[PD] up-down saw-wave

[Martin Peach]

Hans-Christoph Steiner wrote:
>
> On Nov 19, 2006, at 11:19 AM, derek holzer wrote:
>
>> hard off wrote:
>>> ah thanks.  a triangle oscillator is exactly what i need. cheers.
>>
>> Keep in mind that none of these are anti-aliased AFAIK, so you could 
>> easily get aliased harmonic frequencies. There's a few threads in the 
>> archive about avoiding this. My personal solution is to use [plugin~] 
>> with the BLOP LADSPA oscillator plugins.
>
> I wonder how hard it would be to implement the BLOP LADSPA algorithm 
> in Pd, so that there would be native anti-aliased oscilators.  Its 
> something that Pd sorely needs.

I made the [sqosc~] object to do band-limited pulse-width modulated 
square wave.
(http://pure-data.cvs.sourceforge.net/pure-data/externals/mrpeach/sqosc~/)
You can choose the bandwidth at creation time. It wouldn't be too hard 
to make it do triangle waves as well. Sine waves are naturally 
bandlimited if you keep them below 1/2 sampling frequency.
Running everything through a few [lop~]s should work as well unless the 
aliasing has already been introduced, by a table lookup with a too-large 
stride, or something like that.
Martin