Adaptive Variable and Fixed Length Coding Functions

Transform coefficients coding proceeds in the following stages:

• Adaptive scanning of each 4x4 block of transform coefficients to identify the number of non-zero coefficients as a measure of the statistical variance of the block.

• Transform coefficients are dynamically partitioned into more significant bits and less significant bits (flexbits). The more significant bits are coded using entropy, or variable length coding (VLC), and the flexbits are coded using adoptive fixed length coding (FLC).

• VLCGetStateSize_JPEGXR
  Calculates the size of the VLC state structure.
• VLCInit_JPEGXR
  Initializes the VLC state structure.
• VLCAdapt_JPEGXR
  Adapts the VLC model.
• VLCScanSet_JPEGXR, VLCScanReset
  Sets or resets the VLC scan type.
• VLCScan4x4DC_JPEGXR
  Performs adaptive scanning of the DC coefficients.
• VLCEncode_JPEGXR
  Performs VLC encoding.
• VLCDecode_JPEGXR
  Performs VLC decoding.
• FLCEncode_JPEGXR
  Performs FLC encoding.
• FLCDecode_JPEGXR
  Performs FLC decoding.

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