Image encoding apparatus

• US 6,256,413 B1
• Filed: 05/18/1995
• Issued: 07/03/2001
• Est. Priority Date: 05/23/1994
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Hirabayashi, Yasuji
• Primary Examiner(s): Couso, Jose L.
• Assistant Examiner(s): Do, Anh Hong
• Application Number:
  US08/444,012
• Time in Patent Office: 2,238 Days
• Field of Search: 382/232, 382/236, 382/248, 382/251, 382/233, 382/130, 382/289, 382/291, 358/433, 358/426, 348/391, 348/405, 348/419, 364/725, 375/249, 375/2.35
• US Class Current: 382/232
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/146 Data rate or code amount at the encoder output
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/18 the unit being a set of transform coefficients
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

There are disclosed an image encoding apparatus comprising an input unit for inputting image data, a calculation unit for calculating an entropy of the image data inputted by the input unit, a control unit for controlling a quantization step in accordance with the entropy calculated by the calculation unit, and an encoding unit for encoding the image data inputted by the input unit in accordance with the quantization step controlled by the control unit, an image encoding apparatus comprising an input unit for inputting image data, a calculation unit for calculating an entropy of the image data inputted by the input unit, a transform unit for orthogonally transforming the image data inputted by the input unit, a mask unit for masking transform coefficients of the image data transformed by the transform unit, and an encoding unit for encoding the image data masked by the mask unit. The mask area by the mask unit is determined in accordance with the entropy calculated by the calculation unit, and an image encoding apparatus comprising an input unit for inputting image data of block comprising a plurality of pixels, a transform unit for orthogonally transforming the block image data inputted by the input unit, a mask unit for masking transform coefficients of the block image data transformed by the transform unit, and an encoding unit for encoding the block image data masked by the mask unit.

Claims

1. An image encoding apparatus comprising:

input means for inputting image data;

frame rate input means for inputting frame rate information representing a frame rate;

calculation means for calculating an inter-picture difference entropy of the image data;

control means for controlling a quantization step in accordance with the inter-picture difference entropy and the frame rate information; and

encoding means for encoding the image data in accordance with the quantization step controlled by said control means.

2. An image encoding apparatus according to claim 1, wherein said encoding means includes transform means for orthogonally transforming the image data and quantization means for quantizing the image data transformed by said transform means.

3. An image encoding apparatus according to claim 2, wherein said transform means includes mask means for partially masking transform coefficients of the image data transformed by said transform means.

4. An image encoding apparatus according to claim 3, further comprising multiplexing means for multiplexing the image data encoded by said encoding means and step data for the quantization step controlled by said control means.

5. An image encoding apparatus according to claim 4, further comprising record means for recording the image data multiplexed by said multiplexing means on a recording medium.

6. An image encoding apparatus according to claim 1, wherein the entropy is calculated using a summation, over plural data values, of an estimated probability of each said data value occurring in a data block times a logarithm of the estimated probability of said data value occurring in the data block, wherein the data block is based on a block of the input image data.

7. An image encoding apparatus according to claim 1, wherein said input means includes image pickup means for photographing an object image.

8. An image encoding apparatus comprising:

input means for inputting image data;

frame rate input means for inputting frame rate information representing a frame rate;

calculation means for calculating an entropy of the image data;

mask means for performing a masking processing on the image data by using a mask, said mask means determining a mask area of said mask in accordance with a predetermined relationship between the entropy and the frame rate information; and

encoding means for encoding the image data processed by said mask means.

9. An image encoding apparatus according to claim 8, wherein the image data inputted by said input means is data of block comprising a plurality of pixels.

10. An image encoding apparatus according to claim 8, further comprising record means for recording the image data encoded by said encoding means on a recording medium.

11. An image encoding apparatus according to claim 8, wherein the entropy is calculated using a summation, over plural data values, of an estimated probability of each said data value occurring in a data block times a logarithm of the estimated probability of said data value occurring in the data block, wherein the data block is based on a block of the input image data.

12. An image encoding apparatus according to claim 8, wherein said input means includes image pickup means for photographing an object image.

13. An image encoding apparatus according to claim 8, further comprising transform means for transforming the image data into at least one orthogonal transform coefficient,

wherein said mask means masks the at least one transform coefficient.

14. An image encoding apparatus according to claim 13, wherein the at least one transform coefficient includes a transform coefficient of a high frequency component of the image data, and wherein said mask means masks the transform coefficient of the high frequency component.

15. An image encoding apparatus according to claim 8, further comprising control means for controlling a quantization step in accordance with the entropy,

wherein said encoding means encodes the image data processed by said mask means in accordance with the quantization step controlled by said control means.

16. An image encoding apparatus according to claim 15, wherein said mask means performs the mask processing only when the entropy is greater than a predetermined value.

17. An image encoding method comprising the steps of:

inputting image data;

inputting frame rate information representing a frame rate;

calculating an inter-picture difference entropy of the image data;

controlling a quantization parameter in accordance with the inter-picture difference entropy and the frame rate information; and

encoding the image data in accordance with the quantization parameter controlled in said controlling step.

18. An image encoding method according to claim 17, wherein the entropy is calculated using a summation, over plural data values, of an estimated probability of each said data value occurring in a data block times a logarithm of the estimated probability of said data value occurring in the data block, wherein the data block is based on a block of the input image data.

19. An image encoding method comprising the steps of:

inputting image data;

inputting frame rate information representing a frame rate;

calculating an entropy of the image data;

masking, by performing a masking processing on the image data by sing a mask, said masking step including a step, of determining a mask area of said mask in accordance with a predetermined relationship between the entropy and the frame rate information; and

encoding the image data processed in said masking step.

20. An image encoding method according to claim 19, wherein the entropy is calculated using a summation, over plural data values, of an estimated probability of each said data value occurring in a data block times a logarithm of the estimated probability of said data value occurring in the data block, wherein the data block is based on a block of the input image data.