Docu:: Alsa Audio API:: A minimal capture program

Docu:: Alsa Audio API:: A minimal capture program

[Torsten Mohr]

Hi,

i copied the "minimal capture program" from the
Alsa page -> Documentation -> Tutorial on using the
ALSA Audio API -> A minimal capture program.

I added "int rate = 44100" and changed the wrong
parameter "44100" in "snd_pcm_hw_params_set_rate_near"
to "&rate".

bash# gcc capture.c -lasound
bash# a.out default

But if i add a "sleep(1)" in the "for(i = 0; i < 10; i++)",
the whole program crashes.


I want to write a program where some chunk of
data is sampled from time to time, with some delay
inbetween.  The behaviour above (with sleep(1))
is a good example for what i want to do.

Can anybody tell me what i need to change to make
the program work ok?


Thanks for any hints,
Torsten.




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Re: Docu:: Alsa Audio API:: A minimal capture program

[Clemens Ladisch]

Torsten Mohr wrote:
> I want to write a program where some chunk of
> data is sampled from time to time, with some delay
> inbetween.

Your program wants to ignore any buffer overruns.  To do this, you
have to change the sw_params: set the stop_threshold to either 0 or
the buffer size in frames (I don't remember which).


HTH
Clemens




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Re: Docu:: Alsa Audio API:: A minimal capture program

[Torsten Mohr]

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Hi,

thanks for that hint.

But sadly, the attached program doesn't work, though
i set stop_threshold to 0.  I didn't find any functions
to set buffersize to 0, it doesn't seem to be in the
software parameters.


It would be great, if anybody had a hint.


Regards,
Torsten.



> Torsten Mohr wrote:
> > I want to write a program where some chunk of
> > data is sampled from time to time, with some delay
> > inbetween.
>
> Your program wants to ignore any buffer overruns.  To do this, you
> have to change the sw_params: set the stop_threshold to either 0 or
> the buffer size in frames (I don't remember which).
>
>
> HTH
> Clemens
>
>
>
>
> -------------------------------------------------------
> The SF.Net email is sponsored by EclipseCon 2004
> Premiere Conference on Open Tools Development and Integration
> See the breadth of Eclipse activity. February 3-5 in Anaheim, CA.
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> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/alsa-devel

[-- Attachment #2: sound.c --]
[-- Type: text/x-csrc, Size: 3451 bytes --]

#define _GNU_SOURCE
#include <stdio.h>
#include <malloc.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <alsa/asoundlib.h>
#include <sys/signal.h>

#include "sound.h"
#include "settings.h"

#define QWE	fprintf(stderr, "File %s, Line %i\n", __FILE__, __LINE__)

int periodsize = 128;
int rate = 44100;
int i;
int err;
unsigned char* data;
snd_pcm_t *capture_handle;
snd_pcm_hw_params_t *hw_params;
snd_pcm_sw_params_t *sw_params;


unsigned char* sound_get_data(void) {
	return data;
}


int sound_init2(void) {

	if ((err = snd_pcm_open (&capture_handle, "plughw:0,0", SND_PCM_STREAM_CAPTURE, 0)) < 0) {
		fprintf (stderr, "cannot open audio device plughw:0,0 (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
		   
	if ((err = snd_pcm_hw_params_malloc (&hw_params)) < 0) {
		fprintf (stderr, "cannot allocate hardware parameter structure (%s)\n",
			 snd_strerror (err));
		exit (1);
	}

	if ((err = snd_pcm_hw_params_any (capture_handle, hw_params)) < 0) {
		fprintf (stderr, "cannot initialize hardware parameter structure (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
	
	if ((err = snd_pcm_hw_params_set_access (capture_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
		fprintf (stderr, "cannot set access type (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
	
	if ((err = snd_pcm_hw_params_set_format (capture_handle, hw_params, SND_PCM_FORMAT_S16_LE)) < 0) {
		fprintf (stderr, "cannot set sample format (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
	
	if ((err = snd_pcm_hw_params_set_rate_near (capture_handle, hw_params, &rate, 0)) < 0) {
		fprintf (stderr, "cannot set sample rate (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
	
	if ((err = snd_pcm_hw_params_set_channels (capture_handle, hw_params, 2)) < 0) {
		fprintf (stderr, "cannot set channel count (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
	
	if ((err = snd_pcm_hw_params (capture_handle, hw_params)) < 0) {
		fprintf (stderr, "cannot set parameters (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
	
	snd_pcm_hw_params_free (hw_params);

