Samples Tuning

Audio Plugins
1

What's the best way of tuning a sample in SamplerSound? I'm using several SamplerSounds and I need to tune each one individually and in real time (both tune/finetune). I copied the SamplerSound/SamplerVoice classes and played a bit with them, changing the pitchRatio worked for all sounds (but every now and then it crashes in the interpolation). I guess I can use an array but still there will be problem in the interpolation, don't know why. 

I also tried changing the samplerate but everytime the sound stops and I need something in real time.

Thanks.

2

With a lot of caveats (see the comments) you can do something like this....

template <typename FloatType>

FloatType cubicInterpolation(const FloatType y0, const FloatType y1,

                             const FloatType y2, const FloatType y3,

                             const FloatType alpha)

{

    const FloatType alpha2 = alpha * alpha;


    const FloatType a0 = y3 - y2 - y0 + y1;

    const FloatType a1 = y0 - y1 - a0;

    const FloatType a2 = y2 - y0;

    const FloatType a3 = y1;

    

    return (a0 * alpha * alpha2) + (a1 * alpha2) + (a2 * alpha) + a3;

}

   
 /* This function is not efficient. */

    const float getSampleWithCubicInterpolation(int chan, double pos) {

        const int posFloor = pos;

        const float alpha = pos - posFloor;

        const float * sdata = channelData[chan];

        const int maxSamples = buffer->getNumSamples();


        if (posFloor == 0)

        {

            return sdata[0];

        }

        else

        if (posFloor >= (maxSamples - 3))

        {

            return sdata[maxSamples-1]; /* This is not right. */

        }

        else

        {

            return cubicInterpolation(sdata[posFloor-1], sdata[posFloor], sdata[posFloor+1], sdata[posFloor+2], alpha);

        }

    }
3

Thanks for the reply. I'm not really sure what I should do with that code. Should I replace the linear interpolation in the juce class? 

Also still trying to figure out the best way of handling this for multiple sounds.

4

Ah - maybe I"m solving a problem you've not got - that wasn't a useful reply from me.

So, to solve for samplerSound you need to control this calcuation: 

        pitchRatio = pow (2.0, (midiNoteNumber - sound->midiRootNote) / 12.0)

                        * sound->sourceSampleRate / getSampleRate();

I don't immediately see a way of doing that without re-writing portions of SamplerSound.  So perhaps take it as a template and make your own version. Which you've already done.  And it causes a crash when you modify pitchRatio.

Now there's a test immediately after the pitchRatio is used: 

            if (sourceSamplePosition > playingSound->length)

            {

                stopNote (false);

                break;

            }

Which should stop you reading past  the end of the buffer - the most likely reason for the crash.  Jules seems to have included some padding in the buffer to stop the edge condition crashing. 

I think you need to look into your crash with the debugger, and ignore my previous hasty reply!   Do you have valid values for pos, for example, when it crashes.

 

5

Oh! For some stupid reason I moved the lenght test BEFORE changing the pitchRatio. I didn't realize it. Thanks for the input.

I also solved the pitch for each sound using an array with something like this for the index: playingSound->getName().getIntValue()

So I'm basically using the sound name as index, not very elegant but it works.