.\" $OpenBSD: sndio.7,v 1.23 2020/05/25 12:25:16 ratchov Exp $ .\" .\" Copyright (c) 2007 Alexandre Ratchov .\" .\" Permission to use, copy, modify, and distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .\" .Dd $Mdocdate: May 25 2020 $ .Dt SNDIO 7 .Os .Sh NAME .Nm sndio .Nd interface to audio and MIDI .Sh DESCRIPTION Programs access audio and MIDI hardware using the .Nm sndio library. It allows both access through the .Xr sndiod 8 server and raw access to the hardware. 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 .Ev AUDIODEVICE and .Ev MIDIDEVICE environment variables if there's no device selection method. .Pp Usually, programs access the hardware via the .Xr sndiod 8 server, because raw access to the hardware is exclusive and requires additional privileges. The .Xr sndiod 8 server supports multiple connections at a time, allowing 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 .Xr sndiod 8 may also be established through the network, including from virtual machines. .Pp The .Xr sndiod 8 server exposes .Em 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. .Pp Additionally, .Xr sndiod 8 exposes a MIDI port used to control audio programs using standard MIDI Machine Control (MMC), MIDI Time Code (MTC), and master volume messages. .Sh AUDIO AND MIDI DESCRIPTORS From the user's perspective every audio device or MIDI port has a descriptor of the form: .Bd -literal -offset center type[@hostname][,servnum]/devnum[.option] .Ed .Pp This information is used by programs to determine how to access the audio device or MIDI port. .Bl -tag -width "hostname" .It Ar type The type of the audio device or MIDI port. Possible values are: .Pp .Bl -tag -width "midithru" -offset 3n -compact .It Cm rsnd Raw .Xr audio 4 device. .It Cm rmidi Raw .Xr midi 4 port. .It Cm snd Audio device exposed by .Xr sndiod 8 . .It Cm midithru MIDI thru port created with .Xr sndiod 8 . .It Cm midi MIDI port exposed by .Xr sndiod 8 . .It Cm default Default audio device or MIDI port (see below). .El .It Ar hostname The hostname or address where the remote .Xr sndiod 8 server to connect to is running. .It Ar servnum The number of the .Xr sndiod 8 server to connect to, corresponding to the integer specified using the .Fl U option of .Xr sndiod 8 . Useful only if multiple .Xr sndiod 8 servers are running on the same system. .It Ar devnum Device number. For hardware audio or MIDI ports, this corresponds to the character device minor number. For audio devices or MIDI ports created with .Xr sndiod 8 it corresponds to the number of the corresponding .Fl fq option on the command line. .It Ar option Corresponds to the sub-device string registered using the .Fl s option of .Xr sndiod 8 . .El .Pp For example: .Pp .Bl -tag -width "snd/0.rear" -offset 3n -compact .It Li rsnd/0 Raw access to first audio device. .It Li rmidi/5 Raw access to MIDI port number 5. .It Li snd/0 Audio device referred by first .Fl f option of .Xr sndiod 8 . .It Li snd/0.rear Sub-device registered with .Fl s Fa rear . .It Li midithru/0 First MIDI thru port created with .Xr sndiod 8 . .El .Sh DEFAULTS If .Cm default is used as the audio device, the program will use the one specified in the .Ev AUDIODEVICE environment variable. If it is not set, the program first tries to connect to .Li snd/0 . If that fails, it then tries to use .Li rsnd/0 . This allows the .Xr sndiod 8 audio server to be used by default and the raw hardware as fallback; programs don't have to be reconfigured when .Xr sndiod 8 is started or stopped. .Pp Similarly, if no MIDI descriptor is provided to a program or when the reserved word .Cm default is passed as the device descriptor, the program uses the one specified in the .Ev MIDIDEVICE environment variable. If it is not set, the program first tries to connect to .Li midithru/0 . If that fails, it then tries to use .Li rmidi/0 . As long as .Xr sndiod 8 is running, this allows programs to exchange MIDI data on machines with no MIDI hardware by default, e.g. a MIDI player could use a software synthesizer with no manual configuration required. .Sh AUTHENTICATION For privacy reasons only one user may have connections to .Xr sndiod 8 at a given time. Users are identified by their .Em session cookie , which is automatically generated by audio or MIDI programs upon the first connection to the server. The cookie is stored in .Pa "$HOME/.sndio/cookie" and contains 128 bits of raw random data. .Pp If a session needs to be shared between multiple users, they can connect to the server using the same cookie. .Sh ENVIRONMENT .Bl -tag -width "AUDIODEVICEXXX" -compact .It Ev AUDIODEVICE Audio device descriptor to use when no descriptor is explicitly specified to a program. .It Ev MIDIDEVICE MIDI port descriptor to use when no descriptor is explicitly specified to a program. .El .Pp These environment variables are ignored by .Nm if the program has the set-user-ID or set-group-ID bits set. .Sh FILES .Bl -tag -width "~/.sndio/cookie" -compact .It Pa ~/.sndio/cookie User's session authentication cookie. .It Pa /dev/audioN Audio devices. .It Pa /dev/rmidiN MIDI ports. .El .Sh SEE ALSO .Xr aucat 1 , .Xr midicat 1 , .Xr sndioctl 1 , .Xr mio_open 3 , .Xr sio_open 3 , .Xr sioctl_open 3 , .Xr audio 4 , .Xr midi 4 , .Xr sndiod 8