Apparatus and method for coding a picture and apparatus and method for decoding a picture

• US 6,249,610 B1
• Filed: 02/18/1998
• Issued: 06/19/2001
• Est. Priority Date: 06/19/1996
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Matsumoto, Taisuke, Tanaka, Akiyoshi
• Primary Examiner(s): Couso, Jose L.
• Assistant Examiner(s): Dang, Duy M.
• Application Number:
  US09/011,204
• Time in Patent Office: 1,217 Days
• Field of Search: 382/232-235, 382/236, 382/238-242, 382/248, 382/251, 382/260, 382/261-264, 382/265, 382/266, 382/275, 382/199, 704/200, 704/229, 704/230, 358/261.1, 358/426, 358/432, 358/433, 358/479
• US Class Current: 382/232
• CPC Class Codes: H04N 19/117 Filters, e.g. for pre-processing or post-processing sub-band filter banks H04N19/635
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/147 according to rate distortion criteria rate-distortion as a criterion for motion estimation H04N19/567
• CPC Class Codes: H04N 19/154 Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion use of rate-distortion criteria H04N19/147
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• CPC Class Codes: H04N 19/527 Global motion vector estimation
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/80 Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation H04N19/635, H04N19/86 take precedence
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness

Abstract

In a picture coding apparatus, a picture reproducing section is prepared at the latter part of the picture coding apparatus, detection of noise existing in a reproduced picture and selection of an appropriate filter to correct the reproduced picture according to characteristics of noise are carried out by comparing the input picture and the reproduced picture and information concerning a picture and information concerning a filter are multiplexed to transmit. And in a picture decoding apparatus, the information concerning the picture and the information concerning the filter are extracted from input signals, a picture is reproduced from the information concerning the picture and the filter to correction process to the reproduced picture is switched according to the information concerning filter.

Claims

1. A picture coding apparatus comprising:

a picture coder that codes an input picture to obtain a coded input picture;

a picture reproducing unit that reproduces a picture from coefficients obtained from the coded input picture;

a noise detector that compares a partial area of the reproduced picture with a corresponding area of the input picture to detect a deteriorated part caused by the coding from the partial area of the reproduced picture; and

a filter information generator that generates filter information concerning filter characteristics which is appropriate for correcting the detected deteriorated part,

wherein the coded input picture and the filter information are supplied to a decoding apparatus that decodes the coded input picture by using the filter information.

2. The picture coding apparatus according to claim 1, further comprising:

filter information coder that codes the filter information to produce a code word associated with the filter information; and

a multiplexer that multiplexes the code word associated with the filter information produced by the filter information coder and a code word associated with the coded input picture obtained by the picture coder.

3. The picture coding apparatus according to claim 1, wherein the noise detector determines that a noise is generated when a difference value between pixels of the input picture and the reproduced picture exceeds a threshold value.

4. The picture coding apparatus according to claim 1, wherein the filter information generator determines a direction of noise geneate on a boundary between adjacent partial areas and adds a filter configuration into the filter information, the filter configuration being determined based on the direction of noise.

5. The picture coding apparatus according to claim 1, wherein the filter information generator adds filter strength determined based on an amount of the difference value between pixels of the input picture and the reproduced picture into said filter information.

6. The picture coding apparatus according to claim 1, wherein the filter information generatr generates the filter information from a filter configuration determined in accordance with a direction of noises on a boundary between adjacent partial areas and filter strength determined in accordance with an amount of a difference value between pixels of the input picture and the reproduced picture.

7. The picture coding apparatus according to claim 1, wherein the picture coder has discrete cosine transforming unit that performs a discrete cosine transform of the input picture in a block unit to obtain a DCT coefficient, a quantizer that quantizes the DCT coefficient obtained by discrete cosine transforming the input picture and a code word generator that generates a code word associated with the quantized DCT coefficient;

and the picture reproducing unit has a dequantizer that dequantizer the quantized DCT coefficient to obtain a second DCT coefficient; and

an inverse discrete cosine transforming unit that performs an inverse discrete cosine transform of the second DCT coefficient to generate the reproduced picture.

8. A picture decoding apparatus comprising:

a dividing unit that extracts a code word associated with a picture and a code word associated with filter information from input signals, the filter information representative of filter characteristics appropriate to remove noise in a decoded image due to coding, the filter information being produced in a coding process performed at a coding apparatus;

a picture reproducing unit that reproduces the picture from the extracted code word associated with the picture;

a filter information reproducing unit that reproduces the filter information from the extracted code word associated with the filter information; and

an image processor that has a plurality of correction filters having different filter characteristics and that corrects the reproduced picture by using a selected one of the plurality of correction filters appropriate to the reproduced filter information.

9. The picture decoding apparatus of claim 8, wherein the image processor means has horizontal direction filters, vertical direction filters and two-dimensional low-pass filters as the plurality of filters.

10. A picture decoding apparatus according to claim 8, wherein the image processor has a filter selection table in which effective correction filters are associated with various noises based on filter configuration and filter strength, a selector that selects an appropriate correction filter from the filter selection table based on the filter configuration and the filter strength contained in the filter information and a filter switch that inputs the produced picture into a selected correction filter.

11. The picture decoding apparatus according to claim 8, wherein the filter information is determined, in a coding process, in accordance with a deteriorated part detected by comparing an original picture with a reproduced picture, which is obtained by coding the original picture and then decoding the coded original picture.

12. A picture coding method performed at a coding apparatus that supplies a coded picture to a decoding apparatus, the method comprising:

coding an input picture to obtain a coded input picture;

reproducing a picture from coefficients obtained from the coded input picture;

comparing a partial area of the reproduced picture and a corresponding area of the input picture to detect a deteriorated part caused by coding from the partial area of the reproduced picture;

generating filter information for filter characteristics which is appropriate for correcting the detected deteriorated part;

coding the filter information; and

multiplexing a code word associated with the coded filter information and a code word associated with the coded input picture for supplying the multiplexed code word associated with the multiplexed coded filter information and the code word associated with the coded input picture to the decoding apparatus.

