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

[Craig Latta]

Hi--

     Eliot writes:

> I'm a bit wary of using it on linux because it claims to be
> implemented above ALSA and IME ALSA is poor, especially w.r.t.
> signals. But it looks like a good solution for Mac and Win.

     Does this mean you would rather use OSS than ALSA? As far as I
know, ALSA is the current supported audio device driver framework for
Linux, supplanting OSS.

     PulseAudio is not a device driver framework. It's a multi-platform
sound server which processes audio as it passes between an application
and device drivers (e.g., stream the audio over a network or to another
local application). It does provide an abstract API for the host
platform audio device driver frameworks it uses, but on Linux the audio
device driver framework it uses is ALSA.

     I found an enlightening and sad summary of the Linux audio
processing architecture[1] which, although written in 2010, seems to
jibe with the current Wikipedia pages for ALSA[2], PulseAudio[3],
JACK[4] (another sound server), and OSS[5], and with a similarly sad
Linux MIDI summary[6].

> Is there anything to stop you following Bert's suggestion of
> reimplementing the MIDIPlugin's support in terms of PortMIDI?

     Indeed no, that's what I was suggesting.

     Tim writes:

> The latest release of Raspbian has added some support for bluetooth
> sound and apparently this has some great cosmic fight with ALSA that
> makes a Micheal Bay movie look like a Beatrix Potter story.
>
> Let’s see if I can find a more coherent explanation (warning - I know
> too little about most of this to really judge ‘coherent’ very well)
>
> From Simon Long @ Pi central - "One thing that has been added to this
> image is support for Bluetooth, which includes audio output over
> Bluetooth. Unfortunately, the BlueZ stack does not support audio over
> ALSA; the only way to get audio out to it is via PulseAudio, and it
> is impractical for various reasons to move all our audio support
> across to Pulse. This means that, for the time being, there is a
> rather kludgey hack implemented (by me, to my eternal shame…) in the
> LXPanel audio selector which starts PulseAudio when a Bluetooth
> device is selected (which also breaks ALSA) and then kills PulseAudio
> when a non-BT device is selected (which then unbreaks ALSA).

     This implies that Raspian's PulseAudio implementation is broken,
and the cosmic fight between BlueZ and ALSA isn't a good excuse. :)  And
of course BlueZ is broken as well.

> So would pulseaudio save us from all this?

     No. :)  I would just live with Simon's BlueZ hack for now.


-C

[1] http://tuxradar.com/content/how-it-works-linux-audio-explained
[2] https://en.wikipedia.org/wiki/Advanced_Linux_Sound_Architecture
[3] https://en.wikipedia.org/wiki/PulseAudio
[4] https://en.wikipedia.org/wiki/JACK_Audio_Connection_Kit
[5] https://en.wikipedia.org/wiki/Open_Sound_System
[6] 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)