Josep M Comajuncosas wrote:
> 
> Hi all,
> I recently saw the promotional prospectus of a low-cost PC sound card
> (called MaxiSound or so) and I was *really* disapointed with its specs.
> compared to Csound. Specifically, it is said to use a 3rd order
> polynomial scheme for wavetable interpolation, when Csound only accepts
> linear (1st order) interpolation.
> As you may agree this cannot be accepted ;-), I´d suggest at least 3 new
> 
> opcodes, called maybe
> oscilp
> tablep
> deltapp
> with an additional parameter to choose the polynomial degree used for
> interpolated readout.
> I´m not very sure about the improvement in the s/n ratio and in the
> frequency response in relation to the degree of the Lagrange
> interpolator. Maybe some of you have any clues. But it would be nice to
> implement such feature.

The problem is: does it improve the sound quality? How much does it cost in processing
speed?
My new SoundBlaster Live has an internal wavetable synthesizer who does 8 point
interpolation in realtime. Actually the sound quality is excellent. I don't know if it
depends of the interpolation algorithm or of the hardware analog converter.

Where is it possble to get the algorithm to implement 8 point interpolation? If I could
see an example of it I will implement it in Csound.


 
> Another question related to waveguide opcodes. Does deltapi (and delayw
> btw) accept fractional sample delay lengths (well, fractional 1/kr
> units) ? 

Yes it does.


> If not, is it expected to implement it soon? Otherwise it could
> be difficult to tune a delay line at a precise high frequency, esp. at
> low k-rates.
> This is specially noticeable when developing waveguide models.

The problem is that the first order filters that are implemented in the waveguide opcodes
don't use fractional delay, so the pitch of high notes is not precise.


-- 
Gabriel Maldonado