	if ((err = snd_pcm_sw_params_malloc (&sw_params)) < 0) {
		fprintf (stderr, "cannot allocate software parameter structure (%s)\n",
			 snd_strerror (err));
		exit (1);
	}

	if ((err = snd_pcm_sw_params_current (capture_handle, sw_params)) < 0) {
		fprintf (stderr, "cannot initialize software parameter structure (%s)\n",
			 snd_strerror (err));
		exit (1);
	}

	if ((err = snd_pcm_sw_params_set_stop_threshold (capture_handle, sw_params, 0)) < 0) {
		fprintf (stderr, "cannot set access type (%s)\n",
			 snd_strerror (err));
		exit (1);
	}

	if ((err = snd_pcm_sw_params (capture_handle, sw_params)) < 0) {
		fprintf (stderr, "cannot set sw-parameters (%s)\n",
			 snd_strerror (err));
		exit (1);
	} // */
	snd_pcm_sw_params_free (sw_params);

	
	if ((err = snd_pcm_prepare (capture_handle)) < 0) {
		fprintf (stderr, "cannot prepare audio interface for use (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
}

int sound_init(void) {
    data = (unsigned char *)calloc(SAMPLES*4, 0);
	sound_init2();
}

void sound_capture(void) {
QWE;
	if ((err = snd_pcm_readi (capture_handle, data, periodsize)) != periodsize) {
		fprintf (stderr, "read from audio interface failed (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
QWE;
}

int main(int argc, char** argv) {
	sound_init();
	sound_capture();
	sound_capture();
	sleep(1);
	sound_capture();

	snd_pcm_close(capture_handle);
QWE;
	return 0;
}

Re: Docu:: Alsa Audio API:: A minimal capture program

[Jaroslav Kysela]

On Wed, 28 Jan 2004, Torsten Mohr wrote:

> Hi,
> 
> thanks for that hint.
> 
> But sadly, the attached program doesn't work, though
> i set stop_threshold to 0.  I didn't find any functions

This is wrong. You need to set this value to sw_params->boundary or 
greater value to eliminate the stop detection, otherwise with zero,
the stream is immediately stopped.

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs


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Re: Docu:: Alsa Audio API:: A minimal capture program

[Torsten Mohr]

[-- Attachment #1: Type: text/plain, Size: 668 bytes --]

Hi,

> > thanks for that hint.
> >
> > But sadly, the attached program doesn't work, though
> > i set stop_threshold to 0.  I didn't find any functions
>
> This is wrong. You need to set this value to sw_params->boundary or
> greater value to eliminate the stop detection, otherwise with zero,
> the stream is immediately stopped.

thanks again.

But this doesn't seem to be the problem, the attached file is
basically the example "minimal capture program" with the
suggested additions.

The program fails badly.  It would be so very great if somebody
had a hint for me on that one.  I tried to find the source of
the problem, but i didn't succeed.


Thanks,
Torsten.

[-- Attachment #2: sound.c --]
[-- Type: text/x-csrc, Size: 3809 bytes --]

#define _GNU_SOURCE
#include <stdio.h>
#include <malloc.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <alsa/asoundlib.h>
#include <sys/signal.h>

//#include "sound.h"
//#include "settings.h"

#ifndef SAMPLES
#define SAMPLES 2048
#endif

#define QWE	fprintf(stderr, "File %s, Line %i\n", __FILE__, __LINE__)

int periodsize = 4096;
int rate = 44100;
int i;
int err;
unsigned char* data;
snd_pcm_t *capture_handle;
snd_pcm_hw_params_t *hw_params;
snd_pcm_sw_params_t *sw_params;

snd_pcm_uframes_t boundary;

unsigned char* sound_get_data(void) {
	return data;
}


int sound_init2(void) {

	if ((err = snd_pcm_open (&capture_handle, "plughw:0,0", SND_PCM_STREAM_CAPTURE, 0)) < 0) {
		fprintf (stderr, "cannot open audio device plughw:0,0 (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
		   
	if ((err = snd_pcm_hw_params_malloc (&hw_params)) < 0) {
		fprintf (stderr, "cannot allocate hardware parameter structure (%s)\n",
			 snd_strerror (err));
		exit (1);
	}

	if ((err = snd_pcm_hw_params_any (capture_handle, hw_params)) < 0) {
		fprintf (stderr, "cannot initialize hardware parameter structure (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
	
	if ((err = snd_pcm_hw_params_set_access (capture_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
		fprintf (stderr, "cannot set access type (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
	
	if ((err = snd_pcm_hw_params_set_format (capture_handle, hw_params, SND_PCM_FORMAT_S16_LE)) < 0) {
		fprintf (stderr, "cannot set sample format (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
	
