[Jack-Devel] Avoiding spinlocks in a parallel sequencer

[Paul Davis]

Speaking entirely personally, I think this design is just plain nuts. I
know there are some JACK-ecosystem developers who disagree with me, but I
think that using JACK clients for this purpose is just wrong and is pushing
the design scope for JACK.

What you're doing is precisely what a plugin architecture was intended to
address, and I really think you'd be better off implementing your own audio
graph with plugins. Of course, that requires a version of zyn that can run
as a plugin, which I think has been discussed but I don't think it was
every implemented fully.

On Thu, Apr 9, 2015 at 2:01 AM, Johannes Lorenz <johannes89 at mailueberfall.de
> wrote:

> Hi,
>
> > I try to understand your plan:
> >
> > simple data flow example:
> >
> > zynaddsubfx_1_output
> >
> >           V
> > sequencer_client_1_input
> >
> >           V
> > sequencer_input_ringbuffer
> >
> >           V
> > (sequencer processing stuff)
> >
> >           V
> > sequencer_output_ringbuffer
> >
> >           V
> > sequencer_client_output
> >
> >           V
> > system_client_input(hardware output)
>
> Your picture is indeed correct. To add some more examples:
>
>   * Something like this is also possible
>
>         sequencer_input_ringbuffer_1     sequencer_input_ringbuffer_2
>                 V                                V
>         plus (i.e. addition of sound-waves)
>                 V
>         plus_effect_ringbuffer
>
>   * The part that you labeled "(sequencer processing stuff)" might be
> filled with:
>
>                 V
>         peak_controller_effect        some lfo generator
>                 V (lfo)                       V (lfo)
>         zynaddsubfx_2_volume_input    zynaddsubfx_2_filter_freq_input
>                 V
>         (zynaddsubfx_2)
>                 V
>         zynaddsubfx_2_output
>                 V
>         sequencer_client_2_input
>                 V
>
> > Maybe also what you envision to happen in which thread or which
> > callback?
>
> Let's take the second example. zynaddsubfx itself is in another process,
> so we don't need to run this at all. For feeding each ringbuffer from zyn,
> I planned to use a separate jack client. E.g., if process() of
> sequencer_client_1_input is being called, it simply copies "nframes" into
> sequencer_input_ringbuffer.
>
> Everything that now remains (e.g. lfo generator, peak_controller_effect,
> sending input to zynaddsubfx_2) is done by a process() callback of
> sequencer_client_output. I call this one the master jack client.
>
> About the problem:
>
> A point where I think spinlocks can't be avoided would be, e.g., reading
> from sequencer_output_ringbuffer. The sequencer's master jack client would
> need to do that in process(), but it can not guess when the ringbuffer
> reader from sequencer_client_2_input has even started to feed the
> ringbuffer.
>
> > Do you want to do some signal processing in your sequencer or would it
> > be ok to delegate this to other jack clients? (may be easier)
>
> Hopefully you got it from the explenations above: the master jack client
> would do this right now, as I planned. Other ideas will be fine, too.
> Though, I guess, for "some lfo generator", e.g., a separate jack client
> would be overkill, as this generator simply does, e.g., f(x) = sin(x).
>
> _______________________________________________
> Jack-Devel mailing list
> Jack-Devel at lists.jackaudio.org
> http://lists.jackaudio.org/listinfo.cgi/jack-devel-jackaudio.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.linuxaudio.org/archives/jackaudio/attachments/20150409/3c16a4f4/attachment.html>