Add a more advanced host example

[Bobo1239]

It took me some time to get this to work. (And I'm not sure if that's the intended usage.) Adding a host example which utilizes AudioBuffers and (Midi)Events would make this aspect of the project more approachable.

[zyvitski]

Seems to be a great start at an example! It will be important to find a way to make it platform agnostic though. The most obvious approach in that case might be to have it load an example plugin and use that. The hard part would be the bundling the plugins on OS X. But if we could use the bundler script from a build.rs it could be done.

[phonkee]

Thank you for your example, I have tested it on OS X, but it segfaults.
Does anyone on OS X has the same experience?

The segfault happens on line:

    instance.process(&mut buffer);

[Bobo1239]

It's quite possible that my example isn't doing stuff the right way(tm) but I did test it on Windows and Linux. Which VST did you try? I've tested Pianoteq 5 and sine_synth from the examples.

edit: Some details of the error in Bobo1239/rust-vst-demo#1; I've tried the Spire VST on Windows and also get a segfault. Will try to investigate tomorrow.

[Bobo1239]

After tracing what https://github.com/teragonaudio/MrsWatson is doing, I think I know the problem:

OpCode::GetTime isn't handled here and thus 0 is returned. (MrsWatson handles the opcode like this.)
But Spire expected a pointer to a VstTimeInfo (from the VST2 SDK) and tries to read a field from the struct causing the segfault.
(Dr. Memory reports UNADDRESSABLE ACCESS: reading 0x0000000000000019-0x0000000000000021 8 byte(s))

Somebody would need to clone the struct definition to Rust but I'm not sure if handling timing should be in scope of this library. (I tend to side with no but we'd then need a way to delegate that request to the library user.)

In case anybody else wants to further investigate:
I used mrswatson64 --midi-file c-scale.mid --output out.wav --plugin $PATH_TO_DLL --verbose.
MIDI file: https://my.mixtape.moe/deikbd.mid (MrsWatson only supports Type 0 MIDI files; Type 1 support is a PR)
Partial output (OpCode::GetTime is 7):

Processing audio with plugin 'Spire-1.1.dll'
Plugin 'Spr2' called host dispatcher with 7, 0, 512
Current PPQ position is 4.85451
Plugin 'Spr2' called host dispatcher with 7, 0, 1024
Plugin 'Spr2' called host dispatcher with 7, 0, 1024
Plugin 'Spire-1.1.dll' spent 3ms processing (0% effective CPU usage)
Wrote 1024 samples to PCM file

[Bobo1239]

@phonkee Perhaps #32 will fix your problem.

[phonkee]

Thank you, this is awesome. I have tried other vst and it works. My actual target vst is Virus TI. I will try it in next days.
It's multi output vst that controlls Virus hardware synthesizer, I will share my experience then..

Lastly I want to thanks all people involved in this awesome project and I hope that I will be able to contribute in the future.

Thank you and Merry christmas to you all!

[piedoom]

Merry xmas and happy holidays to you as well! Hope it works out. Feel free to join our telegram group if you'd like to get more involved.

[TailyFair]

Host example that shows how to output to speakers real-time would be super helpful.