JPH0556456A - Image signal transmission method - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the visual quality of color images without expanding the transmission band of image signals. When transmitting an image signal, when a line-sequential and horizontal time-compressed signal is band-compressed by an inter-field offset sub-sample like a color difference signal of TCI (Time Axis Compression Multiplexing) method and transmitted, The two-dimensional spectrum is recombined and transmitted by the two-dimensional filter operation and the two-dimensional modulation operation, and is returned to the receiving side.
The visual image quality is improved without widening the transmission band.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for band-compressing and transmitting a television image signal and a method for transmitting and receiving the same, and more particularly to a method of transmitting original image signals of 2: 1 interlaced scanning.
The present invention relates to a transmission method of a signal component to be band-compressed by line-sequential and field offset sub-sampling and a transmission / reception method thereof. It is applied to satellite transmission of television signals, cable transmission, and the like, and is also applied to signal recording methods such as VTR.

[0002]

2. Description of the Related Art MUSE has been used as a method for compressing and transmitting a 2: 1 interlaced television image signal line-sequentially by field offset sub-sampling.
There is a color difference signal transmission method in the -T method. MUSE
In the -T method, the color difference signals are time-compressed in the horizontal direction by a factor of 1/5, and further in the vertical direction by a band limitation to 1/4 in order to avoid aliasing distortion due to line-sequential processing. In this case, in the still image mode, the ratio of the maximum horizontal frequency to the maximum vertical frequency is 1: 1.3, which can transmit almost square area and is well suited to human visual characteristics. Limits the maximum horizontal frequency to 1/2 of the still image mode in order to prevent the overlapping of spectra due to the folding of carriers on the 30Hz plane, so the ratio of the maximum horizontal frequency to the maximum vertical frequency is 1:
With 2.6, there was a problem that the horizontal resolution and the vertical resolution were unbalanced.

The above-mentioned ratio of 1: 1.3 is generally obtained as follows. NH is the above MUSE-T method
One of the high-definition television (high-definition) band compression transmission methods developed by K Broadcasting Research Laboratories. High-definition 30 frames / second, 1125 horizontal scanning lines, 74.25MHz
Taking into account the sampling frequency and the aspect ratio of 9:16, the shape aspect ratio γ of one pixel is calculated. The number of effective horizontal scanning lines on the screen is 1035, and the effective horizontal sampling point is 1920.
From the point γ = Δv / Δh = (9/1035): (16/192
0) = 0.958 is obtained.

When converting the horizontal resolution of an image into TV lines, it is necessary to take γ into consideration, and when the horizontal frequency is f _h , the horizontal resolution R _h of this high-definition television is R _h = (2 × f _h / 7
4.25 × 10 ⁶ ) × (10 35 / γ), and if the horizontal maximum frequency of HDTV is 20 MHz, then R _h = 566 ≈ 600 (TV
Book). On the other hand, the vertical and horizontal directions are 1/4 and 1 respectively.
When the bandwidth is limited to / 5, the ratio of both resolutions is R _v = 1035/4
≒ 284 (TV present), f _h is in consideration of the Nyquist frequency of the sampling frequency ^{_{f h = (74.25 × 10 6}} /2) × (1/5)
= 7.425 because comprising _{(MHz) R h = (2} × 7.425 × 10 6 /74.2
5 × 10 ⁶ ) × (1035 / 0.958) ≈216 (TV lines), and from these, R _V / R _h becomes 1.3 and 1: 1.3 is obtained.

[0005]

In a band compression transmission method for interlaced scanned image signals combining line-sequential and horizontal time axis compression, field offset sub-sampling, and dynamic / static adaptive processing, a sampling structure of primitive sampling is used. When the (frame unit) is almost a square lattice, the horizontal resolution and the vertical resolution in the moving image mode are poorly balanced, and there arises a problem that the transmittable spectrum region is not effectively utilized. Therefore, an object of the present invention is to perform a spectrum shifting operation by two-dimensional filter processing and two-dimensional modulation processing before performing line-sequential multiplexing and field offset sub-sampling to convert a horizontal high frequency component into a vertical high frequency component. An object of the present invention is to provide an image signal transmission method and a transmission / reception method thereof, in which horizontal resolution and vertical resolution are balanced by transmission to improve visual characteristics.

