AudioProcessorGraph not outputing audio after upgrade from 5.4.2 to 5.4.5 (SOLVED)

I’m having issues after upgrading JUCE from5.4.2 to 5.4.5. Specifically here is what is happening:

We use an AudioProcessorGraph with Nodes, as described in this tutorial:

We have some unit tests, that expect to read the audio and midi coming out of the plugin, the most basic of which is something like this:

TEST_F(APlugin, ProducesAudioWhenAudioIsInput)


    int num_frames = (mPlugin->calcLatencySamples() / mPlugin->getBlockSize()) + 1;    // Enough frames to get over latency hump

    for (int frame = 0; frame < num_frames; ++frame)



        mPlugin->processBlock(mBuffer, mMidiBuffer);


    // Now assert that data is coming out by taking the max of samples

    float maxSample = mBuffer.getMagnitude(0, mBuffer.getNumSamples());

    ASSERT_GT(maxSample, 0.001f);   < — FAILS, maxSample is always 0


Basically, just fill a buffer with data, and expect the data comes out. Simple right?

In 5.4.2 this works as intended, both audio and midi sent into the plugin, come out of the plugin unchanged as we expect in this case.

However, in 5.4.4 and 5.4.5 we no longer have this occurring. At some point, after our nodes are done processing this buffer is cleared. Specifically in this line in juce_AudioProcessorGraph.cpp:


            const Context context { renderingBuffer.getArrayOfWritePointers(), midiBuffers.begin(), audioPlayHead, numSamples };

            for (auto* op : renderOps)

                op->perform (context);


        for (int i = 0; i < buffer.getNumChannels(); ++i)

            buffer.copyFrom (i, 0, currentAudioOutputBuffer, i, 0, numSamples);     <— HERE!!!

In inspecting this further, in 5.4.2 the currentAudioOutputBuffer was filled at some point, in 5.4.5 it is not. The filling happens after our nodes are done, in the audioOutputNode, but in 5.4.5 we never get there.

It appears as if our connections being set up correctly, and all error codes are being checked along the way, the only difference is changing to unique pointers when the input/output nodes are initialized, due to the SDK change:

    mAudioInputNode = this->addNode(


            AudioProcessorGraph::NodeID((uint32_t) - 1));

    mAudioOutputNode = this->addNode(


            AudioProcessorGraph::NodeID((uint32_t) - 2));

    mMidiInputNode = this->addNode(


            AudioProcessorGraph::NodeID((uint32_t) - 3));

    mMidiOutputNode = this->addNode(


            AudioProcessorGraph::NodeID((uint32_t) - 4));

Any ideas on what could have changed that we are missing?

Can we safely assume you mean 5.4.2 to 5.4.5?

1 Like

Thanks for the sanity check. Yes!! Just edited the original

After more investigation, it seems the breaking change happened in 5.4.3

Alright, so this ended up being on our end. In the past we patched this issue out of 5.4.2, so I wasn’t comparing apples to apples.

This is the patch that ended up fixing things:

void AudioProcessorGraph::topologyChanged()

	if (isPrepared.get() != 0)
		if (isNonRealtime() && MessageManager::getInstance()->isThisTheMessageThread())

As of this commit JUCE is now doing something similar. Hopefully your custom patch is no longer required.

1 Like

The current state is definitely broken for me, after updated a tip from half a year.
No audio output, some nodes doesn’t get called even if are connected.
I will try to find out what happened, in the meantime does anybody experience oddities as well?

@chkn did you try patching in that fix I mentioned above? Our issue was only with nonrealtime processing of the audio processor graph. Things like unit tests were failing!

If that doesn’t sound like your situation, I’d maybe recommend you start a new thread, just for visibility :slight_smile:

Thanks for the feedback!
Yes after investigation if found that our bug was introduced through the extensive channel layout option a few yeas ago. I guess its not a juce bug - otherwise i will report. Thanks!