Apparatus and method for encoding/decoding data including the suppression of blocking artifacts

• US 5,384,849 A
• Filed: 05/18/1993
• Issued: 01/24/1995
• Est. Priority Date: 05/18/1992
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Jeong, Je-chang
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US08/062,599
• Time in Patent Office: 616 Days
• Field of Search: 358/433, 371/37.1, 371/37.7, 371/71, 382/56, 380/49, 348/404, 348/420
• US Class Current: 348/425.2
• 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 19/154 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 19/30 using hierarchical techniques, e.g. scalability H04N19/63 takes precedence
• 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 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness

Abstract

A method and apparatus for removing blocking artifacts in an encoder/decoder system. The encoder includes a delay device for delaying original input frame data, a decoder for decoding the compressed data and outputting the restored frame data, and a blocking artifact measurer which receives the restored frame data and the original frame data, and measures the degree of blocking artifact using the above two frame data so as to generate a predetermined post-processing parameter. The post-processing parameter is transmitted to the receiver/decoder together with the encoded data. The decoder includes a receiver for receiving the encoded data and the post-processing parameter, a second decoder for decoding and restoring the encoded transmission data, and a filter for adaptively filtering the restored data output from the second decoder according to the post-processing parameter. As a result, the blocking artifact of the block boundary is removed from the encoded data such that a user does not notice any reduction in the picture quality.

Claims

1. A method for suppressing blocking artifacts in an encoder comprising the steps of:

dividing original frame data into a size of predetermined blocks;

compressing the data through a data transformation and a quantization process on a per unit block basis;

decompressing and restoring the compressed data on a per unit frame basis;

delaying the original frame data for a predetermined period of time;

measuring a degree of blocking artifact by comparing the restored frame data with the delayed original frame data; and

generating a post-processing parameter which represents the degree of blocking artifact.

2. The method as defined in claim 1, wherein said blocking artifact measuring step comprises the step of storing the original frame data on a per unit frame basis.

3. The method as defined in claim 1, wherein said blocking artifact measuring step comprises the steps of:

calculating a frame data error corresponding to a difference between the delayed original frame data and the restored frame data;

calculating a discontinuity degree of a block boundary portion in said frame data error; and

generating a predetermined parameter selected according to the calculated discontinuity degree among a plurality of predetermined parameters as a post-processing parameter.

4. The method as defined in claim 3, wherein said discontinuity degree calculation step comprises the steps of:

delaying said frame data error by a predetermined period of time;

calculating a difference between the delayed frame data error and the frame data error;

selecting the calculated difference that corresponds to the block boundary; and

calculating an average value of the selected data.

5. The method as defined in claim 3, wherein said post-processing parameter is a variable between "0" and "1" according to the calculated discontinuity degree.

6. The method according to claim 4, wherein said average value calculation step comprises the step of resetting the average value to a predetermined initial value on a predetermined periodic basis.

7. A method for suppressing blocking artifacts in a decoder which receives an encoded transmission signal including encoded data and a post-processing parameter from an encoder, said post-processing parameter representing the degree of blocking artifact of said encoded data, said method comprising the steps of:

receiving the encoded data and the post-processing parameter;

decoding and restoring the received data; and

adaptively filtering the decoded and restored data according to the post-process parameter.

8. The method as defined in claim 7, wherein said filtering step comprises the step of setting one or more characteristics of a low-pass filter according to variations in the magnitude of the post-processing parameter.

9. The method as defined in claim 7, wherein said filtering step comprises the step of setting one or more characteristics of an all-pass filtering according to variations in the magnitude of the post-processing parameter.

10. The method as defined in claim 7, wherein said filtering step comprises the step of variably filtering the decoded restored signal so that the blocking artifact generated at the block boundary portion is reduced.

11. An encoding apparatus comprising:

an input terminal for receiving original frame data;

dividing means, coupled to said input terminal, for dividing said original frame data into blocks of a predetermined size;

processing means, responsive to said blocks of data, including means for compressing the data through a data transformation process and for quantizing the data through a quantization process on a per block unit basis;

delaying means, coupled to said input terminal, for delaying the original frame data;

restoring means, coupled to said processing means, for restoring the compressed and quantized data and outputting the restored frame data; and

a blocking artifact measurer, coupled to an output of said delaying means for receiving the delayed original frame data and to an output of said restoring means for receiving the restored frame data, for measuring a degree of blocking artifact based on said delayed and restored frame data so as to generate a predetermined post-processing parameter.

12. The encoding apparatus as defined in claim 11, wherein said delay means comprises a frame memory for storing the original frame data.

13. The encoding apparatus as defined in claim 11, wherein said blocking artifact measurer comprises:

a first adder for calculating a frame data error corresponding to a difference between the delayed frame data and the restored frame data;

discontinuity degree calculating means for receiving the frame data error output from said first adder and calculating a discontinuity degree parameter at the block boundary portion; and

post-processing means, responsive to said discontinuity degree parameter, for generating a predetermined post-processing parameter which is varied according to the discontinuity degree parameter.

14. The encoding apparatus as defined in claim 13, wherein said discontinuity degree calculation means comprises:

a delay circuit for delaying the output data of said first adder by a predetermined period of time;

a second adder for calculating a difference between an output data of said first adder and an output data of said delay circuit;

a block boundary detection means for detecting data corresponding to the block boundary portion from among the output data of said second adder; and

an average error calculation means for calculating an average value of the data which is detected by said block boundary detection means.

15. The encoding apparatus as defined in claim 13, wherein said post-processing means comprises means for generating a variable post-processing parameter between "0" and "1" according to said discontinuity degree parameter output by said discontinuity degree calculation means.

16. The encoding apparatus as defined in claim 13, wherein said post-processing means comprises a read-only-memory (ROM) which stores a predetermined look-up table of post-processing parameters, and for outputting one of said post-processing parameters corresponding to said discontinuity degree.

17. The encoding apparatus according to claim 15, wherein said post-processing means comprises a read-only-memory (ROM) which stores a predetermined look-up table of post-processing parameters, and for outputting one of said post-processing parameters corresponding to said discontinuity degree.

18. The encoding apparatus as defined in claim 14, wherein said block boundary detection means comprises:

a counter for counting an interval corresponding to a block boundary, and for outputting a corresponding control signal; and

a switch, responsive to said control signal, having an input terminal connected to an output of said second adder, and an output coupled to an input of said average error calculation means, said switch being opened and closed in accordance with said control signal so as to selectively transfer data from said second adder to said average error calculation means.

19. The encoding apparatus as defined in claim 11, wherein said average error calculation means comprises means for resetting its output to a predetermined initial value on a periodic basis.

20. A decoding apparatus for suppressing blocking artifacts which receives an encoded transmission signal including encoded data and a post-processing signal from an encoder, said post-processing parameter representing the degree of blocking artifact of said encoded data, said decoding apparatus comprising:

means for receiving the encoded data and the post-processing parameter;

restoring means for decoding and restoring the received encoded data; and

means for adaptively filtering the restored data output from said restoring means according to said post-processing parameter.

21. The decoding apparatus as defined in claim 20, wherein said filtering means comprises means for filtering the signal corresponding to a block boundary portion of the restored data supplied from said restoring means.

22. The decoding apparatus as defined in claim 20, wherein said filtering means comprises filtering characteristics of an all-pass filter, a low-pass filter, and a filter having functions of both said all-pass and low-pass filters, said filter characteristics varying in accordance with said post-processing parameter.