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latency.c

/*
 *  Latency test program
 *
 *     Author: Jaroslav Kysela <perex@suse.cz>
 *
 *     Author of bandpass filter sweep effect:
 *           Maarten de Boer <mdeboer@iua.upf.es>
 *
 *  This small demo program can be used for measuring latency between
 *  capture and playback. This latency is measured from driver (diff when
 *  playback and capture was started). Scheduler is set to SCHED_RR.
 *
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sched.h>
#include <errno.h>
#include <getopt.h>
#include "../include/asoundlib.h"
#include <sys/time.h>
#include <math.h>

char *pdevice = "hw:0,0";
char *cdevice = "hw:0,0";
snd_pcm_format_t format = SND_PCM_FORMAT_S16_LE;
int rate = 22050;
int channels = 2;
int buffer_size = 0;          /* auto */
int period_size = 0;          /* auto */
int latency_min = 32;         /* in frames / 2 */
int latency_max = 2048;       /* in frames / 2 */
int loop_sec = 30;            /* seconds */
int block = 0;                /* block mode */
int tick_time = 0;            /* disabled, otherwise in us */
int tick_time_ok = 0;
int use_poll = 0;
int resample = 1;
unsigned long loop_limit;

snd_output_t *output = NULL;

int setparams_stream(snd_pcm_t *handle,
                 snd_pcm_hw_params_t *params,
                 const char *id)
{
      int err;
      unsigned int rrate;

      err = snd_pcm_hw_params_any(handle, params);
      if (err < 0) {
            printf("Broken configuration for %s PCM: no configurations available: %s\n", snd_strerror(err), id);
            return err;
      }
      err = snd_pcm_hw_params_set_rate_resample(handle, params, resample);
      if (err < 0) {
            printf("Resample setup failed for %s (val %i): %s\n", id, resample, snd_strerror(err));
            return err;
      }
      err = snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
      if (err < 0) {
            printf("Access type not available for %s: %s\n", id, snd_strerror(err));
            return err;
      }
      err = snd_pcm_hw_params_set_format(handle, params, format);
      if (err < 0) {
            printf("Sample format not available for %s: %s\n", id, snd_strerror(err));
            return err;
      }
      err = snd_pcm_hw_params_set_channels(handle, params, channels);
      if (err < 0) {
            printf("Channels count (%i) not available for %s: %s\n", channels, id, snd_strerror(err));
            return err;
      }
      rrate = rate;
      err = snd_pcm_hw_params_set_rate_near(handle, params, &rrate, 0);
      if (err < 0) {
            printf("Rate %iHz not available for %s: %s\n", rate, id, snd_strerror(err));
            return err;
      }
      if ((int)rrate != rate) {
            printf("Rate doesn't match (requested %iHz, get %iHz)\n", rate, err);
            return -EINVAL;
      }
      return 0;
}

int setparams_bufsize(snd_pcm_t *handle,
                  snd_pcm_hw_params_t *params,
                  snd_pcm_hw_params_t *tparams,
                  snd_pcm_uframes_t bufsize,
                  const char *id)
{
      int err;
      snd_pcm_uframes_t periodsize;

      snd_pcm_hw_params_copy(params, tparams);
      periodsize = bufsize * 2;
      err = snd_pcm_hw_params_set_buffer_size_near(handle, params, &periodsize);
      if (err < 0) {
            printf("Unable to set buffer size %li for %s: %s\n", bufsize * 2, id, snd_strerror(err));
            return err;
      }
      if (period_size > 0)
            periodsize = period_size;
      else
            periodsize /= 2;
      err = snd_pcm_hw_params_set_period_size_near(handle, params, &periodsize, 0);
      if (err < 0) {
            printf("Unable to set period size %li for %s: %s\n", periodsize, id, snd_strerror(err));
            return err;
      }
      return 0;
}

int setparams_set(snd_pcm_t *handle,
              snd_pcm_hw_params_t *params,
              snd_pcm_sw_params_t *swparams,
              const char *id)
{
      int err;
      snd_pcm_uframes_t val;
      unsigned int sleep_min = 0;

