JPH06225151A - System and device for companding band - Google Patents

Abstract

PURPOSE:To reduce an information quantity with simple configuration and to transmit an input video signal at a high compression ratio by encoding a low frequency component of the input video signal and applying contour correction to the coded signal so as to code a correction component mixed with a high frequency component. CONSTITUTION:A low frequency component is separated from an input video signal by a low pass filter 12 and the component is outputted to a contour correction circuit 40 and a coder 16. The circuit 40 corrects a signal edge steeply and a subtractor 14 subtracts the corrected signal from the input video signal to output an HPF signal. Since the high frequency component included in the edge part is cancelled in the HPF signal, the data quantity coded by the coder 18 is less. On the other hand, an output of the filter 12 is compressed and coded by the coder 16 and the result is outputted to a multiplexer circuit 20, in which the coded signal is multiplexed with an output of a coder 18 and the result is outputted from an output terminal 22. Thus, the outputted data quantity is reduced with simple configuration and the input video signal is transmitted with a high compression ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to recording / reproducing video signals,
In communication or broadcasting, the present invention relates to a technique in which a video signal is divided into sub-bands, the band is compressed, then transmitted, and then expanded on the receiving side.

[0002]

2. Description of the Related Art In recent years, a subband coding system has been proposed as a system for compressing and expanding information such as a video signal.
The outline of this method is that the transmitting side transmits information signals such as audio signals and video signals to a quadrature mirror filter.
lter (hereinafter referred to as QMF)) is used to divide into low and high frequency bands, 2: 1 sub-sampling is performed for each band, and each band is coded. Is simple quantization, non-linear quantization, DPC
Methods such as M and DCT are conceivable and are described, for example, in "Image Information Compression" (Television Society, 1991 Ohmsha). The sub-band coding method is a coding method suitable for information amount compression because the band can be divided in the frequency band without increasing the overall data amount and the optimum coding method can be selected for each band.

On the other hand, the filter used for dividing the frequency band is not necessarily limited to QMF. As an example, "A new method of constructing a distortionless filter in subband division" IEICE Technical Report IE
89-98 (FEB, 1990) is known. Also, it may be configured such that frequency band division and sub-sampling are repeated multiple times. "A study of sub-band coding method" Inoue et al. 1991 6th Image Coding Symposium (PCS
J) It is described in Image Symposium Material 7-2, P169.

FIG. 6 is a block diagram of a conventional band compression device, FIG. 7 is a spectrum diagram for explaining subband division, and FIG. 8 is a diagram showing a signal waveform of the band compression device shown in FIG.

In FIG. 6, 10 is a terminal through which a video signal comes in, 12 is a low pass filter (hereinafter referred to as LPF), 14
Is a subtracter, 16 and 18 are encoders for compression and encoding, 20 is a multiplexing circuit, and 22 is a terminal for outputting a band-compressed signal.

The video signal input to the terminal 10 is supplied to one input (positive input) of the subtractor 14 and the LPF 12. The output of the LPF 12 is supplied to the other input (negative input) of the encoder 16 and the subtractor 14. Then, the subtractor 14 subtracts the output of the LPF 12 from the input video signal and outputs it. Therefore, the LPF 12 and the subtractor 14 are
A high-pass filter (hereinafter referred to as HPF) is configured, and the HPF and LPF 12 divide the input video signal into subbands into a lowband component and a highband component. Generally, sub-band division is performed using QMF, but band division can also be performed with the above configuration. Subtractor 1
The four outputs, ie, the high frequency components, are supplied to the encoder 18. The low frequency component and the high frequency component are respectively encoded by the encoder 1.
The compression and encoding are performed separately at 6 and 18. The data encoded by the encoders 16 and 18 are multiplexed by the multiplexing circuit 20, extracted from the terminal 22 and transmitted.

