Re: [LAD] handling midi input in a jack app?

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To: David Robillard <d@...>
Cc: <linux-audio-dev@...>
Date: Wednesday, December 28, 2011 - 8:59 pm

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On Wed, Dec 28, 2011 at 12:04 PM, David Robillard wrote:

> On Wed, 2011-12-28 at 14:35 -0500, Paul Davis wrote:

Thanks for all the input everyone. It sounds like my best plan is for the
jack build to use jack midi in the audio process callback and send it to
the rest of the app over a ringbuffer. A few things I hope to achieve:

- keep all jack dependencies, with the exception of the jackringbuffer, in
one file, so far so good, the only use of jack right now is in main.cpp and
my wrapper class for the ring buffer. Everybody else communicates using an
internal message format, that is non-midi (on purpose, I want to make no
assumptions about anyone using midi).
- keep my porting task to a minimum in case I want to get this to run on an
non-jack platform ( Raspberry Pi for instance, no idea if jack runs on ARM?
)
- allow handing off input data to python processes so that users can easily
write algorithmic transforms. These *could* receive midi input directly, or
they could get midi input from jack:
jack_midi_in -> passed to engine -> ringbuffered to nrt-controller -
controller maps to correct child process - socket/pipes/?? to python
processes

Basically, I want power/users to be able to write input plugins with a
really simple api in python, for cases where latency is not an issue
(step-sequencing). So I need to make sure that getting messages to Python
is as quick as possible, but also as reliable and manageable as possible.

Appreciate all the input everyone.
Iain

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On Wed, Dec 28, 2011 at 12:04 PM, David Robillard <d@drobilla.net> wrote:
On Wed, 2011-12-28 at 14:35 -0500, Paul Davis wrote:
[...]

e this property, and
done
to be
ross
n the

Also, in both cases, there is a strong and precise correlation betwee=
n
MIDI time stamps and audio time for Jack MIDI, and not for the other
APIs (which may be useful even if you do your processing in another
thread).Thanks for all the input every=
one. It sounds like my best plan is for the jack build to use jack midi in =
the audio process callback and send it to the rest of the app over a ringbu=
ffer. A few things I hope to achieve:
- keep all jack dependencies, with the exception of the=
jackringbuffer, in one file, so far so good, the only use of jack right no=
w is in main.cpp and my wrapper class for the ring buffer. Everybody else c=
ommunicates using an internal message format, that is non-midi (on purpose,=
I want to make no assumptions about anyone using midi). =A0
- keep my porting task to a minimum in case I want to get this to run =
on an non-jack platform ( Raspberry Pi for instance, no idea if jack runs o=
n ARM? )- allow handing off input data to python processes so th=
at users can easily write algorithmic transforms. These *could* receive mid=
i input directly, or they could get midi input from jack:
=A0 jack_midi_in -> passed to engine -> ringbuffered to nrt-cont=
roller - controller maps to correct child process - socket/pipes/?? to pyth=
on processesBasically, I want power/users to be a=
ble to write input plugins with a really simple api in python, for cases wh=
ere latency is not an issue (step-sequencing). So I need to make sure that =
getting messages to Python is as quick as possible, but also as reliable an=
d manageable as possible.
Appreciate all the input everyone.Iain=

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Messages in current thread:
[LAD] handling midi input in a jack app?, Iain Duncan, (Wed Dec 28, 6:46 pm)
Re: [LAD] handling midi input in a jack app?, Nick Copeland, (Wed Dec 28, 8:01 pm)
Re: [LAD] handling midi input in a jack app?, Paul Davis, (Wed Dec 28, 7:35 pm)
Re: [LAD] handling midi input in a jack app?, David Robillard, (Wed Dec 28, 8:05 pm)
Re: [LAD] handling midi input in a jack app?, Iain Duncan, (Wed Dec 28, 8:59 pm)
Re: [LAD] handling midi input in a jack app?, Iain Duncan, (Wed Dec 28, 7:54 pm)
Re: [LAD] handling midi input in a jack app?, Paul Davis, (Wed Dec 28, 7:59 pm)
Re: [LAD] handling midi input in a jack app?, David Robillard, (Wed Dec 28, 7:35 pm)