      err = snd_pcm_hw_params(handle, params);
      if (err < 0) {
            printf("Unable to set hw params for %s: %s\n", id, snd_strerror(err));
            return err;
      }
      err = snd_pcm_sw_params_current(handle, swparams);
      if (err < 0) {
            printf("Unable to determine current swparams for %s: %s\n", id, snd_strerror(err));
            return err;
      }
      err = snd_pcm_sw_params_set_start_threshold(handle, swparams, 0x7fffffff);
      if (err < 0) {
            printf("Unable to set start threshold mode for %s: %s\n", id, snd_strerror(err));
            return err;
      }
      tick_time_ok = 0;
      if (tick_time > 0) {
            int time, ttime;
            snd_pcm_hw_params_get_period_time(params, &time, NULL);
             snd_pcm_hw_params_get_tick_time(params, &ttime, NULL);
            if (time < ttime) {
                  printf("Skipping to set minimal sleep: period time < tick time\n");
            } else if (ttime <= 0) {
                  printf("Skipping to set minimal sleep: tick time <= 0 (%i)\n", ttime);
            } else {
                  sleep_min = tick_time / ttime;
                  if (sleep_min <= 0)
                        sleep_min = 1;
                  err = snd_pcm_sw_params_set_sleep_min(handle, swparams, sleep_min);
                  if (err < 0) {
                        printf("Unable to set minimal sleep %i for %s: %s\n", sleep_min, id, snd_strerror(err));
                        return err;
                  }
                  tick_time_ok = sleep_min * ttime;
            }
      }
      if (!block)
            val = 4;
      else
            snd_pcm_hw_params_get_period_size(params, &val, NULL);
      if (tick_time_ok > 0)
            val = 16;
      err = snd_pcm_sw_params_set_avail_min(handle, swparams, val);
      if (err < 0) {
            printf("Unable to set avail min for %s: %s\n", id, snd_strerror(err));
            return err;
      }
      val = !block ? 4 : 1;
      err = snd_pcm_sw_params_set_xfer_align(handle, swparams, val);
      if (err < 0) {
            printf("Unable to set transfer align for %s: %s\n", id, snd_strerror(err));
            return err;
      }
      err = snd_pcm_sw_params(handle, swparams);
      if (err < 0) {
            printf("Unable to set sw params for %s: %s\n", id, snd_strerror(err));
            return err;
      }
      return 0;
}

int setparams(snd_pcm_t *phandle, snd_pcm_t *chandle, int *bufsize)
{
      int err, last_bufsize = *bufsize;
      snd_pcm_hw_params_t *pt_params, *ct_params;     /* templates with rate, format and channels */
      snd_pcm_hw_params_t *p_params, *c_params;
      snd_pcm_sw_params_t *p_swparams, *c_swparams;
      snd_pcm_uframes_t p_size, c_size, p_psize, c_psize;
      unsigned int p_time, c_time;

      snd_pcm_hw_params_alloca(&p_params);
      snd_pcm_hw_params_alloca(&c_params);
      snd_pcm_hw_params_alloca(&pt_params);
      snd_pcm_hw_params_alloca(&ct_params);
      snd_pcm_sw_params_alloca(&p_swparams);
      snd_pcm_sw_params_alloca(&c_swparams);
      if ((err = setparams_stream(phandle, pt_params, "playback")) < 0) {
            printf("Unable to set parameters for playback stream: %s\n", snd_strerror(err));
            exit(0);
      }
      if ((err = setparams_stream(chandle, ct_params, "capture")) < 0) {
            printf("Unable to set parameters for playback stream: %s\n", snd_strerror(err));
            exit(0);
      }

      if (buffer_size > 0) {
            *bufsize = buffer_size;
            goto __set_it;
      }

      __again:
            if (buffer_size > 0)
                  return -1;
            if (last_bufsize == *bufsize)
            *bufsize += 4;
      last_bufsize = *bufsize;
      if (*bufsize > latency_max)
            return -1;
      __set_it:
      if ((err = setparams_bufsize(phandle, p_params, pt_params, *bufsize, "playback")) < 0) {
            printf("Unable to set sw parameters for playback stream: %s\n", snd_strerror(err));
            exit(0);
      }
      if ((err = setparams_bufsize(chandle, c_params, ct_params, *bufsize, "capture")) < 0) {
            printf("Unable to set sw parameters for playback stream: %s\n", snd_strerror(err));
            exit(0);
      }

