--- /dev/null
+/*
+ * This program only tracks the difference between system time
+ * and audio time, as reported in snd_pcm_status(). It should be
+ * helpful to verify the information reported by drivers.
+ */
+
+#include "../include/asoundlib.h"
+#include <math.h>
+
+static char *device = "hw:0,0";
+
+snd_output_t *output = NULL;
+
+long long timestamp2ns(snd_htimestamp_t t)
+{
+ long long nsec;
+
+ nsec = t.tv_sec * 1000000000;
+ nsec += t.tv_nsec;
+
+ return nsec;
+}
+
+long long timediff(snd_htimestamp_t t1, snd_htimestamp_t t2)
+{
+ long long nsec1, nsec2;
+
+ nsec1 = timestamp2ns(t1);
+ nsec2 = timestamp2ns(t2);
+
+ return nsec1 - nsec2;
+}
+
+void gettimestamp(snd_pcm_t *handle, snd_htimestamp_t *timestamp,
+ snd_htimestamp_t *trigger_timestamp,
+ snd_pcm_uframes_t *avail, snd_pcm_sframes_t *delay)
+{
+ int err;
+ snd_pcm_status_t *status;
+
+ snd_pcm_status_alloca(&status);
+ if ((err = snd_pcm_status(handle, status)) < 0) {
+ printf("Stream status error: %s\n", snd_strerror(err));
+ exit(0);
+ }
+ snd_pcm_status_get_trigger_htstamp(status, trigger_timestamp);
+ snd_pcm_status_get_htstamp(status, timestamp);
+ *avail = snd_pcm_status_get_avail(status);
+ *delay = snd_pcm_status_get_delay(status);
+}
+
+#define PERIOD 6000
+#define PCM_LINK /* sync start for playback and capture */
+#define TRACK_CAPTURE /* dump capture timing info */
+#define TRACK_PLAYBACK /* dump playback timing info */
+#define PLAYBACK_BUFFERS 4
+
+
+int main(void)
+{
+ int err;
+ unsigned int i;
+ snd_pcm_t *handle_p = NULL;
+ snd_pcm_t *handle_c = NULL;
+ snd_pcm_sframes_t frames;
+ snd_htimestamp_t tstamp_c, tstamp_p;
+ snd_htimestamp_t trigger_tstamp_c, trigger_tstamp_p;
+ unsigned char buffer_p[PERIOD*4*4];
+ unsigned char buffer_c[PERIOD*4*4];
+
+ snd_pcm_sw_params_t *swparams_p;
+ snd_pcm_sw_params_t *swparams_c;
+
+ snd_pcm_uframes_t curr_count_c;
+ snd_pcm_uframes_t frame_count_c = 0;
+ snd_pcm_uframes_t curr_count_p;
+ snd_pcm_uframes_t frame_count_p = 0;
+
+ snd_pcm_sframes_t delay_p, delay_c;
+ snd_pcm_uframes_t avail_p, avail_c;
+
+ if ((err = snd_pcm_open(&handle_p, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
+ printf("Playback open error: %s\n", snd_strerror(err));
+ goto _exit;
+ }
+ if ((err = snd_pcm_set_params(handle_p,
+ SND_PCM_FORMAT_S16,
+ SND_PCM_ACCESS_RW_INTERLEAVED,
+ 2,
+ 48000,
+ 0,
+ 500000)) < 0) { /* 0.5sec */
+ printf("Playback open error: %s\n", snd_strerror(err));
+ goto _exit;
+ }
+
+ snd_pcm_sw_params_alloca(&swparams_p);
+ /* get the current swparams */
+ err = snd_pcm_sw_params_current(handle_p, swparams_p);
+ if (err < 0) {
+ printf("Unable to determine current swparams_p: %s\n", snd_strerror(err));
+ goto _exit;
+ }
+
+ /* enable tstamp */
+ err = snd_pcm_sw_params_set_tstamp_mode(handle_p, swparams_p, SND_PCM_TSTAMP_ENABLE);
+ if (err < 0) {
+ printf("Unable to set tstamp mode : %s\n", snd_strerror(err));
+ goto _exit;
+ }
+
+ /* write the sw parameters */
+ err = snd_pcm_sw_params(handle_p, swparams_p);
+ if (err < 0) {
+ printf("Unable to set swparams_p : %s\n", snd_strerror(err));
+ goto _exit;
+ }
+
+ if ((err = snd_pcm_open(&handle_c, device, SND_PCM_STREAM_CAPTURE, SND_PCM_NONBLOCK)) < 0) {