13. A picture decoding method performed in a decoding apparatus, the method comprising:

extracting a code word associated with a picture and a code word associated with filter information from input signals, the filter information representing filter characteristics appropriate to remove noise in a decoded image due to coding, the filter information being produced in a coding process performed at a coding apparatus;

reproducing the picture from the extracted code word associated with the picture;

reproducing filter information from the extracted code word associated with the filter information; and

correcting the reproduced picture by using a correction filter suiting the reproduced filter information.

14. An image processing system comprising;

a picture coding apparatus producing signals and including;

a picture coder that codes an input picture to obtain a coded input picture;

a picture reproducing unit that reproduces a picture from coefficients obtained from the coded input picture;

a noise detector that detects a deteriorated part caused be the coding from a partial area of the reproduced picture, by comparing the partial area of the reproduced picture with a corresponding area of the input picture;

a filter information generator that generates filter information concerning filter characteristics which is appropriate for correcting the detected deteriorated part;

a filter information coder that codes the filter information to produce a code word associated with the filter information; and

a multiplexer that multiplexes the code word associated with the filter information produced by the filter information coder and a code word associated with the coded input picture obtained by the picture coder to produce the signals;

a recording medium to record the signals produced by the picture coding apparatus; and

a picture decoding apparatus that reads the signals from the recording medium, the picture decoding apparatus including;

a dividing unit that extracts a code word associated with a picture and a code word associated with filter information from the signals read from the recording medium, the filter information representative of filter characteristics appropriate to remove noise in a decoded image due to coding;

a picture reproducing unit that reproduces the picture from the extracted code word associated with the picture;

a filter information reproducing unit that reproduces the filter information from the extracted code word associated with the filter information; and

an image processor that has a plurality of correction filters having different filter characteristics and that corrects the reproduced picture by using a selected one of the plurality of correction filters appropriate to the reproduced filter information.

15. The image processing system according to claim 14, wherein the signals produced by the picture coding apparatus are recorded on the recording medium by at least one of magnetic and optical recordings.

16. The image processing system of claim 14 applied for one of digital still camera, video CD system, DVD system and digital VTR.

17. An image processing system comprising:

a picture coding apparatus producing signals and including;

a picture coder that codes an input picture to obtain a coded input picture;

a picture reproducing unfit that reproduces a picture from coefficients obtained from the coded input picture;

a noise detector that detects a deteriorated part caused by the coding from a partial area of the reproduced picture, by comparing the partial area of the reproduced picture with a corresponding area of the input picture;

a filter information generator that generates filter information concerning filter characteristic which is appropriate for correcting the detected deteriorated part;

a filter information coder that codes the filter information to produce a code word associated with the filter information; and

a multiplexer that multiplexes the code word associated with the filter information produced by the filter information coder and a code word associated with the coded input picture obtained by the picture coder to produce the signals;

a picture decoding apparatus receiving the signals and including;

a dividing unit that extracts a code word associated with a picture and a code word associated with filter information from the received signals, the filter information representative of filter characteristics appropriate to remove noise in a decoded image due to coding;

a picture reproducing unit that reproduces the picture from the extracted code word associated with the picture;

a filter information reproducing unit that reproduces the filter information from the extracted code word associated with the filter information; and

an image processor that has a plurality of correction filters having different filter characteristics and that corrects the reproduced picture by using a selected one of the plurality of correction filters appropriate to the reproduced filter information; and

transmission path connecting the picture coding apparatus and the picture decoding apparatus, the signals produced by the picture coding apparatus being transmitted to the picture decoding apparatus via the transmission path to be decoded by the picture decoding apparatus.

18. The image processing system claim 17 applied for a digital conferencing system.

19. A computer program product for operating a computer to encodes an input picture, the computer program product comprising:

a computer readable medium having computer program instruction codes embodied therein, the computer program product having;

a first computer program instruction code for instructing a computer processor to code the input picture to obtain a coded input picture,

a second computer program instruction code for instructing a computer processor to reproduce a picture from coefficients obtained from the coded picture,

a third computer program instruction code for instructing a computer processor to compare a partial area of the reproduced picture and a corresponding area of the input picture to detect a deteriorated part caused by coding in the reproduced picture; and

a fourth computer program instruction code for instructing a computer processor to form filter information for filter characteristics which is appropriate for correcting the detected deteriorated part; and

wherein the coded picture and the filter information are subjected to be supplied to a decoding process, in which the coded picture is decoded in accordance with the filter information, and

wherein each of the computer program instruction codes is recorded on the computer readable medium in executable form and is loadable into a computer memory for executing by the computer processor.

20. A computer program product for operating a computer to decode input signals including a code word associated with a picture and a code word associated with filter information produced in a coding process, the computer program product comprising:

a computer readable medium having computer program instruction codes embodied therein, the computer program product having;

a first computer program instruction code for instructing a computer processor to extract the code word associated with the picture and the code word associated with filter information from the input signals, the filter information representing filter characteristics appropriate to remove noise in a decoded image due to coding;

a second computer program instruction code for instructing a computer processor to reproduce a picture from the extracted code word associated with the picture,

a third computer program instruction code for instructing a computer processor to reproduce the filter information from the extracted code word associated with the filter information; and

a fourth computer program instruction code for instructing a computer processor to switch correction filters according to the reproduced filter information, and wherein each of the program instruction codes is recorded on the computer readable medium in executable form and is loadable into a computer memory for executing by the computer processor.