Data Compression VLC functions

Variable length coding (VLC) is a data compression method that uses statistical modeling to define which values occur more frequently than others to build tables for subsequent encoding and decoding operations. Data in the bitstream is encoded with VLC table so that the shortest codes correspond to the most frequent values and the longer codes correspond to the less frequent values. Intel IPP functions use the structure IppsVLCTable for storing the VLC table:

struct VLCTable_32s { Ipp32s value, Ipp32s code, Ipp32s length; } typedef struct VLCTable_32s IppsVLCTable_32s

Here

value - the current code,

code - the actual bit code for the value,

length - the bit length of the value.

The value can be both positive and negative. The code denotes the length least significant bits in binary representation of the code value. Thus, valid lengths are within the range of 0 to 32. Note that you are responsible for specifying correct tables with prefix codes for values specified in the value field of the IppsVLCTable structure.

• VLCEncodeInitAlloc
  Allocates memory and initializes the VLC encoder structure.
• VLCEncodeFree
  Frees memory allocated for the VLC encoder structure.
• VLCEncodeInit
  Initializes the VLC encoder structure.
• VLCEncodeGetSize
  Computes the size of the VLC encoder structure.
• VLCEncodeBlock
  Performs VLC encoding of a block of data.
• VLCEncodeOne
  Performs VLC encoding of a single element.
• VLCCountBits
  Computes a number of bits required to encode the source block.
• VLCDecodeInitAlloc
  Allocates memory and initializes the VLC decoder structure.
• VLCDecodeFree
  Frees memory allocated for the VLC decoder structure.
• VLCDecodeInit
  Initializes the VLC decoder structure.
• VLCDecodeGetSize
  Computes the size of the VLC decoder structure.
• VLCDecodeBlock
  Decodes a block of VLC encoded data.
• VLCDecodeOne
  Decodes a single VLC encoded element.
• Example of Using VLC Coding Functions
  
• VLCDecodeUTupleInitAlloc
  Allocates memory and initializes the VLCDecodeUTuple structure based on the input parameters.
• VLCDecodeUTupleFree
  Frees memory allocated for the VLC decoder structure.
• VLCDecodeUTupleInit
  Initializes the VLCDecodeUTuple structure.
• VLCDecodeUTupleGetSize
  Computes the size of the VLCDecodUTuple structure.
• VLCDecodeUTupleBlock
  Decodes a block of VLC encoded data.
• VLCDecodeUTupleOne
  Decodes a single VLC encoded tuple.

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