Context-adaptive variable length coder with simultaneous storage of incoming data and generation of syntax elements

Abstract

A variable-length coding apparatus which receives image data block by block, and generates coded data from syntax elements. A storage unit temporarily stores the image data, while, at the same time, a first syntax element calculating unit calculates a first syntax element from the image data. A first coding unit generates coded data of the first syntax element from a value of the first syntax element. A second syntax element is calculated from the image data by a second syntax element calculating unit that reads out the image data stored in the storage unit. A second coding unit generates coded data of the second syntax element on the basis of the values of the first and second syntax elements, and a packing unit connects the coded data of the first and second syntax elements.

What is claimed is: 
     
       1. A variable-length coding apparatus which receives a block of image data block by block, and generates coded data from syntax elements, comprising:
 a storage unit that temporarily stores the block of image data; 
 a first syntax element calculating unit that calculates a first syntax element from the block of image data, at the same time the block of image data is stored in said the storage unit; 
 a first coding unit that generates coded data of the first syntax element from a value of based on the first syntax element; 
 a second syntax element calculating unit that reads out the block of image data stored in said from the storage unit, and calculates a value of a second syntax element from the block of image data which is read out from the storage unit; 
 a second coding unit that generates coded data of the second syntax element based on the basis of the values of the first syntax element and the second syntax elements element; and 
 a packing unit that packs the coded data of the first syntax element and the coded data of the second syntax elements element. 
 
     
     
       2. The apparatus according to  claim 1 , wherein said the second syntax element calculating unit reads out the block of image data stored in said the storage unit in a reverse zigzag scan order, and calculates to calculate the second syntax element. 
     
     
       3. The apparatus according to  claim 1 , wherein the first syntax element includes at least one of the number of nonzero data in a the block of image data, the number of zero data in the block of image data, the number of zero data input before last nonzero data in the block of image data, and the number of data having an absolute value of 1 and input after last data having an absolute value of not less than 2 in the block of image data. 
     
     
       4. The apparatus according to  claim 1 , wherein the second syntax element includes at least one of a zero run length of corresponding to the block of image data and a level value of corresponding to the block of image data. 
     
     
       5. The apparatus according to  claim 1 , wherein said the first syntax element calculating unit comprises:
 an additional information calculating unit that calculates additional information indicating based on the block of image data, the additional information including at least one of the number of zero data and the number of nonzero data from the input image data; and 
 a first syntax element generation generating unit that calculates the first syntax element based on the basis of the additional information and the block of image data temporarily stored in said which is read out from the storage unit and the additional information calculated by said additional information calculating unit. 
 
     
     
       6. The apparatus according to  claim 5 , wherein the block of image data from said storage unit is read out from the storage unit in a reverse zigzag scan order, and is supplied to said the first syntax element generation generating unit. 
     
     
       7. A variable-length coding method which receives image data block by block, and generates coded data from syntax elements, comprising:
 receiving a block of image data;  
 temporarily storing the block of image data in a storage unit; 
 calculating a first syntax element from the block of image data, at the same time the block of image data is stored in the storage unit; 
 generating coded data of the first syntax element from a value of based on the first syntax element; 
 reading out the block of image data stored in from the storage unit, and calculating a value of a second syntax element from the block of image data which is read out from the storage unit; 
 generating coded data of the second syntax element based on the basis of the values of the first syntax element and the second syntax elements element; and 
 connecting the coded data of the first syntax element and the coded data of the second syntax elements element. 
 
     
     
       8. The method according to  claim 7 , wherein said second syntax element calculation, the block of image data stored in the storage unit is read out in a reverse zigzag scan order, and to calculate the second syntax element is calculated. 
     
     
       9. The method according to  claim 7 , wherein the first syntax element includes a at least one of the number of nonzero data in a the block of image data, the number of zero data in the block of image data, the number of zero data input before last nonzero data in the block of image data, and the number of data having an absolute value of 1 and input after last data having an absolute value of not less than 2 in the block of image data. 
     
     
       10. The method according to  claim 7 , wherein the second syntax element includes at least on one of a zero run length of corresponding to the block of image data and a level value of corresponding to the block of image data. 
     
