wiki:ShmDocFilterFiles
Last modified 14 years ago Last modified on 01/23/2009 10:37:41 AM

Format of filter files

The filter files are line oriented, that means there is one information entry per line. Blank lines are not allowed! The format of the filter files is as follows:

FFT filter

  • All lines at the beginning of the file starting with exclamation sign ! are comments and ignored by the program.
  • The first data line is a magic number and must be 1357913578
  • The next data line contains the number 1, which is an ID for FFT filters.
  • Normalization value (real number), which is multiplied to the output samples of the filter.
  • Number of zeros z (integer)
  • z lines following with one zero each in the format (<real-part>,<imag-part>). Both parts of a complex conjugate pair must be specified.
  • Number of poles p
  • p lines following with one pole each in the same format as zeros.

Example of an FFT filter file.

Recursive filters

  • All lines at the beginning of the file starting with exclamation sign ! are comments and ignored by the program.
  • The first data line is a magic number and must be 1357913578.
  • The next data line contains the number 3, which is an ID for recursive filters.
  • Sample rate for which this file is valid (real number)
  • Normalization value (real number), which is multiplied to the output samples of the filter.
  • Number of numerator coefficients n (integer)
  • n lines following, one coefficient (real number) in each.
  • Number of denominator coefficients d (integer)
  • d lines following, one coefficient per line.
  • Optional following other stages of the filter, new stage indicated by a line containing a single @.
  • Additional stages are repeating the entries 'ID number 3' until denominator coefficients.

Example of a recursive filter file.

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