JPH06101027B2 - Image encoding / decoding device - Google Patents

Description

The present invention relates to an image encoding / decoding device.

[Conventional technology]

Conventionally, in this type of image encoding / decoding device, when a part of an image is cut out, (i) the area to be cut out is limited to a quadrangle and orthogonal transform coding is applied, or (ii) the shape of the cut out area. It used other encoding schemes that could be applied independently of.

By the way, in the former method, the image data to be transmitted may be reduced by performing spatial sub-sampling and orthogonal transformation may be performed. At this time, in line-quincunx subsampling in which the phase of subsampling is inverted for each horizontal scanning line, it is assumed that pixels that are not aligned in the vertical direction are aligned as shown in FIG. It realized conversion with little deterioration.

[Problems to be solved by the invention]

In the above-mentioned conventional image coding / decoding apparatus, even if the line Kinkan sub-sampling is performed on the cut-out area, it is divided into rectangular blocks and orthogonal transformation is performed, so that there is a problem that compression efficiency deteriorates. It was Further, if an encoding method other than the orthogonal transform for dividing the cutout area into square blocks is used to avoid this problem, there is a problem that the amount of transmitted information cannot be reduced efficiently.

Therefore, it is an object of the present invention to provide an image encoding / decoding device capable of reducing the amount of transmission information with high efficiency and having high compression efficiency.

[Means for solving problems]

An image encoding / decoding device of the present invention includes (i) a prefilter for band-limiting the image signal, and (ii) sub-sampling for performing line-Kinkan sub-sampling on the image signal band-limited by the pre-filter. Section, and (iii) the image data sub-sampled by the line Kinkang in this sub-sampling section is decomposed into rectangular blocks with each side having an inclination of 45 degrees and −45 degrees with respect to the horizontal scanning line, and each square block An orthogonal transform unit that performs an orthogonal transform with respect to, (iv) an encoding unit that encodes the image data that has been orthogonally transformed by this orthogonal transform unit, and (v) an image data that is encoded by this encoding unit. A decoding unit for decoding, (vi) an inverse orthogonal transformation unit that performs an inverse orthogonal transformation on the image data decoded by this decoding unit, and (vii) an image data that is inverse transformed by this inverse orthogonal transformation unit. To the line Those formed by and a post filter for reproducing the image signal subjected to the interpolation with respect to the can subsampling.

Therefore, the image signal is band-limited by the pre-filter, line-Kinkan sub-sampling is performed, and then the image data is divided into square blocks having slopes of 45 degrees and −45 degrees with respect to the horizontal scanning line. The image signal is reproduced by performing orthogonal transformation on the block, encoding the image data, performing inverse orthogonal transformation on the decoded image data, and interpolating the line data with the Kinkkin subsampling for the image data with the post-filter. Therefore, it is possible to provide an image encoding / decoding device with high compression efficiency. In transmission, the amount of transmitted information can be reduced with high efficiency.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of an image transmission device to which the present invention is applied.

On the transmitting side, the image cutout setting unit 5 sets the image cutout area while displaying the target image on the TV monitor. The setting method is performed by enclosing the cutout part in a closed curve with a coordinate specification device such as a touch sensor or digitizer attached to the TV monitor. The cut out part is
It is displayed by being surrounded by a white curve on the TV monitor. The address information of the cutout portion and the block size for orthogonal transformation are transmitted from the central control unit 6 to the receiving side. The setting information of the cutout portion is transmitted each time it is newly set, and does not change unless it is updated.

The central control unit 6 controls the address control unit 4 based on the address information of the image cutout setting unit 5, and the image memory unit 3
To access the image data. The image data taken in by the central control unit 6 is stored in the temporary image memory unit 7.

The image data stored in the temporary image memory unit 7 is stored in the central control unit 6 according to the processing speed of the pre-filter unit 8.
It is further output to the pre-filter unit 8 and band-limited. The data band-limited by the pre-filter unit 8 is line-Kinkan subsampled by the sub-sampling unit 9,
It is output to the orthogonal transformation unit 10. In the orthogonal transformation unit 10, the image data is divided into rectangular blocks 21 each side of which has an inclination of 45 ° and −45 ° with respect to the horizontal scanning line, and orthogonal transformation is performed on each rectangular block 21, as shown in FIG. To do. Note that, in FIG. 2, the circles indicate the pixels left by the line Kinkan subsampling, and the crosses indicate the pixels subjected to the line Kinkan subsampling (the same applies in FIG. 3).

The image data orthogonally transformed by the orthogonal transformation unit 10 is encoded by the encoding unit 11
The image data encoded by the encoding unit 11 and output by the encoding unit 11 is output to the public line 22 through the line interface unit 12.