     
       11. The method according to  claim 7 , wherein in said first syntax element calculation, further comprising:
 calculating additional information indicating based on the block of image data, the additional information including at least one of the number of zero data and the number of nonzero data, from the input image data are calculated; and 
 wherein the first syntax element is calculated based on the basis of the additional information and the block of image data temporarily stored in which is read out from the storage unit and the additional information calculated in said additional information calculation. 
 
     
     
       12. The method according to  claim 11 , wherein the block of image data from the storage unit is read out from the storage unit in a reverse zigzag scan order, and used in said to calculate the first syntax element synthesizing. 
     
     
       13. A non-transitory computer-readable storage medium having stored thereon that stores a program which is executable by an image processing apparatus, the program having a program code for performing the variable-length coding method cited in  claim 7  for causing a computer to execute a variable-length coding method, the variable-length coding method comprising:
 receiving a block of image data; 
 storing the block of image data in a storage unit; 
 calculating a first syntax element from the block of image data, at the same time the block of image data is stored in the storage unit; 
 generating coded data of the first syntax element based on the first syntax element; 
 reading out the block of image data from the storage unit, and calculating a second syntax element from the block of image data which is read out from the storage unit; 
 generating coded data of the second syntax element based on the first syntax element and the second syntax element; and 
 connecting the coded data of the first syntax element and the coded data of the second syntax element. 
 
     
     
       14. A coding apparatus which receives a block of image data, comprising:
 a storage unit that stores the block of image data;   a first syntax element calculating unit that calculates a first syntax element from the block of image data, in parallel with the block of image data being stored in the storage unit;   a first coding unit that generates coded data of the first syntax element based on the first syntax element;   a second syntax element calculating unit that calculates a second syntax element from the block of image data which is read out from the storage unit; and   a second coding unit that generates coded data of the second syntax element based on the first syntax element and the second syntax element.   
     
     
       15. The apparatus according to claim 14, wherein the second coding unit selects a variable-length coding table in accordance with the first syntax element. 
     
     
       16. The apparatus according to claim 15, wherein the second coding unit codes the second syntax element in accordance with the selected variable-length coding table. 
     
     
       17. The apparatus according to claim 14, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to the second syntax element calculating unit. 
     
     
       18. The apparatus according to claim 14, wherein the first syntax element includes at least one of the number of nonzero data in the block of image data, the number of zero data in the block of image data, the number of zero data input before last nonzero data in the block of image data, and the number of data having an absolute value of 1 and input after last data having an absolute value of not less than 2 in the block of image data. 
     
     
       19. The apparatus according to claim 14, wherein the second syntax element includes at least one of a zero run length corresponding to the block of image data and a level value corresponding to the block of image data. 
     
     
       20. The apparatus according to claim 14, wherein the first syntax element calculating unit calculates additional information based on the block of image data, the additional information including at least one of the number of zero data and the number of nonzero data, and
 wherein the first syntax element calculating unit calculates the first syntax element based on the additional information and the block of image data which is read out from the storage unit.   
     
     
       21. The apparatus according to claim 20, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to the first syntax element calculating unit. 
     
     
       22. The apparatus according to claims 14, further comprising
 a packing unit that packs the coded data of the first syntax element and the coded data of the second syntax element.   
     
     
       23. A coding apparatus which receives a block of image data, comprising:
 a storage unit that stores the block of image data;   a first syntax element calculating unit that calculates a first syntax element from the block of image data, in parallel with the block of image data being stored in the storage unit;   a first coding unit that codes the first syntax element to generate coded data of the first syntax element;   a second syntax element calculating unit that calculates a second syntax element from the block of image data which is read out from the storage unit; and   a second coding unit that codes the second syntax element based on the first syntax element to generate coded data of the second syntax element.   
     
     
       24. The apparatus according to claim 23, wherein a process of calculating the second syntax element is performed in parallel with a process of storing another block of image data in the storage unit. 
     
     
       25. The apparatus according to claim 23, wherein a process of coding the second syntax element is performed in parallel with a process of storing another block of image data in the storage unit. 
     
     
       26. The apparatus according to claim 23, wherein a process of coding the first syntax element is performed in parallel with a process of calculating first syntax element from another block of image data. 
     
