JPH10322722A - Picture signal encoder and picture signal decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a picture signal encoder for encoding a high quality digital picture signal having compatibility with a conventional digital picture signal and to provide a picture signal decoding device decoding the signal. SOLUTION: A component obtained by converting the sampling frequency of the chroma signal C of a basic picture signal inputted from an input terminal 120 into 1/2 is added to the luminance signal Y of the original picture signal of 4:2:2, which is inputted from an input terminal 110. Then, a compression encoding is executed on it. A base data being the picture signal of 4:1:1 or 4:2:0 following a former digital picture signal format is generated. An encoding residual extraction part 123 extracts an encoding residual between the basic picture signal and the base data. Enhancement data containing the high pass component of the chroma signal C is generated by encoding the encoding residual. When compatibility with the conventional digital picture signal is required, only base data is used and enhancement data is added to base data when a high-quality digital picture signal is required.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image signal encoding device for compressing and encoding an image signal, and an image signal decoding device for decompressing and decoding the compressed and encoded image signal.

[0002]

2. Description of the Related Art Digital video tape recorders (VTRs) are used as means for recording / reproducing image signals such as television broadcast programs. There are several types of digital VTRs, such as D1 for program production.
Standards and the D2 standard for broadcasting stations are typical. In such digital VTRs for program production and broadcasting stations, extremely high quality is required for recorded and reproduced images. Therefore, image signals recorded on a magnetic tape are not compressed or have a data amount of one. Typically, a relatively low compression ratio of about / 2 is used.

On the other hand, digital VTRs have begun to spread for consumer use. Digital VTRs for consumer use have less demands on image quality than digital VTRs for business use, but are required to be able to record for a long time using a small cassette tape. A compression format is adopted in which the data is band-compressed at a relatively high compression ratio and recorded. The compression format of the consumer digital VTR is used for video equipment for broadcasting because of its high image quality. The high-efficiency compression method used here utilizes the fact that human visual characteristics are less sensitive to chrominance information than luminance information of an image, and reduces the amount of information of chrominance signals. ing. The method of compressing the image data will be described later.

According to the D1 standard, which is one of the digital VTR standards for program production and broadcasting stations, digital image data recorded on a magnetic tape is not compressed, and a luminance signal Y and color difference signals Cr and Cb are converted. Recorded separately. The luminance signal Y is a signal representing the brightness of the image, and the color difference signal is a signal representing the chromaticity of the image. The color difference signals are R, G,
This is a signal obtained by removing the luminance signal Y from the three primary color signals B, and two of Cr = RY and Cb = BY are used. For example, the sampling frequency of the luminance signal Y is 1
The sampling frequency of the color difference signals Cb and Cr is 3.5 MHz, and the sampling frequency of each of the color difference signals Cb and Cr is 6.75 MHz. Therefore, the ratio of the sampling frequencies of these signals is 4: 2: 2.

On the other hand, if the above-mentioned image data of the consumer digital VTR standard is similarly expressed, the luminance signal Y
And the sampling frequency ratio of the color difference signals Cb and Cr is expressed as 4: 1: 1 in the NTSC system (525 lines), and as 4: 2: 0 in the PAL system (625 lines). That is, by reducing the sampling frequency of the two color difference signals to half the sampling frequency of the luminance signal, the information amount of image data recorded on the magnetic tape is reduced. As described above, in the standard of the consumer digital VTR, a signal in which the band of the chroma signal of the baseband signal is narrowed is generated, and the digital compression by the DCT in the frame is performed to reduce the image data amount to about 1/5. And recorded.

[0006]

As described above, different image data compression methods (formats) are used for digital VTRs, and none of them can support a plurality of data compression formats. For this reason, for example, when editing the above-described 4: 1: 1: compressed image data and 4: 2: 2 compressed image data, one of the compressed image data is once decompressed and then the editing operation is performed. Therefore, when the edited image data is compressed again, the deterioration of the image quality cannot be avoided.

Further, in a broadcasting digital VTR requiring high image quality, the performance of the conventional digital VTR is required, for example, a 4: 2: 2 baseband band is required or an image with less compression noise is required. In some cases, higher image quality is required. In addition, consumer digital VTR
Also, it is expected that a standard with higher image quality will be adopted.

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and has been made to solve the problem of the conventional digital image data format of 4: 1: 1 or 4: 2: 0 image data and 4: 2: 2 image data. It is an object of the present invention to provide an image signal encoding device and an image signal decoding device having compatibility with high-quality image data.

[0009]

According to the present invention, there is provided an image signal encoding apparatus for compressing and encoding an image signal, comprising a luminance signal and two color difference signals. A basic image signal whose sampling frequency ratio is 4: 2: 2 is converted to a ratio of each sampling frequency of the luminance signal and the two color difference signals to 4: 1: 1 or 4: 2: 0 and compressed. First compression encoding means for encoding to generate first compressed data, encoding residual extraction means for extracting an encoding residual between the basic image signal and the compressed data, and the extracted code And second compression encoding means for compressing and encoding the coded residual to generate second compressed data.

