Rev 654 | Blame | Compare with Previous | Last modification | View Log | Download
/** This small demo sends a simple sinusoidal wave to your speakers.*/#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;} elseres = 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;}/** Transfer method - write only*/static int write_loop(snd_pcm_t *handle,signed short *samples,snd_pcm_channel_area_t *areas){double phase = 0;signed short *ptr;int err, cptr;while (1) {generate_sine(areas, 0, period_size, &phase);ptr = samples;cptr = period_size;while (cptr > 0) {err = snd_pcm_writei(handle, ptr, cptr);if (err == -EAGAIN)continue;if (err < 0) {if (xrun_recovery(handle, err) < 0) {printf("Write error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}break; /* skip one period */}ptr += err * channels;cptr -= err;}}}/** Transfer method - write and wait for room in buffer using poll*/static int wait_for_poll(snd_pcm_t *handle, struct pollfd *ufds, unsigned int count){unsigned short revents;while (1) {poll(ufds, count, -1);snd_pcm_poll_descriptors_revents(handle, ufds, count, &revents);if (revents & POLLERR)return -EIO;if (revents & POLLOUT)return 0;}}static int write_and_poll_loop(snd_pcm_t *handle,signed short *samples,snd_pcm_channel_area_t *areas){struct pollfd *ufds;double phase = 0;signed short *ptr;int err, count, cptr, init;count = snd_pcm_poll_descriptors_count (handle);if (count <= 0) {printf("Invalid poll descriptors count\n");return count;}ufds = malloc(sizeof(struct pollfd) * count);if (ufds == NULL) {printf("No enough memory\n");return -ENOMEM;}if ((err = snd_pcm_poll_descriptors(handle, ufds, count)) < 0) {printf("Unable to obtain poll descriptors for playback: %s\n", snd_strerror(err));return err;}init = 1;while (1) {if (!init) {err = wait_for_poll(handle, ufds, count);if (err < 0) {if (snd_pcm_state(handle) == SND_PCM_STATE_XRUN ||snd_pcm_state(handle) == SND_PCM_STATE_SUSPENDED) {err = snd_pcm_state(handle) == SND_PCM_STATE_XRUN ? -EPIPE : -ESTRPIPE;if (xrun_recovery(handle, err) < 0) {printf("Write error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}init = 1;} else {printf("Wait for poll failed\n");return err;}}}generate_sine(areas, 0, period_size, &phase);ptr = samples;cptr = period_size;while (cptr > 0) {err = snd_pcm_writei(handle, ptr, cptr);if (err < 0) {if (xrun_recovery(handle, err) < 0) {printf("Write error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}init = 1;break; /* skip one period */}if (snd_pcm_state(handle) == SND_PCM_STATE_RUNNING)init = 0;ptr += err * channels;cptr -= err;if (cptr == 0)break;/* it is possible, that the initial buffer cannot store *//* all data from the last period, so wait awhile */err = wait_for_poll(handle, ufds, count);if (err < 0) {if (snd_pcm_state(handle) == SND_PCM_STATE_XRUN ||snd_pcm_state(handle) == SND_PCM_STATE_SUSPENDED) {err = snd_pcm_state(handle) == SND_PCM_STATE_XRUN ? -EPIPE : -ESTRPIPE;if (xrun_recovery(handle, err) < 0) {printf("Write error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}init = 1;} else {printf("Wait for poll failed\n");return err;}}}}}/** Transfer method - asynchronous notification*/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);}}/** Transfer method - asynchronous notification + direct write*/static void async_direct_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);const snd_pcm_channel_area_t *my_areas;snd_pcm_uframes_t offset, frames, size;snd_pcm_sframes_t avail, commitres;snd_pcm_state_t state;int first = 0, err;while (1) {state = snd_pcm_state(handle);if (state == SND_PCM_STATE_XRUN) {err = xrun_recovery(handle, -EPIPE);if (err < 0) {printf("XRUN recovery failed: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}first = 1;} else if (state == SND_PCM_STATE_SUSPENDED) {err = xrun_recovery(handle, -ESTRPIPE);if (err < 0) {printf("SUSPEND recovery failed: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}}avail = snd_pcm_avail_update(handle);if (avail < 0) {err = xrun_recovery(handle, avail);if (err < 0) {printf("avail update failed: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}first = 1;continue;}if (avail < period_size) {if (first) {first = 0;err = snd_pcm_start(handle);if (err < 0) {printf("Start error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}} else {break;}continue;}size = period_size;while (size > 0) {frames = size;err = snd_pcm_mmap_begin(handle, &my_areas, &offset, &frames);if (err < 0) {if ((err = xrun_recovery(handle, err)) < 0) {printf("MMAP begin avail error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}first = 1;}generate_sine(my_areas, offset, frames, &data->phase);commitres = snd_pcm_mmap_commit(handle, offset, frames);if (commitres < 0 || (snd_pcm_uframes_t)commitres != frames) {if ((err = xrun_recovery(handle, commitres >= 0 ? -EPIPE : commitres)) < 0) {printf("MMAP commit error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}first = 1;}size -= frames;}}}static int async_direct_loop(snd_pcm_t *handle,signed short *samples ATTRIBUTE_UNUSED,snd_pcm_channel_area_t *areas ATTRIBUTE_UNUSED){struct async_private_data data;snd_async_handler_t *ahandler;const snd_pcm_channel_area_t *my_areas;snd_pcm_uframes_t offset, frames, size;snd_pcm_sframes_t commitres;int err, count;data.samples = NULL; /* we do not require the global sample area for direct write */data.areas = NULL; /* we do not require the global areas for direct write */data.phase = 0;err = snd_async_add_pcm_handler(&ahandler, handle, async_direct_callback, &data);if (err < 0) {printf("Unable to register async handler\n");exit(EXIT_FAILURE);}for (count = 0; count < 2; count++) {size = period_size;while (size > 0) {frames = size;err = snd_pcm_mmap_begin(handle, &my_areas, &offset, &frames);if (err < 0) {if ((err = xrun_recovery(handle, err)) < 0) {printf("MMAP begin avail error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}}generate_sine(my_areas, offset, frames, &data.phase);commitres = snd_pcm_mmap_commit(handle, offset, frames);if (commitres < 0 || (snd_pcm_uframes_t)commitres != frames) {if ((err = xrun_recovery(handle, commitres >= 0 ? -EPIPE : commitres)) < 0) {printf("MMAP commit error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}}size -= frames;}}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);}}/** Transfer method - direct write only*/static int direct_loop(snd_pcm_t *handle,signed short *samples ATTRIBUTE_UNUSED,snd_pcm_channel_area_t *areas ATTRIBUTE_UNUSED){double phase = 0;const snd_pcm_channel_area_t *my_areas;snd_pcm_uframes_t offset, frames, size;snd_pcm_sframes_t avail, commitres;snd_pcm_state_t state;int err, first = 1;while (1) {state = snd_pcm_state(handle);if (state == SND_PCM_STATE_XRUN) {err = xrun_recovery(handle, -EPIPE);if (err < 0) {printf("XRUN recovery failed: %s\n", snd_strerror(err));return err;}first = 1;} else if (state == SND_PCM_STATE_SUSPENDED) {err = xrun_recovery(handle, -ESTRPIPE);if (err < 0) {printf("SUSPEND recovery failed: %s\n", snd_strerror(err));return err;}}avail = snd_pcm_avail_update(handle);if (avail < 0) {err = xrun_recovery(handle, avail);if (err < 0) {printf("avail update failed: %s\n", snd_strerror(err));return err;}first = 1;continue;}if (avail < period_size) {if (first) {first = 0;err = snd_pcm_start(handle);if (err < 0) {printf("Start error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}} else {err = snd_pcm_wait(handle, -1);if (err < 0) {if ((err = xrun_recovery(handle, err)) < 0) {printf("snd_pcm_wait error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}first = 1;}}continue;}size = period_size;while (size > 0) {frames = size;err = snd_pcm_mmap_begin(handle, &my_areas, &offset, &frames);if (err < 0) {if ((err = xrun_recovery(handle, err)) < 0) {printf("MMAP begin avail error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}first = 1;}generate_sine(my_areas, offset, frames, &phase);commitres = snd_pcm_mmap_commit(handle, offset, frames);if (commitres < 0 || (snd_pcm_uframes_t)commitres != frames) {if ((err = xrun_recovery(handle, commitres >= 0 ? -EPIPE : commitres)) < 0) {printf("MMAP commit error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}first = 1;}size -= frames;}}}/** Transfer method - direct write only using mmap_write functions*/static int direct_write_loop(snd_pcm_t *handle,signed short *samples,snd_pcm_channel_area_t *areas){double phase = 0;signed short *ptr;int err, cptr;while (1) {generate_sine(areas, 0, period_size, &phase);ptr = samples;cptr = period_size;while (cptr > 0) {err = snd_pcm_mmap_writei(handle, ptr, cptr);if (err == -EAGAIN)continue;if (err < 0) {if (xrun_recovery(handle, err) < 0) {printf("Write error: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}break; /* skip one period */}ptr += err * channels;cptr -= err;}}}/***/struct transfer_method {const char *name;snd_pcm_access_t access;int (*transfer_loop)(snd_pcm_t *handle,signed short *samples,snd_pcm_channel_area_t *areas);};static struct transfer_method transfer_methods[] = {{ "write", SND_PCM_ACCESS_RW_INTERLEAVED, write_loop },{ "write_and_poll", SND_PCM_ACCESS_RW_INTERLEAVED, write_and_poll_loop },{ "async", SND_PCM_ACCESS_RW_INTERLEAVED, async_loop },{ "async_direct", SND_PCM_ACCESS_MMAP_INTERLEAVED, async_direct_loop },{ "direct_interleaved", SND_PCM_ACCESS_MMAP_INTERLEAVED, direct_loop },{ "direct_noninterleaved", SND_PCM_ACCESS_MMAP_NONINTERLEAVED, direct_loop },{ "direct_write", SND_PCM_ACCESS_MMAP_INTERLEAVED, direct_write_loop },{ NULL, SND_PCM_ACCESS_RW_INTERLEAVED, NULL }};static void help(void){int k;printf("Usage: pcm [OPTION]... [FILE]...\n""-h,--help help\n""-D,--device playback device\n""-r,--rate stream rate in Hz\n""-c,--channels count of channels in stream\n""-f,--frequency sine wave frequency in Hz\n""-b,--buffer ring buffer size in us\n""-p,--period period size in us\n""-m,--method transfer method\n""-o,--format sample format\n""-v,--verbose show the PCM setup parameters\n""-n,--noresample do not resample\n""-e,--pevent enable poll event after each period\n""\n");printf("Recognized sample formats are:");for (k = 0; k < SND_PCM_FORMAT_LAST; ++k) {const char *s = snd_pcm_format_name(k);if (s)printf(" %s", s);}printf("\n");printf("Recognized transfer methods are:");for (k = 0; transfer_methods[k].name; k++)printf(" %s", transfer_methods[k].name);printf("\n");}int main(int argc, char *argv[]){struct option long_option[] ={{"help", 0, NULL, 'h'},{"device", 1, NULL, 'D'},{"rate", 1, NULL, 'r'},{"channels", 1, NULL, 'c'},{"frequency", 1, NULL, 'f'},{"buffer", 1, NULL, 'b'},{"period", 