libsent/src/adin/adin_mic_linux_alsa.c File Reference

Microphone input on Linux/ALSA. More...

#include <sent/stddefs.h>
#include <sent/adin.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <alsa/asoundlib.h>

Go to the source code of this file.

Defines
#define	MAXPOLLINTERVAL   300
	Read timeout in msec.
Functions
static void	output_card_info (char *pcm_name, snd_pcm_t *handle)
	Output detailed device information.
boolean	adin_alsa_standby (int sfreq, void *dummy)
	Device initialization: check device capability and open for recording.
static int	xrun_recovery (snd_pcm_t *handle, int err)
	Error recovery when PCM buffer underrun or suspend.
boolean	adin_alsa_begin ()
	Start recording.
boolean	adin_alsa_end ()
	Stop recording.
int	adin_alsa_read (SP16 *buf, int sampnum)
	Read samples from device.
Variables
static snd_pcm_t *	handle
	Audio handler.
static char *	pcm_name = "default"
	Name of the PCM device, can be overridden by env ALSADEV.
static int	latency = 32
	Lantency time in msec. You can override this value by specifying environment valuable "LATENCY_MSEC".
static boolean	need_swap
	Whether samples need byte swap.
static struct pollfd *	ufds
	Poll descriptor.
static int	count
	Poll descriptor count.

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Detailed Description

Microphone input on Linux/ALSA.

Low level I/O functions for microphone input on Linux using Advanced Linux Sound Architechture (ALSA) API, developed on version 0.9.x.

Julius does not alter any mixer device setting at all on Linux. You should configure the mixer for recording source (mic/line) and recording volume correctly using other audio tool such as alsamixer.

Note that sound card should support 16bit monaural recording, and multiple cards are not supported (in that case the first one will be used).

This file supports alsa version 1.x, and tested on 1.0.13.

The default PCM device name is "default", and can be overwritten by environment variable "ALSADEV".

See also:

http://www.alsa-project.org/

Author:

Akinobu LEE

Date:

Sun Feb 13 16:18:26 2005

Revision

1.9

Definition in file adin_mic_linux_alsa.c.

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Function Documentation

static void output_card_info	(	char *	pcm_name,
		snd_pcm_t *	handle
	)			[static]

Output detailed device information.

Parameters:

	pcm_name	[in] device name string
	handle	[in] pcm audio handler

Definition at line 95 of file adin_mic_linux_alsa.c.

Referenced by adin_alsa_standby().

boolean adin_alsa_standby	(	int	sfreq,
		void *	dummy
	)

Device initialization: check device capability and open for recording.

Parameters:

	sfreq	[in] required sampling frequency.
	dummy	[in] a dummy data

Returns:

TRUE on success, FALSE on failure.

< Pointer to device hardware parameters

Definition at line 163 of file adin_mic_linux_alsa.c.

Referenced by adin_mic_standby(), and adin_select().

static int xrun_recovery	(	snd_pcm_t *	handle,
		int	err
	)			[static]

Error recovery when PCM buffer underrun or suspend.

Parameters:

	handle	[in] audio handler
	err	[in] error code

Returns:

0 on success, otherwise the given errno.

Definition at line 385 of file adin_mic_linux_alsa.c.

Referenced by adin_alsa_begin().

boolean adin_alsa_begin

(

)

Start recording.

Returns:

TRUE on success, FALSE on failure.

Definition at line 412 of file adin_mic_linux_alsa.c.

Referenced by adin_mic_begin(), and adin_select().

boolean adin_alsa_end

(

)

Stop recording.

Returns:

TRUE on success, FALSE on failure.

Definition at line 465 of file adin_mic_linux_alsa.c.

Referenced by adin_mic_end(), and adin_select().

int adin_alsa_read	(	SP16 *	buf,
		int	sampnum
	)

Read samples from device.

Try to read sampnum samples and returns actual number of recorded samples currently available. This function will block until at least one sample can be obtained.

Parameters:

	buf	[out] samples obtained in this function
	sampnum	[in] wanted number of samples to be read

Returns:

actural number of read samples, -2 if an error occured.

Definition at line 483 of file adin_mic_linux_alsa.c.

Referenced by adin_mic_read(), and adin_select().

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