An image signal decoding apparatus according to the present invention proposed to solve the above-mentioned problem is an image signal decoding apparatus for expanding and decoding a compression-encoded image signal. First decompression decoding means for decompressing image data of a predetermined signal standard in which the ratio between the sampling frequency of the luminance signal and the sampling frequency of the two color difference signals is 4: 1: 1 or 4: 2: 0; A second decompression decoding means for decompressing and decoding the enhancement data having a sampling frequency ratio of the two color difference signals of 4: 2: 2, and combining outputs from the first decompression decoding means and the second decompression decoding means. And synthesizing means for generating extended image data in which the ratio of the sampling frequency of the luminance signal to the sampling frequency of the two color difference signals is 4: 2: 2.

According to the above-described image signal encoding apparatus and image signal decoding apparatus, 4: 2: 4 which is compatible with 4: 1: 1 or 4: 2: 0 image data according to the conventional digital image data format. 2, high-quality image data can be compression-encoded and decompressed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an image signal encoding apparatus and an image signal decoding apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a basic configuration of a conventional digital VTR coding apparatus and a first compression coding means in an image signal coding apparatus of the present invention. The luminance signal Y of the original image signal, which is the 4: 2: 2 extension data input from the input terminal 110, is sent to the blocking unit 111. Also, two color difference signals C of the chroma signal C of the original image signal input from the input terminal 120 are input.
r and Cb are sent to the down-conversion unit 117 via the LPF 116 and the sampling frequency of the color difference signal is 1 /
After being converted (down-converted) to 2, the signal is sent to the blocking 111.

In the blocking section 111, the input terminal 11
The luminance signal Y from 0 and the two down-converted chrominance signals from the down-conversion unit 117 are both blocked on a macroblock (hereinafter referred to as MB) unit. The blocked image signal is DCT
(Discrete cosine transform) unit 112 converts the DCT coefficients into DCT coefficients, quantizes them in quantization unit 113, performs variable length coding in VLC (variable length coding) unit 114, further performs framing in framing unit 115, and uses Then 4:
It is output from the output terminal 210 as 1: 1 compressed digital image data, or as 4: 2: 0 compressed digital image data in the PAL system.

FIG. 2 shows a first compression / encoding means for generating the base data shown in FIG. 1, its output and 4: 2:
FIG. 2 is a block diagram illustrating the overall configuration of an image signal encoding apparatus according to the present invention including: a second compression encoding unit that extracts an encoding residual from an original image signal of No. 2 and generates enhancement data.

This image signal encoding apparatus performs compression by limiting the band of an original picture signal whose sampling frequency ratio of the luminance signal Y and the chroma signal C is 4: 2: 2, and generates the above-described base data. Enhancement data, which is data lost by compression encoding (hereinafter referred to as encoding residual data), is generated from a difference value between the compression-encoded data and the original image data.

4: 2: 2 input from input terminal 110
Is supplied to the blocking unit 111. The blocking section 111 includes a chroma signal C of the original image signal input from the input terminal 120.
Is also supplied via an LPF (low-pass filter) 116 and a down-conversion unit 117.

The ratio between the luminance signal Y of the input original image signal and the chroma signal (Y and two color difference signals Cb and Cr of the chroma signal) whose sampling frequency is converted is 4: 1: 1.
(In the case of PAL, 4: 2: 0)), one frame of image data is divided into (8 pixels × 8 lines) macroblocks, which are basic units of DCT conversion. Here, the color difference signal has only one block (one sample) for four blocks (four samples) of the luminance signal.
The DCT block corresponds to a 4DCT block of the luminance signal.

The above-mentioned down-conversion unit 117
Are two color difference signals C supplied through the LPF 116.
This is for converting (down-converting) the sampling frequencies of r and Cb to lower frequencies, and specifically down-converting the sampling frequencies to 1/2.

The LPF 116 limits the band of the color difference signal in order to avoid the occurrence of aliasing noise or the like when sampling is performed by the down-converting section 117 at the subsequent stage.

In the DCT section 112, the blocking section 11
DCT (discrete cosine) transformation, which is a type of orthogonal transformation, is performed on the DCT block divided into 1 blocks. Also, the pixel values of the image data are decorrelated and converted to values on the frequency axis. The macroblock subjected to the discrete cosine transform is temporarily stored in a buffer (not shown) in segments each having five macroblocks as one unit.
The data is sent to the quantization unit 113.

The quantization unit 113 divides the DCT coefficient by a certain divisor (quantization step) for each macroblock described above, rounds the remainder, and performs quantization. At this time, adaptive quantization using different quantization steps is performed in consideration of human visual characteristics. The visual characteristics considered here are:
For example, quantization distortion is not conspicuous even when coarsely quantized in a portion with high precision on an image screen, and quantization distortion is easily conspicuous in a portion that changes smoothly.

In the above adaptive quantization, each block in a segment of image data is classified into, for example, four types,
This is performed by allocating different quantization steps constituting the quantizer according to the class number. This allows
The image quality can be improved by increasing the number of bits allocated to blocks on the screen where the image quality is visually noticeable. The image data (DCT coefficient) quantized in this way is converted to VLC
(Variable length coding) section 114 and coding residual extracting section 123 described later.

The VLC unit 114 performs variable length coding such as two-dimensional Huffman coding. That is, when the quantizer number (QNo.) Is selected based on the data amount estimation, the image data segment stored in the buffer described above is replaced with the QNo. , And then variable-length coded.