	if ((err = snd_pcm_hw_params_set_rate_near (capture_handle, hw_params, &rate, 0)) < 0) {
		fprintf (stderr, "cannot set sample rate (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
	
	if ((err = snd_pcm_hw_params_set_channels (capture_handle, hw_params, 2)) < 0) {
		fprintf (stderr, "cannot set channel count (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
	
	if ((err = snd_pcm_hw_params (capture_handle, hw_params)) < 0) {
		fprintf (stderr, "cannot set parameters (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
	
	snd_pcm_hw_params_free (hw_params);

	if ((err = snd_pcm_sw_params_malloc (&sw_params)) < 0) {
		fprintf (stderr, "cannot allocate software parameter structure (%s)\n",
			 snd_strerror (err));
		exit (1);
	}

	if ((err = snd_pcm_sw_params_current (capture_handle, sw_params)) < 0) {
		fprintf (stderr, "cannot initialize software parameter structure (%s)\n",
			 snd_strerror (err));
		exit (1);
	}

	if ((err = snd_pcm_sw_params_get_boundary (sw_params, &boundary)) < 0) {
		fprintf (stderr, "cannot set access type (%s)\n",
			 snd_strerror (err));
		exit (1);
	}


	if ((err = snd_pcm_sw_params_set_stop_threshold (capture_handle, sw_params, boundary)) < 0) {
		fprintf (stderr, "cannot set access type (%s)\n",
			 snd_strerror (err));
		exit (1);
	}

	if ((err = snd_pcm_sw_params (capture_handle, sw_params)) < 0) {
		fprintf (stderr, "cannot set sw-parameters (%s)\n",
			 snd_strerror (err));
		exit (1);
	} // */
	snd_pcm_sw_params_free (sw_params);

	
	if ((err = snd_pcm_prepare (capture_handle)) < 0) {
		fprintf (stderr, "cannot prepare audio interface for use (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
}

int sound_init(void) {
    data = (unsigned char *)calloc(SAMPLES*4, 0);
	sound_init2();
}

void sound_capture(void) {
QWE;
	if ((err = snd_pcm_readi (capture_handle, data, periodsize)) != periodsize) {
		fprintf (stderr, "read from audio interface failed (%s)\n",
			 snd_strerror (err));
		exit (1);
	}
QWE;
}


int main(int argc, char** argv) {
	sound_init();
	sound_capture();
	sound_capture();
	sleep(1);
	sound_capture();
	sound_capture();

QWE;
	snd_pcm_drop(capture_handle);
QWE;
//	snd_pcm_drain(capture_handle);
QWE;
	snd_pcm_close(capture_handle);
QWE;
	return 0;
} // */

Re: Docu:: Alsa Audio API:: A minimal capture program

[Jaroslav Kysela]

On Mon, 9 Feb 2004, Torsten Mohr wrote:

> Hi,
> 
> > > thanks for that hint.
> > >
> > > But sadly, the attached program doesn't work, though
> > > i set stop_threshold to 0.  I didn't find any functions
> >
> > This is wrong. You need to set this value to sw_params->boundary or
> > greater value to eliminate the stop detection, otherwise with zero,
> > the stream is immediately stopped.
> 
> thanks again.
> 
> But this doesn't seem to be the problem, the attached file is
> basically the example "minimal capture program" with the
> suggested additions.
> 
> The program fails badly.  It would be so very great if somebody
> had a hint for me on that one.  I tried to find the source of
> the problem, but i didn't succeed.

You've made this stupid bug:

data = (unsigned char *)calloc(SAMPLES*4, 0);

should be:

data = (unsigned char *)calloc(periodsize*4, 1);

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs


-------------------------------------------------------
The SF.Net email is sponsored by EclipseCon 2004
Premiere Conference on Open Tools Development and Integration
See the breadth of Eclipse activity. February 3-5 in Anaheim, CA.
http://www.eclipsecon.org/osdn

Re: Docu:: Alsa Audio API:: A minimal capture program

[Torsten Mohr]

Hi,

> You've made this stupid bug:
>
> data = (unsigned char *)calloc(SAMPLES*4, 0);
>
> should be:
>
> data = (unsigned char *)calloc(periodsize*4, 1);


thank you so very much for that hint, that was the problem.


Best regards,
Torsten.



-------------------------------------------------------
The SF.Net email is sponsored by EclipseCon 2004
Premiere Conference on Open Tools Development and Integration
See the breadth of Eclipse activity. February 3-5 in Anaheim, CA.
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