[0006]

In order to achieve this object, the image signal transmission method of the present invention performs band compression processing by line-sequential and field offset sub-sampling of a television image signal which has been subjected to 2: 1 interlace scanning. The signal component to be transmitted by the two-dimensional filter processing and the two-dimensional filtering processing on the transmitting side prior to the band compression processing.
The horizontal high frequency component of the signal component is replaced with the vertical high frequency component by dimensional modulation processing, and then the band compression processing is performed to balance the horizontal high frequency component and the vertical high frequency component of the transmittable signal component. While encoding and transmitting,
On the receiving side, the encoded and transmitted signal component is subjected to a two-dimensional filter process and a two-dimensional demodulation process to also obtain a horizontal high-frequency component replaced with a vertical high-frequency component of the signal component. It is characterized by decoding so as to return to the horizontal high range of.

The image signal transmitting method of the present invention is 2: 1.
In the interlaced-scanned television image signal, a signal component to be band-compressed by line-sequential and field offset subsampling and transmitted is subjected to a two-dimensional filter process and a two-dimensional modulation process prior to the band compression process. The horizontal high frequency component of the signal component is replaced with the vertical high frequency component, and then band compression processing is performed to encode and transmit so that the horizontal high frequency component and the vertical high frequency component of the transmittable signal component are balanced. It is characterized by doing.

In the image signal receiving method of the present invention, the signal component encoded and transmitted by the above-mentioned transmitting method is subjected to a two-dimensional filter process and a two-dimensional demodulation process to obtain a vertical high frequency component of the signal component. It is characterized by decoding so that the horizontal high-frequency component replaced by is returned to the original horizontal high-frequency.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. A case will be described in which the present invention is applied to band compression of a color difference signal in a moving image mode in a TCI (time axis compression multiplex) signal having 1125 scanning lines, a field frequency of 60 Hz, and an interlace ratio of 2: 1. The horizontal time-axis compression ratio of the color difference signal is 5 (the reason is that the ratio of the resolution of the luminance signal to the resolution of the color difference signal is 4: 1 in this embodiment. Therefore, the luminance signal is 5 minutes smaller than the original signal. 4 time axis compression, the color difference signal needs to be time axis compressed to 1/5 of the original signal). The description of the luminance signal processing, the horizontal time axis compression / expansion processing, the TCI processing, the gamma processing, and the transmission system processing will be omitted, and only one part of the two color difference signals will be described. The sampling frequency is 74.25MHz. The primitive sampling grid (frame unit) in this case is a substantially square grid with a ratio of the horizontal and vertical grid intervals of 1: 1.18.

First, the encoder side (transmission side) will be described. FIG. 1 shows the configuration of the processing circuit on the encoder side, and the states of the T = OHz plane in the three-dimensional spectrum display of the signals of each part in the encoder are sequentially shown in FIGS. In these figures, V _S is 1125 cph be vertical sampling frequency. H _S is a horizontal sampling frequency, and if the sampling frequency after horizontal time axis compression is ⅕ is set to 74.25 MHz, the horizontal sampling frequency of the signal restored to the original time width even if the horizontal time axis is expanded is ( 7
4.25 / 5) MHz. In addition, the white circles in the figure are the basic carriers by primitive sub-sampling, and the black circles are the positions in the horizontal (H) and vertical (V) planes of the modulation carrier. The spectrum of the color difference signal a ₁ compressed in the horizontal time axis is shown in FIG. Since the moving image signal is considered, the signal a ₁ is V in the vertical direction in order to avoid overlapping of the spectrum with the aliasing component from the interlaced carrier in the T = 30 Hz plane.
Bandwidth limited to _S / 4 (ie half of the still image). Further, since the time axis is compressed to 1: 5 in the horizontal direction, the resolution is ⅕ of that in the vertical direction.
Therefore, the ratio of the horizontal and vertical resolutions of the signal a ₁ is about 2.5 times vertical.

