Fix for issue #3816 - FM or heavy PM in TripleOscillator makes output…#5651
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…tputs odd for some target waveforms. The internal waveforms of the class Oscillator produces the wrong amplitude when the input is a negative phase. When doing PM or FM, negative phases may occur. When a negative phase is e.g. passed to the the saw sample, it produces values less than -1.0, hence going out of range. Converted all fraction calls to absFraction calls. Removed the +2 in the function Oscillator::recalcPhase. The comment here was that it was needed to avoid negative phases in case of PM. But by converting fraction to absFraction in the waveforms, negative phases are not an issue anymore. On top of that the m_phase variable gains about 2 extra bits in precision. As side effect of that, it improves the behaviour of the issue LMMS#2047 - TripleOscillator: Oscillators are getting out of sync. Though I did not investigate it thoroughly over different notes and samplerates. Add documentation to the fraction and absFraction functions in lmms_math.h as it was not immediately clear by the name what the functions do. Correct the implementation of the functions in case the flag __INTEL_COMPILER is set. (floorf rounds always down).
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PhysSong
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Sep 10, 2020
Spekular
approved these changes
Sep 10, 2020
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Code looks good, and I approve of the changes in principle, but what effect does this have on existing presets and projects? TripleOscillator is one of the more commonly used synths in LMMS, so we don't want to change its behaviour too much. |
Contributor
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FYI - The fix will affect only the sound when:
The resulting sound will be less distorted compared to before. |
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It's probably fine then, since turning the volume of the modulating oscillator up high tends to produce objectionable noise anyway. I checked all the built-in presets and couldn't notice any difference between this PR and 1.2.2, so I'm happy with this. |
DomClark
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Sep 10, 2020
sdasda7777
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Jun 28, 2022
…tputs odd for some target waveforms. (LMMS#5651) The internal waveforms of the class Oscillator produces the wrong amplitude when the input is a negative phase. When doing PM or FM, negative phases may occur. When a negative phase is e.g. passed to the the saw sample, it produces values less than -1.0, hence going out of range. Converted all fraction calls to absFraction calls. Removed the +2 in the function Oscillator::recalcPhase. The comment here was that it was needed to avoid negative phases in case of PM. But by converting fraction to absFraction in the waveforms, negative phases are not an issue anymore. On top of that the m_phase variable gains about 2 extra bits in precision. As side effect of that, it improves the behaviour of the issue LMMS#2047 - TripleOscillator: Oscillators are getting out of sync. Though I did not investigate it thoroughly over different notes and samplerates. Add documentation to the fraction and absFraction functions in lmms_math.h as it was not immediately clear by the name what the functions do. Correct the implementation of the functions in case the flag __INTEL_COMPILER is set. (floorf rounds always down).
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…s odd for some target waveforms.
The internal waveforms of the class Oscillator produces the wrong amplitude when the input is a
negative phase. When doing PM or FM, negative phases may occur. When a negative phase is e.g. passed
to the the saw sample, it produces values less than -1.0, hence going out of range.
Converted all fraction calls to absFraction calls.
Removed the +2 in the function Oscillator::recalcPhase. The comment here was that it was needed to avoid
negative phases in case of PM. But by converting fraction to absFraction in the waveforms, negative phases
are not an issue anymore. On top of that the m_phase variable gains about 2 extra bits in precision.
As side effect of that, it improves the behaviour of the issue #2047 - TripleOscillator: Oscillators are getting out of sync.
Though I did not investigate it thoroughly over different notes and samplerates.
Add documentation to the fraction and absFraction functions in lmms_math.h as it was not immediately clear by the name what the
functions do. Correct the implementation of the functions in case the flag __INTEL_COMPILER is set. (floorf rounds always down).