IMAGE CODER AND IMAGE DECODER CAPABLE OF POWER-SAVING CONTROL IN IMAGE COMPRESSION AND DECOMPRESSION

• US 20080212884A1
• Filed: 04/08/2008
• Published: 09/04/2008
• Est. Priority Date: 09/09/2002
• Status: Active Grant

• Current Assignee: Keiichi Suzuki, Minoru Fukuda, Shogo Oneda, Takanori Yano, Tooru Suino, Yukio Kadowaki, Yutaka Sano
• Original Assignee: Keiichi Suzuki, Minoru Fukuda, Shogo Oneda, Takanori Yano, Tooru Suino, Yukio Kadowaki, Yutaka Sano
• Inventors: Suino, Tooru, Yano, Takanori, Suzuki, Keiichi, Fukuda, Minoru, Sano, Yutaka, Kadowaki, Yukio, Oneda, Shogo
• Granted Patent: US 7,609,897 B2
• Time in Patent Office: Days
• US Class Current: 382/232
• 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 19/156 Availability of hardware or computational resources, e.g. encoding based on power-saving criteria
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object
• CPC Class Codes: H04N 19/18 the unit being a set of transform coefficients
• CPC Class Codes: H04N 19/184 the unit being bits, e.g. of the compressed video stream
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets

Abstract

An image decoder comprises a code decompression/decoding unit that decodes code data produced through compression and encoding of image data, a power supply state detection unit that detects a current state of a power supply of the image decoder, and a controller that controls the code decompression/decoding unit based on the current state of the power supply so as to reduce power consumption in performing decompression and decoding of the code data.

Claims

1. An image coder comprising:

an image compression/encoding unit to divide an image into a plurality of tiles through a tiling process and perform compression and encoding of the image in a hierarchical manner for each of the tiles;

a power supply state detector to detect a current state of a power supply of the image coder; and

a first mode setting unit to select a tiling processing mode in accordance with the current state of the power supply.

2. The image coder according to claim 1, wherein the first mode setting unit selects an overlap tiling mode when the current state of the power supply is above a reference state and selects a non-overlap tiling processing mode when the current state of the power supply is at or below the reference state.

8. The image coder according to claim 1 or 3, further comprising a second mode setting unit to accept a user'"'"'s selection of an operation mode and to select a processing mode of the image compression/encoding unit, regardless of the selection of the mode by the first mode setting unit.

9. The image coder according to claim 8, further comprising:

a variable voltage source to supply a variable voltage to the image compression/encoding unit, the variable voltage being changed in accordance with the operation mode selected by the second mode setting unit.

10. The image coder according to claim 8, further comprising:

a clock generator to generate and supply a clock signal to the image compression/encoding unit, the frequency of the clock signal being changed in accordance with the operation mode selected by the second mode setting unit.

11. The image coder according to claim 1 or 3, further comprising:

a variable voltage source to supply a variable voltage to the image compression/encoding unit, the variable voltage being changed in accordance with the processing mode selected by the first mode setting unit.

12. The image coder according to claim 1 or 3, further comprising:

a clock generator to generate and supply a clock signal to the image compression/encoding unit, the frequency of the clock signal being changed in accordance with the processing mode selected by the first mode setting unit.

3. An image coder comprising:

an image compression/encoding unit to perform compression and encoding of an image using wavelet transform for frequency transform;

a power supply state detector to detect a current state of a power supply of the image coder; and

a first mode setting unit to select a processing mode of wavelet transform in accordance with the current state of the power supply.

4. The image coder according to claim 3, further comprising a wavelet filter, wherein the first mode setting unit selects the number of taps of the wavelet filter in accordance with the current state of the power supply.

5. The image coder according to claim 4, wherein the first mode setting unit selects a 9-tap/7-tap filter when the current state of the power supply is above a reference state, and it selects a 5-tap/3-tap filter when the current state of the power supply is at or below the reference state.

6. The image coder according to claim 3, wherein the first mode setting unit selects a hierarchical level of wavelet transform in accordance with the current state of the power supply.

7. The image coder according to claim 6, wherein the first mode setting unit selects a 5-level wavelet transform when the current state of the power supply is above a reference state and selects a 3-level wavelet transform when the current state of the power supply is at or below the reference state.

13. An image coder comprising:

image compression/encoding means for dividing an image into a plurality of tiles through a tiling process and for performing compression and encoding of the image in a hierarchical manner for each of the tiles;

detection means for detecting a remaining battery level when a power supply of the image coder is a battery cell; and

first setting means for designating a tiling processing mode in accordance with the detected battery level.

17. The image coder according to claim 13, wherein the first setting means designates an overlap tiling mode when the remaining battery level is above a reference level designates a non-overlap tiling processing mode when the remaining battery level is at or below the reference level.

20. The image coder according to claim 13, further comprising:

second setting means for designating the tiling mode or a rate control mode of the compression and encoding, regardless of the mode designated by the first setting means.

24. The image coder according to any one of claims 20 through 23, further comprising:

a variable voltage source to supply a variable voltage to the image compression/encoding unit; and

voltage level control means for changing a voltage level of the variable voltage source in accordance with a change in a setting state designated by the first or the second setting means.