First, this signal is band-limited to a diagonal region having a vertical resolution of V _S / 8 and a horizontal resolution of (H _S / 2) MHz by the two-dimensional LPF of the circuit 1 to obtain a signal b ₁ . This filter is an in-field process. The spectrum of the signal b ₁ is shown in FIG. The inside of the broken line in the figure is the Nyquist region of the moving image at the basic sampling. Next, the circuit 2 generates a carrier signal c ₁ having a horizontal frequency H _S / 2, a vertical frequency V _S / 8, and a time frequency OHz as shown in FIG. This is actually R
It can be realized by using OM. This signal c ₁ and signal b
₁ is multiplied by the multiplication circuit 3 to obtain the signal d ₁ . As shown in FIG. 6, in the signal d ₁ , the low band and the high band of the spectrum are inverted, and the diamond-shaped region centering on the origin is empty. The signal d ₁ and the signal b ₁ are added by the adder circuit 4 to obtain a signal e ₁ .
The spectrum of the signal e ₁ is shown in FIG. Next, the signal e ₁ is band-limited by the vertical LPF of the circuit 5 in the vertical direction V _S / 8 to obtain the signal f ₁ . The spectrum of the signal f ₁ is shown in FIG. This filter is an in-field process. Further, the signal f ₁ is band-limited to the horizontal direction H _S / 4 by the horizontal LPF of the circuit 6 to obtain the signal g ₁ . The spectrum of the signal g ₁ is shown in FIG.

The signal g ₁ is then subjected to line-sequential processing in the circuit 7, that is, vertical intra-field sub-sampling is performed to obtain a signal h ₁ . Originally, when line-sequential processing is performed for an interlaced signal of 2: 1, line pairing occurs, and as shown in FIG. 10, a sub-sampling carrier (black circle in the figure) exists at a position of V _S / 4 on the vertical frequency axis. Occurs.
Next, the signal h ₁ is subjected to field offset sub-sampling by the circuit 8 to obtain a signal i ₁ . The spectrum of the signal i ₁ is shown in FIG. In the figure, white triangles indicate carrier positions by field offset sub-sampling, and black triangles indicate carrier positions by line-sequential processing and field offset sub-sampling. The order of the line sequential processing and the field offset sub-sampling processing may be interchanged. The signal i ₁ is subjected to transmission system processing (actually, transmission gamma, synchronization signal addition, transmission roll-off filter processing, etc.), and the encoder processing ends. Although only one color difference signal is described in the above description, the two color difference signals are usually processed simultaneously after the line-sequential processing circuit of the circuit 7, but the processing method and spectrum do not change.

Next, the processing on the decoder side (reception side) will be described. FIG. 2 shows the configuration of the processing circuit on the decoder side.
12 to 18 show the states of the T = OHz plane in the three-dimensional spectrum display of the signals of the respective parts in the decoder. On the decoder side, first, with respect to the signal a ₂ from the transmission system, zeros are interpolated to signal b ₂ corresponding to the field offset sub-sample on the encoder side in the circuit 21 at the sampling points thinned during the field offset sub-sampling. .. The spectra of the signal a ₂ and the signal b ₂ are shown in FIG. Zero interpolation itself does not change the spectrum at all. Next, the signal b ₂ is interpolated by the horizontal interpolation LPF of the circuit 22, and the spectrum generated from the subsample carrier generated in the field offset subsample is removed to obtain the signal c ₂ . The cutoff frequency of this horizontal interpolation LPF is H _S / 4. Signal c
The spectrum of ₂ is shown in FIG. Subsequently, two color-difference signals that are line-sequentially multiplexed are separated from the signal c ₂ , and the line thinned out by the line-sequential processing is subjected to zero interpolation in the circuit 23 to obtain a signal d ₂ . The signal d ₂ has the same spectrum as the signal c ₂ . Next, the signal d ₂ is the vertical interpolation of the circuit 24.
Interpolation is performed by LPF to remove the spectrum generated from the carrier having the vertical frequency V _S / 4 generated by the line-sequential processing to obtain the signal e ₂ . V _S / 8 is the cut-off frequency of the vertical interpolation LPF
FIG. 14 shows the spectrum of the signal e ₂ which is Next circuit 25
The two-dimensional carrier generation circuit of ₂ generates a carrier signal f ₂ having a spectrum as shown in FIG. This signal is the same as the signal generated by the circuit 2 on the encoder side. The signal f ₂ and the signal e ₂ are multiplied by the multiplication circuit 26 to obtain a signal g ₂ . The spectrum of the signal g ₂ is shown in FIG. Further, the signal g ₂ and the signal e ₂ are added by the adder circuit 27 to obtain a signal h ₂ . The spectrum of the signal h ₂ is shown in FIG. The signal h ₂ is a signal i ₂ by removing the unnecessary spectrum in the oblique direction by the two-dimensional LPF of the circuit 28, and a signal having the same spectrum as the signal b ₁ on the encoder side is reproduced (FIG. 18). FIG. 19 shows a sampling pattern when line sequential processing + field offset sub-sampling processing is applied to a 2: 1 interlaced signal. FIG. 20 shows a three-dimensional display of carrier allocation when line sequential processing + field offset sub-sampling processing is applied to a 2: 1 interlaced signal.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the invention described in the claims. Would be obvious. Finally, in order to help more accurate understanding of the present invention, the accompanying drawings will be collectively described below. This description has some overlap with the above description.

