Synthesizer Class - renderNextBlock - App crash

General JUCE discussion
1

Hi Everyone,

I'm trying to get a synthesiser (sampler) to play a sampled piano note.

I seems that all works except the "renderNextBlock"-Method. The method throws following error:

juce_AudioSampleBuffer.h

Type* getWritePointer (int channelNumber, int sampleIndex)
jassert (isPositiveAndBelow (sampleIndex, size));

My first step is to create a component which is a subclass of " AudioAppComponent". I specify the number of input and output channels, initialize my synth with SamplerVoice and SamplerSound and set the current playback rate for the synth.

My next step was to create a MidiBuffer:

MidiMessage note  = MidiMessage::noteOn(1, 64, (uint8)127);

midiBuffer = new MidiBuffer();

midiBuffer->addEvent(note, 0);

The error is thrown in the "getNextAudioBlock"-Method. Here I do the following:

bufferToFill.clearActiveBufferRegion();

bufferToFill.buffer->clear();

synth->renderNextBlock(*bufferToFill.buffer, *midiBuffer, counter, bufferToFill.numSamples);
counter += bufferToFill.numSamples;

I use the "counter"-Member to track the offset for the synth-rendering.

All I get is a very short sound (I think the first 512 bytes from the first block) and then the error is thrown. If I replace the counter with "0" then my app doesn't crash but I'm hearing a shuttering sound (again the 512 bytes in a loop?).

I have read the synthesizer class reference again and again but I can't figure out where the problem is. 

I think the solution is very obvious but I don't get it. Would be nice if somebody can push me in the right direction. wink

Thanks!

2

Could you use the "Styles" pulldown to format code blocks?

 It would make your question much easier to parse.

e.g.

//juce_AudioSampleBuffer.h
Type* getWritePointer (int channelNumber, int sampleIndex) 
{
    :
    jassert (isPositiveAndBelow (sampleIndex, size));).

 Much nicer!

Have you checked what size is? Maybe it is 0, which would suggest there is some problem with loading your sound WAV into a buffer.

π

3

The size of my write buffer ist 512 bytes and starts always from index 0. And the method getWritePointer tries to get the write pointer from startIndex 512. 

 

4

Solved the problem.

The startSample for the audio buffer "bufferToFill" has to be 0.
Every "getNextAudioBlock" cycle I send a midi buffer with a message timestamp of 0.
And that was the issue. I have to send the buffer only once.

Thank!