[Vm-dev] re: Mac OS Cocoa MIDI Plugin

[Eliot Miranda]

Hi Craig,

On Fri, May 20, 2016 at 4:02 AM, Craig Latta <craig at blackpagedigital.com>
wrote:

>
>
> Hi Eliot--
>
> > First, Cog on Linux in 2010 had to use the itimer heartbeat because
> > pthreads only supported one priority, and so the heartbeat couldn't
> > be a thread. The itimer heartbeat works by delivering signals, and
> > ALSA didn't cope with interrupted system calls.  Second, the X11 GUI
> > and socket i/o depend on delivering SIGIO and ALSA interfered with
> > signal delivery.  When ALSA loaded it installed its own SIGIO handler
> > but didn't check for any previously installed handler and so broke
> > the system.
> >
> > To fix these two problems I had to maintain my own corrected version
> > of the ALSA code, we were under time pressure and this was quicker
> > than trying to engage the ALSA author(s) to correct the code.
>
>      Aha, I'm curious to know if your signal fix involved a separate
> host process for ALSA, and/or the SIGRTMIN signals, as mentioned in [1].
> I guess I'll find out soon enough. :)
>
> > So if ALSA is the only game in town I guess we must get the code
> > fixed.  How is ALSA maintained and by whom?
>
>      The project hosts a git repository[2]. The core team is listed at [3].
>
> > Is the code still broken as described above?
>
>      I suspect so; do you have a minimal regression test I can build and
> run?
>

Thanks for the links.  I checked-out alas-lib (via ) today and indeed the
code is still broken.  Look at the sigaction calls in src/async.c and they
don't ask for the old action.  I'll try contacting the authors and
suggesting they fix things.

> > I found an enlightening and sad summary of the Linux audio
> > > processing architecture[4] which, although written in 2010, seems
> > > to jibe with the current Wikipedia pages for ALSA[5],
> > > PulseAudio[6], JACK[7] (another sound server), and OSS[8], and with
> > > a similarly sad Linux MIDI summary[9].
> >
> > I'll try and find time to read this.  Care to summarize?
>
>      Oh, just that there are far too many pieces, with feature sets that
> overlap and build on each other in ever stranger ways over time. It's
> easy to think that one piece is "standard" for a particular role, when
> it actually does something very different. But at least there are
> reasonable overviews now.
>
>      For Linux Squeak MIDI, the upshot is that we want to play nicely
> with ALSA, and PortMIDI is a good way to do that. More broadly, using
> the PortMedia libraries/APIs would make Squeak audio and MIDI much more
> pleasant on Linux, Windows, and Mac OS. Indeed, let's start by getting
> your ALSA bug confirmed for 2016, then probably get your fix integrated.
>
>
>      thanks again,
>
> -C
>
> [1] https://tinyurl.com/z2o58km (linuxquestions.org)
> [2] http://www.alsa-project.org/main/index.php/GIT_Server
> [3] http://www.alsa-project.org/main/index.php/Alsa_Team
>
> [4] http://tuxradar.com/content/how-it-works-linux-audio-explained
> [5] https://en.wikipedia.org/wiki/Advanced_Linux_Sound_Architecture
> [6] https://en.wikipedia.org/wiki/PulseAudio
> [7] https://en.wikipedia.org/wiki/JACK_Audio_Connection_Kit
> [8] https://en.wikipedia.org/wiki/Open_Sound_System
> [9] http://www.tedfelix.com/linux/linux-midi.html
>
> --
> Craig Latta
> Black Page Digital
> Amsterdam
> craig at blackpagedigital.com
> +31 6 2757 7177 (SMS ok)
> + 1 415 287 3547 (no SMS)
>

_,,,^..^,,,_
best, Eliot
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.squeakfoundation.org/pipermail/vm-dev/attachments/20160520/6fd50215/attachment.htm