[LAU] How to get started writing a JACK app? (also what distro for BeagleBone)

[Benoît Rouits]

I'm not an expert, but if you are looking something like AU or VST,
maybe you should consider writing an LV2 plugin (most of linux DAWs
can host LV2 plugins). An LV2 plugin is a small shared object with
a few callbacks to process sound or midi, or controls. They can have
a graphical interface too, but this is not mandatory.

main entry point url is there : http://lv2plug.in/

Cheers,
  Benoît

Le 10/01/2018 à 05:07, Andrew Voelkel a écrit :
> Hi,
> 
>  
> 
> Maybe I need to ask a different question. My goal is to stick my real
> time processing algorithm in between x number of audio inputs coming
> from a USB audio interface, and then send the outputs to y number of
> audio outputs on the same USB audio interface. Low latency is important.
> Being able to add in other processing from third parties would be nice,
> but it isn’t essential.
> 
>  
> 
> Is writing a JACK client the right way to do this? If so, what is the
> right approach? If not, what is the right way to do this? 
> 
>  
> 
> On the Apple platform, I do this by writing an Audio Unit, and either
> leverage a DAW host application like Logic or the Apple AVAudioEngine to
> serve as a host for my processing algorithm. The host gets the inputs
> from the audio interface, I process the audio in my Audio Unit in a
> callback routine, and the host sends the outputs to the audio interface.
> In Windows a similar thing happens, but with VST plugins and an ASIO
> host, which is either a DAW or a custom ASIO host. I’ve done both.
> 
>  
> 
> So what is the best “linux way” to do this? Out-of-process seems high
> overhead and not suited for low latency, so I figure I must be
> misunderstanding something quite fundamental.
> 
>  
> 
> Thanks so much for the help, I really do appreciate it.
> 
>  
> 
>   * Andy
> 
>  
> 
> *From: *Paul Davis <paul at linuxaudiosystems.com>
> *Date: *Tuesday, January 9, 2018 at 8:22 PM
> *To: *Andrew Voelkel <jandyman.voelkel at gmail.com>
> *Cc: *Benoît Rouits <brouits at free.fr>, linux-audio-user
> <linux-audio-user at lists.linuxaudio.org>
> *Subject: *Re: [LAU] How to get started writing a JACK app? (also what
> distro for BeagleBone)
> 
>  
> 
> In-process JACK clients are a very special case and almost nobody
> implements or uses them. They are like plugins for the JACK server, and
> that's not really the point of JACK (which was designed to connect
> distinct processes).
> 
> Look at the out-of-process ("normal") example(s) instead.
> 
>  
> 
> On Tue, Jan 9, 2018 at 9:39 PM, Andrew Voelkel
> <jandyman.voelkel at gmail.com <mailto:jandyman.voelkel at gmail.com>> wrote:
> 
>     Hi and thanks.
> 
>      
> 
>     So looking at the in-process example, I’m guessing it compiles to a
>     dynamic library which the server loads? If so, how does the server
>     know the capabilities of the in-process client.
> 
>      
> 
>     I’m coming from writing VST plug-ins on Windows or Audio Units on
>     Apple platforms, in case I sound confused.
> 
>      
> 
>     I’m also having trouble getting used to the idea of the client being
>     the plug in, normally I would think the client would be what is
>     called the “host” on Windows or Apple, and the plug-in would closer
>     to a “server”. But here the terminology is reversed. Am I
>     understanding correctly? The “client” in JACK is the plug-in (for
>     in-process use), correct?
> 
>      
> 
>     Finally, I’d like to get started seeing whether the eco-system works
>     for low latency with existing apps and components for diving in. Is
>     AVLinux the way to go, and is there any reason it will not work on
>     BeagleBone?
> 
>      
> 
>     I’m not a Linux expert in case you can’t already tell! It’s not that
>     I have zero experience, but sometimes it’s close, depending on context.
> 
>      
> 
>     But I do know audio, and operating system design, and threading, and
>     SIMD, and etc.
> 
>      
> 
>       * Andy
> 
>      
> 
>     *From: *Linux-audio-user
>     <linux-audio-user-bounces at lists.linuxaudio.org
>     <mailto:linux-audio-user-bounces at lists.linuxaudio.org>> on behalf of
>     Paul Davis <paul at linuxaudiosystems.com
>     <mailto:paul at linuxaudiosystems.com>>
>     *Date: *Tuesday, January 9, 2018 at 4:41 PM
>     *To: *Benoît Rouits <brouits at free.fr <mailto:brouits at free.fr>>
>     *Cc: *linux-audio-user <linux-audio-user at lists.linuxaudio.org
>     <mailto:linux-audio-user at lists.linuxaudio.org>>
>     *Subject: *Re: [LAU] How to get started writing a JACK app?
> 
>      
> 
>     please. not sourceforge.
> 
>     JACK code lives on github ... 
>     https://github.com/jackaudio/example-clients
> 
>      
> 
>     On Tue, Jan 9, 2018 at 6:21 PM, Benoît Rouits <brouits at free.fr
>     <mailto:brouits at free.fr>> wrote:
> 
>         Hello  Andy
> 
>         as a starting point, you could look at:
> 
>         http://jackit.sourceforge.net/cgi-bin/lxr/http/source/example-clients/
> 
>         This is C client code samples for jack.
> 
>         HTH,
>          Benoît
> 
>         Le 09/01/2018 à 16:19, Andrew Voelkel a écrit :
>         >
>         >     Hi,____
>         >
>         >     __ __
>         >
>         >     I’m new to this list. I’m thinking of giving low latency
>         real time
>         >     audio in Linux another try after my last unsuccessful
>         attempt a few
>         >     years ago. My goal is to put some of my own DSP code into
>         a hardware
>         >     appliance and use it to process audio signals during music
>         >     rehearsals and performances.____
>         >
>         >     __ __
>         >
>         >     I think this boils down to getting an appropriate distro,
>         getting
>         >     JACK working in a low latency configuration with a
>         multichannel USB
>         >     interface. And then …____
>         >
>         >     __ __
>         >
>         >     Writing a JACK app to process the audio. ____
>         >
>         >     __ __
>         >
>         >     I’ve done some googling and found a lot about _/using/_
>         JACK, but
>         >     not much about writing a JACK app. ____
>         >
>         >     __ __
>         >
>         >     Are there any examples or tutorials out there?____
>         >
>         >     __ __
>         >
>         >     I’m already up to speed on doing C++ cross development
>         with Eclipse.____
>         >
>         >     __ __
>         >
>         >     I’ve got a BeagleBone black sitting around here I could use to
>         >     experiment.____
>         >
>         >     __ __
>         >
>         >       * Andy____
> 
>         >
>         >
>         >
>         >
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>         >
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>      
> 
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