FIG. 1 is a diagram showing the configuration of a basic processing circuit on the encoder side according to the present invention. In a normal video processing apparatus, line-sequential processing is performed in order to combine two color difference signals into one signal by time division multiplexing for each line. In FIG. 1, circuits 1 to 6 require the same circuit separately for two color difference signals. In FIG. 1, only the signal system on one side is described, and the other is omitted. Circuit 7
1 to circuit 8 may be one circuit.

FIG. 2 is a diagram showing the configuration of a basic processing circuit on the decoder side according to the present invention. For the same reason as on the encoder side, circuits 21 to 22 may be one circuit,
Circuits 23 to 28 require the same circuit separately for the two color difference signals. In FIG. 2, only the signal system on one side is described, and the other is omitted.

3 to 11 and 12 to 18, V _S indicates a vertical sampling frequency and H _S indicates a horizontal sampling frequency. A white circle indicates a basic sampling carrier by primitive sampling. Black circles indicate subsampling carriers by line sequential processing. White triangles indicate subsampling carriers by field offset subsampling. Black triangles indicate subsampling carriers by line sequential processing + field offset subsampling. The display is a horizontal-vertical two-dimensional display with a time frequency T = OHz. The shaded area indicates the spectrum of the fundamental wave. In the case of moving images, the spectrum generated by the carriers in the 30 Hz plane also occurs in the OHz plane, but it complicates the figure, so the spectrum due to the carriers in the 30 Hz plane is omitted and not displayed.

FIG. 3 shows the spectrum of the signal a ₁ in FIG. The shaded area indicates the Nyquist zone. 4 is shown in FIG.
3 shows the spectrum of the signal b ₁ in FIG. The dotted line shows the Nyquist region, and the shaded portion showing the spectrum also shows the pass band of the two-dimensional filter. Figure 5 shows the spectrum of the signal c ₁ in FIG. The dotted line shows the Nyquist zone. Figure 6 shows the spectrum of the signal d ₁ in FIG. 1. The shaded area indicates the area where the component exists. Figure 7 shows the spectrum of the signal e ₁ in FIG. Two areas with different diagonal lines show the fundamental wave component and the modulated wave component. Figure 8 shows the spectrum of the signal f ₁ in FIG. 1. The dash-dotted line indicates the passband of the vertical LPF. FIG. 9 shows the signal g in FIG.
The spectrum of ₁ is shown. The alternate long and short dash line indicates the passband of the horizontal LPF. Figure 10 shows the spectrum of the signal h ₁ in FIG. 1. A new carrier exists due to the line-sequential processing. Figure 11
Shows the spectrum of the signal i ₁ in Figure 1. Field offset sub-sampling introduces newer carriers. The Nyquist range is horizontal ± H _S /
4, a rectangular area of vertical ± V _S / 8. Figure 12 is Figure 2
11 shows the spectra of the signal a ₂ and the signal b ₂ of the above, and is the same as the spectrum shown in FIG. FIG. 13 shows the spectra of the signal c ₂ and the signal d ₂ of FIG.
The sub-sample carrier, the white triangle triangle mark, and the black triangle mark that were present at the position corresponding to the diagonal component are removed. Figure
14 shows the spectrum of the signal e ₂ of FIG. The vertical interpolation filter removes the black circles of the sub-sample carrier generated by the line sequential processing. Figure 15 shows the spectrum of the signal f ₂ in FIG. This spectrum is
It is the same as FIG. Figure 16 shows the spectrum of the signal g ₂ in FIG. The spectrum is moving due to the two-dimensional modulation. FIG. 17 shows the spectrum of the signal h ₂ of FIG. The modulated wave and the fundamental wave are combined. FIG. 18 shows the signal i _{2 of} FIG.
Shows the spectrum of. Unwanted harmonic components are removed by the two-dimensional LPF, and the same spectrum as in Fig. 4 is reproduced. FIG. 19 shows a sampling pattern when line sequential processing + field offset sub-sampling processing is applied to a 2: 1 interlaced signal. Figure 20 shows line sequential processing +
It is a two-dimensional representation of the position of the sampling carrier when the field offset sub-sampling process is applied to a 2: 1 interlaced signal. T = OHz plane
(a) and T = ± 30 Hz There are carriers in the plane (b). T
= No carrier exists on ± 15Hz plane or ± 7.5Hz plane.

