TECHNIQUES FOR CONTEXT-ADAPTIVE BINARY DATA ARITHMETIC CODING (CABAC) DECODING

1 . A method for decoding transform coefficients, comprising:

decoding consecutive bits of an input compressed bitstream;

computing a first symbol value using a number of the decoded bits;

returning the first symbol value, if a total number of the decoded bits is less than a specified bit count;

computing a second symbol value, if the total number of the decoded bits equals the specified bit count; and

returning the second symbol value.

2 . The method of claim 1 , wherein computing the first symbol value further comprising:

adding one to the total number of the decoded bits.

3 . The method of claim 1 , wherein computing the second symbol value further comprises:

decoding the input compressed bitstream using an Exponential-Golomb code; and

adding the first symbol value to a result generated by the Exponential-Golomb code decoding.

4 . The method of claim 1 , wherein the input compressed bitstream is a decoded context-adaptive binary data arithmetic coding (CABAC) bitstream.

5 . The method of claim 4 , wherein decoding the consecutive bits, further comprising:

decoding multiple bits having a same value using a same CABAC context.

6 . The method of claim 5 , further comprising:

receiving a context value, the input compressed bitstream, and a CABAC decoder object, wherein the CABAC decoder object includes a range value and an offset value;

computing a sub-range value;

computing a new range value by subtracting the sub-range value from the range value;

checking if the offset value is less than the new range value;

returning a decompressed output bit having a value equal to a most probable symbol (MPS) value, if the offset is less than the new range value; and

returning a decompressed output bit having a value equal to a least probable symbol (LPS), if the offset is bigger or equal to the new range value.

7 . The method of claim 6 , further comprising:

performing a renormalization process;

checking if a zero bit is encountered;

returning a total number of the decoded bits, if a zero bit is encountered;

incrementing a counter counting the total number of the decoded bits, if a zero bit is not encountered; and

returning the total number of the decoded bits, if a specified maximum number of bits were decoded.

8 . The method of claim 7 , wherein performing the renormalization process comprises:

consecutively reading new bits from the input compressed bitstream until a range value is bigger than or equal to a predefined range value (PRV).

9 . The method of claim 1 , wherein decoding the consecutive bits comprises:

computing a minimum number of consecutive most probable symbol bits in the input compressed bitstream; and

advancing a state machine of a CABAC decoder for each bit in the consecutive most probable symbol bits without checking the value of each bit.

10 . The method of claim 9 , further comprising:

receiving a context value, the input compressed bitstream, and a CABAC decoder object, wherein the CABAC decoder object includes a range value and an offset value;

computing a sub-range value using the range value and the offset value;

computing a minimum number of consecutive most probable symbol bits (mpbits) in the input compressed bitstream;

returning a decompressed output bit having a value equals to a most probable symbol value, if the minimum number of consecutive most probable symbol bits is greater than zero; and

returning a decompressed output bit having a value equals to a least probable symbol value, if the minimum number of consecutive most probable symbol bits is equal to zero.

11 . The method of claim 10 , wherein returning the decompressed output bit having a value equal to the most probable symbol value, further comprising:

computing a new range value by subtracting the range value from the sub-range value;

performing a normalization process;

upon completion of the normalization process, checking if a zero bit is encountered in the consecutive most probable symbol bits;

iteratively advancing the state machine of the CABAC decoder for each bit in most probable symbol consecutive bits, if a zero bit is not encountered; and

returning a total number of decoded bits when the zero bit is encountered or a specified bit count is achieved.

12 . A computer readable medium having stored thereon instructions which, when executed by a computer, perform a method for decoding transform coefficients, comprising:

decoding consecutive bits of an input compressed bitstream;

computing a first symbol value using a number of the decoded bits;

returning the first symbol value, if a total number of the decoded bits is less than a specified bit count;

computing a second symbol value, if the total number of the decoded bits equals the specified bit count; and

returning the second symbol value.

13 . A decoder for decoding transform coefficients, comprising:

a context-adaptive binary data arithmetic coding (CABAC) decoder for decoding consecutive bits of an input compressed bitstream;

a first adder for computing a first symbol value by adding one to a number of the decoded bits;

a comparator for determining if a total number of the decoded bits equal to a specified maximum number;

an Exponential-Golomb code decoder for decoding the input compressed bitstream if the total number of the decoded bits equal to the specified bit count; and

a second adder for generating a second symbol value by adding the first symbol valve to a result generated by the Exponential-Golomb code decoder.

14 . The decoder of claim 4 , wherein decoding the consecutive bits, further comprising:

decoding multiple bits having a same value using a same CABAC context.

15 . The decoder of claim 14 , further comprising:

receiving a context value, the input compressed bitstream, and a CABAC decoder object, wherein the CABAC decoder object includes a range value and an offset value;

computing a sub-range value;

computing a new range value by subtracting the range value from the sub-range value;

checking if the offset value is teas than the new range value;

returning a decompressed output bit having a value equal to a most probable symbol (MPS) value, if the offset is less than the new range value; and

returning a decompressed output bit having a value equal to a least probable symbol (LPS), if the offset is bigger or equal to the new range value.

16 . The decoder of claim 15 , further comprising:

performing a renormalization process;

checking if a zero bit is encountered;

returning a total number of the decoded bits, if a zero bit is encountered;

incrementing a counter counting the total number of the decoded bits, if a zero bit is not encountered; and

returning the total number of decoded bits, if a specified maximum number of bits were decoded.

17 . The decoder of claim 16 , wherein performing the renormalization process comprises:

consecutively reading new bits from the input compressed bitstream until a range value is bigger than or equal to a predefined range value (PRV).

18 . The decoder of claim 13 , wherein decoding the consecutive bits comprises:

computing a minimum number of consecutive most probable symbol bits in the input compressed bitstream; and

advancing a state machine of a CABAC decoder for each bit in the consecutive most probable symbol bits without checking the value of each bit.

19 . The decoder of claim 18 , further comprising:

receiving a context value, the Input compressed bitstream, and a CABAC decoder object, wherein the CABAC decoder object includes a range value and an offset value;

computing a sub-range value using the range value and the offset value;

computing a minimum number of consecutive most probable symbol bits (mpbits) in the input compressed bitstream;

returning a decompressed output bit having a value equals to a most probable symbol value, if the minimum number of consecutive most probable symbol bits is greater than zero; and

returning a decompressed output bit having a value equals to a least probable symbol value, if the minimum number of consecutive most probable symbol bits is equal to zero.

20 . The decoder of claim 19 , wherein returning the decompressed output bit having a value equals to the most probable symbol value, further comprising:

computing a new range value by subtracting the range value from the sub-range value;

performing a normalization process;

upon completion of the normalization process, checking if a zero bit is encountered in the consecutive most probable symbol bits;

iteratively advancing the state machine of the CABAC decoder for each bit in most probable symbol consecutive bits, if a zero bit is not encountered; and

returning a total number of decoded bits when the zero bit is encountered or a specified bit count is achieved.