[Audacity-nyquist] Fwd: [Audacity-devel] moving clips when selected + crossfade

[Dominic M. <do...@au...>]

Can any of the Nyquist gurus help with this one?

Begin forwarded message:
> From: Mar...@ao...
> Date: October 7, 2006 2:22:44 PM PDT
> To: aud...@li...
> Subject: Re: [Audacity-devel] moving clips when selected + crossfade
> Reply-To: aud...@li...
>
> ...
>>> 2. working with windows you can use effects > fade  (in/out) *and*
> effects >
>>> crossfade (in/out). is there any  difference? and: users who like to
> create a
> ...
>
> I've never had chance/excuse to look at Nyquist before but I think  
> I can  see
> where the nasty click at the end of the fadein is coming from  
> (testing on a
> generated tone), and how to fix it, but I am not convinced it's the  
> way to  go.
>
> If I read the manual correctly at
> _http://www.cs.cmu.edu/~rbd/doc/nyquist/part6.html#index362_  
> (http://www.cs.cmu.edu/~rbd/doc/nyquist/part6.html#index362)
> ,  in crossfadein.ny
>  (ramp 1)
> generates a ramp with a length 1s and the sample rate of  *control- 
> srate*.
> This appears to be 2205Hz, although I don't see where  this is  
> set.  After
> further processing this signal is multiplied by the  audio, which  
> is at a
> different sampling rate (normally!), and so the processed  ramp is  
> up-sampled, leading
> to a nasty on the last 20 samples (if the audio is  at 44100Hz).
>
> One fix is to do, in crossfadein.ny could read
> (control-srate-abs *sound-srate* (setq a (diff (const 1) (ramp  1))))
> (control-srate-abs *sound-srate* (mult s (diff (const 1) (mult a   
> a))))
> or
> (set-control-srate *sound-srate*)
> (setq a (diff (const 1) (ramp  1)))
> (mult s (diff (const 1) (mult a a)))
>
> Am I right here?  Any nyquist experts out there?
> Martyn