Methods and apparatus for performing MQ-decoding operations

A computer readable medium embodying computer executable instructions for implementing a method of processing encoded image data representing at least a portion of an image, the method comprising the steps of:

• accessing a set of stored encoded image data;
• performing a JPEG video decoding operation on the accessed set of stored image data, said step of performing a JPEG video decoding operation including:
• performing MQ decoding by processing:
• i) a base value D,
• ii) a subinterval length Q which is a sub-portion of the total coding interval length A;
• iii) a discounted total interval value Ad, said discounted total interval value being equal to a full coding interval A, plus said subinterval length Q, minus said base value D;
• iv) a discounted code value, Cd, said discounted code value being equal to a code value, C, plus said subinterval length Q, minus said base value D;
• and
• v) a predicted symbol bit value S;
• said processing including:
• i) computing a first value Amqmq which is equal to (Ad+D−Q);
• ii) computing a second value Cmq which is equal to Cd +D;
• and
• iii) performing a logical shift right operation by the number of bit positions (N+1) on the value (Cmq XOR Amqmq) where N is the number of bit positions used to represent each of Cmq and Amqmq, to generate a symbol indicator value indicating whether the received predicated symbol bit value S is incorrect, said generated symbol indicator value indicating that said received predicted symbol bit value is incorrect when said generated symbol indicator value assumes the value one;
• generating a set of decoded image data, from a result of the processing performed as part of said MQ decoder operations, said result including said generated symbol indicator value;
• and
• supplying decoded image data from said generated set of decoded image data to a display device.

A system for implementing a method of processing encoded image data representing at least a portion of an image, the system comprising:

• means for accessing a set of stored encoded image data;
• means for performing a JPEG video decoding operation on the accessed set of stored image data, said step of performing a JPEG video decoding operation including:
• means for performing MQ decoding by processing:
• i) a base value D,
• ii) a subinterval length Q which is a sub-portion of the total coding interval length A;
• iii) a discounted total interval value Ad, said discounted total interval value being equal to a full coding interval A, plus said subinterval length Q, minus said base value D;
• iv) a discounted code value, Cd, said discounted code value being equal to a code value, C, plus said subinterval length Q, minus said base value D;
• and
• v) a predicted symbol bit value S;
• said processing including:
• i) computing a first value Amqmq which is equal to (Ad+D−Q);
• ii) computing a second value Cmq which is equal to Cd+D;
• and
• iii) performing a logical shift right operation by the number of bit positions (N−1) on the value (Cmq XOR Amqmq) where N is the number of bit positions used to represent each of Cmq and Amqmq, to generate a symbol indicator value indicating whether the received predicated symbol bit value S is incorrect, said generated symbol indicator value indicating that said received predicted symbol bit value is incorrect when said generated symbol indicator value assumes the value one;
• means for generating a set of decoded image data, from a result of the processing performed as part of said MQ decoder operations, said result including said generated symbol indicator value, a set of decoded image data;
• and
• means for supplying decoded image data from said generated set of decoded image data to a display device.