     
       27. The apparatus according to claim 23, further comprising
 a packing unit that packs the coded data of the first syntax element and the coded data of the second syntax element.   
     
     
       28. The apparatus according to claim 23, wherein a data line for the block of image data is connected to the storage unit and the first syntax element calculating unit,
 the first syntax element calculating unit and the second syntax element calculating unit are connected to the second coding unit, and   the first syntax element calculating unit is connected to the first coding unit.   
     
     
       29. A method comprising:
 receiving a block of image data;   storing the block of image data in a storage unit;   calculating a first syntax element from the block of image data, in parallel with the block of image data being stored in the storage unit;   generating coded data of the first syntax element based on the first syntax element;   calculating a second syntax element from the block of image data which is read out from the storage unit; and   generating coded data of the second syntax element based on the first syntax element and the second syntax element.   
     
     
       30. The method according to claim 29, wherein when a process of calculating the second syntax element is performed, a variable-length coding table is selected in accordance with the first syntax element. 
     
     
       31. The method according to claim 30, wherein the second syntax element is coded in accordance with the selected variable-length coding table. 
     
     
       32. The method according to claim 29, wherein the block data stored in the storage unit is read out in a reverse zigzag scan order. 
     
     
       33. The method according to claim 29, wherein the first syntax element includes at least one of the number of nonzero data in the block of image data, the number of zero data in the block of image data, the number of zero data input before last nonzero data in the block of image data, and the number of data having an absolute value of 1 and input after last data having an absolute value of not less than 2 in the block of image data. 
     
     
       34. The method according to claim 29, wherein the second syntax element includes at least one of a zero run length corresponding to the block of image data and a level value corresponding to the block of image data. 
     
     
       35. The method according to claim 29, further comprising
 calculating additional information based on the block of image data, the additional information including at least one of the number of zero data and the number of nonzero data; and   calculating the first syntax element based on the additional information and the block of image data which is read out from the storage unit.   
     
     
       36. The method according to claim 35, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to a first syntax element calculating unit that calculates the first syntax element from the block of image data. 
     
     
       37. A method comprising:
 receiving a block of image data;   storing the block of image data in a storage unit;   calculating a first syntax element from the block of image data, in parallel with the block of image data being stored in the storage unit;   coding the first syntax element to generate coded data of the first syntax element;   calculating a second syntax element from the block of image data which is read out from the storage unit; and   coding the second syntax element based on the first syntax element to generate coded data of the second syntax element.   
     
     
       38. The method according to claim 37, wherein a process of calculating the second syntax element is performed in parallel with a process of storing another block of image data in the storage unit. 
     
     
       39. The method according to claim 37, wherein a process of coding the second syntax element is performed in parallel with a process of storing another block of image data in the storage unit. 
     
     
       40. The method according to claim 37, wherein a process of coding the first syntax element is performed in parallel with a process of calculating first syntax element from another block of image data. 
     
     
       41. The method according to claim 37, further comprising
 packing the coded data of the first syntax element and the coded data of the second syntax element.   
     
     
       42. A non-transitory computer-readable storage medium that stores a program for causing a computer to execute a method, the method comprising:
 receiving a block of image data;   storing the block of image data in a storage unit;   calculating a first syntax element from the block of image data, in parallel with the block of image data being stored in the storage unit;   generating coded data of the first syntax element based on the first syntax element;   calculating a second syntax element from the block of image data which is read out from the storage unit; and   generating coded data of the second syntax element based on the first syntax element and the second syntax element.   
     
     
       43. A non-transitory computer-readable storage medium that stores a program for causing a computer to execute a method, the method comprising:
 receiving a block of image data;   storing the block of image data in a storage unit;   calculating a first syntax element from the block of image data, in parallel with the block of image data being stored in the storage unit;   coding the first syntax element to generate coded data of the first syntax element;   calculating a second syntax element from the block of image data which is read out from the storage unit; and   coding the second syntax element based on the first syntax element to generate coded data of the second syntax element.   
     