1, NULL, 'p'},{"method", 1, NULL, 'm'},{"format", 1, NULL, 'o'},{"verbose", 1, NULL, 'v'},{"noresample", 1, NULL, 'n'},{"pevent", 1, NULL, 'e'},{NULL, 0, NULL, 0},};snd_pcm_t *handle;int err, morehelp;snd_pcm_hw_params_t *hwparams;snd_pcm_sw_params_t *swparams;int method = 0;signed short *samples;unsigned int chn;snd_pcm_channel_area_t *areas;snd_pcm_hw_params_alloca(&hwparams);snd_pcm_sw_params_alloca(&swparams);morehelp = 0;while (1) {int c;if ((c = getopt_long(argc, argv, "hD:r:c:f:b:p:m:o:vne", long_option, NULL)) < 0)break;switch (c) {case 'h':morehelp++;break;case 'D':device = strdup(optarg);break;case 'r':rate = atoi(optarg);rate = rate < 4000 ? 4000 : rate;rate = rate > 196000 ? 196000 : rate;break;case 'c':channels = atoi(optarg);channels = channels < 1 ? 1 : channels;channels = channels > 1024 ? 1024 : channels;break;case 'f':freq = atoi(optarg);freq = freq < 50 ? 50 : freq;freq = freq > 5000 ? 5000 : freq;break;case 'b':buffer_time = atoi(optarg);buffer_time = buffer_time < 1000 ? 1000 : buffer_time;buffer_time = buffer_time > 1000000 ? 1000000 : buffer_time;break;case 'p':period_time = atoi(optarg);period_time = period_time < 1000 ? 1000 : period_time;period_time = period_time > 1000000 ? 1000000 : period_time;break;case 'm':for (method = 0; transfer_methods[method].name; method++)if (!strcasecmp(transfer_methods[method].name, optarg))break;if (transfer_methods[method].name == NULL)method = 0;break;case 'o':for (format = 0; format < SND_PCM_FORMAT_LAST; format++) {const char *format_name = snd_pcm_format_name(format);if (format_name)if (!strcasecmp(format_name, optarg))break;}if (format == SND_PCM_FORMAT_LAST)format = SND_PCM_FORMAT_S16;if (!snd_pcm_format_linear(format) &&!(format == SND_PCM_FORMAT_FLOAT_LE ||format == SND_PCM_FORMAT_FLOAT_BE)) {printf("Invalid (non-linear/float) format %s\n",optarg);return 1;}break;case 'v':verbose = 1;break;case 'n':resample = 0;break;case 'e':period_event = 1;break;}}if (morehelp) {help();return 0;}err = snd_output_stdio_attach(&output, stdout, 0);if (err < 0) {printf("Output failed: %s\n", snd_strerror(err));return 0;}printf("Playback device is %s\n", device);printf("Stream parameters are %iHz, %s, %i channels\n", rate, snd_pcm_format_name(format), channels);printf("Sine wave rate is %.4fHz\n", freq);printf("Using transfer method: %s\n", transfer_methods[method].name);if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {printf("Playback open error: %s\n", snd_strerror(err));return 0;}if ((err = set_hwparams(handle, hwparams, transfer_methods[method].access)) < 0) {printf("Setting of hwparams failed: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}if ((err = set_swparams(handle, swparams)) < 0) {printf("Setting of swparams failed: %s\n", snd_strerror(err));exit(EXIT_FAILURE);}if (verbose > 0)snd_pcm_dump(handle, output);samples = malloc((period_size * channels * snd_pcm_format_physical_width(format)) / 8);if (samples == NULL) {printf("No enough memory\n");exit(EXIT_FAILURE);}areas = calloc(channels, sizeof(snd_pcm_channel_area_t));if (areas == NULL) {printf("No enough memory\n");exit(EXIT_FAILURE);}for (chn = 0; chn < channels; chn++) {areas[chn].addr = samples;areas[chn].first = chn * snd_pcm_format_physical_width(format);areas[chn].step = channels * snd_pcm_format_physical_width(format);}err = transfer_methods[method].transfer_loop(handle, samples, areas);if (err < 0)printf("Transfer failed: %s\n", snd_strerror(err));free(areas);free(samples);snd_pcm_close(handle);return 0;}