FIG. 7 is a spectrum diagram for explaining the above subband division. The spectrum 23 shown in FIG. 3A is a spectrum showing the band of the video signal input to the terminal 10, and has a band up to the frequency f. The spectrum 24 shown in FIG.
It is the spectrum of the LPF output which is the output signal of 12 and has a low frequency component up to a frequency of about f / 2. The spectrum 25 shown in FIG. 7C is the spectrum of the HPF output which is the output of the subtractor 14, and the frequency is about f.
It has high frequency components from / 2 to f. in this way,
The video signal supplied to the terminal 10 is divided into two bands.

Signal waveforms of respective parts of the block diagram shown in FIG. 6, that is, signal waveforms of an input video signal, an LPF output which is an output of the LPF 12, and an HPF output which is an output of the subtractor 14 are respectively shown in FIG. 8A. , (B), (C), or
They are shown in FIGS. 8D, 8E, and 8F, respectively. 8A, 8B, and 8C are signal waveforms when the video signal of the edge portion changing from white to black is supplied to the terminal 10 of FIG. 6, and FIG. , (E), (F) are signal waveforms when a video signal of a fine pattern portion occupied by high frequency components is supplied. As can be seen from the figure, the edge portion 26 of the input signal has an LPF of the signal 27 having a gentle slope portion due to the sub-band division.
The output is divided into the HPF output of the high frequency component 28 of the edge portion. On the other hand, in the case of the input signal 29 of the fine pattern portion, there is no signal in the LPF output as indicated by 30 in the LPF output, and the input signal is directly output as indicated by 31 in the HPF output.

[0009]

According to the above-mentioned conventional technique, the HPF output, that is, the high frequency component obtained by sub-band-dividing the input video signal is encoded as it is. Therefore, especially in the edge portion of the input video signal, the high frequency component 28 shown in FIG. 8C is transmitted as it is, and there is a problem that the amount of information on the high frequency side to be transmitted increases and the compression rate cannot be increased. It was

[0010]

In view of the above-mentioned problems, the present invention divides an input video signal into at least a low band component and a high band component, and encodes them respectively to obtain coded data of the low band component. In the band compression / expansion method in which the encoded data of the high frequency component is generated, and the two encoded data are respectively decoded and then combined, by performing contour correction on the video signal of the low frequency component, The obtained contour correction component is not encoded as the encoded data of the high frequency component, but the contour correction is performed on the video signal of the low frequency component obtained by decoding the encoded data of the low frequency component, The present invention provides a band compression / expansion method characterized by synthesizing encoded data of a high frequency component with a decoded high frequency component video signal.

Further, on the transmitting side, a low-pass filter for separating low-pass components from the input video signal, a first contour correction circuit for correcting the contour of the output signal of the low-pass filter, the input video signal and the An arithmetic circuit that extracts a difference component from the output signal of the contour correction circuit, a first encoder that compresses and encodes the output signal of the low-pass filter and outputs a first signal, and an output signal of the arithmetic circuit Compresses and encodes the second
Second decoder for outputting the above signal, and a first decoder for expanding and decoding the first signal and a second decoder for expanding and decoding the second signal on the receiving side. A second contour correction circuit for correcting the contour of the output signal of the first decoder, an output signal of the second contour correction circuit and the second contour correction circuit.
And a mixer that mixes with the output signal of the decoder and outputs a video signal in the form of the original input video signal.

[0012]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a block diagram of a band compression device according to a first embodiment of the present invention. The same components as those described above are designated by the same reference numerals and the description thereof will be omitted. The configuration of the apparatus of the present invention shown in FIG. 1 is obtained by adding a contour correction circuit 40 to the configuration of the apparatus shown in FIG. 6 described above, and in FIG.
Is supplied to the contour correction circuit 40, and the output of the contour correction circuit 40 is the other input (negative input) of the subtraction circuit 14.
Is being supplied to.

