Subject: Re: [linux-audio-dev] Pitchshift/Timestretch project..
From: Cournapeau David (cournape_AT_enst.fr)
Date: Tue Apr 06 2004 - 10:09:00 EEST
Christian Schoenebeck wrote:
>Es geschah am Montag, 5. April 2004 23:33 als Erik de Castro Lopo schrieb:
>
>
>>Well me. I've been working on this since the start of the year, but
>>been thinking about the problem for over 10 years.
>>
>>
>
>Which brings me to the question: how old are you? :P
>
>Just kidding, But I also planned to do some research on pitchshifting in
>conjunction with formant correction. If anybody has good material about that,
>don't hide it! Seems this field screams for getting elaborated.
>
>
>
>
I have already played with that stuff, only on the pure dsp side. For
time scaling, one of the best approach, I think, is to use a phase
vocoder with phase locking and adaptative frame size. The trick it to
detect correctly the transients in the file: when there is a transient,
choose a small frame (ie ~256 samples_AT_44100), when there is no
transient, choose a bigger frame.
Check for example the article of dolson and Laroche on phase locked
phase vocoder
4 *Improved phase vocoder time-scale modification of audio*
/Laroche, J.; Dolson, M.;/
Speech and Audio Processing, IEEE Transactions on ,Volume: 7 , Issue: 3
, May 1999
Pages:323 - 332
About time transient detection, I happened to do my DSP master-like in