[music-dsp] Real Time Pitch Scaling?

Ian Lewis ILewis at acclaim.com
Fri Jul 27 12:36:15 EDT 2001


I'm no DJ, but doesn't beat matching have more to do with time scaling than
pitch scaling?
Ian

> -----Original Message-----
> From: Richard Dobson [mailto:RWD at cableinet.co.uk]
> Sent: Friday, July 27, 2001 6:10 AM
> To: music-dsp at shoko.calarts.edu
> Subject: Re: [music-dsp] Real Time Pitch Scaling?
> 
> 
> The bass-drum smearing is a problem (as generally with pvoc), but a
> better shifting algorithm may much improve that, in time. 
> Throwing large
> FFT sizes and/or high analysis rates can do much to minimise smearing,
> if you have the CPU power. There are no clicks or artefacts when
> changing pitch; under SONAR, with low latency, I can get a smooth
> portamento. Smoothness depends ultimately on the analysis rate, which
> typically may have a granularity of 160 samples, so some audible
> stepping cannot be totally eliminated. I will have a go at making some
> example files; I had been thinking of doing that already, it 
> is just a 
> matter of organizing it, and getting suitable samples.
> 
> I also have a standalone version of PVStream that just reads a mono
> soundfile and renders it MediaPlayer-style, with pvoc 
> processing; it was
> actually the prototype for the plugin version. I will post 
> that as well,
> as a self-contained demo; perhaps that will be even better 
> than posting
> sound examples? It has one other token feature; you can 'freeze' the
> file at any point and render one spectral frame, while 
> playing with the
> effect controls. But the playback code is fairly naive (plaim MME) and
> not especially robust, as it was only implemented quickly as a
> proof-of-concept.
> 
> As for beat-mixing; probably it is suitable, but it is not a creative
> domain I have much knowledge of, so I hesitate to give a hard 
> assertion
> about that. But the current implementation is nothing more 
> than a single
> slider to change pitch.
> 
> 
> 
> 
> Richard Dobson
> 
> 
> 
> Benno Senoner wrote:
> > 
> > On Friday 27 July 2001 03:35, Richard Dobson wrote:
> > > I recently posted my PVSTREAM demonstration DirectX plugin on my
> > (...)>
> > > The PVSTREAM pitch shifter offers up to +- one octave, 
> and needs either
> > > FFT = 1024, overlap = 160 samps, or FFT = 2048, to get 
> reasonably clean
> > > transposition over the whole range. It is not a 
> sophisticated algorithm,
> > > but IMHO works remarkably well nevertheless.
> > 
> > Interesting.
> > Could you please post some short mp3s with audio examples of
> > stuff processed with you pitch shifter ?
> > (without requiring people to setup a VST enviroment in 
> order to hear how it
> > sounds)
> > 
> > Eg it would be cool if you could post a voice clip at 
> speeds: original, -20%
> > , +20%
> > and a regular song (with drums) at speeds: original , -20% , +20%
> > 
> > I was just wondering if your pitchshifter would be suitable 
> to perform
> > beat-mixing of songs by using mp3s/wavs as sources while 
> adjusting the song's
> > BPM in order to get beat-accurate mixing.
> > Well , normal turntables permit adjustments of only +/-8% 
> or so but with
> > pitchshifting +/-20% would be quite useful while being able 
> to retian a good
> > soundquality (without bassdrum smearing, clicks or other 
> nasty artifacts when
> > shifting)
> > 
> > Thoughts ?
> > 
> > cheers,
> > Benno.
> > 
> > >
> > > you can find PVStream via:
> > >
> > > http://www.bath.ac.uk/~masrwd/pvplugs.html
> > >
> > >
> > > Richard Dobson
> > >
> > >
> > 
> > dupswapdrop -- the music-dsp mailing list and website: 
> subscription info,
> > FAQ, source code archive, list archive, book reviews, dsp links
> > http://shoko.calarts.edu/musicdsp/
> 
> -- 
> Test your DAW with my Soundcard Attrition Page!
> http://www.bath.ac.uk/~masrwd (LU: 3rd July 2000)
> CDP: http://www.bath.ac.uk/~masjpf/CDP/CDP.htm (LU: 23rd 
> February 2000)
> 
> dupswapdrop -- the music-dsp mailing list and website: 
> subscription info,
> FAQ, source code archive, list archive, book reviews, dsp links
> http://shoko.calarts.edu/musicdsp/
> 

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