On 03/11/2013, robert bristow-johnson <r...@audioimagination.com> wrote: > the point is that if you upsample, then soft-clip, then LPF, and finally > downsample back to the original sample rate, you need only prevent the > aliases from getting back into your *original* baseband. it doesn't > matter that *some* of the images have folded over and become > non-harmonic aliases, just as long as they do not survive into the final > output. > > i don't know how better to explain it, without a drawing.
Oh, hang on, I think I get it. So an nth-order polynomial expands the spectrum produced by n times. Let's say a 3rd-order poly turns a bandwidth of 22kHz into one of 66kHz. What you're saying is that you only need to upsample a 44.1kHz signal by 2, do the shaping, and run a low pass at the original 22kHz - because whilst everything above 44.1kHz will fold back, it'll only fold back down to frequencies above 22.3kHz and leave your original 0-22kHz bandwidth alone, right? (But, say, a 4th-order poly would require upsampling by more than 2, otherwise it'd produce harmonics up to 88kHz, which would fold back into your desired bandwidth.) Have I understood properly? -- 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