As described above, since the output of the LPF 12 is the low frequency component of the input video signal, the contour correction circuit 40
Known contour correction processing is applied only to this low frequency component,
The gentle slope of the edge portion of the video signal output from the LPF 12 is made steep. Then, the subtractor 14 subtracts the output of the contour correction circuit 40 from the input video signal and outputs it. This output is the HPF output. Subtractor 14
Constitutes an arithmetic circuit for extracting a difference component between the input video signal and the output signal of the contour correction circuit 40.

The above operation will be described with reference to FIG. This figure is a diagram showing signal waveforms of the band compression apparatus shown in FIG. In the same figure, (A), (B), and (C) show the respective signal waveforms of the input, the contour correction output, and the HPF output when the input to the terminal 10 is the video signal at the edge portion where the white changes to black. 26, 42 and 43 are shown. LPF
The signal waveform of the LPF output obtained by separating the low frequency component from the input by 12 is similar to the signal waveform 27 shown in FIG. By subjecting the LPF output to contour correction processing by the contour correction circuit 40, the signal waveform of the contour correction output becomes a signal waveform 42 similar to the input signal waveform 26, as shown in FIG. 2B. Become. Therefore, the signal waveform 42 of the contour correction output of the edge portion is substantially the restoration of the input signal waveform 26. As a result, since the signal waveforms 26 and 42 of the input and the contour correction output are substantially the same, the signal waveform 43 of the HPF output, which is the output of the subtractor 14, is as shown in FIG. It does not include the high frequency components of the edge part.

Next, FIGS. 2D, 2E, and 2F show the signal waveforms 29, 45, and 56 of the input, the contour correction output, and the HPF output for the high frequency component of the input video signal. ing. In this case, L which is the output of the LPF 12
Since the PF output is not taken out, the LPF 12 and the subtractor 1
Even if the contour correction circuit 40 is provided between 4 and 4, the signal waveform of the contour correction output is not extracted as shown by the signal waveform 45 of FIG. 2 (E). Therefore, the signal waveform of the HPF output becomes a signal waveform similar to the input signal waveform 29, as the signal waveform 46 shown in FIG. The operation described above is performed with respect to the high frequency component of the image in which the input is occupied by only the fine pattern in the spectrum 25 of the high frequency component as shown in FIG. 7C. Only. It is the spectrum 25 of the high frequency component as shown in FIG. 7C, and corresponds to the high frequency component whose contour is corrected by the contour correction circuit 40 among the high frequency components included in the edge portion of the input video signal. As described above, the high-frequency component of the
It does not appear in the HPF output due to the action of.

The operation of the contour correction circuit 40 will be described with reference to FIG. FIG. 3 is a spectrum diagram for explaining the operation of the contour correction circuit 40 of FIG. Four
Reference numeral 8 denotes the LPF output, that is, the spectrum of the low-frequency component of the input video signal, and the band is limited by the LPF 12 at a frequency of f / 2. Further, 47 is a spectrum of the contour correction output. A region 49 surrounded by the spectra 47 and 48 is a contour correction component, and the high frequency component of the edge portion of the input video signal removed by the LPF 12 is
It is a high frequency component restored by the contour correction circuit 40. The high frequency component corresponding to the area 49 is subtracted from the input video signal by the subtractor 14, and thus is not supplied to the encoder 18. Therefore, the high frequency component corresponding to the region 49 is not transmitted from the band compression device of the present invention.

As described above, the information amount of the LPF output and the amount of encoded data output from the encoder 16 are the same as those of the conventional example, but the information of the high frequency component of the HPF output of FIG. 1 described above is used. The amount is smaller than the HPF output of the conventional example shown in FIG. Therefore, the amount of encoded data output from the encoder 18 can be reduced, and as a result, the amount of data extracted and transmitted from the terminal 22 of FIG. 1 can be reduced. That is, the band compression apparatus of FIG. 1 can transmit the input video signal at a higher compression rate than the conventional band compression apparatus shown in FIG. Here, transmission means recording / reproducing,
Communication and broadcasting shall be included.