25. The image coder according to any one of claims 20 through 23, further comprising:

clock generating means for generating and supply a clock signal to the image compression/encoding unit; and

frequency control means for changing a frequency of the clock signal in accordance with a change in a setting state designated by the first or the second setting means.

14. An image coder comprising:

image compression/encoding means for performing compression and encoding of an image using wavelet transform for frequency transform;

detection means for detecting a remaining battery level when a power supply of the image coder is a battery cell; and

first setting means for setting a number of taps of a wavelet filter used for the wavelet transform in accordance with the detected battery level.

18. The image coder according to claim 14, wherein the first setting means designates a 9-tap/7-tap filter when the detected battery level is above a reference level designates a 5-tap/3-tap filter when the detected battery level is at or below the reference state.

22. The image coder according to claim 14, further comprising:

second setting means for designating the number of taps of the wavelet filter or a hierarchical level of the wavelet transform, regardless of a value designated by the first setting means.

37. The image compression method according to any one of claims 14 through 38, further comprising:

controlling a voltage level of the battery cell in accordance with a change in a state designated by the operation of setting the tile processing mode or selecting the number of taps.

38. The image compression method according to any one of claims 14 through 38, further comprising:

generating a clock signal; and

controlling a frequency of the clock signal in accordance with a change in a state designated by the operation of setting the tile processing mode or selecting the number of taps.

15. An image coder comprising:

image compression/encoding means for performing compression and encoding of an image using wavelet transform for frequency transform;

detection means for detecting a remaining battery level when a power supply of the image coder is a battery cell; and

first setting means for designating a hierarchical level of the wavelet transform in accordance with the detected battery level.

19. The image coder according to claim 15, wherein the first setting means designates a 5-level wavelet transform when the detected battery level is above a reference state designates a 3-level wavelet transform when the detected battery level is at or below the reference level.

23. The image coder according to claim 15, further comprising:

second setting means for designating a number of taps of a wavelet filter used for the wavelet transform or the hierarchical level of the wavelet transform, regardless of a value designated by the first setting means.

16. An image coder comprising:

image compression/encoding means for performing compression and encoding of an image using wavelet transform for frequency transform;

detection means for detecting a remaining battery level when a power supply of the image coder is a battery cell; and

first setting means for designating a rate control mode of the compression and encoding in accordance with the detected battery level,

wherein the first setting means designates a Lagragian rate control more when the remaining battery level is above a reference level designates a plain rate control mode when the detected battery level is at or below the reference level.

21. The image coder according to claim 16, further comprising:

second setting means for designating a tiling mode or the rate control mode of the compression and encoding, regardless of the mode designated by the first setting means.

26. An image compression method comprising:

tiling an image into a plurality of tiles and performing compression and encoding of the image in a hierarchical manner for each of the tiles;

detecting a remaining battery level when a power supply of the image coder is a battery cell; and

selecting a tiling processing mode in accordance with the detected battery level.

30. The image compression method according to claim 26, wherein an overlap tiling mode is selected when the remaining battery level is above a reference level, and a non-overlap tiling processing mode is selected when the remaining battery level is at or below the reference level.

33. The image compression method according to 26, further comprising:

selecting the tiling mode or a rate control mode of the compression and encoding, regardless of the mode designated by the operation of setting the tile processing mode.

27. An image compression method comprising:

performing compression and encoding of an image using wavelet transform for frequency transform;

detecting a remaining battery level when a power supply of the image coder is a battery cell; and

selecting a number of taps of a wavelet filter used for the wavelet transform in accordance with the detected battery level.

31. The image compression method according to claim 27, wherein a 9-tap/7-tap filter is selected when the detected battery level is above a reference level, and a 5-tap/3-tap filter is selected when the detected battery level is at or below the reference state.

35. The image compression method according to claim 27, further comprising:

selecting the number of taps of the wavelet filter or a hierarchical level of the wavelet transform, regardless of a value designated by the operation of setting the tile processing mode.

28. An image compression method comprising:

performing compression and encoding of an image using wavelet transform for frequency transform;

detecting a remaining battery level when a power supply of the image coder is a battery cell; and

selecting a hierarchical level of the wavelet transform in accordance with the detected battery level.

32. The image compression method according to claim 28, wherein a 5-level wavelet transform is selected when the detected battery level is above a reference state, and a 3-level wavelet transform is selected when the detected battery level is at or below the reference level.

36. The image compression method according to claim 28, further comprising:

selecting a number of taps of a wavelet filter used for the wavelet transform or the hierarchical level of the wavelet transform, regardless of a value designated by the operation of setting the tile processing mode.

29. An image compression method comprising:

performing compression and encoding of an image using wavelet transform for frequency transform;

detecting a remaining battery level when a power supply of the image coder is a battery cell;

selecting a rate control mode of the compression and encoding in accordance with the detected battery level,

wherein a Lagragian rate control more is selected when the remaining battery level is above a reference level, and a plain rate control mode is selected when the detected battery level is at or below the reference level.

34. The image compression method according to claim 29, further comprising:

selecting a tiling mode or the rate control mode of the compression and encoding, regardless of the mode designated by the operation of setting the tile processing mode.