     
       44. A coding apparatus comprising:
 a storage unit that stores a block of image data;   a first syntax element calculating unit that calculates a first syntax element of the block of image data;   a first coding unit that generates coded data of the first syntax element based on the first syntax element;   a second syntax element calculating unit that calculates a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   a second coding unit that generates coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein in a case where the block of image data is encoded,   the first syntax element calculating unit calculates the first syntax element of the block of image data in parallel with storing the block of image data in the storage unit, and   the second syntax element calculating unit calculates the second syntax element of the block of image data based on the block of image data which is read out from the storage unit.   
     
     
       45. The apparatus according to claim 44, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to the second syntax element calculating unit. 
     
     
       46. The apparatus according to claim 44, wherein the first syntax element includes at least one of the number of nonzero data in the block of image data, the number of zero data in the block of image data, the number of zero data input before last nonzero data in the block of image data, and the number of data having an absolute value of 1 and input after last data having an absolute value of not less than 2 in the block of image data. 
     
     
       47. The apparatus according to claim 44, wherein the second syntax element includes at least one of a zero run length corresponding to the block of image data and a level value corresponding to the block of image data. 
     
     
       48. The apparatus according to claim 44, wherein the first syntax element calculating unit calculates additional information based on the block of image data, the additional information including at least one of the number of zero data and the number of nonzero data, and
 wherein the first syntax element calculating unit calculates the first syntax element based on the additional information and the block of image data which is read out from the storage unit.   
     
     
       49. The apparatus according to claim 48, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to the first syntax element calculating unit. 
     
     
       50. The apparatus according to claims 44, further comprising
 a packing unit that packs the coded data of the first syntax element and the coded data of the second syntax element.   
     
     
       51. A method comprising:
 storing a block of image data in a storage unit;   calculating a first syntax element of the block of image data;   generating coded data of the first syntax element based on the first syntax element;   calculating a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   generating coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein in a case where the block of image data is encoded,   the first syntax element of the block of image data is calculated in parallel with storing the block of image data in the storage unit, and   the second syntax element of the block of image data is calculated based on the block of image data which is read out from the storage unit.   
     
     
       52. A non-transitory computer-readable storage medium that stores a program for causing a computer to execute a method, the method comprising:
 storing a block of image data in a storage unit;   calculating a first syntax element of the block of image data;   generating coded data of the first syntax element based on the first syntax element;   calculating a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   generating coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein in a case where the block of image data is encoded,   the first syntax element of the block of image data is calculated in parallel with storing the block of image data in the storage unit, and   the second syntax element of the block of image data is calculated based on the block of image data which is read out from the storage unit.   
     
     
       53. A coding apparatus comprising:
 a storage unit that stores a block of image data;   a first syntax element calculating unit that calculates a first syntax element of the block of image data;   a first coding unit that generates coded data of the first syntax element based on the first syntax element;   a second syntax element calculating unit that calculates a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   a second coding unit that generates coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein in a case where the block of image data is encoded,   the first syntax element calculating unit calculates the first syntax element of the block of image data when the block of image data is stored in the storage unit, and   the second syntax element calculating unit calculates the second syntax element of the block of image data based on the block of image data which is read out from the storage unit.   
     
     
       54. The apparatus according to claim 53, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to the second syntax element calculating unit. 
     
     
       55. The apparatus according to claim 53, wherein the first syntax element includes at least one of the number of nonzero data in the block of image data, the number of zero data in the block of image data, the number of zero data input before last nonzero data in the block of image data, and the number of data having an absolute value of 1 and input after last data having an absolute value of not less than 2 in the block of image data. 
     
     
       56. The apparatus according to claim 53, wherein the second syntax element includes at least one of a zero run length corresponding to the block of image data and a level value corresponding to the block of image data. 
     
     
       57. The apparatus according to claim 53, wherein the first syntax element calculating unit calculates additional information based on the block of image data, the additional information including at least one of the number of zero data and the number of nonzero data, and
 wherein the first syntax element calculating unit calculates the first syntax element based on the additional information and the block of image data which is read out from the storage unit.   
     
     
       58. The apparatus according to claim 57, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to the first syntax element calculating unit. 
     
     
       59. The apparatus according to claims 53, further comprising
 a packing unit that packs the coded data of the first syntax element and the coded data of the second syntax element.   
     
