W3C home > Mailing lists > Public > public-audio@w3.org > January to March 2017

Oscillator [square] suffer from severe alias

From: André Michelle <andre.michelle@audiotool.com>
Date: Sat, 4 Mar 2017 10:27:24 +0100
Message-Id: <BC174766-F9FE-4F6D-B9A7-422BC99CD580@audiotool.com>
To: Audio Working Group <public-audio@w3.org>
Hi all,

I am developing a bandlimited oscillator for our synthesiser in www.audiotool.com and could not get it quite right. I tested the web-audio-api as a reference and voila: There is alias as well.

I downloaded the sources from here to reimplement it in Java to find the problem.

My port produces the exact same amount of alias at the same frequencies. The code in "PeriodicWave::waveDataForFundamentalFrequency" obviously chooses a table with too much harmonics but I could not find a fix and an obvious error. I could however replace the look-up code for a test, that it always returns the tables with just a single harmonic (sine-wave) and the alias is gone. That means that the wavetable size is big enough and the linear interpolation is working well.

Any thoughts on this?

André Michelle
Received on Monday, 6 March 2017 10:24:13 UTC

This archive was generated by hypermail 2.3.1 : Monday, 6 March 2017 10:24:14 UTC