Systems and methods for performing binary arithmetic coding in video coding
View Patent ↗A method for subdividing an interval during entropy decoding for a bitstream representing a set of video pictures is provided. A sub-interval value is computed by (i) performing an initial right bit-shifting operation on a probability estimator value to reduce a length in bits of the probability estimator value, (ii) multiplying the right bit-shifted probability estimator value by a range value representing the interval, (iii) performing another right bit-shifting operation on a result of the multiplication, and (iv) adding a constant value to a result of the other right bit-shifting operation, wherein the probability estimator value is associated with a probability of a bin having a particular value. The sub-interval value computed based on the right bit-shifted probability estimator value is used to update the interval.
1. A method for updating a probability estimator value during entropy decoding for a bitstream representing a set of video pictures, the method comprising:
updating the probability estimator value by (i) performing an initial right bit-shifting operation on the probability estimator value to reduce a length, in bits, of the probability estimator value, (ii) multiplying the right bit-shifted probability estimator value by a range value representing an interval, (iii) performing another right bit-shifting operation on a result of the multiplication generated by multiplying the right bit-shifted probability estimator value by the range value, and (iv) adding a constant value to a result of the other right bit-shifting operation, wherein the probability estimator value is associated with a probability of a bin having a particular value.
2. The method of claim 1 , wherein an amount by which the result of the multiplication is right bit-shifted in the other right bit-shifting operation is based on an amount by which the probability estimator value is right bit-shifted in the initial right bit-shifting operation.
3. The method of claim 2 , wherein the amount by which the result of the multiplication is right bit-shifted in the other right bit-shifting operation is equal to a constant minus the amount by which the probability estimator value is right bit-shifted in the initial right bit-shifting operation.
4. The method of claim 1 , wherein the probability estimator value is further associated with a current bin value being equal to a least probable state for the current bin value.
5. The method of claim 4 , wherein 1 minus the probability estimator value is right bit-shifted and multiplied by the range value representing the interval when the current bin value is equal to a most probable state for the current bin value.
6. The method of claim 1 , further comprising updating the probability estimator value further based on a current bin value.
7. The method of claim 6 , wherein updating the probability estimator value based on the current bin value comprises applying a bit-shifting operation to a value based on the probability estimator value.
8. The method of claim 1 , wherein if the updated probability estimator value exceeds a threshold, a most probable state for a subsequent bin value is modified.
9. The method of claim 8 , wherein if the most probable state for the subsequent bin value is modified, the updated probability estimator value is also modified.
10. The method of claim 9 , wherein the updated probability estimator value is modified by inverting each bit of the updated probability estimator value.
11. The method of claim 1 , further comprising:
updating the interval based on the right bit-shifted probability estimator value;
determining whether the updated interval is smaller than a threshold value; and
when the updated interval is smaller than the threshold value, renormalizing the updated interval.
12. The method of claim 11 , wherein renormalizing the updated interval comprises doubling the updated interval.
13. An electronic device for updating a probability estimator value during entropy decoding for a bitstream representing a set of video pictures, the electronic device comprising:
at least one processor; and
at least one non-transitory computer-readable medium coupled to the at least one processor and storing one or more computer-executable instructions which, when executed by the at least one processor, cause the electronic device to:
update the probability estimator value by (i) performing an initial right bit-shifting operation on the probability estimator value to reduce a length, in bits, of the probability estimator value, (ii) multiplying the right bit-shifted probability estimator value by a range value representing an interval, (iii) performing another right bit-shifting operation on a result of the multiplication generated by multiplying the right bit-shifted probability estimator value by the range value, and (iv) adding a constant value to a result of the other right bit-shifting operation, wherein the probability estimator value is associated with a probability of a bin having a particular value.
14. The electronic device of claim 13 , wherein an amount by which the result of the multiplication is right bit-shifted in the other right bit-shifting operation is based on an amount by which the probability estimator value is right bit-shifted in the initial right bit-shifting operation.
15. The electronic device of claim 14 , wherein the amount by which the result of the multiplication is right bit-shifted in the other right bit-shifting operation is equal to a constant minus the amount by which the probability estimator value is right bit-shifted in the initial right bit-shifting operation.
16. The electronic device of claim 13 , wherein:
the probability estimator value is further associated with a current bin value being equal to a least probable state for the current bin value, and
1 minus the probability estimator value is right bit-shifted and multiplied by the range value representing the interval when the current bin value is equal to a most probable state for the current bin value.
17. The electronic device of claim 13 , wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the electronic device to:
update the probability estimator value further based on a current bin value.
18. The electronic device of claim 17 , wherein updating the probability estimator value based on the current bin value comprises applying a bit-shifting operation to a value based on the probability estimator value.
19. The electronic device of claim 13 , wherein:
if the updated probability estimator value exceeds a threshold, a most probable state for a subsequent bin value is modified,
if the most probable state for the subsequent bin value is modified, the updated probability estimator value is also modified, and
the updated probability estimator value is modified by inverting each bit of the updated probability estimator value.
20. The electronic device of claim 13 , wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the electronic device to:
update the interval based on the right bit-shifted probability estimator value;
determine whether the updated interval is smaller than a threshold value; and
when the updated interval is smaller than the threshold value, renormalize the updated interval, wherein renormalizing the updated interval comprises doubling the updated interval.