In the framing section 115, the VLC section 11
Each segment of the image data variable-length coded in
A process called framing assigned to 77 bytes is performed. Here, of the five macroblocks described above, for a macroblock having a data amount exceeding 77 bytes, the overflowed data is allocated to a free area of another macroblock and packed. As a result, the data amount of each macro block is made equal, and the basic image data (base data) in which the ratio of the sampling frequency of the luminance signal Y and the two color difference signals Cr and Cb is 4: 1: 1 or 4: 2: 0. ) Is 25 Mbp from output terminal 210.
Output at the rate of s. As described above, this base data has the format (D
V-format digital image data.

On the other hand, the encoding residual extraction unit 123 has a luminance signal Y of the 4: 2: 2 original image signal input from the input terminal 110 and a luminance signal Y of the original image signal input from the input terminal 120. The chroma signal C and the quantized image data from the quantization unit 113 are supplied, and an encoding residual is extracted.

The coding residual extracted here is, for example,
Original image data in which the sampling frequency ratio of the luminance signal Y and the two color difference signals Cr and Cb is 4: 2: 2, and the sampling frequency ratio of these is 4: 1: 1 or 4: 2:
The chroma signal is extracted using the DCT coefficients of the down-converted compressed image data (base data) so as to become 0. That is, using the original image data and the DCT coefficient quantized by the first compression unit, the encoding residual, that is, the process of extracting the data lost by quantization is performed.

The encoding residual encoding unit 124 encodes the image data which is the encoding residual extracted by the encoding residual extracting unit 123. Here, various coding methods such as DCT (discrete cosine transform) and subband coding can be used.

The framing unit 125 performs a framing process on the coded residual coded by the coded residual coding unit 124, and outputs the coded residual from an output terminal 220 as enhancement data. Here, the enhancement data rate (αMbps) is a value set as needed. For example, when α = 25 Mbps, 4: 2: 2 extended image data is encoded at 50 Mbps together with the base data.

The enhancement data is image data that is not included in the base data but includes high-frequency components of the luminance signal Y and the chroma signal C necessary for expressing the details of the image. This enhancement data,
By adding to the above base data, extended image data, which is 4: 2: 2 high quality image data used for a digital VTR for business use or the like can be configured.
The details will be described later.

In the following description, DCT coding is used as an example of a method for performing coding in the coding residual coding unit 124 as the second compression coding means. Does not correspond only to DCT coding, but includes wavelet transform, subband coding, DPC
Various coding methods such as M (Differential Pulse Code Modulation) can be used. That is, the encoding method of the encoding residual used as the second compression encoding means is arbitrary.

In the following, the encoding residual extracting unit 123
, And an embodiment in which various methods are applied to the encoding method in the encoding residual encoding unit 124.

FIG. 3 is a diagram schematically showing the structure of digital image data generated by compressing and encoding an image signal by the above-described image signal encoding apparatus of the present invention. In other words, the compressed image data generated by the image signal encoding apparatus according to the present invention is obtained by adding luminance to base data which is basic image data of 4: 1: 1 (NTSC system) or 4: 2: 0 (PAL system). It is configured by adding enhancement data including the high frequency components of the signal Y and the chroma signal C.

The above-mentioned base data is image data that also conforms to the conventional digital image data compression format. The transfer rate of this base data is usually 25 Mb
ps. The transfer rate (α Mbps) of the enhancement data is appropriately set as needed. For example, when the enhancement data is added to the base data to form the extended image data of 4: 2: 2 of 50 Mbps, the transfer rate of the enhancement data is set to 25 Mbps (α = 2
5).

According to such a data structure, when compatibility with the format of the conventional digital image data is required, that is, when image data of 4: 1: 1 or 4: 2: 0 is required, the base is used. Only data needs to be used. Further, in order to obtain higher image quality, enhancement data including the high frequency components of the luminance signal Y and the chroma signal C is added to the base data to substantially form 4: 2: 2 extended image data. Can be used. That is, base data and enhancement data are input to a multiplexer (not shown), and the two data are multiplexed to output extended image data. The extended image data may be transmitted to a predetermined transmission path and may be recorded on a predetermined recording medium. When transmitted over a transmission path, the extended image data is converted into the transmission format of the transmission path. For example, if the data is an ATM transmission path, the extended image data is converted into the ATM format and output. Of course, each of the base data and the enhancement data may be transmitted to a predetermined transmission path or a recording medium without being multiplexed by the multiplexer.

Next, an embodiment of the image signal decoding apparatus of the present invention will be described. FIG. 4 shows a conventional digital VTR.
FIG. 1 is a block diagram showing a basic configuration of a decoding device and a first decompression decoding device for decoding base data output from a first compression encoding device in an embodiment of an image signal encoding device of the present invention. is there. 4: 1: 1 or 4: 2: 0 compressed digital image data input from the input terminal 130 is deframed by the deframing unit 131, decoded by the VLC (variable length code) decoding unit 132, and dequantized. The inverse quantization is performed by the unit 133, and the inverse DCT is performed by the inverse DCT unit 134. And the deblocking unit 13
6. Deblocking is performed.

From the deblocking section 136, the luminance signal Y is output from the output terminal 230, and the chroma signal C is further output from the output terminal 240 via the up-convert section 152 and the LPF 153.

FIG. 5 to FIG. 7 show an embodiment of the present invention comprising first expansion decoding means for decoding the base data shown in FIG. 4 and second expansion decoding means for decoding the enhancement data. It is a block diagram which shows the whole structure of a decoding device.