The data in the image memory unit 3 is constantly updated with the digital image data from the analog / digital (A / D) conversion unit 1. In addition, digital / analog (D /
A) The conversion unit 2 constantly reads out the image memory unit 3 at a speed such that it can be displayed on the screen of the TV monitor. The address control at this time is performed by the address control unit 4.

Next, on the receiving side, the encoded image data is received from the line 22 through the line interface unit 13 and decoded by the decoding unit 14. The image data decoded by the decoding unit 14 is sent to the inverse orthogonal transform unit 15, and inverse orthogonal transform is performed for each rectangular block according to the block size information from the transmitting side. After that, the post-filter unit 16 interpolates the thinned-out image data for the line Kinkan subsample performed on the transmission side. The image data restored by the post-filter unit 16 is written in the image memory unit 19 via the central control unit 17. At this time, the central control unit 17 controls the address control unit 18 based on the cut-out address information from the transmitting side. As a result, the image is reproduced in the cut out form. The image in the image memory unit 19 is the D / A conversion unit 20.
Is read out and output. The address control at this time is performed by the address control unit 18.

As can be seen from the above, in the present embodiment, the image signal on the transmitting side is band-limited by the pre-filtering unit 8, the line sampling is performed by the sub-sampling unit 9, and the orthogonal transforming unit 10 converts the image data to each side. Divides into rectangular blocks having inclinations of 45 ° and −45 ° with respect to the horizontal scanning line, and performs orthogonal transformation on each rectangular block. And after this the encoding unit
It is encoded with 11 and transmitted. On the receiving side, the image data decoded by the decoding unit 14 is subjected to the inverse orthogonal transformation by the inverse orthogonal transformation unit 15, and the post-filtering unit 16 performs the image data decimated by the line Kinkan subsampling performed on the transmission side. The image signal is reproduced by performing interpolation. In this case, the orthogonal transformation unit 10 divides the image data into square blocks having inclinations of 45 degrees and −45 degrees with respect to each horizontal scanning line, and performs orthogonal transformation on each of these square blocks. Pixels aligned in parallel with the block sides are orthogonally transformed, and thus an image encoding / decoding device having higher compression efficiency than in the past can be provided. Further, when the present invention is applied to an image transmission device, an orthogonal transform coding system is adopted, so that the amount of transmission information can be reduced with high efficiency.

Although the present embodiment refers to the case where the present invention is applied to the image transmission device, the present invention is not limited to this. For example, the present invention can be applied as an image storage device. In this case, referring to FIG. 1, by replacing the line interface units 12 and 13 with a magnetic disk interface, the pre-filter unit 8, the sub-sampling unit 9, the orthogonal transform unit 10, the encoding unit 11, and the line interface. A magnetic disk interface replacing the part 12 and a magnetic disk interface replacing the line interface part 13 can be obtained as an image storage device having a high compression rate, which includes a decoding part 14, an inverse orthogonal transform part 15, and a post-filter part 16. .

〔The invention's effect〕

As described above, according to the image coding / combining apparatus of the present invention, since the orthogonal transform coding method is adopted, it is possible to highly efficiently reduce the amount of transmission information in transmission.
Further, the orthogonal transform unit divides the image data into rectangular blocks each side of which has an inclination of 45 degrees and −45 degrees with respect to the horizontal scanning line, and performs orthogonal transformation on each of these rectangular blocks. Pixels aligned in parallel with each other are orthogonally transformed, so that an image encoding / decoding device with high compression efficiency can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an image encoding / decoding device to which the present invention is applied, FIG. 2 is an explanatory diagram showing a block division method in an orthogonal transform unit according to the present invention, and FIG. It is explanatory drawing which shows the block division method in an orthogonal transformation part. 8 ... Pre-filter section, 9 ... Sub-sampling section, 10 ... Orthogonal transform section, 11 ... Encoding section, 14 ... Decoding section, 15 ... Inverse orthogonal transform section, 16 ... Post-filter Department.

Claims (1)

[Claims] 1. A prefilter for band-limiting an image signal, a sub-sampling unit for performing Line-Kinkan sub-sampling on the image signal band-limited by the pre-filter, and a line-Kinkan sub-sampling by this sub-sampling unit. The divided image data is divided into rectangular blocks each side of which has an inclination of 45 degrees and −45 degrees with respect to the horizontal scanning line, and an orthogonal transformation unit that performs an orthogonal transformation on each rectangular block and the orthogonal transformation unit. A coding unit that codes the image data that has been orthogonally transformed by the decoding unit, a decoding unit that decodes the image data that has been coded by this coding unit, and an image data that is decoded by this decoding unit. An inverse orthogonal transform unit that performs an orthogonal transform and an image signal that is inversely transformed by the inverse orthogonal transform unit is interpolated for the line Kinkan subsampling to reproduce the image signal. And a post-filter for performing image coding / decoding.