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SNDIO(7)	   FreeBSD Miscellaneous Information Manual	      SNDIO(7)

NAME
     sndio -- audio and	MIDI device descriptors

DESCRIPTION
     Programs access audio and MIDI hardware using the sndio library.  It al-
     lows both access through the sndiod(8) server and raw access to the hard-
     ware.  The	audio device or	MIDI port, as well as the access method, are
     designated	by the sndio descriptor.  It is	provided by the	user with the
     program device selection method, or with the AUDIODEVICE and MIDIDEVICE
     environment variables if there's no device	selection method.

     Usually, programs access the hardware via the sndiod(8) server, because
     raw access	to the hardware	is exclusive and requires additional privi-
     leges.  The sndiod(8) server supports multiple connections	at a time, al-
     lowing multiple programs to use the hardware concurrently.	 It performs
     the necessary audio processing on the fly to overcome any incompatibility
     between software and hardware.  Connections to sndiod(8) may also be es-
     tablished through the network, including from virtual machines.

     The sndiod(8) server exposes MIDI thru ports, allowing one	program	to
     send MIDI data to other programs, for instance to allow a sequencer to
     send events to a synthesizer.

     Additionally, sndiod(8) exposes a MIDI port used to control audio pro-
     grams using standard MIDI Machine Control (MMC), MIDI Time	Code (MTC),
     and master	volume messages.

   Server device descriptors
     From the user's perspective, every	audio device or	MIDI port exposed by
     sndiod(8) has a descriptor	of the form:

		       type[@hostname][,servnum]/devnum[.option]

     This information is used by programs to determine how to access the audio
     device or MIDI port.

     type      The type	of the audio device or MIDI port.  Possible values
	       are:

		  snd	    Audio device exposed by sndiod(8).
		  midithru  MIDI thru port created with	sndiod(8).
		  midi	    MIDI port exposed by sndiod(8).

     hostname  The hostname or address where the remote	sndiod(8) server to
	       connect to is running.

     servnum   The number of the sndiod(8) server to connect to, corresponding
	       to the integer specified	using the -U option of sndiod(8).
	       Useful only if multiple sndiod(8) servers are running on	the
	       same system.

     devnum    Device number.  It corresponds to the number of the correspond-
	       ing -f or -q option on the sndiod(8) command line.

     option    Corresponds to the sub-device string registered using the -s
	       option of sndiod(8).

   Raw device descriptors
     Every raw audio device or MIDI port has a descriptor of the form:

	   type/devnum

     The type can be either rsnd or rmidi.  The	rsnd/0 device descriptor ac-
     cesses the	/dev/audio0 device, rsnd/1 accesses /dev/audio1, and so	on.
     Similarly,	rmidi/0	accesses /dev/rmidi0 and so on.

   Default Audio and MIDI devices
     When no audio device descriptor is	provided to a program or when the re-
     served word default is used as the	audio device, the program will use the
     one specified in the AUDIODEVICE, AUDIOPLAYDEVICE and/or AUDIORECDEVICE
     environment variables.  If	they are not set, the program first tries to
     connect to	snd/0.	If that	fails, it then tries to	use rsnd/0.

     Similarly,	if no MIDI descriptor is provided to a program or when the re-
     served word default is passed as the device descriptor, the program uses
     the one specified in the MIDIDEVICE environment variable.	If it is not
     set, the program first tries to connect to	midithru/0.  If	that fails, it
     then tries	to use rmidi/0.	 As long as sndiod(8) is running, this allows
     programs to exchange MIDI data on machines	with no	MIDI hardware by de-
     fault, e.g. a MIDI	player could use a software synthesizer	with no	manual
     configuration required.

   Authentication
     For privacy reasons only one user may have	connections to sndiod(8) at a
     given time.  Users	are identified by their	session	cookie,	which is auto-
     matically generated by audio or MIDI programs upon	the first connection
     to	the server.  The cookie	is stored in $HOME/.sndio/cookie and contains
     128 bits of raw random data.

     If	a session needs	to be shared between multiple users, they can connect
     to	the server using the same cookie.

ENVIRONMENT
     AUDIODEVICE      Audio device descriptor to use when no descriptor	is ex-
		      plicitly specified to a program.
     AUDIOPLAYDEVICE  Audio device descriptor to use for play-only mode	when
		      no descriptor is explicitly specified to a program.
		      Overrides	AUDIODEVICE.
     AUDIORECDEVICE   Audio device descriptor to use for record-only mode when
		      no descriptor is explicitly specified to a program.
		      Overrides	AUDIODEVICE.
     MIDIDEVICE	      MIDI port	descriptor to use when no descriptor is	ex-
		      plicitly specified to a program.

     These environment variables are ignored by	sndio if the program has the
     set-user-ID or set-group-ID bits set.

FILES
     ~/.sndio/cookie  User's session authentication cookie.
     /dev/audioN      Raw audio	devices.
     /dev/rmidiN      Raw MIDI ports.

EXAMPLES
     snd/0	 Audio device referred to by the first -f option of sndiod(8).
     snd/0.rear	 Sub-device registered with "-s	rear".
     midithru/0	 First MIDI thru port created with sndiod(8).
     default	 Default audio or MIDI device.
     rsnd/0	 Direct	hardware access	to /dev/audio0.
     rmidi/5	 Direct	hardware access	to /dev/rmidi5.

SEE ALSO
     aucat(1), midicat(1), sndioctl(1),	mio_open(3), sio_open(3),
     sioctl_open(3), audio(4), midi(4),	sndiod(8)

FreeBSD	13.0		       November	20, 2020		  FreeBSD 13.0

NAME | DESCRIPTION | ENVIRONMENT | FILES | EXAMPLES | SEE ALSO

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