+ printf("Capture open error: %s\n", snd_strerror(err));
+ goto _exit;
+ }
+ if ((err = snd_pcm_set_params(handle_c,
+ SND_PCM_FORMAT_S16,
+ SND_PCM_ACCESS_RW_INTERLEAVED,
+ 2,
+ 48000,
+ 0,
+ 500000)) < 0) { /* 0.5sec */
+ printf("Capture open error: %s\n", snd_strerror(err));
+ goto _exit;
+ }
+
+ snd_pcm_sw_params_alloca(&swparams_c);
+ /* get the current swparams */
+ err = snd_pcm_sw_params_current(handle_c, swparams_c);
+ if (err < 0) {
+ printf("Unable to determine current swparams_c: %s\n", snd_strerror(err));
+ goto _exit;
+ }
+
+ /* enable tstamp */
+ err = snd_pcm_sw_params_set_tstamp_mode(handle_c, swparams_c, SND_PCM_TSTAMP_ENABLE);
+ if (err < 0) {
+ printf("Unable to set tstamp mode : %s\n", snd_strerror(err));
+ goto _exit;
+ }
+
+ /* write the sw parameters */
+ err = snd_pcm_sw_params(handle_c, swparams_c);
+ if (err < 0) {
+ printf("Unable to set swparams_c : %s\n", snd_strerror(err));
+ goto _exit;
+ }
+
+#ifdef PCM_LINK
+ if ((err = snd_pcm_link(handle_c, handle_p)) < 0) {
+ printf("Streams link error: %s\n", snd_strerror(err));
+ exit(0);
+ }
+#endif
+
+ i = PLAYBACK_BUFFERS;
+ while (i--) {
+ frames = snd_pcm_writei(handle_p, buffer_p, PERIOD);
+ if (frames < 0) {
+ printf("snd_pcm_writei failed: %s\n", snd_strerror(frames));
+ goto _exit;
+ }
+ frame_count_p += frames;
+ }
+
+ if (PLAYBACK_BUFFERS != 4)
+ snd_pcm_start(handle_p);
+
+#ifndef PCM_LINK
+ /* need to start capture explicitly */
+ snd_pcm_start(handle_c);
+#endif
+
+ while (1) {
+
+ frames = snd_pcm_wait(handle_c, -1);
+ if (frames < 0) {
+ printf("snd_pcm_wait failed: %s\n", snd_strerror(frames));
+ goto _exit;
+ }
+
+ frames = snd_pcm_readi(handle_c, buffer_c, PERIOD);
+ if (frames < 0) {
+ printf("snd_pcm_readi failed: %s\n", snd_strerror(frames));
+ goto _exit;
+ }
+ frame_count_c += frames;
+
+ frames = snd_pcm_writei(handle_p, buffer_p, PERIOD);
+ if (frames < 0) {
+ printf("snd_pcm_writei failed: %s\n", snd_strerror(frames));
+ goto _exit;
+ }
+
+ frame_count_p += frames;
+
+#if defined(TRACK_PLAYBACK)
+ gettimestamp(handle_p, &tstamp_p, &trigger_tstamp_p, &avail_p, &delay_p);
+
+ curr_count_p = frame_count_p - delay_p; /* written minus queued */
+
+ printf("playback: systime: %lli nsec, sample time %lli nsec \tsystime delta %lli \n",
+ timediff(tstamp_p,trigger_tstamp_p),
+ (long long)round(((float)curr_count_p * 1000000000.0 / 48000.0)),
+ timediff(tstamp_p, trigger_tstamp_p) - (long long)round((double)curr_count_p * 1000000000.0 / 48000.0)
+ );
+#endif
+
+#if defined(TRACK_CAPTURE)
+ gettimestamp(handle_c, &tstamp_c, &trigger_tstamp_c, &avail_c, &delay_c);
+
+ curr_count_c = frame_count_c + delay_c; /* read plus queued */
+
+ printf("\t capture: systime: %lli nsec, sample time %lli nsec \tsystime delta %lli \n",
+ timediff(tstamp_c,trigger_tstamp_c),
+ (long long)round(((float)curr_count_c * 1000000000.0 / 48000.0)),
+ timediff(tstamp_c, trigger_tstamp_c) - (long long)round((double)curr_count_c * 1000000000.0 / 48000.0)
+ );
+#endif
+
+ }
+
+_exit:
+ if (handle_p)
+ snd_pcm_close(handle_p);
+ if (handle_c)
+ snd_pcm_close(handle_c);
+
+ return 0;
+}