The configuration of the decoding apparatus according to the embodiment of the present invention is different from FIGS. 5 to 7 in that the coding residual extraction unit 123 in the embodiment of the present invention shown in FIG. Is slightly different depending on the extraction method.

That is, the decoding device shown in FIG.
Encoding residuals are extracted from the difference between the 2: 2 original image and the data obtained by decompressing the data that has been down-converted, DCT-transformed and quantized and compressed (local decoding), and outputs enhancement data. 2 shows a configuration of a decoding device for an encoding device.

The decoding device shown in FIG.
Configuration of a decoding apparatus for an encoding apparatus that extracts an encoding residual from a difference between data that has been down-converted into 1 and blocked into a macroblock and the above-described locally decoded data and outputs enhancement data Is shown.

FIG. 7 shows an enhancement in which the encoding residual is extracted from the difference between the DCT-transformed and quantized data obtained by down-converting the original image at a ratio of 4: 1: 1 and the locally decoded data. 3 shows a configuration of a decoding device for an encoding device that outputs data.

A detailed description of the encoding apparatus including the specific configuration of the encoding residual extracting unit 123 for extracting the encoding residual will be described later.

Referring to FIG.

Base data (25 Mbps), which is compressed image data having a sampling frequency ratio of 4: 1: 1 or 4: 2: 0, is input to an input terminal 130, and enhancement data (α Mbps) is input to an input terminal 140.
Is entered.

In the deframing section 131, the input terminal 1
The base data input from 30 is subjected to a process called deframing, which is a reverse operation of the framing process in the framing unit 115 of the image signal encoding device in FIG. The data is returned to the DCT coefficient data in the state of being reset.

The VLC (variable length code) decoding unit 132 is a VLC (variable length coding) unit 1 of the image signal coding apparatus shown in FIG.
The inverse operation of the encoding in 14 is performed, and decoding processing such as two-dimensional Huffman decoding is performed, and variable-length encoded data is decoded.

The inverse quantization unit 133 performs an operation opposite to the quantization performed by the quantization unit 113 of the image signal encoding apparatus shown in FIG. That is, each DCT coefficient is multiplied by a quantization step for each block of (8 × 8) pixels described above.

Inverse DCT (Inverse Discrete Cosine Transform) section 134
Then, an inverse discrete cosine transform (inverse DCT), which is an inverse transform of a discrete cosine transform (DCT), is performed for each inverse-quantized block.
T) is performed. The output of the inverse DCT unit 134 performs a process reverse to that of the deblocking unit 111 to unblock the DCT-blocked data. The output of the deblocking unit 136 is output to the data combining unit 150.

On the other hand, the deframing section 141 performs a deframing process on the enhancement data input from the input terminal 140.

The encoding residual decoding unit 149 performs enhancement data encoding the encoding residual by the reverse procedure of the encoding performed by the encoding residual encoding unit 124 of the image signal encoding apparatus of FIG. Is decoded, and the deblocking unit 146 deblocks the data converted into DCT blocks. The output of the deblocking unit 146 is sent to the data combining unit 150.

In the data synthesizing section 150, the inverse DC
The decoded base data from the T unit 134 and the decoded enhancement data from the encoding residual decoding unit 149 are combined, and output from the output terminal 250 as a 4: 2: 2 reproduced image signal.

The image signal decoding apparatus extracts an encoding residual by using 4: 2: 2 original image data and data obtained by expanding compressed data once (local decoding), and outputs the result as enhancement data. And an encoding device that outputs base data.

FIG. 6 shows that the original image is down-converted 4: 1: 1 by the coding residual extracting unit 123 of the image signal coding apparatus shown in FIG. 13 shows a configuration example of an image signal decoding apparatus in a case where a difference value between data and locally decoded data is extracted as an encoding residual. In this case, since the blocking method of the base data and the enhancement data is the same, the data combining unit 150
The deblocking process is performed by using a common deblocking unit located inside. Therefore, the difference from FIG. 5 is that the deblocking units 136 and 146 are included in the data combining unit 150.

FIG. 7 shows, as described above, in the image signal encoding apparatus shown in FIG. 2, data obtained by down-converting an original image and blocking the macroblocks by DCT transform + quantization, and local data. 14 shows a configuration of an image decoding apparatus in a case where a difference value between decoded data and a decoded data is extracted as an encoding residual.

In this case, after the data obtained by dequantizing the base data and the data obtained by decoding the coded residual are combined, inverse DCT is performed by the inverse DCT section 134, and blocking is released by the deblocking section 136. It differs from the above-described FIGS. 5 and 6 in that it has a configuration.

As a method for extracting an encoding residual in an image signal encoding apparatus, as described above,
A method using a difference (differential image) between an original image and an image obtained by decoding (local decoding) the down-converted image data, an image obtained by down-converting the DCT coefficient of the original image signal and then performing quantization and inverse quantization D of data
There are a method using a difference (coefficient difference) with the CT coefficient, a method using a band division filter such as a sub-band for dividing the image signal into bands, and a method using a band synthesis filter for reconstructing the band-divided image signal. .

Next, a specific configuration of an encoding device including a specific configuration of the encoding residual extracting unit 123 for extracting an encoding residual and a corresponding decoding device will be described in detail with reference to FIGS. Will be described.