      snd_pcm_hw_params_get_period_size(p_params, &p_psize, NULL);
      if (p_psize > (unsigned int)*bufsize)
            *bufsize = p_psize;
      snd_pcm_hw_params_get_period_size(c_params, &c_psize, NULL);
      if (c_psize > (unsigned int)*bufsize)
            *bufsize = c_psize;
      snd_pcm_hw_params_get_period_time(p_params, &p_time, NULL);
      snd_pcm_hw_params_get_period_time(c_params, &c_time, NULL);
      if (p_time != c_time)
            goto __again;

      snd_pcm_hw_params_get_buffer_size(p_params, &p_size);
      if (p_psize * 2 < p_size)
            goto __again;
      snd_pcm_hw_params_get_buffer_size(c_params, &c_size);
      if (c_psize * 2 < c_size)
            goto __again;

      if ((err = setparams_set(phandle, p_params, p_swparams, "playback")) < 0) {
            printf("Unable to set sw parameters for playback stream: %s\n", snd_strerror(err));
            exit(0);
      }
      if ((err = setparams_set(chandle, c_params, c_swparams, "capture")) < 0) {
            printf("Unable to set sw parameters for playback stream: %s\n", snd_strerror(err));
            exit(0);
      }

      if ((err = snd_pcm_prepare(phandle)) < 0) {
            printf("Prepare error: %s\n", snd_strerror(err));
            exit(0);
      }

      snd_pcm_dump(phandle, output);
      snd_pcm_dump(chandle, output);
      fflush(stdout);
      return 0;
}

void showstat(snd_pcm_t *handle, size_t frames)
{
      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);
      }
      printf("*** frames = %li ***\n", (long)frames);
      snd_pcm_status_dump(status, output);
}

void showlatency(size_t latency)
{
      double d;
      latency *= 2;
      d = (double)latency / (double)rate;
      printf("Trying latency %li frames, %.3fus, %.6fms (%.4fHz)\n", (long)latency, d * 1000000, d * 1000, (double)1 / d);
}

void showinmax(size_t in_max)
{
      double d;

      printf("Maximum read: %li frames\n", (long)in_max);
      d = (double)in_max / (double)rate;
      printf("Maximum read latency: %.3fus, %.6fms (%.4fHz)\n", d * 1000000, d * 1000, (double)1 / d);
}

void gettimestamp(snd_pcm_t *handle, snd_timestamp_t *timestamp)
{
      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_tstamp(status, timestamp);
}

void setscheduler(void)
{
      struct sched_param sched_param;

      if (sched_getparam(0, &sched_param) < 0) {
            printf("Scheduler getparam failed...\n");
            return;
      }
      sched_param.sched_priority = sched_get_priority_max(SCHED_RR);
      if (!sched_setscheduler(0, SCHED_RR, &sched_param)) {
            printf("Scheduler set to Round Robin with priority %i...\n", sched_param.sched_priority);
            fflush(stdout);
            return;
      }
      printf("!!!Scheduler set to Round Robin with priority %i FAILED!!!\n", sched_param.sched_priority);
}

long timediff(snd_timestamp_t t1, snd_timestamp_t t2)
{
      signed long l;

      t1.tv_sec -= t2.tv_sec;
      l = (signed long) t1.tv_usec - (signed long) t2.tv_usec;
      if (l < 0) {
            t1.tv_sec--;
            l = -l;
            l %= 1000000;
      }
      return (t1.tv_sec * 1000000) + l;
}

long readbuf(snd_pcm_t *handle, char *buf, long len, size_t *frames, size_t *max)
{
      long r;

      if (!block) {
            do {
                  r = snd_pcm_readi(handle, buf, len);
            } while (r == -EAGAIN);
            if (r > 0) {
                  *frames += r;
                  if ((long)*max < r)
                        *max = r;
            }
            // printf("read = %li\n", r);
      } else {
            int frame_bytes = (snd_pcm_format_width(format) / 8) * channels;
            do {
                  r = snd_pcm_readi(handle, buf, len);
                  if (r > 0) {
                        buf += r * frame_bytes;
                        len -= r;
                        *frames += r;
                        if ((long)*max < r)
                              *max = r;
                  }
                  // printf("r = %li, len = %li\n", r, len);
            } while (r >= 1 && len > 0);
      }
      // showstat(handle, 0);
      return r;
}

long writebuf(snd_pcm_t *handle, char *buf, long len, size_t *frames)
{
      long r;

      while (len > 0) {
            r = snd_pcm_writei(handle, buf, len);
            if (r == -EAGAIN)
                  continue;
            // printf("write = %li\n", r);
            if (r < 0)
                  return r;
            // showstat(handle, 0);
            buf += r * 4;
            len -= r;
            *frames += r;
      }
      return 0;
}
                  
