect to a luminance signal in a moving image area, and the first means. In order to selectively transmit the generated differential signal, a frame or a field is divided into a number of blocks, and a second means for selecting the block according to the amount of generation of the differential signal in the block; In order to transmit the differential signal of the block selected by the means and the control signal for controlling the selection, the color signal is transmitted in the horizontal or vertical direction. A third means for subsampling at a repetition period twice as high as the frequency signal to provide a transmission space, and a decoder of the transmission system has been transmitted using the transmission space of the color signal. Fourth means for reproducing the differential signal and adding the reproduced differential signal to the luminance signal of the moving image area reproduced from the sub-sampling transmission decoder by using the control signal, and the color transmitted by 4: 1 line interlace Since the signal is used for display, high-frequency components are displayed in 4: 1 line interlace for color signal moving images and 2: 1 line interlace for low-frequency components in color signal moving images and color signal still images. 5th to do
It is characterized by including the means of.

(Operation) Since the basic part of the band compression transmission of the transmission system of the present invention is exactly the same as the encoder and decoder of the MUSE system, the description of this part is omitted.

The feature of the transmission method of the present invention is that the moving image portion (moving area) of the luminance (Y) signal of the original image signal and the portion having a high frequency signal component, that is, the MUSE transmission method cannot transmit The residual signal part is transmitted with an index signal, the decoder side demodulates the residual signal by the transmitted index signal, and the demodulated signal is added to the signal demodulated by the MUSE method decoder. That is the point.

In order to transmit the above-mentioned residual signal, that is, the difference signal and the position signal indicating the position where the difference signal should be inserted, it is necessary to make a “vacant” in the transmission capacity of the MUSE transmission system. In order to make this "empty" of the transmission capacity, in the transmission method of the present invention, the sampling of the color (C) signal in the conventional MUSE method was changed to 4 field interlace, but it was changed to 8 field interlace. The amount of information transmitted per field is halved.

When this processing is performed, naturally, the moving image characteristics of the C signal deteriorate, and the resolution of the C signal component with respect to the moving image deteriorates.
However, since there is an experimental result that the visual characteristic is originally not good for the C signal, it does not cause a big problem. Further, since the MUSE transmission method adopts the constant luminance transmission method, there is no mixing of signals from the C signal to the Y signal, and there is no problem from this point as well.

(Embodiment) The transmission system of the present invention will be described in detail with reference to the accompanying drawings.

Before explaining the embodiment of transmitting the differential signal, a comparison was made of how the sample pattern of the C signal was changed in the transmission method of the present invention in order to make the "vacancy" by comparing with the sample pattern of the MUSE method. It is shown in FIGS. 3 (a) to (d).

FIG. 3 (d) shows a part of the sample pattern within one field of the C signal in the conventional MUSE system. Indicate the sampling positions of the first frame and the second frame, respectively. As is well known in the MUSE system, the wideband color signal (C _W ) and the narrowband color signal (C _N ) of the C signal are alternately sampled line by line even within the field.
n, n + 2, n + 4, ... If the line is a C _W signal sample line, the n + 1, n + 3, n + 5, ... line becomes a C _N signal sample line, and the figure shows one of the color signal sample patterns. It can be interpreted as being displayed, and the sample pattern is treated in the same manner thereafter. In the case of the MUSE method, the sampling frequency is 16.2MHz.

On the other hand, the first embodiment of the sample pattern in the field of the C signal of the transmission system of the present invention is shown in FIG. 3 (a). And □ indicate sampling positions of the 1st, 3rd, 5th and 7th fields, respectively, and the MUSE method is 4
In contrast to the field 1 order, the sample pattern of the transmission method of the present invention is 8 field 1 order. FIG. 3 (b) is based on the pattern of FIG. 3 (a). Sampling frequency is MUSE in the pattern where mark positions are extracted
You can see that the frequency is 8.1MHz, which is half the 16.2MHz of the system. Therefore, the amount of information to be transmitted is half that of the MUSE method.

The pattern of FIG. 3 (c) is a second embodiment of the in-field sample pattern of the C signal of the present invention. Shows sampling positions of the first, third, fifth and seventh fields, respectively, as in FIG. 3 (a).