     
       60. A method comprising:
 storing a block of image data in a storage unit;   calculating a first syntax element of the block of image data;   generating coded data of the first syntax element based on the first syntax element;   calculating a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   generating coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein in a case where the block of image data is encoded,   the first syntax element of the block of image data is calculated when the block of image data is stored in the storage unit, and   the second syntax element of the block of image data is calculated based on the block of image data which is read out from the storage unit.   
     
     
       61. A non-transitory computer-readable storage medium that stores a program for causing a computer to execute a method, the method comprising:
 storing a block of image data in a storage unit;   calculating a first syntax element of the block of image data;   generating coded data of the first syntax element based on the first syntax element;   calculating a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   generating coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein in a case where the block of image data is encoded,   the first syntax element of the block of image data is calculated when the block of image data is stored in the storage unit, and   the second syntax element of the block of image data is calculated based on the block of image data which is read out from the storage unit.   
     
     
       62. A coding apparatus comprising:
 a storage unit that stores a block of image data;   a first syntax element calculating unit that calculates a first syntax element of the block of image data;   a first coding unit that generates coded data of the first syntax element based on the first syntax element;   a second syntax element calculating unit that calculates a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   a second coding unit that generates coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein in a case where the block of image data is encoded,   the first syntax element calculating unit calculates the first syntax element of the block of image data before storing the block of image data in the storage unit is finished, and   the second syntax element calculating unit calculates the second syntax element of the block of image data based on the block of image data which is read out from the storage unit after storing the block of image data in the storage unit is finished.   
     
     
       63. The apparatus according to claim 62, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to the second syntax element calculating unit. 
     
     
       64. The apparatus according to claim 62, wherein the first syntax element includes at least one of the number of nonzero data in the block of image data, the number of zero data in the block of image data, the number of zero data input before last nonzero data in the block of image data, and the number of data having an absolute value of 1 and input after last data having an absolute value of not less than 2 in the block of image data. 
     
     
       65. The apparatus according to claim 62, wherein the second syntax element includes at least one of a zero run length corresponding to the block of image data and a level value corresponding to the block of image data. 
     
     
       66. The apparatus according to claim 62, wherein the first syntax element calculating unit calculates additional information based on the block of image data, the additional information including at least one of the number of zero data and the number of nonzero data, and
 wherein the first syntax element calculating unit calculates the first syntax element based on the additional information and the block of image data which is read out from the storage unit.   
     
     
       67. The apparatus according to claim 66, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to the first syntax element calculating unit. 
     
     
       68. The apparatus according to claims 62, further comprising
 a packing unit that packs the coded data of the first syntax element and the coded data of the second syntax element.   
     
     
       69. A method comprising:
 storing a block of image data in a storage unit;   calculating a first syntax element of the block of image data;   generating coded data of the first syntax element based on the first syntax element;   calculating a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   generating coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein in a case where the block of image data is encoded,   the first syntax element of the block of image data is calculated before storing the block of image data in the storage unit is finished, and   the second syntax element of the block of image data is calculated based on the block of image data which is read out from the storage unit after storing the block of image data in the storage unit is finished.   
     
     
       70. A non-transitory computer-readable storage medium that stores a program for causing a computer to execute a method, the method comprising:
 storing a block of image data in a storage unit;   calculating a first syntax element of the block of image data;   generating coded data of the first syntax element based on the first syntax element;   calculating a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   generating coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein in a case where the block of image data is encoded,   the first syntax element of the block of image data is calculated before storing the block of image data in the storage unit is finished, and   the second syntax element of the block of image data is calculated based on the block of image data which is read out from the storage unit after storing the block of image data in the storage unit is finished.   
     
     
       71. A coding apparatus comprising:
 a storage unit that stores a block of image data;   a first syntax element calculating unit that calculates a first syntax element of the block of image data;   a first coding unit that generates coded data of the first syntax element based on the first syntax element;   a second syntax element calculating unit that calculates a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   a second coding unit that generates coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein an order that the first syntax element calculating unit processes the block of image data and an order that the second syntax element calculating unit processes the block of image data are different from each other.   
     
     
       72. The apparatus according to claim 71, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to the second syntax element calculating unit. 
     
