JPH0567112B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a field interpolation method used when decoding a coded signal using a multiple subsample transmission method.

Furthermore, in other words, the present invention relates to a method in which a signal reproduction interpolation filter is made adaptive when performing field interpolation in a decoder for high-vision transmission signal processing.

[Prior Art] A so-called multiple sub-sampling transmission method is known as a method for band-compressing and transmitting a television signal (for example, the IEICE technical research report
IE84−72).

A field interpolation method suitable for such a transmission method (high-vision transmission method) is not yet known.

However, regarding standard television receivers, there are some known examples in which a concept similar to the color/luminance separation circuit is used, although the purpose is different.

[Problems to be Solved by the Invention] In a decoder adapted to encoded signals using a multiplex subsampling transmission method, field interpolation is performed for a moving image region. On this occasion,
If the characteristics of the filter used are ideal, no problem will occur, but due to restrictions on tap length, etc., a filter having characteristics that are considerably narrower than the ideal value will be used.

Therefore, in the video domain, the “blur” of the image
This causes the inconvenience of inviting

[Objective] Therefore, an object of the present invention is to provide a field interpolation method that does not cause "blurring" even in a moving image area.

[Means for solving the problem] In the field interpolation method according to the present invention, vertical edges and horizontal edges are each independently detected when decoding a signal encoded based on a multiple subsample transmission method. A broadband spatial interpolation filter is used only in the time domain where there are vertical edges and no horizontal edges.

That is, in the present invention, in a decoder adapted to the multiplex subsample transmission method, intra-field interpolation is performed by adaptively using a low-pass filter having a predetermined cutoff frequency depending on the image content.

Further, in a preferred embodiment of the present invention, switching between wideband and narrowband is realized using a 12MHz low-pass filter.

Furthermore, it is also possible to use the above-mentioned 12MHz low-pass filter as a reproduction and noise cut filter for the static region.

[Examples] Hereinafter, the present invention will be described in detail based on Examples.

FIG. 1 shows a basic system diagram of the present invention. In this figure, 2 is a frame memory, 4 and 6 are low-pass filters (LPF), 8 is a horizontal edge detection circuit, 10 is a vertical edge detection circuit, 12 is a mixer, and 14 is an AND signal by inverting one input. It is a gate to get.

In the system shown in FIG. 1, a horizontal edge detection circuit 8 and a vertical edge detection circuit 10 are necessary for detecting a moving region when constructing a decoder adapted to the multiple subsample transmission system.

The operation of the circuit shown in FIG. 1 does not need to be particularly explained, but the band of the interpolation filter is expanded at vertical edges (vertical lines, etc.). By doing this,
The "blur" of that part can be reduced.
However, if there is a horizontal edge component, aliasing will occur, but here, this is applied only to areas where there is no aliasing, so no problem occurs.

Further, in FIG. 1, _S1 is a subsample switch. Further, _S2 is a switch unique to this embodiment, and when the control signal is "1", it is turned to the 2 side.

LPF1 is a broadband filter, and LPF2 is a narrowband two-dimensional filter. This LPF 2 has a bandwidth that is just large enough to prevent aliasing.

FIG. 2 shows another practical embodiment to which the present invention is applied. The block 20 labeled "edge detection" in this figure corresponds to the dotted line block shown in FIG. Further, 16 is a frame memory, 18 is a low-pass filter, 22 is a comparator (threshold logic that outputs "1" when moving), 24 is a motion detection circuit, 26 is a mixer, 28
is a 12 MHz low-pass filter, 30 is an AND gate, and S ₁ and S ₂ are switches that perform the same functions as switches S ₁ and S ₂ shown in FIG.

If we were to manufacture a two-dimensional filter with a normal number of taps (approximately 7 x 9) that does not cause aliasing, the desired characteristics would deteriorate considerably in the vicinity of 12 MHz. Therefore, as shown in Figure 3A, 16M
A filter with a pass area that flatly passes horizontal components up to Hz (LPF18 in Figure 2)
and a filter as shown in Figure 3B (LPF28 in Figure 2;
(note that the vertical axes are different) can be connected in cascade to obtain roughly the same filter.

With this configuration, there are no components of 12MHz or higher for still images, so 12M
Pass through a Hz filter to remove noise and aliasing (aliasing when mistakenly judged to be a still image). Furthermore, since the LPF is gascade connected to the video area, the entire system becomes a two-dimensional interpolation filter.

