parameterChanged lose precision

General JUCE discussion
1

Hi,

I notice that when I call

state.getParameter("gain")->setValueNotifyingHost(gain); //where gain is 0.892857

when I’m in parameterChanged the value of newValue is truncated in 0.89

void GainProcessor::parameterChanged (const String& parameterID, float newValue)
{
    DBG("newValue " + String(newValue)); // this print 0.89
}

there’s something I’m missing? how to fix it ? I have a gain that goes from -100 to 48 db and in this way it has only stepped values (where for example I can set gain to 0.000 db but only to -0.320 db or to 0.800 db)

2

Maybe the truncation happens when converting from float to String?

Try

DBG("newValue " + String(newValue, 10)); // this print 0.89

Now you get 10 decimal points

1 Like
3

really thank you for the trick, I think the problem is that between setValueNotifyingHost and parameterChanged the number changed… Debugging:

        state.getParameter("gainL")->setValueNotifyingHost(gain); // here value is 0.8928571343

After is called:

void parameterValueChanged (int, float) override
    {
        const auto newValue = denormalise (parameter.getValue()); // here it become 0.8899999857
        [...]        
    }
4

Not every value can be represented as 32-bit float. The difference is small enough to be imperceptible.

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5

but in a range of “-100” - "48 " it becomes significant…

6

No, it will not be significant. It will be off by something like 0.00001. Doesn’t matter at all.

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7

The interval is defined in the parameter itself. How are you defining your parameter?

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8

I init it with this lines of code:

state( *this, nullptr, Identifier("GainProcessor"),
       { std::make_unique<AudioParameterFloat>(ParameterID { "gainL", 1 }, "gainL", 0.0f, 1.0f, 0.5f),
         std::make_unique<AudioParameterFloat>(ParameterID { "gainR", 2 }, "gainR", 0.0f, 1.0f, 0.5f) } )
9

That constructor for AudioParameterFloat is using the default precision which is 0.01f;

Use the constructor that takes a NormalisableRange:

static NormalisableRange<float> getGainRange()
{
    return { 0.f, 1.f, 0.0001f, 1.f};
}
std::make_unique<AudioParameterFloat>({ "gainL", 1 }, "gainL", getGainRange());
1 Like
10

… I’m an idiot sorry, I known about normalizable range, but I forgot it, sorry