FIG. 8 shows an encoding apparatus for extracting a difference value between a 4: 2: 2 original image and locally decoded data as an encoding residual, and FIG. 9 shows a decoding apparatus corresponding to FIG. (Details of FIG. 5) is shown.

FIG. 10 shows details of an encoding apparatus for extracting an encoding difference from a difference between a macroblock blocked at 4: 1: 1 and locally decoded data, and FIG. (Details of FIG. 6 are shown) of the decoding device corresponding to FIG.

FIG. 12 shows a specific configuration of an encoding apparatus for extracting an encoding residual from a difference between DCT coefficients and locally decoded data. FIG. 13 shows a decoding apparatus corresponding to FIG. Is shown (showing details of FIG. 7).

FIG. 8 will be described.

This image signal encoding apparatus generates enhancement data using a difference value (difference image) between a 4: 2: 2 original image and a locally decoded image as an encoding residual. It is.

In this image signal encoding apparatus, the LPF
116, down-conversion unit 117, blocking unit 111, DCT unit 112, quantization unit 113, VLC
The unit 114 and the framing unit 115 are units for generating base data. The configurations and functions of these units are the same as those in the above-described image signal encoding apparatus as shown in FIG. 2, and thus the description thereof is omitted, and the units for generating enhancement data will be mainly described.
Note that the same reference numerals are given to the same parts as those in the above-described image signal encoding apparatus also in FIG. 8, and description thereof will be omitted.

This image signal encoding apparatus sets the sampling frequency of the chroma signal C of the 4: 2: 2 original image signal to 1 /
2 is added to the luminance signal Y of the original image signal to generate an image signal of 4: 1: 1 or 4: 2: 0. And this 4: 1: 1 or 4: 2: 0
Signal C which is a signal obtained by locally decoding the image signal of
Is converted (up-converted) again to twice the sampling frequency, and a difference value from the original image signal is extracted as an encoding residual.

In the image signal encoding apparatus shown in FIG. 8, the above-mentioned encoding residual extraction is performed by the inverse quantization unit 118, the inverse D
CT unit 119, deblocking unit 126, LPF unit 12
7, an up converter 128 and an adder 129. That is, the above-mentioned portion is the same as that in FIG.
Is a part corresponding to the residual extraction unit 123 of the image signal encoding device shown in FIG.

The inverse quantization unit 118 performs inverse quantization on the quantized DCT coefficient as base data, and performs inverse D
It is sent to the CT unit 119.

In the inverse DCT section 119, the inverse quantization section 118
The inverse DCT (inverse discrete cosine transform) is performed on the DCT coefficient of the image data of 4: 1: 1 or 4: 2: 0, which is inversely quantized, and is sent to the deblocking unit 126.

The locally decoded chroma signal C of the 4: 1: 1 or 4: 2: 0 image signal is further sent to the up-converting unit 128 and the LPF 127 to be up-converted. Then, the up-converted chroma signal C is added to the luminance signal Y of the locally decoded image signal, and sent to the addition unit 129 as an inverted input.

The up-converting unit 128 calculates the difference value between the 4: 2: 2 original image signal and the locally decoded 4: 1: 1 or 4: 2: 0 image signal in the adding unit 129. Therefore, the sampling frequency of the chroma signal C of the locally decoded 4: 1: 1 image signal is doubled.

The adder 129 converts the chroma signal C of the 4: 2: 2 original image signal input from the input terminal 120 from
The locally decoded image data is subtracted, and the difference value is extracted as an encoding residual. The extracted coding residual is input to the blocking unit 124a.

The coding residual extracted by the adding unit 129 is
The encoded data is output from the output terminal 220 as enhancement data. The image signal encoding device in FIG.
This is an example of a configuration in which an encoding residual is encoded using T. In this image signal encoding apparatus, a part that encodes the encoding residual includes a blocking unit 124a, DC
This is a part composed of a T unit 124b, a quantization unit 124c, a VLC unit 124d, and a framing unit 125.
The above-described portion is a portion corresponding to the above-described encoding residual encoding unit 124 of the image signal encoding device in FIG.

The components from the blocking unit 124a to the framing unit 125 are the same as the components from the blocking unit 111 to the framing unit 115 in FIG. 2 described above, and a description thereof will be omitted.

FIG. 9 is a block diagram showing a configuration of an image signal decoding apparatus corresponding to the first embodiment of the image signal encoding apparatus of the present invention shown in FIG.

The same parts as those in the image signal decoding apparatus shown in FIG. 5 are denoted by the same reference symbols in FIG. Also, the input terminal 13 of this image signal decoding device
0, which is a part for decompressing and decoding the base data input from 0, from the deframing unit 131 to the inverse DCT unit 13
4 and the reverse D from the deframing unit 141.
The components up to the CT unit 144 have the same configuration as that of the image signal decoding device in FIG. 5 described above, and thus description thereof will be omitted.

The base data input from the input terminal 130 is supplied to a deframing unit 131, a VLC decoding unit 132,
Inverse quantization section 133, inverse DCT section 134, deblocking section 136, up-convert section 152, LPF 15
3, the data is decompressed and decoded.

On the other hand, the enhancement data input from the input terminal 140 is supplied to the deframing section 141, VL
C decoding section 142, inverse quantization section 143, inverse DCT section 14
4. The signal is decoded through the deblocking unit 146 and returned to the differential signal.

