SNDIO(7) OpenBSD Reference Manual SNDIO(7)NAME
sndio - interface to audio and MIDI
DESCRIPTION
The sndio audio and MIDI system provides access to audio and MIDI
hardware and to services provided by aucat(1) and midicat(1), summarized
below.
Hardware audio(4) devices correspond to peripherals. Only one
application may use any device at a given time. Generally a limited
number of encodings, sample rates and channel numbers are supported by
the hardware, which may not meet the requirements of audio programs.
To overcome hardware limitations and to allow multiple applications to
share the hardware, aucat(1) can be used. It exposes one or more
software subdevices backed by the underlying hardware, while doing all
necessary conversions on the fly. It can mix multiple streams or split
the hardware into multiple subdevices, to allow programs to use the
hardware concurently.
Hardware MIDI ports correspond to serial connectors provided by the
midi(4) driver. They are typically used to access MIDI hardware
(synthesizers, keyboards, control surfaces, etc.), but they do not allow
applications to exchange information using the MIDI protocol.
Software MIDI thru boxes allow one application to send MIDI data to other
applications connected to the thru box (for instance a software sequencer
can send events to multiple software synthesizers). There's no hardware
involved: thru boxes are created by midicat(1).
Additionally, aucat(1) exposes a MIDI device used to control and monitor
audio streams in real time using MIDI.
DEVICE NAMES
From the user's perspective every audio interface, MIDI port, aucat(1) or
midicat(1) service has a name of the form:
type:unit[.option]
This information is used by audio and MIDI applications to determine how
to access the audio or MIDI device or service.
type The type of the audio or MIDI device. Possible values for audio
devices are aucat and sun, corresponding to aucat(1) sockets and
hardware audio(4) devices. Possible values for MIDI devices are
midithru, rmidi, and aucat corresponding to midicat(1) software
MIDI thru boxes, hardware midi(4) ports and aucat(1) control
through MIDI respectively.
unit For hardware audio or MIDI devices, this corresponds to the
character device minor number. For audio or MIDI devices created
with aucat(1) or midicat(1) it corresponds to the server unit
number, typically 0.
option Corresponds to the profile string registered using the -s option
of aucat(1). Only meaningful for aucat device types.
For example:
sun:0 First hardware audio device.
aucat:0 Default audio device of the first aucat(1) audio server.
aucat:0.rear First aucat(1) server; device registered with -s rear.
rmidi:5 Hardware MIDI port number 5.
midithru:0 First software MIDI thru box created with midicat(1).
aucat:0 MIDI port controlling the first aucat(1) audio server.
ENVIRONMENT
AUDIODEVICE Audio device to use if the application provides no device
chooser.
MIDIDEVICE MIDI port to use if the application provides no MIDI port
chooser.
Environment variables are ignored by programs with the set-user-ID or
set-group-ID bits set.
FILES
/dev/audioN Audio devices.
/dev/rmidiN MIDI ports.
/tmp/aucat-xxx/softaudioN Audio devices provided by aucat(1).
/tmp/aucat-xxx/midithruN MIDI thru boxes provided by midicat(1).
SEE ALSOaucat(1), midicat(1), mio_open(3), sio_open(3), audio(4), midi(4)OpenBSD 4.9 August 21, 2009 OpenBSD 4.9
