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Fix VST3 effect plugins rendering dry audio on Windows #476

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Fix VST3 effect plugins rendering dry audio on Windows #476

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6 changes: 5 additions & 1 deletion pedalboard/ExternalPlugin.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1137,7 +1137,11 @@ class ExternalPlugin : public AbstractExternalPlugin {
setNumChannels(spec.numChannels);
}

pluginInstance->setNonRealtime(true);
// Some VST3 effects behave differently, or pass audio through
// unchanged, when the host forces offline rendering mode.
// Use realtime mode for normal processing so effect plugins behave
// consistently across platforms, especially on Windows.
pluginInstance->setNonRealtime(false);
pluginInstance->prepareToPlay(spec.sampleRate, spec.maximumBlockSize);

lastSpec = spec;
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18 changes: 18 additions & 0 deletions tests/test_external_plugins.py
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Expand Up @@ -1005,6 +1005,24 @@ def test_external_plugin_latency_compensation(buffer_size: int, oversampling: in
np.testing.assert_allclose(output, noise, atol=0.05)


@pytest.mark.skipif(not plugin_named("CHOWTapeModel"), reason="Missing CHOWTapeModel plugin.")
@pytest.mark.parametrize("buffer_size", [16, 65536])
def test_external_effect_plugin_changes_audio(buffer_size: int):
"""
Regression test for VST3 effects that expose parameters successfully but
still render dry audio instead of applying processing.
"""
sample_rate = 48000
noise = np.random.rand(sample_rate).astype(np.float32) * 2.0 - 1.0

plugin = load_test_plugin(plugin_named("CHOWTapeModel"), disable_caching=True)
plugin.bypass = False

output = plugin.process(noise, sample_rate, buffer_size=buffer_size)
assert output.shape == noise.shape
assert not np.allclose(output, noise, atol=1e-4)


@pytest.mark.skipif(platform.system() == "Windows", reason="Windows subprocess handling")
@pytest.mark.parametrize("plugin_filename", ONE_AVAILABLE_TEST_PLUGIN)
def test_show_editor(plugin_filename: str):
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