Methods and systems for rate-distortion optimized quantization of transform blocks in block transform video coding

1. A computer-implemented method for rate-distortion optimized quantization comprising:

determining a distortion corresponding to each level at one or more processors;

determining a number of bits required to encode a level by a table look-up using a plurality of entropy code tables, wherein designing the plurality of entropy code tables comprises executing computer executable code operable to cause one or more processors to perform a process comprising:

receiving an initial probability distribution;

inputting at least one level value into an entropy encoder initialized with the initial probability distribution;

receiving an output codeword from the encoder;

forming an entropy code table from the output codeword; and

indexing a different table out of K tables according to a predetermined value; and

selecting the level that minimizes a rate-distortion cost composed of the distortion and the bits.

2. The method of claim 1 , wherein, the plurality of entropy code tables are designed prior to the table look-up.

3. The method of claim 1 , wherein the predetermined value is the number of consecutive zero levels, r, before a nonzero coefficient in encoders that encode (r, l) where l is level for the current coefficient.

4. The method of claim 1 , wherein the predetermined value is a context number for a transform coefficient in encoders using CAVLC (Context-adaptive variable length coding).

5. The method of claim 1 , wherein the predetermined value is a component index in encoders using CABAC (Context-adaptive binary arithmetic coding).

6. The method of claim 1 , wherein the entropy code tables are designed offline and quantization is performed by a simple table look up with one of the K tables.

7. A computer-implemented method for rate-distortion optimized quantization comprising:

determining a distortion corresponding to each level at a processor;

determining a number of bits required to encode a level at a processor, comprising:

receiving a set of current probability distributions;

converting a quantization level into a series of bits;

inputting a current bit into an entropy encoder with the set of current probability distributions;

updating the set of current probability distributions according to the current bit processed;

determining if the current bit is the last bit forming the quantization level; and

receiving an output codeword from the encoder; and

selecting the level that minimizes a rate-distortion cost composed of the distortion and the bits.

8. The method of claim 7 , further comprising:

repeating the steps of inputting and updating until the current bit is the last bit.