RNBO C++ export running natively on Android

Jan 17 2023 | 2:16 pm

I've had an itch to really explore what is possible with the C++ export functionality provided by RNBO and what its limitations are...

While it seemed to work pretty flawlessly in desktop applications I thought about the many years of using UDP to send signals from my phone to Max MSP over networks and wondered whether it would be finally possible to have everything packaged up as an Android app.

After a few brain-scratching days, I've come up with a slightly hacky solution - fixing problems as they arise in the exported RNBO library code. It's early days but I've put up a Git repository which I'll keep updating as I make the process a little more stable.

https://github.com/StuartMellor/Max-MSP-RNBO-CPP-Native-Android

StuartM
Jan 17 2023 | 2:34 pm
One of the first issues that arises when trying to include the RNBO files in an Android project is that the "RNBO_PlatformInterface" class produces a "SIGSEGV" error - a segmentation error when a function is retrieved via "Platform::get()-> ..." . This works fine when building for desktop (using MSVC 14.34.31933) but doesn't with Clang (Android Studio's compiler of choice). I assume the issue lies with LLVM libc++. I'll do some more digging. By converting all Platform::get()-> calls to their counterpart stdlib calls (and just including the stdlib platforminterface to cover the "toString()" call) the library builds properly and runs!
void setName(const char *name) { if (_name) Platform::get()->free(_name); size_t len = Platform::get()->strlen(name); _name = static_cast<char *>(Platform::get()->malloc((len + 1) * sizeof(char))); Platform::get()->strcpy(_name, name); }
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StuartM

Jan 17 2023 | 2:40 pm

In terms of actually getting sound out, the Oboe library (which polyfills AAaudio configurations for older versions of Android) provides a useful custom callback to call the rnbo process function.

oboe::DataCallbackResult
SimpleNoiseMaker::onAudioReady(oboe::AudioStream *oboeStream, void *audioData, int32_t numFrames) {
    rnboObject.process(nullptr, 0, pMyCustomData->outputs,1, numFrames);
    float* fOutput = (float*)audioData;

    float temp = 0;

    for(unsigned int i = 0; i < numFrames; i++) {

        *fOutput++ = (float) (pMyCustomData->outputs[0][i]);
    }

    return DataCallbackResult::Continue;
}

👽R∆J∆ The Resident ∆lien👽
Jan 17 2023 | 2:49 pm
(Just wanted to give a quick: "Thank You" for documenting your process here 💜)
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Alex Norman
Jan 19 2023 | 12:03 am
STUARTM,
Have you tried explicitly setting a platform interface before running the RNBO code?
I *think* the stdlib one should work but maybe there is some issue with static initialization since you're building RNBO as a library?
See: https://rnbo.cycling74.com/cpp/ref/sources/platform_interface_8h https://rnbo.cycling74.com/cpp/ref/sources/platform_interface_std_lib_8h
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StuartM
Jan 19 2023 | 9:53 am
Yes! This was going to be my next step. The sigsegv fault is pretty tedious to navigate during debug. I'll post an update once I get round to it.
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Pedro Nonino
Jan 20 2023 | 4:19 pm
Wow thats really cool! Didn't tested yet but that was exactly what I was looking for :), thank you!!
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StuartM
Jan 24 2023 | 5:45 pm
That's it! I think I had some issues with the "build.gradle" project configuration that have been resolved by starting afresh and using the latest NDK - it runs with or without the platform interface being explicitly set.
It's now working with automatically generated UI sliders and is available at: https://github.com/StuartMellor/Max-MSP-RNBO-CPP-Native-Android
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Alex Norman
Jan 24 2023 | 7:41 pm
STUARTM, Do you mean that you no longer have to alter the generated code?
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StuartM
Jan 24 2023 | 8:40 pm
That's right! I'll compare the versions to see what was different in each and post here.
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Alex Norman
Jan 24 2023 | 9:18 pm
Happy to hear that!
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