In the sample pattern, the first embodiment shows that the horizontal resolution is 1/4 that of the still image, and the second embodiment shows that the resolution is 1/2 that of the still image both horizontally and vertically. It is necessary to perform a visual experiment to determine which of the above-described first and second embodiments is better, but the visual dynamic characteristics with respect to the C signal are weak, and the moving direction of the moving object is often horizontal. In consideration of this, it is considered that the sample pattern of the first embodiment is more advantageous, and the sample pattern of the second embodiment is more advantageous in terms of the balance of resolution in both the horizontal and vertical directions.

Now, the "vacant" provided in this way, that is, the conventional MU
The difference signal and the control signal are transmitted by using half the information amount of the C signal of the SE method. In this case, the amount of information that can be used for this is about 47 pixels / line.

Next, consider the differential signal to be transmitted. First
The figure conceptually shows a block diagram of only the portion related to the present invention in the configuration of the first embodiment for realizing the transmission method of the present invention. At the same time, a lead wire is drawn out from a portion considered necessary, and a signal at that portion is shown. The two-dimensional spatial frequency characteristics are shown with the horizontal resolution (MHz) on the horizontal axis and the vertical resolution (books) on the vertical axis. In this figure, the two-dimensional spatial frequency characteristics shown by the leader line from the block difference interpolation 7 are shown. The shaded portion 71 of is the difference signal to be transmitted. And the blank part 72 is
This is the part of the spatial frequency characteristics that had already been transmitted by the MUSE method. In order to transmit the portion 71, a sample rate of MUSE video mode, that is, the sample rate of MUSE of 16.2MHz, and a basic sample rate of MUSE transmission of 48.6MHz, for example, a sample rate of 32.4MHz is required. I understand that. Here the basic sample rate is 48.6MH
The reason why z is taken is that the high-definition television Y signal requires 22 MHz as its baseband, and M
The sample rate of the USE transmission method is derived from the need to set the basic sample rate to an integral multiple of 16.2MHz.

In the configuration of the first embodiment of the present invention shown in FIG. 1, the Y signal of the high-definition television signal at the input 1 is A / D at 48.6 MHz.
It shall be converted and input. The moving area pre-filter 2 is the moving area pre-filter itself used on the encoder side of the MUSE method. MUSE on the encoder side in the figure
The video signal of the Y signal of the method and the difference signal between the original image signal at the basic sample rate and the above-mentioned video signal are extracted (4), and both are 16.2MHz (3) and 32.4MHz, respectively.
In (5), subsampling is performed and transmission is performed. On the decoder side, in addition to the conventional motion area interpolation (6), interpolation processing (7) for the differential signal is performed, and both are added at the end (8).

In the case described above, the interpolation filter for the differential signal described above becomes a considerably extra circuit, but if this is omitted, the transmission of the moving image signal is sent as a signal without the pre-filter (2), or Send the difference signal in 48MHz full sample, or
You need to take one. In the former case, the moving image signal cannot be demodulated by the conventional MUSE-type decoder, and if an error occurs in the control signal indicating the portion transmitting the difference signal, the difference signal cannot be added to the main line signal, At this time, aliasing distortion occurs. In the latter case, the transmission information increases.

FIG. 2 shows a block diagram of only the portion relating to the present invention in the configuration of the second embodiment for realizing the transmission system of the present invention, in the same relationship as FIG. In this embodiment, the vertical resolution of the differential signal is suppressed and the amount of transmitted information is reduced to about 1/2.

Next, considering the above two embodiments, although the second embodiment has a smaller amount of information to be transmitted,
The effect is not as small as on the left. Therefore, regarding the method of transmitting the differential signal and the control signal, the second embodiment will be considered below.

Since the C signal has already been processed to obtain the “vacant” of the transmission capacity of 47 samples / line, it is considered to use this to transmit the differential signal and the control signal.