The luminance signal Y of the decoded base data from the deblocking unit 136 is sent to the adding unit 155 as it is, and the chroma signal C of the base data is supplied to the luminance signal Y via the up-conversion unit 152 and the LPF 153. Added to Y. Thus, the 4: 2: 2 reproduced image signal of the base data is sent to the adding section 155.

The up-conversion unit 152 and L
The PF 153 doubles the sampling frequency of the locally decoded image signal so that the adding section 155 adds the 4: 2: 2 original image signal and the locally decoded 4: 1: 1 image signal. Things.

In the adder 155, the deblocking 136
And the base data decoded up to 4: 2: 2 and the enhancement data decoded from the deblocking unit 146 are added. And
The image signal from the adder 155 is output from the output terminal 250 as a reproduced image signal.

Next, a description will be given of a second embodiment of the image signal encoding apparatus and the image signal decoding apparatus according to the present invention.

FIG. 10 shows an example of the configuration of an image signal encoding apparatus in which an encoding residual is extracted using a difference image and a band division filter to generate enhancement data.

4: 2: 2 input from input terminal 120
Is divided into two frequency bands by an LPF (low-pass filter) 116 and an HPF (high-pass filter) 216, which are band division filters for dividing a frequency band. The low-frequency component of the chroma signal C output from the LPF 116 has the same band as that of the chroma signal of the digital image data to be output as the base data. By performing the conversion, the data is output from the output terminal 210 as base data of 4: 1: 1 or 4: 2: 0. That is, on the HPF 216 side of the band division filter, this corresponds to extracting a high-frequency component of the chroma signal C not included in the base data as a residual.

The adder 129 performs DCT coding on the 4: 1: 1 or 4: 2: 0 image from the blocking unit 111 and the above-mentioned 4: 1: 1 or 4: 2: 0 image signal. , The difference value between the image and the image locally decoded by the inverse DCT unit 119 is extracted as an encoding residual. The extracted coding residual is a difference value between the low frequency components of the luminance signal Y of the image signal and the chroma signal C.

The extracted coding residual from the adding section 129 is output to the DCT section 124 as the second compression coding means.
a, and is sent to the quantization unit 124c.

On the other hand, the high-frequency component of the chroma signal C output from the HPF 216 is down-converted by the down-conversion unit 217. Then, after being blocked by the blocking unit 211 and subjected to DCT coding by the DCT unit 212, it is sent to the quantization unit 124c.

The DCT coefficient of the residual of the low-frequency component of the luminance signal Y and the chroma signal C from the DCT section 124a,
The DCT coefficient of the high frequency component of the chroma signal C from the unit 212 is quantized together by the quantization unit 124c, and the VLC unit 12
The data is variable-length coded by 4d, framed by the framing unit 125, and output from the output terminal 220 as enhancement data.

FIG. 11 is a block diagram showing a configuration example of an image signal decoding device corresponding to the second embodiment of the image signal encoding device of the present invention shown in FIG.

The base data input from the input terminal 130 is supplied to a deframing unit 131, a VLC decoding unit 132,
Decoding is performed via an inverse quantization unit 133 and an inverse DCT unit 134. Then, in the adding section 154, the inverse DCT section 13
4 and the DCT coefficient from the deframing unit 141, VLC
After the luminance signal and the low-frequency component difference value of the chroma signal C, which are a part of the enhancement data returned to the coding residual via the decoding unit 142, the inverse quantization unit 143, and the inverse DCT unit 144, are added. The signal is deblocked by the deblocking unit 136 and becomes an output reproduction signal of the luminance signal Y from the output terminal 230. On the other hand, the low frequency component of the chroma signal C is
After being up-converted by the up-converting unit 152 and the LPF 153, the signal is output from the inverse DCT unit 144 in the adding unit 155 and is output from the deblocking unit 14.
6. The signal is combined with the high-frequency component of the chroma signal C, which is a part of the enhancement data that has passed through the up-converting unit 162 and the HPF 163, and is output from the output terminal 240 as the chroma signal C.

Thus, 4: 2: 2 high-quality image data is reproduced from the base data and the enhancement data.

Next, a description will be given of a third embodiment of the image signal encoding apparatus and the image signal decoding apparatus according to the present invention.

FIG. 12 shows an example of the configuration of an image signal encoding apparatus in which an encoding residual is extracted by using a coefficient difference and a band division filter to generate enhancement data.

In this image signal encoding apparatus, FIG.
The difference from the image signal encoding device shown in is that instead of using the difference value between the original image signal and the image signal in which the base data is locally decoded, as the encoding residual for generating the enhancement data, , D of the original image signal
The difference is that a difference value at the DCT coefficient level between the CT coefficient and the base data is used.

In this image signal encoding apparatus,
The part from the blocking unit 111 to the framing unit 115, which is a part for generating base data, is shown in FIG.
Since it is the same as the means for generating the base data in the image coding apparatus shown in FIG. 0, the description thereof is omitted here, and only the part for generating the enhancement data will be described.

4: 2: 2 input from input terminal 120
The original chroma signal C is divided into two frequency bands by an LPF (low-pass filter) 116 and an HPF (high-pass filter) 216, which are band division filters for dividing the frequency band. The low-frequency component of the chroma signal C output from the LPF 116 has a band of 4:
Since the band of the chroma signal C of the digital image data output as the base data of 1: 1 or 4: 2: 0 is the same as that of the luminance signal Y of the original signal input from the input terminal 110, As a result, the data is output from the output terminal 210 as base data of 4: 1: 1 or 4: 2: 0.

