freqt

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2011-08-15
2013-05-20
  • Akira Tamamori

    Akira Tamamori - 2011-08-15

    This is a question about 'freqt' command from anonymous.

    Dear Prof. Tamamori,
    I have two small questions regarding the latest version of SPTK,
    (I know this should be asked in the forum but I have seen it is abondoned)
    in the file
    "_freqt.c"
    in the function
    freqt
    regarding the "for" loop towards the end of the function :

    I have two questions :

    1) shoudn't there be a minus instead of a plus before the "a" inside the loop
    my reason for asking : I understand this is the implementation of
    the allpass transfer function the warps the phase, but the interpretation of
    z^-1-alpha/1-alpha z^-1
    should be
    y = x + alpha(y - x)
    and in your code it seems you put a minus before the alpha

    2) what is the reason for multiplying
    b*d
    where
    b=1-alpha^2
    when the value of g is computed
    shouldn't b=1 ?

     
  • Akira Tamamori

    Akira Tamamori - 2011-08-15

    Thank you for your questions.

    This is the reference paper about 'freqt' command.

    A. V. Oppenheim and D. H. Johnson, “Discrete representation of signals,”
    in Proc. IEEE, vol.60, no. 7, pp.681-691, June 1972.

    In this paper, the algorithms about 'freqt' is described.
    you can download it from IEEE Xplore.

    Best regards,
    Akira Tamamori

     

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