alsa.c

/*
 *  Copyright (c) 2014 Thierry Leconte (f4dwv)
 *
 *   
 *   This code is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Library General Public License version 2
 *   published by the Free Software Foundation.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU Library General Public License for more details.
 *
 *   You should have received a copy of the GNU Library General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <pthread.h>
#include <alsa/asoundlib.h>
#include "acarsdec.h"

#define MAXNBFRAMES 1024

static snd_pcm_t *capture_handle;
int initAlsa(char **argv,int optind)
{
	snd_pcm_hw_params_t *hw_params;
	int err,n;
	unsigned int Fs;

	if ((err = snd_pcm_open(&capture_handle, argv[optind],
			  SND_PCM_STREAM_CAPTURE, 0)) < 0) {
		fprintf(stderr, "Alsa cannot open audio device %s (%s)\n",argv[optind], snd_strerror(err));
		return 1;
	}

	if ((err = snd_pcm_hw_params_malloc(&hw_params)) < 0) {
		fprintf(stderr,
			"Alsa cannot allocate hardware parameter structure (%s)\n",snd_strerror(err));
		return 1;
	}

	if ((err = snd_pcm_hw_params_any(capture_handle, hw_params)) < 0) {
		fprintf(stderr,
			"Alsa cannot initialize hardware parameter structure (%s)\n",snd_strerror(err));
		return 1;
	}

	if ((err = snd_pcm_hw_params_set_access(capture_handle, hw_params,SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
		fprintf(stderr, "Alsa cannot set access type (%s)\n",snd_strerror(err));
		return 1;
	}

	if ((err = snd_pcm_hw_params_set_format(capture_handle, hw_params,SND_PCM_FORMAT_S16)) < 0) {
		fprintf(stderr, "Alsa cannot set sample format (%s)\n",snd_strerror(err));
		return 1;
	}

	snd_pcm_hw_params_set_rate_resample(capture_handle, hw_params,0);
	Fs=19200;n=1;
	if ((err = snd_pcm_hw_params_set_rate_near(capture_handle, hw_params, &Fs,&n)) < 0) {
		fprintf(stderr, "Alsa cannot set sample rate (%s)\n",snd_strerror(err));
		return 1;
	}
	fprintf(stderr, "Alsa sample rate %d\n",Fs);

	if(snd_pcm_hw_params_get_channels (hw_params, &nbch)!=0) {
		fprintf(stderr, "Alsa cannot get number of channels\n");
		return 1;
	}
	if(nbch>4) {
		fprintf(stderr, "Alsa too much channels\n");
		return 1;

	}
        if ((err = snd_pcm_hw_params(capture_handle, hw_params)) < 0) {
                fprintf(stderr, "Alsa cannot set parameters (%s)\n",snd_strerror(err));
		return 1;
	}
        snd_pcm_hw_params_free(hw_params);

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

	for(n=0;n<nbch;n++) {
		channel[n].chn=n;
		channel[n].Infs=Fs;
		channel[n].InBuff=malloc(MAXNBFRAMES*sizeof(sample_t));
	}
	for(;n<MAXNBCHANNELS;n++) channel[n].Infs=0;
	
	return (0);
}


int getAlsaSample(void)
{
	int r,n,i;
	signed short sndbuff[MAXNBFRAMES*MAXNBCHANNELS];

	r = snd_pcm_readi(capture_handle, sndbuff,MAXNBFRAMES );
	if (r <= 0) {
		fprintf(stderr,"Alsa cannot read from interface (%s)\n", snd_strerror(r));
		return -1;
	}

	pthread_mutex_lock(&datamtx);
	while(wrkmask) pthread_cond_wait(&datawcd, &datamtx);
	pthread_mutex_unlock(&datamtx);

	for(n=0;n<nbch;n++)
		if(channel[n].Infs) {
		  int len=r;
		  for(i=0;i<len;i++) channel[n].InBuff[i]=(float)(sndbuff[n+i*nbch])/32768.0;
		  channel[n].lenIn=len;
		}

	return 0;
}