In addition, in the adder 129, the DCT coefficient of the 4: 1: 1 or 4: 2: 0 image that has been blocked by the blocking unit 111 and subjected to DCT by the DCT unit 112, and the above 4: 1 :: The image signal of 1 or 4: 2: 0 is converted into a DCT coefficient, and a DCT coefficient difference value between the image signal and the quantized DCT coefficient inversely quantized by the inverse quantization unit 118 is extracted as an encoding residual. Then, the extracted coding residual is sent to the quantization unit 124c.

On the other hand, the high-frequency component of the chroma signal C output from the HPF 216 is down-converted by the down-converting section 217. Then, after being blocked by the blocking unit 211 and subjected to DCT coding by the DCT unit 212, it is sent to the quantization unit 124c.

The DCT coefficient from the adder 129 and the DCT coefficient from the DCT unit 212 are quantized together by the quantization unit 124c, variable-length coded by the VLC unit 124d, framed by the framing unit 125, and output terminal. 22
0 is output as enhancement data.

FIG. 13 is a block diagram showing a configuration example of an image signal decoding apparatus corresponding to the third embodiment of the image signal encoding apparatus of the present invention shown in FIG.

4: 1: 1 input from input terminal 130
Alternatively, 4: 2: 0 base data is returned to DCT coefficients via a deframing unit 131, a VLC decoding unit 132, and an inverse quantization unit 133. Similarly, the enhancement data input from the input terminal 140 is returned to the DCT coefficient via the deframing unit 141, the VLC decoding unit 142, and the inverse quantization unit 143. Then, the DCT coefficient from the inverse quantization unit 133 and the DCT coefficient from the inverse quantization unit 143 are added by the addition unit 154 and sent to the inverse DCT unit 134. Then, the signal is deblocked by the deblocking unit 136 and output from the output terminal 230 as a luminance signal Y.

The composite output from the adder 154 is obtained by decoding the difference value between the luminance signal Y of the original image signal and the low-frequency component of the chroma signal C.

The output of the deblocking unit 136 and
The signal from the deblocking 146 is up-converted by the up-converting unit 152 and the LPF 153 and up-converted by the up-converting unit 162 and the HPF 163, respectively, added by the adding unit 155, and output as the chroma reproduction signal C from the output terminal 240.

As a result, 4: 2: 2 extended image data is reproduced.

In each of the above embodiments, 4: 1:
An example in which enhanced data including high-frequency components of a luminance signal Y and a chroma signal C is added to 1: or 2: 2: 0 base data to form 4: 2: 2 high-quality extended image data However, the ratio of the sampling frequency of the high-quality image data is not limited to 4: 2: 2, and may be, for example, 4: 4: 4. In this case, the frequency component of the enhancement data added to the base data is higher than the sampling frequency in the present embodiment.

[0105]

According to the image signal encoding apparatus and the image signal decoding apparatus of the present invention, the luminance signal Y and the chroma signal C of the image signal are used.
Ratio of the sampling frequency of the two color difference signals is 4: 1:
By adding enhancement data including the high frequency component of the chroma signal C to the base data obtained by compressing and encoding the basic image data of 1: 2: 4: 2: 0, the compressed image data of substantially 4: 2: 2 is obtained. It constitutes. According to this data configuration, when compatibility with the conventional digital image data in accordance with the 4: 1: 1 or 4: 2: 0 image signal is required, only the base data needs to be transferred, and high definition You can get the image of the spirit 4:
When 2: 2 extended image data is required, enhancement data may be added to the base data.
As a result, high-quality image data having compatibility between these digital image data having different compression formats can be obtained.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of the present invention for encoding base data.
2 is a block diagram illustrating a configuration of an encoding device.

FIG. 2 is a block diagram illustrating an overall configuration of an image signal encoding device according to an embodiment of the present invention.

FIG. 3 is a diagram for explaining a configuration of compressed digital image data generated by the image signal encoding device of the present invention.

FIG. 4 is a block diagram illustrating a configuration of a first image signal decoding device of the present invention for decoding base data.

FIG. 5 is a block diagram illustrating an overall configuration of an image signal decoding device according to an embodiment of the present invention.

FIG. 6 is a block diagram illustrating a modification of the configuration of the image signal decoding device according to the embodiment of the present invention.

FIG. 7 is a block diagram showing another modification of the configuration of the image signal decoding device according to the embodiment of the present invention;

FIG. 8 is a block diagram illustrating a first embodiment of an image signal encoding device according to the present invention.

FIG. 9 is a block diagram illustrating a first embodiment of an image signal decoding device according to the present invention.

FIG. 10 is a block diagram showing a second embodiment of the image signal encoding device of the present invention.

FIG. 11 is a block diagram showing a second embodiment of the image signal decoding device of the present invention.

FIG. 12 is a block diagram showing a third embodiment of the image signal encoding device of the present invention.

FIG. 13 is a block diagram illustrating a third embodiment of the image signal decoding device according to the present invention.