[0019]

EFFECT OF THE INVENTION Sampling grid for primitive sampling
When a line-sequential color difference signal is horizontally time-compressed to about 5: 1 and a time-division multiplexed TCI signal is band-compressed by field offset subsampling in a 2: 1 interlace signal (frame unit) close to a square lattice. In the moving image mode, the horizontal resolution and the vertical resolution were poorly balanced, and the horizontal resolution was insufficient with respect to the vertical resolution. However, by applying the present invention, in terms of visual characteristics,
We could improve the image quality visually without expanding the transmission band by removing the less important diagonal component, replacing the horizontal high frequency component with the vertical high frequency component, and transmitting again.

[Brief description of drawings]

FIG. 1 shows an embodiment of the encoder side processing circuit configuration of the present invention.

FIG. 2 shows an embodiment of the decoder side processing circuit configuration of the present invention.

FIG. 3 shows a spectrum of an encoder side signal a ₁ .

FIG. 4 shows a spectrum of an encoder side signal b ₁ .

FIG. 5 shows a spectrum of an encoder side signal c ₁ .

FIG. 6 shows a spectrum of an encoder side signal d ₁ .

FIG. 7 shows a spectrum of an encoder side signal e ₁ .

FIG. 8 shows a spectrum of an encoder side signal f ₁ .

FIG. 9 shows a spectrum of an encoder side signal g ₁ .

FIG. 10 shows a spectrum of an encoder-side signal h ₁ .

FIG. 11 shows a spectrum of an encoder side signal i ₁ .

FIG. 12 shows spectra of decoder side signals a ₂ and b ₂ .

FIG. 13 shows spectra of decoder side signals c ₂ and d ₂ .

FIG. 14 shows a spectrum of a decoder side signal e ₂ .

FIG. 15 shows a spectrum of a decoder-side signal f ₂ .

FIG. 16 shows a spectrum of a decoder-side signal g ₂ .

FIG. 17 shows a decoder-side signal h ₂ and a spectrum.

FIG. 18 shows a spectrum of a decoder side signal i ₂ .

FIG. 19 shows sampling patterns by line sequential and field offset sub-sampling.

FIG. 20 shows carrier arrangement by line-sequential and field offset sub-sampling, (a) T = OHz plane, (b) T = 30.
Shows the Hz plane.

[Explanation of symbols]

 1,28 Two-dimensional LPF 2,25 Two-dimensional carrier generation circuit 3,26 Multiplier 4,27 Adder 5 Vertical LPF 6 Horizontal LPF 7 Line sequential processing circuit 8 Field offset sub-sample processing circuit 21, 23 Zero interpolation circuit 22 Horizontal interpolation LPF 24 Vertical interpolation LPF

Claims (3)

[Claims] 1. A signal component to be band-compressed by line-sequential and field offset sub-sampling in a 2: 1 interlace-scanned television image signal to be transmitted, at the transmitting side, said band-compressing process. Prior to the above, two-dimensional filter processing and two-dimensional modulation processing are performed to replace the horizontal high-frequency components of the signal components with vertical high-frequency components, and then band compression processing is performed to transmit the horizontal high-frequency components of the signal components. And the encoded high-frequency components are balanced and transmitted, and on the receiving side, the encoded and transmitted signal components are two-dimensionally filtered and two-dimensionally demodulated. An image signal transmission characterized in that the horizontal high-frequency component replaced with the vertical high-frequency component of the signal component is decoded so as to return to the original horizontal high-frequency component. Method. 2. A signal component to be band-compressed by line-sequential and field offset sub-sampling and transmitted in a 2: 1 interlaced television image signal is two-dimensionally filtered prior to the band-compressing process. And a two-dimensional modulation process to replace the horizontal high frequency component of the signal component with a vertical high frequency component, and then band compression processing is performed to balance the transmissible horizontal high frequency component and vertical high frequency component of the signal component. A method for transmitting an image signal, characterized in that the image signal is encoded and transmitted. 3. A horizontal signal obtained by performing a two-dimensional filter process and a two-dimensional demodulation process on the signal component encoded and transmitted by the transmission method according to claim 2, and replacing the signal component with a vertical high frequency component. An image signal receiving method characterized in that decoding is performed so that high frequency components are returned to the original horizontal high frequency range.