alsa

Bindings for the ALSA library which provides functions for using soundcards
IN THIS PACKAGE
Module Alsa . Pcm
type handle

Handle to a device.

type params

Parameters of a device.

type stream =
| Playback(*

Playback stream.

*)
| Capture(*

Capture stream.

*)

Wanted stream.

type mode =
| Async(*

Asynchronous notification (not supported yet).

*)
| Non_blocking(*

Non blocking I/O.

*)

Modes for opening a stream.

val open_pcm : string -> stream list -> mode list -> handle
val close : handle -> unit
val prepare : handle -> unit

Prepare PCM for use.

val resume : handle -> unit

Resume from suspend, no samples are lost.

val recover : ?verbose:bool -> handle -> exn -> unit

Recover the stream state from an error or suspend. * This a high-level helper function building on other functions. * This functions handles Interrupted, Buffer_xrun and Suspended * exceptions trying to prepare given stream for next I/O. * Raises the given exception when not recognized/used.

val start : handle -> unit
val drain : handle -> unit

Stop a PCM preserving pending frames.

val drop : handle -> unit

Stop a PCM dropping pending frames.

val pause : handle -> bool -> unit

pause hnd pause pauses (when pause is true) or resume (when pause * is false) a PCM.

val reset : handle -> unit
val wait : handle -> int -> bool

Wait for a PCM to become ready. The second argument is the timeout in * milliseconds (negative for infinite). Returns false if a timeout * occured.

val readi : handle -> bytes -> int -> int -> int

readi handle buf ofs len reads len interleaved frames in buf * starting at offset ofs (in bytes). It returns the actual number of * frames read.

val writei : handle -> bytes -> int -> int -> int

writei handle buf ofs len writes len interleaved frames of buf * starting at offset ofs (in bytes).

val readn : handle -> bytes array -> int -> int -> int
val writen : handle -> bytes array -> int -> int -> int
val readn_float : handle -> float array array -> int -> int -> int
val writen_float : handle -> float array array -> int -> int -> int
val readn_float_ba : handle -> ( float, Bigarray.float32_elt, Bigarray.c_layout ) Bigarray.Array1.t array -> int
val writen_float_ba : handle -> ( float, Bigarray.float32_elt, Bigarray.c_layout ) Bigarray.Array1.t array -> int
val writei_float_ba : handle -> int -> ( float, Bigarray.float32_elt, Bigarray.c_layout ) Bigarray.Array1.t -> int
val readn_float64 : handle -> float array array -> int -> int -> int
val writen_float64 : handle -> float array array -> int -> int -> int
val get_delay : handle -> int

Get the delay (in frames).

type state =
| St_open(*

open

*)
| St_setup(*

setup installed

*)
| St_prepared(*

ready to start

*)
| St_running(*

running

*)
| St_xrun(*

stopped: underrun (playback) or overrun (capture) detected

*)
| St_draining(*

draining: running (playback) or stopped (capture)

*)
| St_paused(*

paused

*)
| St_suspended(*

hardware is suspended

*)
| St_disconnected(*

hardward is disconnected

*)

State.

val get_state : handle -> state

Get the current state.

val get_params : handle -> params
val set_params : handle -> params -> unit
type access =
| Access_rw_interleaved
| Access_rw_noninterleaved

Access mode.

val set_access : handle -> params -> access -> unit

Set the access mode.

type fmt =
| Format_s16_le(*

16 bits, little endian

*)
| Format_s24_3le
| Format_float(*

float 32 bit CPU endian

*)
| Format_float64(*

float 64 bit CPU endian

*)

Format of audio data.

val set_format : handle -> params -> fmt -> unit

Set the format of audio data.

val set_rate_near : handle -> params -> int -> direction -> int

set_rate_near handle params rate dir sets the sampling rate (in Hz). * If the rate is not avalaible, dir is used to determine the direction of * the nearest available sampling rate to use . The actual sampling rate used * is returned.

val set_channels : handle -> params -> int -> unit

Set the number of channels.

val set_periods : handle -> params -> int -> direction -> unit

Set the number of periods.

val get_periods_min : params -> int * direction

Get the number of periods.

val get_periods_max : params -> int * direction
val get_period_size : params -> int
val set_buffer_size : handle -> params -> int -> unit

Set the buffer size in frames.

val set_buffer_size_near : handle -> params -> int -> int

Set the buffer size near a value in frames.

val get_buffer_size : params -> int
val get_buffer_size_min : params -> int
val get_buffer_size_max : params -> int
val set_nonblock : handle -> bool -> unit

Set blocking mode (true means non-blocking).

val get_frame_size : params -> int

Get the size of a frame in bytes.