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#include <alsa/asoundlib.h>
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static uint64_t timespec_us(const struct timespec *ts) {
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ts->tv_sec * 1000000LLU +
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ts->tv_nsec / 1000LLU;
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int main(int argc, char *argv[]) {
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snd_pcm_hw_params_t *hwparams;
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snd_pcm_sw_params_t *swparams;
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snd_pcm_status_t *status;
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unsigned rate = 44100;
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snd_pcm_uframes_t boundary, buffer_size = 44100/10; /* 100s */
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struct timespec start, last_timestamp = { 0, 0 };
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snd_pcm_sframes_t last_avail = 0, last_delay = 0;
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struct pollfd *pollfds;
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int64_t sample_count = 0;
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snd_pcm_hw_params_alloca(&hwparams);
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snd_pcm_sw_params_alloca(&swparams);
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snd_pcm_status_alloca(&status);
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r = clock_gettime(CLOCK_MONOTONIC, &start);
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start_us = timespec_us(&start);
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dev = argc > 1 ? argv[1] : "front:AudioPCI";
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r = snd_pcm_open(&pcm, dev, SND_PCM_STREAM_PLAYBACK, 0);
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r = snd_pcm_hw_params_any(pcm, hwparams);
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r = snd_pcm_hw_params_set_rate_resample(pcm, hwparams, 0);
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r = snd_pcm_hw_params_set_access(pcm, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED);
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r = snd_pcm_hw_params_set_format(pcm, hwparams, SND_PCM_FORMAT_S16_LE);
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r = snd_pcm_hw_params_set_rate_near(pcm, hwparams, &rate, NULL);
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r = snd_pcm_hw_params_set_channels(pcm, hwparams, 2);
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r = snd_pcm_hw_params_set_periods_integer(pcm, hwparams);
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r = snd_pcm_hw_params_set_periods_near(pcm, hwparams, &periods, &dir);
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r = snd_pcm_hw_params_set_buffer_size_near(pcm, hwparams, &buffer_size);
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r = snd_pcm_hw_params(pcm, hwparams);
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r = snd_pcm_hw_params_current(pcm, hwparams);
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r = snd_pcm_sw_params_current(pcm, swparams);
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r = snd_pcm_sw_params_set_avail_min(pcm, swparams, 1);
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r = snd_pcm_sw_params_set_period_event(pcm, swparams, 0);
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r = snd_pcm_hw_params_get_buffer_size(hwparams, &buffer_size);
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r = snd_pcm_sw_params_set_start_threshold(pcm, swparams, buffer_size);
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r = snd_pcm_sw_params_get_boundary(swparams, &boundary);
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r = snd_pcm_sw_params_set_stop_threshold(pcm, swparams, boundary);
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r = snd_pcm_sw_params_set_tstamp_mode(pcm, swparams, SND_PCM_TSTAMP_ENABLE);
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r = snd_pcm_sw_params(pcm, swparams);
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r = snd_pcm_prepare(pcm);
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r = snd_pcm_sw_params_current(pcm, swparams);
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/* assert(snd_pcm_hw_params_is_monotonic(hwparams) > 0); */
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n_pollfd = snd_pcm_poll_descriptors_count(pcm);
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assert(n_pollfd > 0);
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pollfds = malloc(sizeof(struct pollfd) * n_pollfd);
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r = snd_pcm_poll_descriptors(pcm, pollfds, n_pollfd);
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assert(r == n_pollfd);
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snd_pcm_sframes_t avail, delay;
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struct timespec now, timestamp;
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unsigned short revents;
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uint64_t now_us, timestamp_us;
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snd_pcm_state_t state;
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r = poll(pollfds, n_pollfd, 0);
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r = snd_pcm_poll_descriptors_revents(pcm, pollfds, n_pollfd, &revents);
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assert((revents & ~POLLOUT) == 0);
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avail = snd_pcm_avail(pcm);
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r = snd_pcm_status(pcm, status);
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/* This assertion fails from time to time. ALSA seems to be broken */
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/* assert(avail == (snd_pcm_sframes_t) snd_pcm_status_get_avail(status)); */
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/* printf("%lu %lu\n", (unsigned long) avail, (unsigned long) snd_pcm_status_get_avail(status)); */
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snd_pcm_status_get_htstamp(status, ×tamp);
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delay = snd_pcm_status_get_delay(status);
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state = snd_pcm_status_get_state(status);
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r = clock_gettime(CLOCK_MONOTONIC, &now);
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assert(!revents || avail > 0);
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snd_pcm_sframes_t sframes;
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static const uint16_t samples[2] = { 0, 0 };
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sframes = snd_pcm_writei(pcm, samples, 1);
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assert(sframes == 1);
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memcmp(×tamp, &last_timestamp, sizeof(timestamp)) == 0 &&
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avail == last_avail &&
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delay == last_delay) {
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now_us = timespec_us(&now);
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timestamp_us = timespec_us(×tamp);
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printf("%llu\t%llu\t%llu\t%li\t%li\t%i\t%i\t%i\n",
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(unsigned long long) (now_us - start_us),
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(unsigned long long) (timestamp_us ? timestamp_us - start_us : 0),
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(unsigned long long) ((sample_count - 1 - delay) * 1000000LU / 44100),
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/** When this assert is hit, most likely something bad
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* happened, i.e. the avail jumped suddenly. */
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assert((unsigned) avail <= buffer_size);
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last_timestamp = timestamp;