On Tue, Apr 10, 2012 at 12:25 AM, Julian Schmidt <julian_schm...@chipmusik.de> wrote: > Am 09.04.2012 23:22, schrieb Olli Niemitalo: > >> On Mon, Apr 9, 2012 at 11:32 PM, Julian Schmidt >> <julian_schm...@chipmusik.de> wrote: >>> >>> I really think it is an aliasing problem. >>> but not due to the wrong wavetable content, but due to a cheap audio >>> codec with poor filters. >>> [...] >>> even when i output a single 440hz sine i get harmonics starting at -48db >>> up to nyquist and beyond. >> >> Lemme guess your wavetable size is 256? That's the amount of >> distortion that would be expected from using "no interpolation". If >> that's what you have then the codec is not at fault. > > i use code similar to what RBJ has posted with linear interpolation > (although with a tablesize of 256 at the moment).
Okay, that should give a -96 dB spectral distortion floor for a single-sinusoid wavetable, compared to your -48 dB. If the codec is causing all that then it should also show up if you use a sin() function instead of playing back the wavetable. I'm just a bit skeptical because the specs of the codec don't seem that bad. -olli -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
