Aliasing?

[andrei s]

Hello!

Does HISE distort sound?

Here are the screenshots with the same sample played in DAW independently, through Kontakt and through HISE.

Project sample rate 44100 Hz:

Sample

Kontakt

HISE

Project sample rate 96000 Hz:

Sample

Kontakt

HISE

The sample itself has a sampling rate of 48000 Hz and 24 bit.

When the pitch of the sample is lowered in HISE VSTi, the distortions become more pronounced and are very noticeable to the ear.

Why it happens and how can this be fixed?

[ustk]

@problema So I imagine the sample is played as it is, no FX, filter or envelope of any kind right? Sorry if it seems obvious but it worth to ask...

[andrei s]

@ustk yes, it's a dry signal without any FX, filter or envelope.

[Lindon]

@problema

What happens when you set the project to this sample rate:

The sample itself has a sampling rate of 48000 kHz and 24 bit.

[ustk]

Yeah the same question I was about to ask...

Since it's the plugin job to provide the samplerate the DAW is asking for, there's a conversion algorithm when the project SR isn't matching the samples SR. In the case of Hise, I guess it uses the Langrange interpolator from JUCE. Kontakt might use a different/better interpolator, and the DAW again a different one (when you just place the sample on a track)... Has the sample on the DAW track been converted or is it playing at the original SR? (so a different pitch)

Running the DAW project to the exact SR and bit depth will cancel out any conversion process in the chain (I hope so), so no conversion noise should appear (be it from interpolation or decimation).
If there is still some noise though, it might come from somewhere else than the SR conversion...

[andrei s]

@Lindon

When project sample rate is 48000 and sample isn't pitched down HISE sounds without any distortion:

But when the midi note with the same sample is pitched down to 6 semitones HISE shows this:

Kontakt with same pitched down note:

Reaper:

[d.healey]

@problema Which pitch shifting algorithm are you using in Reaper?

[andrei s]

@d-healey élastique 3.3.3 Efficient

[d.healey]

@problema Try something like soundtouch, that's probably closer to what HISE is using.

[andrei s]

@ustk the sample on the DAW track have a 48000 Hz sample rate and 24 bit depth, it's the same sample that loaded in HISE and Kontakt

[Christoph Hart]

The sampler in HISE is using plain ol’ linear interpolation which is the best compromise between quality and performance IMHO - I never had the urge to implement a more complex algorithm.

[ustk]

@Christoph-Hart Well, if it becomes audibly negative, it might worth the overhead of a better interpolation, or at least a pre-processor to choose. Maybe even a dynamic selection at runtime if possible ;)

[Frankbeat]

To my old machine, it is pretty comfortable to have linear interpolation, I guess

But I can relate to @ustk it'd be nice to have options.

[Frankbeat]

I’m running a sample based Synth with 44.1kHz/16 bit (internally obersampling 4x) and I don’t hear aliasing though when I look at the waveform I can see it is distorted a little. So, what’s your experience? Where does it become audible to you?

I have to add that I use to not transpose a sample by more than +/-2 semitones with this synth so I can’t tell how it sounds with more than that