Coding/decoding apparatus and coding/decoding method

A coding method comprising:

• a generating step of generating an address by referring to a plurality of pixels in a predetermined template;
• an outputting step of outputting an occurrence probability of a target pixel from a storage device based on the address generated in said generating step, the storage device consisting of a plurality of memory banks which store different occurrence probabilities from each other;
• a coding step of coding a target pixel based on an occurrence probability output from one of the plurality of memory banks of the storage device;
• and
• an updating step of updating an occurrence probability stored in one of the plurality of memory banks based on a coding result obtained in said coding step, wherein when a memory bank to be updated is different from a memory bank from which an occurrence probability is to be output, a first occurrence probability is output while a second occurrence probability is being updated.

A decoding apparatus comprising:

• generating means for generating an address by referring to a plurality of pixels in a predetermined template;
• storage means for storing occurrence probabilities of a target pixel and outputting an occurrence probability based on the address generated by said generating means, said storage means consisting of a plurality of memory banks which store different occurrence probabilities from each other;
• decoding means for decoding a target pixel based on an occurrence probability output from one of the plurality of memory banks of said storage means;
• and
• updating means for updating an occurrence probability stored in one of the plurality of memory banks based on a decoding result of said decoding means, wherein when a memory bank to be updated is different from a memory bank from which an occurrence probability is to be output, a first occurrence probability is output while a second occurrence probability is being updated.

A decoding method comprising:

• a generating step of generating an address by referring to a plurality of pixels in a predetermined template;
• an outputting step of outputting an occurrence probability of a target pixel from a storage device based on the address generated in said generating step, the storage device consisting of a plurality of memory banks which store different occurrence probabilities from each other;
• a decoding step of decoding a target pixel based on an occurrence probability output from one of the plurality of memory banks of the storage device;
• and
• an updating step of updating an occurrence probability stored in one of the plurality of memory banks based on a decoding result obtained in said decoding step, wherein when a bank to be updated is different from a memory bank from which an occurrence probability is to be output, a first occurrence probability is output while a second occurrence probability is being updated.

A decoding apparatus comprising:

• generating means for generating an address for each of a plurality of target pixels to be decoded by referring to a plurality of pixels near the target pixel to be decoded in a template, wherein the template alternates between a first template and a second template which is different from the first template for successive target pixels, and wherein the first and second templates indicate a plurality of pixel positions excluding a pixel position of a preceding pixel of the target pixel to be decoded;
• first storage means for storing occurrence probabilities of a target pixel for which the preceding pixel has a predetermined value and for outputting an occurrence probability based on an address generated by referring to the plurality of pixels in the first template;
• second storage means for storing occurrence probabilities of a target pixel for which the preceding pixel does not have the predetermined value and for outputting an occurrence probability based on an address generated by referring to the plurality of pixels in the first template;
• third storage means for storing occurrence probabilities of a target pixel for which the preceding pixel has the predetermined value and for outputting an occurrence probability based on an address generated by referring to the plurality of pixels in the second template;
• fourth storage means for storing occurrence probabilities of a target pixel for which the preceding pixel does not have the predetermined value and for outputting an occurrence probability based on an address generated by referring to the plurality of pixels in the second template;
• selecting means for selecting one of said first, second, third and fourth storage means based on whether said generating means refers to the plurality of pixels in the first template or the second template and based on whether the preceding pixel has the predetermined value or not;
• and
• decoding means for decoding a target pixel based on an occurrence probability output from the one of said first, second, third and fourth storage means selected by said selecting means.

A decoding method comprising:

• a generating step of generating an address for each of a plurality of target pixels to be decoded by referring to a plurality of pixels near the target pixel to be decoded in a template, wherein the template alternates between a first template and a second template which is different from the first template for successive target pixels, and wherein the first and second templates indicate a plurality of pixel positions excluding a pixel position of a preceding pixel of the target pixel to be decoded;
• a first outputting step of outputting an occurrence probability of a target pixel from a first storage device based on an address generated by referring to a plurality of pixels in the first template, the first storage device storing occurrence probabilities of a target pixel for which the preceding pixel has a predetermined value;
• a second outputting step of outputting an occurrence probability of a target pixel from a second storage device based on an address generated by referring to a plurality of pixels in the first template, the second storage device storing occurrence probabilities of a target pixel for which the preceding pixel does not have the predetermined value;
• a third outputting step of outputting an occurrence probability of a target pixel from a third storage device based on an address generated by referring to a plurality of pixels in the second template, the third storage device storing occurrence probabilities of a target pixel for which the preceding pixel has the predetermined value;
• a fourth outputting step of outputting an occurrence probability of a target pixel from a fourth storage device based on an address generated by referring to a plurality of pixels in the second template, the fourth storage device storing occurrence probabilities of a target pixel for which the preceding pixel does not have the predetermined value;
• a selecting step of selecting one of the first, second, third and fourth storage devices based on whether said generating step refers to the plurality of pixels in the first template or the second template and based on whether the preceding pixel has the predetermined value or not;
• and
• a decoding step of decoding a target pixel based on an occurrence probability output from the one of the first, second, third and fourth storage devices selected in said selecting step.