pitch shifting algorm

I would like to know if anyone is familiar with this technique (pitch shifting, ie, speeding up/slowing down playback rates of mp3s). I would like to know how it is done. If anyone has any information/book titles or whatever, it would be highly appreciated.



Stefan


Comments

  • : I would like to know if anyone is familiar with this technique (pitch shifting, ie, speeding up/slowing down playback rates of mp3s). I would like to know how it is done. If anyone has any information/book titles or whatever, it would be highly appreciated.

    :

    : Stefan



    if you mean shifting the pitch but not the speed then this is the basic idea:



    ok, imagine you split a 10 second sample into 100 even 'pieces', right?



    now take each piece, copy it and then paste it next to itself. so



    ABCDEFG



    becomes



    AABBCCDDEEFFGG



    i.e. twice as long.

    now if you play that the pitch will appear unchanged, but the speed will be half.



    so if you played it an octave higher, the speed would appear unchanged but the pitch an octave up.



    the quality of the pitch-shift depends greatly on what the size of the 'pieces' you take are.



    as long as they're wavelength is longer than is audible to the human ear you should be ok. if you do them at 100hz or something (the 10 per second example is 10hz) then you'll probably get a bass hum or something. which is undesirable.



    now that you have the basics i.e. how to shift it up an octave, you should pretty easily be able to apply it to reaching any pitch you want.



    ok, later.

    bye






  • : : I would like to know if anyone is familiar with this technique (pitch shifting, ie, speeding up/slowing down playback rates of mp3s). I would like to know how it is done. If anyone has any information/book titles or whatever, it would be highly appreciated.

    : :

    : : Stefan

    :

    : if you mean shifting the pitch but not the speed then this is the basic idea:

    :

    : ok, imagine you split a 10 second sample into 100 even 'pieces', right?

    :

    : now take each piece, copy it and then paste it next to itself. so

    :

    : ABCDEFG

    :

    : becomes

    :

    : AABBCCDDEEFFGG

    :

    : i.e. twice as long.

    : now if you play that the pitch will appear unchanged, but the speed will be half.

    :

    : so if you played it an octave higher, the speed would appear unchanged but the pitch an octave up.

    :

    : the quality of the pitch-shift depends greatly on what the size of the 'pieces' you take are.

    :

    : as long as they're wavelength is longer than is audible to the human ear you should be ok. if you do them at 100hz or something (the 10 per second example is 10hz) then you'll probably get a bass hum or something. which is undesirable.

    :

    : now that you have the basics i.e. how to shift it up an octave, you should pretty easily be able to apply it to reaching any pitch you want.

    :

    : ok, later.

    : bye

    :

    :

    :



    Thanks a lot both of u this helped me loads, but something seems wrong, wouldn't you need to use some interpolation to avoid the clipping when slicing up samples?



    Peace out


  • Yeah, but what happens if you want to change it without changing the speed ?!?! Not that easy ...


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