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518 kaklik 1 
//ALSA Audio playback testing program
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//
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	#include <stdio.h>
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	#include <stdlib.h>
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	#include <alsa/asoundlib.h>
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	int exact_rate=44100;
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int linear_chirp(int *pole, int delka_pole, int spozdeni){  // vygeneruje linearni chirp a vzorky ulozi do pole
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static const double pi = 3.141592653589793238462643383279502884197; // Archimedes constant pi
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static const float f0 = 0.01;
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static const float k = 0.0001;
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int t;
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float ble;
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  if((spozdeni+delka_pulsu) < delka_pole)
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    for(t=0;t < delka_pulsu;t++) pole[spozdeni+t] = round ( 100*sin(2*pi*t*(f0+(k/2)*t)) );
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  else return 0;
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}
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static void async_callback(snd_async_handler_t *ahandler)
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{
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	snd_pcm_t *handle = snd_async_handler_get_pcm(ahandler);
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	struct async_private_data *data = snd_async_handler_get_callback_private(ahandler);
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	signed short *samples = data->samples;
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	snd_pcm_channel_area_t *areas = data->areas;
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	snd_pcm_sframes_t avail;
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	int err;
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	avail = snd_pcm_avail_update(handle);
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	while (avail >= period_size) {
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		generate_sine(areas, 0, period_size, &data->phase);
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		err = snd_pcm_writei(handle, samples, period_size);
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		if (err < 0) {
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			printf("Write error: %s\n", snd_strerror(err));
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			exit(EXIT_FAILURE);
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		}
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		if (err != period_size) {
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			printf("Write error: written %i expected %li\n", err, period_size);
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			exit(EXIT_FAILURE);
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		}
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		avail = snd_pcm_avail_update(handle);
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	}
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}
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static int async_loop(snd_pcm_t *handle,
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		      signed short *samples,
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		      snd_pcm_channel_area_t *areas)
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{
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	struct async_private_data data;
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	snd_async_handler_t *ahandler;
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	int err, count;
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	unsigned int i;
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	data.samples = samples;
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	data.areas = areas;
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	data.phase = 0;
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	err = snd_async_add_pcm_handler(&ahandler, handle, async_callback, &data);
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	if (err < 0) {
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		printf("Unable to register async handler\n");
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		exit(EXIT_FAILURE);
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	}
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	for (count = 0; count < 2; count++) {
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		generate_sine(areas, 0, period_size, &data.phase);
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		err = snd_pcm_writei(handle, samples, period_size);
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		if (err < 0) {
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			printf("Initial write error: %s\n", snd_strerror(err));
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			exit(EXIT_FAILURE);
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		}
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		if (err != period_size) {
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			printf("Initial write error: written %i expected %li\n", err, period_size);
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			exit(EXIT_FAILURE);
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		}
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	}
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	if (snd_pcm_state(handle) == SND_PCM_STATE_PREPARED) {
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		err = snd_pcm_start(handle);
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		if (err < 0) {
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			printf("Start error: %s\n", snd_strerror(err));
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			exit(EXIT_FAILURE);
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		}
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	}
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	/* because all other work is done in the signal handler,
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	   suspend the process */
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	for(i=0; i<=10;i++) {
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		sleep(1);
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	}
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}
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	main (int argc, char *argv[])
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	{
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		int i;
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		int err;
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		short buf[128];
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		snd_pcm_t *playback_handle;
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		snd_pcm_hw_params_t *hw_params;
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		snd_pcm_channel_area_t *areas;
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		if ((err = snd_pcm_open (&playback_handle, argv[1], SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
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			fprintf (stderr, "cannot open audio device %s (%s)\n",
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				 argv[1],
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				 snd_strerror (err));
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			exit (1);
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		}
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		if ((err = snd_pcm_hw_params_malloc(&hw_params)) < 0) {
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			fprintf (stderr, "cannot allocate hardware parameter structure (%s)\n",
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				 snd_strerror (err));
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			exit (1);
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		}
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		if ((err = snd_pcm_hw_params_any (playback_handle, hw_params)) < 0) {
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			fprintf (stderr, "cannot initialize hardware parameter structure (%s)\n",
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				 snd_strerror (err));
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			exit (1);
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		}
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		if ((err = snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
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			fprintf (stderr, "cannot set access type (%s)\n",
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				 snd_strerror (err));
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			exit (1);
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		}
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		if ((err = snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE)) < 0) {
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			fprintf (stderr, "cannot set sample format (%s)\n",
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				 snd_strerror (err));
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			exit (1);
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		}
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		if ((err = snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, &exact_rate, 0)) < 0) {
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			fprintf (stderr, "cannot set sample rate (%s)\n",
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				 snd_strerror (err));
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			exit (1);
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		}
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		if ((err = snd_pcm_hw_params_set_channels (playback_handle, hw_params, 2)) < 0) {
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			fprintf (stderr, "cannot set channel count (%s)\n",
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				 snd_strerror (err));
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			exit (1);
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		}
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		if ((err = snd_pcm_hw_params (playback_handle, hw_params)) < 0) {
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			fprintf (stderr, "cannot set parameters (%s)\n",
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				 snd_strerror (err));
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			exit (1);
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		}
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		if ((err = snd_pcm_prepare (playback_handle)) < 0) {
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			fprintf (stderr, "cannot prepare audio interface for use (%s)\n",
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				 snd_strerror (err));
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			exit (1);
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		}
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	async_loop(playback_handle, samples, areas);
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/*		for (i = 0; i < 100; ++i) {
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			if ((err = snd_pcm_writei (playback_handle, buf, 128)) != 128) {
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				fprintf (stderr, "write to audio interface failed (%s)\n",
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					 snd_strerror (err));
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				exit (1);
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			}
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		}*/
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		snd_pcm_close (playback_handle);
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		exit (0);
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	}
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