[Csnd] FM - Running at different sampling rates
| Date | 2013-07-08 16:14 |
| From | lppier |
| Subject | [Csnd] FM - Running at different sampling rates |
Hi, I have a question on signals, I think. I'm trying to do phase modulation in the following way. I realised that for the high notes, when I run the csd at 44100, there seems to be something there that causes ear fatigue, at least to me. When I double it to 88200, the same high notes seem to be rounder. I'm wondering if it's my imagination. Is this what is known as aliasing? amodsig oscili a1*(avel+istrength)*avibamp, kcps*imodulator1*kvibfreq, imodwave acarphas phasor kcps * icarrier asine tablei acarphas + amodsig , icarwave, 1, 0, 1 What are my options if I don't want to run the csd at 88200? (to save on cpu) Thanks. -- View this message in context: http://csound.1045644.n5.nabble.com/FM-Running-at-different-sampling-rates-tp5725269.html Sent from the Csound - General mailing list archive at Nabble.com. |
| Date | 2013-07-08 16:32 |
| From | Justin Smith |
| Subject | Re: [Csnd] FM - Running at different sampling rates |
This is likely frequency foldover. You could try using a different version of your imodwave table, which has less high frequency content. Sometimes it is helpful to have a few tables to choose from, based on base frequency, and you use a table with less and less high frequency energy for higher notes (so your frequencies don't fold over).
On Mon, Jul 8, 2013 at 8:14 AM, lppier <madstrum@gmail.com> wrote: Hi, |
| Date | 2013-07-08 16:52 |
| From | Aidan Collins |
| Subject | Re: [Csnd] FM - Running at different sampling rates |
I believe that is an example of aliasing, where the higher frequency harmonics of your signal are higher than the nyquist frequency (the highest frequency that can be represented by that sampling rate), so they're represented in the signal as a different frequency .
You could always try bandlimiting your signal to the nyquist frequency (sampling rate / 2) before output and then you shouldn't have that problem. Aidan On Mon, Jul 8, 2013 at 11:32 AM, Justin Smith <noisesmith@gmail.com> wrote:
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| Date | 2013-07-08 17:01 |
| From | Justin Smith |
| Subject | Re: [Csnd] FM - Running at different sampling rates |
bandlimiting the signal before output does not work because the frequencies have already folded over to a lower frequency - you need a bandlimited way of producing the waveforms so the foldover never happens
On Mon, Jul 8, 2013 at 8:52 AM, Aidan Collins <mr.aidan.collins@gmail.com> wrote:
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| Date | 2013-07-08 17:52 |
| From | Aidan Collins |
| Subject | Re: [Csnd] FM - Running at different sampling rates |
I did not realize that, thanks for the pointer.
Are there any oscil type opcodes that bandlimit internally? On Mon, Jul 8, 2013 at 12:01 PM, Justin Smith <noisesmith@gmail.com> wrote:
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