Method of performing quantization within a multimedia bitstream utilizing division-free instructions

A method of converting a block of discrete cosine transform (DCT) coefficients into integers by dividing quantizer step size without using division operations during quantization of a multimedia bit-stream executed within a processor having single instruction multiple data (SIMD) instructions, comprising:

• constructing a look-up table M for a range of quantization step values 1/a;
• loading data for SIMD instructions to operate on multiple data in a data packet in parallel within the same operation for executing the following steps;
• looking up in said look-up table M an integer value associated with a particular value of quantization step size 1/a for each element in the block;
• performing integer multiplication for each integer b within the block of fixed integer set S and mantissa A using said SIMD instructions;
• executing an integer shift operation for each integer in a resultant block of data by right-shifting to arrive at an integer solution block solving for b/a;
• constructing two mantissa tables M1 and M0 as modifications of said mantissa A;
• splitting the multiplication operations of b with mantissa A across the split mantissa tables M1 and M0 subject to shifting and addition;
• and
• wherein the bit-width of the operations is narrowed.

A method of performing integer divisions b/a during quantization of a multimedia bit-stream within a processor having single instruction multiple data (SIMD) instructions, without utilizing division instructions, comprising:

• constructing a table M of numbers according to the value of 1/a for use during quantization;
• loading data for SIMD instructions to operate on multiple data in a data packet in parallel within the same operation for executing the following;
• finding corresponding values in said table for a particular value 1/a, associated with the division b/a, in said tables during quantization for each of the elements in the data block;
• computing a result for said division value b/a for each integer b within the block of fixed integer set S and mantissa A using a combination of SIMD block multiplication and logical shifting without utilizing a division instruction;
• and
• wherein integers a and b belong to a fixed integer set S;
• wherein said combination of said SIMD block multiplication and logical shifting executes the operation b/a=(b×(A<<(p−n)))>>p having the logical shift operation (>>) within said operation adapted for execution on a processor that does not support non-uniform logical shift operations;
• and
• wherein modifying said table M entries of mantissa A and exponent values n is performed according to the relation M(x)=(A(x)<<(p−n(x))) so that said shift operations in the block during quantization can be executed to the same number of places p.

A method of performing integer divisions b/a during quantization of a multimedia bit-stream within a processor having single instruction multiple data (SIMD) instructions, without the need of executing non-uniform shift instructions, comprising:

• constructing a table M of mantissa A values and exponent n for a for use during quantization;
• modifying said table M in which the mantissas are modified by right shifting in response to relation M(x)=(A(x)<<(p−n(x))), wherein p is a constant;
• loading data for SIMD instructions to operate on multiple data in a data packet in parallel within the same operation for executing the following;
• finding a mantissa A within table M for 1/a for each element in the block of data;
• and
• computing value b/a according to the relation:
• b/a=(b×M)>>p across the block of integers using SIMD instructions.

A method of converting a block of discrete cosine transform (DCT) coefficients into integers by dividing quantizer step size without using division operations during quantization of a multimedia bit-stream executed within a processor having single instruction multiple data (SIMD) instructions, comprising:

• constructing a look-up table M for a range of quantization step values 1/a;
• loading data for SIMD instructions to operate on multiple data in a data packet in parallel within the same operation for executing the following steps;
• looking up in said look-up table M an integer value associated with a particular value of quantization step size 1/a for each element in the block;
• performing integer multiplication for each integer b within the block of fixed integer set S and mantissa A using said SIMD instructions;
• and
• executing an integer shift operation for each integer in a resultant block of data by right-shifting to arrive at an integer solution block solving for b/a;
• wherein on processors having SIMD instructions not configured for performing non-uniform shifting operations, said integer-shift operation comprises:
• modifying said table M into a set of mantissa A values subject to a fixed exponent, by left shifting each mantissa A entry by an amount equal to p−n wherein p is a constant and n is the original exponent value;
• and
• executing said shift operations, after said integer multiplication, during said quantization by performing an integer right shift for each integer in the resultant block of data by a fixed number of places p.