Next, the band compression / expansion device of the present invention will be described. FIG. 4 is a diagram showing a block diagram of the band expanding apparatus in the first embodiment of the present invention. This figure shows a band compression device that operates in a manner complementary to that of the band compression device of FIG.
It is used together with the band compression device shown in FIG. 1 to form a band compression / decompression device according to the first embodiment of the present invention. Reference numeral 50 is a terminal to which the data transmitted by the band compression device shown in FIG. 1 is supplied, 52 and 54 are decoders for expanding and decoding, 56 is a contour correction circuit, 58 is an adder, and 60 is an output terminal. Is.

The decoder 52 performs a complementary operation to the encoder 16 shown in FIG. 1, and expands and decodes the encoded data of the low frequency component of the compressed data supplied to the terminal 50. Similarly, the decoder 54 performs a complementary operation to the encoder 18 shown in FIG. 1 to expand and decode the encoded data of the high frequency component of the data supplied to the terminal 50. The output spectrum of the decoder 52 is the same as the spectrum 48 shown in FIG. The output of the decoder 52 is supplied to the contour correction circuit 56, where the contour of the decoded low-frequency component video signal is corrected. The spectrum of the output of the contour correction circuit 56 is similar to the spectrum 47 shown in FIG. Therefore, the contour correction circuit 56 is similar to that shown in FIG.
Area 4 shown in FIG. 3 which is not transmitted by the band compression apparatus shown in FIG.
The high frequency component corresponding to 9 is restored from the transmitted low frequency component. On the other hand, the output of the decoder 54 does not include the above-described area 49, that is, the high frequency component of the edge portion of the video signal. Then, the adder 58 adds the output of the contour correction circuit 56 and the output of the decoder 54, and outputs the output from the output terminal 60. Therefore, from the output terminal 60, a video signal of the same form as the video signal supplied to the terminal 10 of the band compression device of FIG. 1 is taken out.

Next, FIG. 5 is a block diagram of a band compression device in the second embodiment of the present invention. The same components as those described above are designated by the same reference numerals and the description thereof will be omitted. In the figure, 62 is an HPF, and 64 and 66 are subtractors.

In FIG. 5, the output of the contour correction circuit 40 is supplied to one terminal (positive input) of the subtractor 64, and the output of the LPF 12 is supplied to the other terminal (negative input). The subtraction circuit 64 outputs LP from the output of the contour correction circuit 40.
It operates to subtract the output of F12. Therefore,
From the output of the subtracter 64, the high frequency component of the edge portion restored by the contour correction circuit 40 is extracted. Subtractor 6
The output of 4 is supplied to one terminal (negative input) of the subtractor 66.

On the other hand, the HPF 62 has its cutoff frequency set to the same as that of the LPF 12, and separates and outputs the high frequency component of the video signal supplied to the terminal 10. HP
The output of F62 is supplied to the other terminal (positive input) of the subtractor 66. Subtractor 66 operates to subtract the output of subtractor 64 from the output of HPF 62. Therefore, the output of the subtractor 66 is the remaining component obtained by removing the high frequency component of the edge portion restored by the contour correction circuit 40 from the output of the HPF 62. This signal is
This is the same as the HPF output described with reference to FIG. 1 or 2. In this embodiment, the HPF 62 and the subtractors 64 and 6
Reference numeral 6 constitutes an arithmetic circuit for extracting a difference component between the input video signal and the output signal of the contour correction circuit 40. L in FIG.
The PF 12 and the HPF 62 may be replaced with a low-frequency QMF and a high-frequency QMF.

In each of the embodiments described above, the LPF 12
May divide the band in the horizontal direction of the video signal or may divide the band in the vertical direction. Further, it is possible to perform the two-dimensional processing by dividing the horizontal direction and the vertical direction. Further, the encoders 16 and 18 can use simple quantization, non-linear quantization, DPCM, DCT and the like.

Regarding the sub-band division, it has been explained that the frequency band f of the video signal is divided at a frequency of f / 2, but it is divided at another frequency, for example, a frequency of 3f / 4. Good. The sub-sampling and over-sampling processing in sub-band division are the same as the conventional ones, and therefore, the description is given assuming that they are processed by the encoders 16 and 18 and the decoders 52 and 54, respectively, and the description of the block configuration is omitted.