Now, in order to implement the present invention according to the system described above, it is sufficient to set the 12 MHz filter 28 to a through state only for moving images when there are no horizontal edges and there are vertical edges. In order to perform such control, the switch control logic shown in FIG. 2 is constructed.

By using the system described above, it is possible to make the dynamic area filter adaptive without adding any extra filters.

FIG. 4 is an overall configuration diagram of a decoder for processing multiple subsample transmission signals to which the present invention is applied.

In this figure, 41 is a signal detection synchronization detection circuit, which is a transmission signal that does not include interframe aliasing components in the low frequency range input from the signal input terminal 52 (the interframe subsampling frequency is 16MHz:
It is also mentioned in No. 60-106132. However, at the time of filing of the present invention, this was not publicly known. ) to generate a synchronization signal and control the synchronization of this decoder.

SW1 is a switch for sub-sample shifting, and is applied to the transmission signal input to the input terminal 52.
A signal delayed by one frame whose motion has been corrected by the frame memory 42 and the motion correction circuit 43 is inserted to obtain a signal interpolated between frames sampled at 32 MHz (obtained at A in the figure). Note that the switch SW1 is not a simple switch, but can be given noise reduction characteristics by taking in a 16MHz input with an appropriate mixing ratio.

The 32MHz sampling interframe interpolated signal from switch SW1 is sent to the motion detection circuit 44.
is input as one input to the switch, and the switch
The signal is inputted to the field interpolation circuit 45 via the switch SW2 which operates together with SW1, and is further inputted as one input to the MIX circuit.

The other input of the motion detection circuit 44 includes an input terminal 5.
The transmission signal from 2 is input. Motion detection circuit 4
4 produces a motion detection signal based on the two input signals.

Switch SW2 switches the signal of only the sampling point corresponding to the current field to switch SW1.
It is extracted from the signal from , interpolated within the field by an intra-field interpolation circuit 45 consisting of a low-pass filter, and inputted into the mix circuit 46 .

The mixer circuit 46 uses the output signal of the motion detection circuit 44 to output a moving image signal (from the field interpolation circuit 45) and a switch signal (from the field interpolation circuit 45) according to the amount of motion.
(from SW1) is mixed with the still image signal.

The interfield interpolation circuit 49 inputs the output signal from the mixer circuit 46 into the field memory 4.
7 and the one-field delayed signal obtained by the motion correction circuit 48 are interpolated to obtain an inter-field interpolated signal sampled at 48 MHz, which is input as one input to the frequency conversion/mixing circuit 50. Ru.

The 32 MHz sampling signal from the mix circuit 46 input to the other input of the frequency conversion/mix circuit 50 is
It is converted to a sampling frequency of 48 MHz, mixed with the signal from the inter-field interpolation circuit 49 according to the amount of motion (by the output signal from the motion detection circuit 44), and is converted to a TCI (Time-Compressed-
(Integration) The signal is input to the decoder 51, where it is converted into a desired television signal and output from the output terminal.

[Effects of the Invention] By implementing the present invention, the image quality can be significantly improved with respect to vertical edge portions where "blur" is noticeable when the image moves slightly.

Although we carefully investigated and observed any side effects caused by the introduction of this method, almost no such adverse effects were observed.

Further, according to the above-described embodiment to which the present invention is applied, image quality can be improved without substantially increasing the circuit scale on the receiver side.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing the basic configuration of the present invention.
FIG. 2 is a block diagram showing an actual embodiment to which the present invention is applied, FIG. 3A is a diagram showing the characteristics of the low-pass filter 18 shown in FIG.
A diagram showing the characteristics of the 12 MHz low-pass filter 28 shown in the figure, and FIG. 4 is an overall configuration diagram of a decoder for multiple subsampling transmission signal processing to which the present invention is applied. 2... Frame memory, 4, 6... Low pass filter, 8... Horizontal edge detection circuit, 10... Vertical edge detection circuit, 12... Mixer, 14... Gate, 16... Frame memory, 18... Low pass Filter, 20... Edge detection circuit, 22...
Comparator, 24...Motion detection circuit, 28...
Low-pass filter (cutoff 12MHz), 30...gate, _S1 , _S2 ...switch.

Claims (1)

[Claims] 1. When decoding a signal encoded based on a multiple subsample transmission method, a vertical edge and a horizontal edge are each independently detected, and if the vertical edge exists and the horizontal edge A field interpolation method characterized in that a wideband spatial interpolation filter is applied only to a time domain where there is no field.