[Explanation of symbols]

110, 120 input terminals, 111 blocking unit, 112 DCT (discrete cosine transform) unit, 11
3 Quantizer, 114 VLC (Variable Length Coding),
115, 125 Framing section, 116 LPF
(Low-pass filter), 117 down-converter, 123 coded residual extractor, 124 coded residual coder, 210, 220 output terminals

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Takizuka 6-35 Kita Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (19)

[Claims] 1. An image signal encoding apparatus for compressing and encoding an image signal, comprising: a basic image signal having a sampling frequency ratio of 4: 2: 2 between a luminance signal and two color difference signals;
The ratio of each sampling frequency to one color difference signal is 4: 1:
First compression encoding means for converting the data to 1 or 4: 2: 0 and performing compression encoding to generate first compressed data; and encoding for extracting an encoding residual between the basic image signal and the compressed data. An image signal encoding apparatus comprising: a residual extracting unit; and a second compression encoding unit that compresses and encodes the extracted encoded residual to generate second compressed data. 2. The apparatus according to claim 1, wherein said first compression encoding means includes sampling frequency conversion means for converting a sampling frequency of a chroma signal of the image signal.
An image signal encoding device according to claim 1. 3. The image signal coding apparatus according to claim 1, wherein said first compression coding means and said second compression coding means perform compression coding using discrete cosine transform. 4. The image signal coding apparatus according to claim 1, wherein said second compression coding means performs compression coding using wavelet transform or subband subdivision coding. 5. The image signal encoding apparatus according to claim 1, further comprising a band division filter for dividing a frequency band of a chroma signal of the original image signal. 6. The encoding residual extracting means includes a basic image signal in which a ratio of a sampling frequency of a luminance signal to a sampling frequency of two color difference signals is 4: 2: 2; Sampling frequency ratio of 4: 1:
2. The image signal encoding apparatus according to claim 1, wherein a difference between the decoded image signal and 1: 2: 0 is extracted. 7. The encoding residual extracting means, wherein a ratio of a sampling frequency of the luminance signal to a sampling frequency of the two color difference signals is 4: 1: 1.
2. The method according to claim 1, wherein a difference between the decoded image signal and the original image signal in which the ratio of the sampling frequency of the luminance signal to the sampling frequency of the two color difference signals is set to 4: 1: 1 is extracted. Image signal encoding apparatus. 8. The encoding residual extracting means, wherein a ratio of a sampling frequency of the luminance signal to a sampling frequency of the two color difference signals is 4: 2: 0.
2. The method according to claim 1, wherein a difference between the decoded image signal and the original image signal whose sampling frequency ratio of the luminance signal and the two chrominance signals is 4: 2: 0 is extracted. Image signal encoding apparatus. 9. The encoding residual extracting means according to claim 1, wherein a ratio between a sampling frequency of the luminance signal and a sampling frequency of the two chrominance signals is 4: 1: 1.
Extracting a difference between a DCT coefficient of the image signal and a DCT coefficient of an original image signal in which the ratio of the sampling frequency of the luminance signal to the sampling frequency of the two color difference signals is set to 4: 1: 1. Item 3. The image signal encoding device according to Item 1. 10. The encoding residual extracting means, wherein a ratio of a sampling frequency of a luminance signal to a sampling frequency of two color difference signals is 4: 2:
A difference between a DCT coefficient of an image signal which is 0 and a DCT coefficient of an original image signal in which a ratio of a sampling frequency between a luminance signal and two color difference signals is set to 4: 2: 0 is extracted. The image signal encoding device according to claim 1. 11. The image signal of the predetermined signal standard is N
2. The image signal encoding apparatus according to claim 1, wherein the image signal is a TSC television signal. 12. The image signal of the predetermined signal standard is P
2. The image signal encoding apparatus according to claim 1, wherein the image signal encoding apparatus is an AL television signal. 13. An image signal decoding apparatus for decompressing an image signal which has been compression-encoded, wherein the ratio of the sampling frequency of a luminance signal to that of two color difference signals is 4: 1: 1 by compression-encoding an original image signal. Or 4: 2:
A first decompression decoding means for decompressing image data of a predetermined signal standard of 0, and a second decompression decoding means for decompressing enhancement data having a sampling frequency ratio of a luminance signal and two color difference signals of 4: 2: 2. And the ratio of the sampling frequency of the luminance signal to the sampling frequency of the two chrominance signals is 4: 2: 2 by combining the outputs from the first and second decompression decoding means. An image signal decoding device comprising: a synthesizing unit that generates extended image data. 14. The apparatus according to claim 1, wherein said first decompression decoding means includes sampling frequency conversion means for converting a sampling frequency of a chroma signal of an image signal.
3. The image signal decoding device according to 3. 15. The image signal decoding apparatus according to claim 13, wherein said first and second expansion decoding means perform expansion decoding using inverse discrete cosine transform. 16. The image signal decoding apparatus according to claim 13, wherein said second expansion decoding means performs expansion decoding using inverse wavelet transform or subband band synthesis processing. 17. The apparatus according to claim 1, further comprising a band synthesizing filter for synthesizing the chroma signal expanded and decoded by said first expansion decoding means and said second expansion decoding means.
3. The image signal decoding device according to 3. 18. The image signal of the predetermined signal standard is N
14. The image signal decoding apparatus according to claim 13, wherein the image signal is a TSC television signal. 19. The image signal of the predetermined signal standard is P
14. The image signal decoding device according to claim 13, wherein the image signal is an AL television signal.