Antialiasing- what's wrong with this method ?

[Olli Niemitalo]

I'd use doubled samplerate in the FM part and then downsample the
signal to the intended samplerate, using a halfband lowpass filter to
remove the above sr/2 frequencies. This pushes the limits where shit
happens to -1..1, compared to your -1/2..1/2.

-olli

On Thu, 15 Oct 1998, P-Tar wrote:

> Now, regarding my own problem: I'm working on a win95 based
> synth, using FM to generate audio that then goes into a filter.
> The FM is done using a sine wavetable (all generators thus are
> sine waves, a nod to my beloved dx7). In an attempt to antialias
> the FM-generated signal, I've tried to limit the variation of the
> index in the wavetable to 0.5 or -0.5 (I use a float index going
> 0..1 into the wavetable. From a theorical point of view, moving by
> increments of 0.5 generates frequencies of sr/2 which is the
> maximum frequency I want to get).