5 #include <alsa/asoundlib.h>
7 static uint64_t timespec_us(const struct timespec *ts) {
9 ts->tv_sec * 1000000LLU +
10 ts->tv_nsec / 1000LLU;
13 int main(int argc, char *argv[]) {
16 snd_pcm_hw_params_t *hwparams;
17 snd_pcm_sw_params_t *swparams;
18 snd_pcm_status_t *status;
20 unsigned rate = 44100;
22 snd_pcm_uframes_t boundary, buffer_size = 44100/10; /* 100s */
24 struct timespec start, last_timestamp = { 0, 0 };
26 snd_pcm_sframes_t last_avail = 0, last_delay = 0;
27 struct pollfd *pollfds;
29 int64_t sample_count = 0;
31 snd_pcm_hw_params_alloca(&hwparams);
32 snd_pcm_sw_params_alloca(&swparams);
33 snd_pcm_status_alloca(&status);
35 r = clock_gettime(CLOCK_MONOTONIC, &start);
38 start_us = timespec_us(&start);
40 dev = argc > 1 ? argv[1] : "front:AudioPCI";
42 r = snd_pcm_open(&pcm, dev, SND_PCM_STREAM_PLAYBACK, 0);
45 r = snd_pcm_hw_params_any(pcm, hwparams);
48 r = snd_pcm_hw_params_set_rate_resample(pcm, hwparams, 0);
51 r = snd_pcm_hw_params_set_access(pcm, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED);
54 r = snd_pcm_hw_params_set_format(pcm, hwparams, SND_PCM_FORMAT_S16_LE);
57 r = snd_pcm_hw_params_set_rate_near(pcm, hwparams, &rate, NULL);
60 r = snd_pcm_hw_params_set_channels(pcm, hwparams, 2);
63 r = snd_pcm_hw_params_set_periods_integer(pcm, hwparams);
66 r = snd_pcm_hw_params_set_periods_near(pcm, hwparams, &periods, &dir);
69 r = snd_pcm_hw_params_set_buffer_size_near(pcm, hwparams, &buffer_size);
72 r = snd_pcm_hw_params(pcm, hwparams);
75 r = snd_pcm_hw_params_current(pcm, hwparams);
78 r = snd_pcm_sw_params_current(pcm, swparams);
81 r = snd_pcm_sw_params_set_avail_min(pcm, swparams, 1);
84 r = snd_pcm_sw_params_set_period_event(pcm, swparams, 0);
87 r = snd_pcm_hw_params_get_buffer_size(hwparams, &buffer_size);
89 r = snd_pcm_sw_params_set_start_threshold(pcm, swparams, buffer_size);
92 r = snd_pcm_sw_params_get_boundary(swparams, &boundary);
94 r = snd_pcm_sw_params_set_stop_threshold(pcm, swparams, boundary);
97 r = snd_pcm_sw_params_set_tstamp_mode(pcm, swparams, SND_PCM_TSTAMP_ENABLE);
100 r = snd_pcm_sw_params(pcm, swparams);
103 r = snd_pcm_prepare(pcm);
106 r = snd_pcm_sw_params_current(pcm, swparams);
109 /* assert(snd_pcm_hw_params_is_monotonic(hwparams) > 0); */
111 n_pollfd = snd_pcm_poll_descriptors_count(pcm);
112 assert(n_pollfd > 0);
114 pollfds = malloc(sizeof(struct pollfd) * n_pollfd);
117 r = snd_pcm_poll_descriptors(pcm, pollfds, n_pollfd);
118 assert(r == n_pollfd);
121 snd_pcm_sframes_t avail, delay;
122 struct timespec now, timestamp;
123 unsigned short revents;
125 uint64_t now_us, timestamp_us;
126 snd_pcm_state_t state;
128 r = poll(pollfds, n_pollfd, 0);
131 r = snd_pcm_poll_descriptors_revents(pcm, pollfds, n_pollfd, &revents);
134 assert((revents & ~POLLOUT) == 0);
136 avail = snd_pcm_avail(pcm);
139 r = snd_pcm_status(pcm, status);
142 /* This assertion fails from time to time. ALSA seems to be broken */
143 /* assert(avail == (snd_pcm_sframes_t) snd_pcm_status_get_avail(status)); */
144 /* printf("%lu %lu\n", (unsigned long) avail, (unsigned long) snd_pcm_status_get_avail(status)); */
146 snd_pcm_status_get_htstamp(status, ×tamp);
147 delay = snd_pcm_status_get_delay(status);
148 state = snd_pcm_status_get_state(status);
150 r = clock_gettime(CLOCK_MONOTONIC, &now);
153 assert(!revents || avail > 0);
156 snd_pcm_sframes_t sframes;
157 static const uint16_t samples[2] = { 0, 0 };
159 sframes = snd_pcm_writei(pcm, samples, 1);
160 assert(sframes == 1);
167 memcmp(×tamp, &last_timestamp, sizeof(timestamp)) == 0 &&
168 avail == last_avail &&
169 delay == last_delay) {
174 now_us = timespec_us(&now);
175 timestamp_us = timespec_us(×tamp);
177 printf("%llu\t%llu\t%llu\t%li\t%li\t%i\t%i\t%i\n",
178 (unsigned long long) (now_us - start_us),
179 (unsigned long long) (timestamp_us ? timestamp_us - start_us : 0),
180 (unsigned long long) ((sample_count - 1 - delay) * 1000000LU / 44100),
187 /** When this assert is hit, most likely something bad
188 * happened, i.e. the avail jumped suddenly. */
189 assert((unsigned) avail <= buffer_size);
193 last_timestamp = timestamp;