APPARATUS AND METHOD FOR LOSSLESS/NEAR-LOSSLESS IMAGE COMPRESSION

• US 20110129162A1
• Filed: 11/30/2010
• Published: 06/02/2011
• Est. Priority Date: 11/30/2009
• Status: Abandoned Application

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kim, Young Ro, Park, HyunSang, Lee, Woo Yong, Kim, Kyeongpyo
• Application Number:
  US12/957,207
• Publication Number:
  US 20110129162A1
• Time in Patent Office: Days
• US Class Current: 382/238
• CPC Class Codes: H04N 19/105 Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
• CPC Class Codes: H04N 19/146 Data rate or code amount at the encoder output
• CPC Class Codes: H04N 19/196 being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters processing of motion vectors H04N19/513
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques

Abstract

Provided is a lossless/near-lossless image compression apparatus and method. The lossless/near-lossless image compression method may include calculating a predicted value by predicting a pixel of a current location based on adjacent pixels, calculating an error that is a difference between the predicted value and a pixel value, and modulating the error to output the modulated error, encoding the modulated error, and controlling a tolerance based on a slice unit to enable a number of encoded bits to be the same as a target number of encoded bits. The tolerance may be set to be gradually increased or to be decreased to prevent a rapid change in the tolerance.

Claims

1. A lossless/near-lossless image compression apparatus, the apparatus comprising:

a ratio controller to control a tolerance based on a slice unit to enable a number of encoded bits to be the same as a target number of encoded bits;

a prediction modulator to predict a pixel of a current location based on adjacent pixels to calculate a predicted value, to calculate an error that is a difference between the predicted value and a pixel value, and to modulate the error to output the modulated error; and

an encoder to encode the modulated error.

2. The apparatus of claim 1, further comprising:

a decoder to decode the predicted pixel based on the error,

wherein the prediction modulator predicts the pixel based on adjacent decoded pixels.

3. The apparatus of claim 1, wherein the radio controller controls the tolerance to be gradually increased or decreased to prevent a rapid change in the tolerance.

4. The apparatus of claim 1, wherein the ratio controller performs:

increasing the tolerance by a predetermined value when the number of encoded bits is greater than the target number of encoded bits; and

decreasing the tolerance by the predetermined value when the number of the encoded bits is less than the target number of encoded bits.

5. The apparatus of claim 1, wherein the ratio controller performs:

increasing the tolerance by a predetermined value when the number of encoded bits is greater than a value of a sum of a change-alleviating value and the target number of encoded bits; and

decreasing the tolerance by the predetermined value when the number of encoded bits is less than the value of the sum of the change-alleviating value and the target number of encoded bits.

6. The apparatus of claim 5, wherein the change-alleviating value is a value acting as a buffer to reduce a number of changes incurred due to a frequent increase or decrease of the tolerance.

7. The apparatus of claim 1, wherein the radio controller sets the tolerance to zero when the tolerance is a negative number.

8. The apparatus of claim 1, wherein the encoder comprises:

an error mapping unit to map the modulated error to be a positive number; and

a Golomb-encoder to calculate, based on errors of the adjacent pixels, Golombk that is a parameter used for performing Golomb-encoding, and to Golomb-encode the mapped modulated error.

9. The apparatus of claim 8, wherein the Golomb encoder calculates Golombk as a smallest n satisfying Equation 5:

MVcnt×

2ⁿ≧

TSAD, 

 

[Equation 5]

wherein MVcnt denotes a number of adjacent pixels used for calculating Golombk, and TSAD denotes a value of summing up all absolute values of errors of the adjacent pixels.

10. A lossless/near-lossless image compression method, the method comprising:

calculating a predicted value by predicting a pixel of a current location based on adjacent pixels;

calculating an error that is a difference between the predicted value and a pixel value, and modulating the error to output the modulated error;

encoding the modulated error; and

controlling a tolerance based on a slice unit to enable a number of encoded bits to be the same as a target number of encoded bits.

11. The method of claim 10, further comprising:

decoding the predicted pixel based on the error,

wherein the calculating calculates the predicted value by predicting the pixel based on adjacent decoded pixels.

12. The method of claim 10, wherein the controlling comprises:

controlling the tolerance to be gradually increased or decreased to prevent a rapid change in the tolerance.

13. The method of claim 10, wherein the controlling comprises:

increasing the tolerance by a predetermined value when the number of encoded bits is greater than the target number of encoded bits; and

decreasing the tolerance by the predetermined value when the number of the encoded bits is less than the target number of encoded bits.

14. The method of claim 10, wherein the controlling comprises:

increasing the tolerance by a predetermined value when the number of encoded bits is greater than a value of a sum of a change-alleviating value and the target number of encoded bits; and

decreasing the tolerance by a predetermined value when the number of encoded bits is less than the value of a sum of the change-alleviating value and the target number of encoded bits.

15. The method of claim 14, wherein the change-alleviating value is a value acting as a buffer to reduce a number of changes incurred due to a frequent increase or decrease of the tolerance.

16. The method of claim 10, wherein the controlling comprises:

setting the tolerance to zero when the tolerance is a negative number.

17. The method of claim 10, wherein the encoding comprises:

mapping the modulated error to be a positive number; and

calculating, based on errors of the adjacent pixels, Golombk that is a parameter used for performing Golomb-encoding, and Golomb-encoding the mapped modulated error.

18. The method of claim 17, wherein the Golomb-encoding comprises:

calculating Golombk as a smallest n satisfying Equation 6;

MVcnt×

2ⁿ≧

TSAD, 

 

[Equation 6]

wherein MVcnt denotes a number of adjacent pixels used for calculating Golombk, and TSAD denotes a value of summing up all absolute values of errors of the adjacent pixels.