Further, the contour correction of the low frequency component of the video signal can be performed by speed modulation used in a television receiver. It is also possible to provide a plurality of contour correction circuits having different characteristics in parallel, select the optimum contour correction circuit according to the encoder 18, and perform the optimum contour correction on the video signal. The selection information may also be transmitted during transmission, and the same contour correction circuit may be provided on the receiving side, and contour correction may be performed by selecting and using a plurality of contour correction circuits according to the received selection information.

[0026]

As described above, according to the present invention, the transmitting side encodes and transmits the low frequency component obtained by sub-band dividing the video signal, and the contour correction is performed on the low frequency component video signal. Then, the difference between the contour correction output and the input video signal is encoded as a high frequency component and transmitted, and on the receiving side,
Perform contour correction on the received low-frequency component video signal,
Since the contour correction output and the received high frequency component are mixed, information that is not transmitted by the contour correction of the low frequency component on the transmitting side can be restored by the contour correction of the low frequency component received on the receiving side. Therefore, the amount of information to be transmitted can be reduced, and the input image signal can be transmitted at a high compression rate with a simple structure to obtain the original image signal.

[Brief description of drawings]

FIG. 1 is a diagram showing a block diagram of a band expansion device in a first embodiment of the device of the present invention.

FIG. 2 is a diagram showing a signal waveform of the band compression device shown in FIG.

FIG. 3 is a spectrum diagram for explaining the operation of the contour correction circuit in FIG.

FIG. 4 is a diagram showing a block diagram of a band expanding device in the first embodiment of the device of the present invention.

FIG. 5 is a diagram showing a block diagram of a band compression device in a second embodiment of the device of the present invention.

FIG. 6 is a diagram showing a block diagram of a conventional band compression device.

FIG. 7 is a spectrum diagram for explaining subband division.

8 is a diagram showing a signal waveform of the band compression device shown in FIG.

[Explanation of symbols]

 10, 22, 50, 60 terminals 12 LPF (low-pass filter) 14 subtractor (arithmetic circuit) 64, 66 subtractor 16 encoder (first encoder) 18 encoder (second encoder) 20 multiplex circuit 40 contour correction circuit (first contour correction circuit) 56 contour correction circuit (second contour correction circuit) 52 decoder (first decoder) 54 decoder (second decoder) 58 adder (mixer ) 62 HPF

Claims (2)

[Claims] 1. An input video signal is divided into at least a low-frequency component and a high-frequency component, each of which is coded to generate coded data of the low-frequency component and coded data of the high-frequency component,
In the band compression / expansion method in which the two encoded data are respectively decoded and then combined, the contour correction component obtained by performing contour correction on the video signal of the low frequency component is the high frequency component. Encoding is not performed as encoded data, but contour correction is performed on the video signal of the low frequency component obtained by decoding the encoded data of the low frequency component, and the contour signal is corrected to the high frequency obtained by decoding the encoded data of the high frequency component. A band compression / decompression method characterized by combining with component video signals. 2. A low-pass filter for separating a low-pass component from an input video signal, a first contour correction circuit for correcting a contour of an output signal of the low-pass filter on a transmitting side, the input video signal and the An arithmetic circuit that extracts a difference component from the output signal of the contour correction circuit, a first encoder that compresses and encodes the output signal of the low-pass filter and outputs a first signal, and an output signal of the arithmetic circuit A second encoder that compresses and encodes the second signal to output a second signal, and a first decoder that expands and decodes the first signal on the receiving side, and expands the second signal And a second decoder for decoding, a second contour correction circuit for correcting the contour of the output signal of the first decoder, an output signal of the second contour correction circuit, and a second decoder of the second decoder. Mixing with the output signal to output a video signal in the form of the original input video signal. A band compression / expansion device comprising: a combiner.