Thanks Brian, that's really helpful.
I'm trying to establish whether I can avoid Xcode because I'm working
with a very specific toolchain which handles Makefiles & build pipeline
automatically, completely independent from Xcode. My usual process for
building this kind of lib is to find out whether I can do what I want as
a straight C/Makefile proof-of-concept first, then implement that into
my main project and have the toolchain manage the build for me.
As for the MIDI send/receive, on reflection I think I'll be able to use
normal MIDI I/O. I just need to establish what other outputs I can get
from the plugins via the AU API, which is obviously going to be
dependent on individual plugins.
Thanks again!
On 01/04/2018 04:19, Brian Willoughby wrote:
You can host an AU in Standard C. Just because AudioUnits are written in C++
doesn’t mean that the host must be written in C++. In fact, I tend to prefer to
avoid C++ in favor of Standard C and Objective C. About the only time I use C++
for CoreAudio is when creating an AudioUnit (but not when hosting one).
I would recommend using AUGraph if you want to host multiple AUs. If your
connections are simpler then you can just host the AU(s) directly without an
AUGraph. Your choice may be influenced by whether you need live audio output
during your processing, or just offline. Obviously, offline processing is quite
easy in a command line program - the biggest challenge is not terminating
before the audio is complete.
Writing a command line program is very much supported. I do it all the time.
It’s typically more difficult to weave the Objective C User Interface with the
Standard C CoreAudio API, but even that isn’t difficult. You should find it
even easier to access CoreAudio and AudioUnits in a CLI program written in
Standard C.
As for Xcode, the tool supports command line programs just as easily as GUI
programs. I write a large number of CLU programs and I always use Xcode because
it is familiar. It presents no hurdles for CLI development. Are you trying to
avoid Xcode because you have specific issues? I’ve certainly written a few
projects with a simple Makefile and command-line make, but I tend to get weary
of manually managing the Makefile(s). Xcode makes this work with much less
effort, and it supports all kinds of development: GUI apps, CLI programs,
plugins, etc.
About the only question I don’t have an answer for off-the-cuff is how to send
MIDI events to an AU. If I needed to do that, I’d get the basic structure of
the AU loading and processing audio first, then look for some documentation or
examples that send MIDI events. I have done CLI programs that send and receive
MIDI, but those always communicated with external devices. I’m not quite sure
how to target an AU. As Paul suggested, it might be possible to look through
Ardour to find a hint, but you should get everything else working first before
diving into Ardour sources.
Brian
On Mar 30, 2018, at 6:10 AM, Igor Clark <[email protected]> wrote:
Hi all,
Is it possible to load an existing AudioUnit MIDI plugin and interact it with
it from a CLI program written in C? I'd like to be able to use commercial
plug-ins in my MIDI processing app.
I'm comfortable with how to communicate between C & C++ using 'extern' etc, so
that's not the main issue. Rather, I'm wondering whether it's possible to have a C
CLI app that loads the AU and sends MIDI passages to it, so that the AU processes
the data (ideally async) and then returns its result back to the C app. I guess
it's effectively writing an AU host app, but does that all have to be done in
Xcode, or is it possible to do it as a straight C/C++ program using clang/llvm at
the shell?
Also, the AU Hosting Guide docs talk about I/O, Mixer and Effect units - is
there any other material that focuses on how to do MIDI in AU? Or is a
adaptor/translator layer necessary?
Thanks for any pointers,
Igor
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