The control signal is for each block, and the size of the block is MUSE
Considering the transmission signal to be about 4 lines × 8 pixels, it is sufficient to allocate 1 bit to each block for the control signal and to indicate whether or not to send the difference signal. Therefore, 12 bits / line (374/8 X4≈12) is required. Binary, 16.2M
Transmission at Hz Baud requires 12 samples per line. If even one control signal is erroneous, the difference signal allocation after that will be greatly affected, but since there is not enough margin for erroneous correction, erroneous detection is performed by performing a sum check-like erroneous detection for each field. If so, the MUSE decoder signal is not corrected by the difference signal. The block is about 6000 in 1 field (1038 × 374/2 × 4 × 8 ≒ 6000)
Since the error rate is ^10-6 or less, the number of such errors is small. Moreover, in the case of the transmission system of the present invention,
Even if the above correction is stopped, the resolution of the moving image area of the luminance (Y) signal simply becomes the same as that of the MUSE system, and since the image quality itself is good, there is almost no problem.

The remaining 47-12 = 35 samples / line are then used to transmit the differential signal. Since the number of MUSE samples per line of Y signal is about 370, 35 samples / line can transmit a differential signal having an information amount equivalent to about 1/10 of all samples. As for the actual difference signal, the occurrence of the difference signal for one field period is stored in the moving image area, and the block having the largest influence, that is, the block having the largest absolute value of the generated difference signal is preferentially selected sequentially, and To transmit. The transmission of the selected signal itself does this in the sequence of television scanning.

In the above description, the transmission of the "vacant" and the C signal for transmitting the differential signal and its control signal has been sought. However, the present invention is not limited to this, and the stationary portion of the Y signal or the Y and C signals. The number of images transmitted per second in the stationary portion of the signal may be reduced. Also, two C signals for each frame of the C signal,
Alternatively, C _W and C _N may be obtained by alternately lowering the vertical resolution.

(Effect of the Invention) By using the transmission method of the present invention, the conventional MUSE
The image quality of the moving image of the Y signal is improved as compared with the transmission method. On the other hand, the side effect that occurs is nothing but a slight decrease in the resolution of the moving image of the C signal.

Furthermore, the transmission system of the present invention complicates the decoder and doubles the circuit scale. However, even a decoder having no additional portion according to the present invention can receive the transmission signal of the present system. Images of MUSE format can be decoded. In other words, it has the effect of being compatible with the MUSE method.

[Brief description of drawings]

1 and 2 are conceptual block diagrams of the configurations of the first and second embodiments for realizing the transmission method of the present invention, and FIGS. 3 (a) to (d) are the present invention method and the conventional method. FIG. 7 is a diagram showing various patterns for explaining the difference in the sample pattern of the C signal of the MUSE method of FIG. 1 ... Encoder input, 2 ... Moving area pre-filter 3 ... 16.2 MHz subsample 4 ... Subtraction circuit 5 ... 32.4 MHz subsample 6 ... Moving area interpolation, 7 ... Differential interpolation 8 ... Summing circuit, 9 ... Decoder output 10 ... Vertical filter

Claims (1)

[Claims] 1. A television signal transmission system for band-compressing and transmitting a component signal of a color television by using multiple sub-sampling means, wherein an encoder of the transmission system has an original image signal and an encoder side for a luminance signal in a moving image area. First means for obtaining a differential signal from the signal obtained through the motion domain pre-filter,
In order to selectively transmit the differential signal obtained by the first means, the frame or the field is divided into a large number of blocks, and the block is selected according to the generation amount of the differential signal in the block. Means for transmitting the differential signal of the block selected by the second means and the control signal for controlling the selection, so that the chrominance signal is sub-sampled in the horizontal or vertical direction at a repetition cycle twice as long as the luminance signal. And a third means for providing an empty space for transmission, wherein the decoder of the transmission system reproduces the differential signal transmitted by utilizing the empty space for transmission of the color signal, and reproduces this reproduced differential signal. The fourth means for adding to the luminance signal of the moving picture area reproduced from the sampling transmission decoder using the control signal, and the color signal transmitted by the 4: 1 line interlace are displayed. For use, the high frequency component is displayed with 4: 1 line interlace for the moving image of the color signal, and the low frequency component of the moving image of the color signal and the still image of the color signal are displayed with the 2: 1 line interlace. A television signal transmission system comprising means.