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test@linux:~/signalgenerator> gcc -o audio audio_backup.c -lasound
/usr/lib64/gcc/x86_64-suse-linux/4.5/../../../../lib64/crt1.o: In function `_start':
/usr/src/packages/BUILD/glibc-2.11.3/csu/../sysdeps/x86_64/elf/start.S:109: undefined reference to `main'
collect2: ld returned 1 exit status
Can anyone please help me with this?
The code is below. It is from the sample code test.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sched.h>
#include <errno.h>
#include <getopt.h>
#include <alsa/asoundlib.h>
#include <sys/time.h>
#include <math.h>
static char *device = "plughw:0,0"; /* playback device */
static snd_pcm_format_t format = SND_PCM_FORMAT_S16; /* sample format */
static unsigned int rate = 44100; /* stream rate */
static unsigned int channels = 1; /* count of channels */
static unsigned int buffer_time = 500000; /* ring buffer length in us */
static unsigned int period_time = 100000; /* period time in us */
static double freq = 440; /* sinusoidal wave frequency in Hz */
static int verbose = 0; /* verbose flag */
static int resample = 1; /* enable alsa-lib resampling */
static int period_event = 0; /* produce poll event after each period */
static snd_pcm_sframes_t buffer_size;
static snd_pcm_sframes_t period_size;
static snd_output_t *output = NULL;
static void generate_sine(const snd_pcm_channel_area_t *areas,
snd_pcm_uframes_t offset,
int count, double *_phase)
{
static double max_phase = 2. * M_PI;
double phase = *_phase;
double step = max_phase*freq/(double)rate;
unsigned char *samples[channels];
int steps[channels];
unsigned int chn;
int format_bits = snd_pcm_format_width(format);
unsigned int maxval = (1 << (format_bits - 1)) - 1;
int bps = format_bits / 8; /* bytes per sample */
int phys_bps = snd_pcm_format_physical_width(format) / 8;
int big_endian = snd_pcm_format_big_endian(format) == 1;
int to_unsigned = snd_pcm_format_unsigned(format) == 1;
int is_float = (format == SND_PCM_FORMAT_FLOAT_LE ||
format == SND_PCM_FORMAT_FLOAT_BE);
/* verify and prepare the contents of areas */
for (chn = 0; chn < channels; chn++) {
if ((areas[chn].first % 8) != 0) {
printf("areas[%i].first == %i, aborting...\n", chn, areas[chn].first);
exit(EXIT_FAILURE);
}
samples[chn] = /*(signed short *)*/(((unsigned char *)areas[chn].addr) + (areas[chn].first / 8));
if ((areas[chn].step % 16) != 0) {
printf("areas[%i].step == %i, aborting...\n", chn, areas[chn].step);
exit(EXIT_FAILURE);
}
steps[chn] = areas[chn].step / 8;
samples[chn] += offset * steps[chn];
}
/* fill the channel areas */
while (count-- > 0) {
union {
float f;
int i;
} fval;
int res, i;
if (is_float) {
fval.f = sin(phase) * maxval;
res = fval.i;
} else
res = sin(phase) * maxval;
if (to_unsigned)
res ^= 1U << (format_bits - 1);
for (chn = 0; chn < channels; chn++) {
/* Generate data in native endian format */
if (big_endian) {
for (i = 0; i < bps; i++)
*(samples[chn] + phys_bps - 1 - i) = (res >> i * 8) & 0xff;
} else {
for (i = 0; i < bps; i++)
*(samples[chn] + i) = (res >> i * 8) & 0xff;
}
samples[chn] += steps[chn];
}
phase += step;
if (phase >= max_phase)
phase -= max_phase;
}
*_phase = phase;
}
static int set_hwparams(snd_pcm_t *handle,
snd_pcm_hw_params_t *params,
snd_pcm_access_t access)
{
unsigned int rrate;
snd_pcm_uframes_t size;
int err, dir;
/* choose all parameters */
err = snd_pcm_hw_params_any(handle, params);
if (err < 0) {
printf("Broken configuration for playback: no configurations available: %s\n", snd_strerror(err));
return err;
}
/* set hardware resampling */
err = snd_pcm_hw_params_set_rate_resample(handle, params, resample);
if (err < 0) {
printf("Resampling setup failed for playback: %s\n", snd_strerror(err));
return err;
}
/* set the interleaved read/write format */
err = snd_pcm_hw_params_set_access(handle, params, access);
if (err < 0) {
printf("Access type not available for playback: %s\n", snd_strerror(err));
return err;
}
/* set the sample format */
err = snd_pcm_hw_params_set_format(handle, params, format);
if (err < 0) {
printf("Sample format not available for playback: %s\n", snd_strerror(err));
return err;
}
/* set the count of channels */
err = snd_pcm_hw_params_set_channels(handle, params, channels);
if (err < 0) {
printf("Channels count (%i) not available for playbacks: %s\n", channels, snd_strerror(err));
return err;
}
/* set the stream rate */
rrate = rate;
err = snd_pcm_hw_params_set_rate_near(handle, params, &rrate, 0);
if (err < 0) {
printf("Rate %iHz not available for playback: %s\n", rate, snd_strerror(err));
return err;
}
if (rrate != rate) {
printf("Rate doesn't match (requested %iHz, get %iHz)\n", rate, err);
return -EINVAL;
}
/* set the buffer time */
err = snd_pcm_hw_params_set_buffer_time_near(handle, params, &buffer_time, &dir);
if (err < 0) {