     
       73. The apparatus according to claim 71, wherein the first syntax element includes at least one of the number of nonzero data in the block of image data, the number of zero data in the block of image data, the number of zero data input before last nonzero data in the block of image data, and the number of data having an absolute value of 1 and input after last data having an absolute value of not less than 2 in the block of image data. 
     
     
       74. The apparatus according to claim 71, wherein the second syntax element includes at least one of a zero run length corresponding to the block of image data and a level value corresponding to the block of image data. 
     
     
       75. The apparatus according to claim 71, wherein the first syntax element calculating unit calculates additional information based on the block of image data, the additional information including at least one of the number of zero data and the number of nonzero data, and
 wherein the first syntax element calculating unit calculates the first syntax element based on the additional information and the block of image data which is read out from the storage unit.   
     
     
       76. The apparatus according to claim 75, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to the second syntax element calculating unit. 
     
     
       77. The apparatus according to claims 71, further comprising
 a packing unit that packs the coded data of the first syntax element and the coded data of the second syntax element.   
     
     
       78. A method comprising:
 storing a block of image data in a storage unit;   calculating a first syntax element of the block of image data;   generating coded data of the first syntax element based on the first syntax element;   calculating a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   generating coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein an order that the block of image data is processed to calculate the first syntax element and an order that the block of image data is processed to calculate the second syntax element are different from each other.   
     
     
       79. A non-transitory computer-readable storage medium that stores a program for causing a computer to execute a method, the method comprising:
 storing a block of image data in a storage unit;   calculating a first syntax element of the block of image data;   generating coded data of the first syntax element based on the first syntax element;   calculating a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   generating coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein an order that the block of image data is processed to calculate the first syntax element and an order that the block of image data is processed to calculate the second syntax element are different from each other.   
     
     
       80. A coding apparatus comprising:
 a storage unit that stores a block of image data;   a first syntax element calculating unit that calculates a first syntax element of the block of image data;   a first coding unit that generates coded data of the first syntax element based on the first syntax element;   a second syntax element calculating unit that calculates a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   a second coding unit that generates coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein the block of image data is stored in the storage unit in parallel with being processed by the first syntax element calculating unit.   
     
     
       81. The apparatus according to claim 80, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to the second syntax element calculating unit. 
     
     
       82. The apparatus according to claim 80, wherein the first syntax element includes at least one of the number of nonzero data in the block of image data, the number of zero data in the block of image data, the number of zero data input before last nonzero data in the block of image data, and the number of data having an absolute value of 1 and input after last data having an absolute value of not less than 2 in the block of image data. 
     
     
       83. The apparatus according to claim 80, wherein the second syntax element includes at least one of a zero run length corresponding to the block of image data and a level value corresponding to the block of image data. 
     
     
       84. The apparatus according to claim 80, wherein the first syntax element calculating unit calculates additional information based on the block of image data, the additional information including at least one of the number of zero data and the number of nonzero data, and
 wherein the first syntax element calculating unit calculates the first syntax element based on the additional information and the block of image data which is read out from the storage unit.   
     
     
       85. The apparatus according to claim 84, wherein the block of image data is read out from the storage unit in a reverse zigzag scan order, and is supplied to the first syntax element calculating unit. 
     
     
       86. The apparatus according to claims 80, further comprising
 a packing unit that packs the coded data of the first syntax element and the coded data of the second syntax element.   
     
     
       87. A method comprising:
 storing a block of image data in a storage unit;   calculating a first syntax element of the block of image data;   generating coded data of the first syntax element based on the first syntax element;   calculating a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   generating coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein the block of image data is stored in the storage unit in parallel with being processed to calculate the first syntax element.   
     
     
       88. A non-transitory computer-readable storage medium that stores a program for causing a computer to execute a method, the method comprising:
 storing a block of image data in a storage unit;   calculating a first syntax element of the block of image data;   generating coded data of the first syntax element based on the first syntax element;   calculating a second syntax element of the block of image data based on the block of image data which is read out from the storage unit; and   generating coded data of the second syntax element based on the first syntax element and the second syntax element,   wherein the block of image data is stored in the storage unit in parallel with being processed to calculate the first syntax element.