printf("Unable to set buffer time %i for playback: %s\n", buffer_time, snd_strerror(err));
return err;
}
err = snd_pcm_hw_params_get_buffer_size(params, &size);
if (err < 0) {
printf("Unable to get buffer size for playback: %s\n", snd_strerror(err));
return err;
}
buffer_size = size;
/* set the period time */
err = snd_pcm_hw_params_set_period_time_near(handle, params, &period_time, &dir);
if (err < 0) {
printf("Unable to set period time %i for playback: %s\n", period_time, snd_strerror(err));
return err;
}
err = snd_pcm_hw_params_get_period_size(params, &size, &dir);
if (err < 0) {
printf("Unable to get period size for playback: %s\n", snd_strerror(err));
return err;
}
period_size = size;
/* write the parameters to device */
err = snd_pcm_hw_params(handle, params);
if (err < 0) {
printf("Unable to set hw params for playback: %s\n", snd_strerror(err));
return err;
}
return 0;
}
static int set_swparams(snd_pcm_t *handle, snd_pcm_sw_params_t *swparams)
{
int err;
/* get the current swparams */
err = snd_pcm_sw_params_current(handle, swparams);
if (err < 0) {
printf("Unable to determine current swparams for playback: %s\n", snd_strerror(err));
return err;
}
/* start the transfer when the buffer is almost full: */
/* (buffer_size / avail_min) * avail_min */
err = snd_pcm_sw_params_set_start_threshold(handle, swparams, (buffer_size / period_size) * period_size);
if (err < 0) {
printf("Unable to set start threshold mode for playback: %s\n", snd_strerror(err));
return err;
}
/* allow the transfer when at least period_size samples can be processed */
/* or disable this mechanism when period event is enabled (aka interrupt like style processing) */
err = snd_pcm_sw_params_set_avail_min(handle, swparams, period_event ? buffer_size : period_size);
if (err < 0) {
printf("Unable to set avail min for playback: %s\n", snd_strerror(err));
return err;
}
/* enable period events when requested */
if (period_event) {
err = snd_pcm_sw_params_set_period_event(handle, swparams, 1);
if (err < 0) {
printf("Unable to set period event: %s\n", snd_strerror(err));
return err;
}
}
/* write the parameters to the playback device */
err = snd_pcm_sw_params(handle, swparams);
if (err < 0) {
printf("Unable to set sw params for playback: %s\n", snd_strerror(err));
return err;
}
return 0;
}
/*
* Underrun and suspend recovery
*/
static int xrun_recovery(snd_pcm_t *handle, int err)
{
if (verbose)
printf("stream recovery\n");
if (err == -EPIPE) { /* under-run */
err = snd_pcm_prepare(handle);
if (err < 0)
printf("Can't recovery from underrun, prepare failed: %s\n", snd_strerror(err));
return 0;
} else if (err == -ESTRPIPE) {
while ((err = snd_pcm_resume(handle)) == -EAGAIN)
sleep(1); /* wait until the suspend flag is released */
if (err < 0) {
err = snd_pcm_prepare(handle);
if (err < 0)
printf("Can't recovery from suspend, prepare failed: %s\n", snd_strerror(err));
}
return 0;
}
return err;
}
struct async_private_data {
signed short *samples;
snd_pcm_channel_area_t *areas;
double phase;
};
static void async_callback(snd_async_handler_t *ahandler)
{
snd_pcm_t *handle = snd_async_handler_get_pcm(ahandler);
struct async_private_data *data = snd_async_handler_get_callback_private(ahandler);
signed short *samples = data->samples;
snd_pcm_channel_area_t *areas = data->areas;
snd_pcm_sframes_t avail;
int err;
avail = snd_pcm_avail_update(handle);
while (avail >= period_size) {
generate_sine(areas, 0, period_size, &data->phase);
err = snd_pcm_writei(handle, samples, period_size);
if (err < 0) {
printf("Write error: %s\n", snd_strerror(err));
exit(EXIT_FAILURE);
}
if (err != period_size) {
printf("Write error: written %i expected %li\n", err, period_size);
exit(EXIT_FAILURE);
}
avail = snd_pcm_avail_update(handle);
}
}
static int async_loop(snd_pcm_t *handle,
signed short *samples,
snd_pcm_channel_area_t *areas)
{
struct async_private_data data;
snd_async_handler_t *ahandler;
int err, count;
data.samples = samples;
data.areas = areas;
data.phase = 0;
err = snd_async_add_pcm_handler(&ahandler, handle, async_callback, &data);
if (err < 0) {
printf("Unable to register async handler\n");
exit(EXIT_FAILURE);
}
for (count = 0; count < 2; count++) {
generate_sine(areas, 0, period_size, &data.phase);
err = snd_pcm_writei(handle, samples, period_size);
if (err < 0) {
printf("Initial write error: %s\n", snd_strerror(err));
exit(EXIT_FAILURE);
}
if (err != period_size) {
printf("Initial write error: written %i expected %li\n", err, period_size);
exit(EXIT_FAILURE);
}
}
if (snd_pcm_state(handle) == SND_PCM_STATE_PREPARED) {
err = snd_pcm_start(handle);
if (err < 0) {
printf("Start error: %s\n", snd_strerror(err));
exit(EXIT_FAILURE);
}
}
/* because all other work is done in the signal handler,
suspend the process */
while (1) {
sleep(1);
}
}
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