#define FILTERSWEEP_LFO_CENTER 2000.
#define FILTERSWEEP_LFO_DEPTH 1800.
#define FILTERSWEEP_LFO_FREQ 0.2
#define FILTER_BANDWIDTH 50

/* filter the sweep variables */
float lfo,dlfo,fs,fc,BW,C,D,a0,a1,a2,b1,b2,*x[3],*y[3];

void applyeffect(char* buffer,int r)
{
      short* samples = (short*) buffer;
      int i;
      for (i=0;i<r;i++)
      {
            int chn;

            fc = sin(lfo)*FILTERSWEEP_LFO_DEPTH+FILTERSWEEP_LFO_CENTER;
            lfo += dlfo;
            if (lfo>2.*M_PI) lfo -= 2.*M_PI;
            C = 1./tan(M_PI*BW/fs);
            D = 2.*cos(2*M_PI*fc/fs);
            a0 = 1./(1.+C);
            a1 = 0;
            a2 = -a0;
            b1 = -C*D*a0;
            b2 = (C-1)*a0;

            for (chn=0;chn<channels;chn++)
            {
                  x[chn][2] = x[chn][1];
                  x[chn][1] = x[chn][0];

                  y[chn][2] = y[chn][1];
                  y[chn][1] = y[chn][0];

                  x[chn][0] = samples[i*channels+chn];
                  y[chn][0] = a0*x[chn][0] + a1*x[chn][1] + a2*x[chn][2] 
                        - b1*y[chn][1] - b2*y[chn][2];
                  samples[i*channels+chn] = y[chn][0];
            }
      }
}

void help(void)
{
      int k;
      printf(
"Usage: latency [OPTION]... [FILE]...\n"
"-h,--help      help\n"
"-P,--pdevice   playback device\n"
"-C,--cdevice   capture device\n"
"-m,--min       minimum latency in frames\n"
"-M,--max       maximum latency in frames\n"
"-F,--frames    frames to transfer\n"
"-f,--format    sample format\n"
"-c,--channels  channels\n"
"-r,--rate      rate\n"
"-B,--buffer    buffer size in frames\n"
"-E,--period    period size in frames\n"
"-s,--seconds   duration of test in seconds\n"
"-b,--block     block mode\n"
"-t,--time      maximal tick time in us\n"
"-p,--poll      use poll (wait for event - reduces CPU usage)\n"
"-e,--effect    apply an effect (bandpass filter sweep)\n"
);
        printf("Recognized sample formats are:");
        for (k = 0; k < SND_PCM_FORMAT_LAST; ++(unsigned long) k) {
                const char *s = snd_pcm_format_name(k);
                if (s)
                        printf(" %s", s);
        }
        printf("\n\n");
        printf(
"Tip #1 (usable latency with large periods, non-blocking mode, good CPU usage,\n"
"        superb xrun prevention):\n"
"  latency -m 8192 -M 8192 -t 1 -p\n"
"Tip #2 (superb latency, non-blocking mode, but heavy CPU usage):\n"
"  latency -m 128 -M 128\n"
);
}

int main(int argc, char *argv[])
{
      struct option long_option[] =
      {
            {"help", 0, NULL, 'h'},
            {"pdevice", 1, NULL, 'P'},
            {"cdevice", 1, NULL, 'C'},
            {"min", 1, NULL, 'm'},
            {"max", 1, NULL, 'M'},
            {"frames", 1, NULL, 'F'},
            {"format", 1, NULL, 'f'},
            {"channels", 1, NULL, 'c'},
            {"rate", 1, NULL, 'r'},
            {"buffer", 1, NULL, 'B'},
            {"period", 1, NULL, 'E'},
            {"seconds", 1, NULL, 's'},
            {"block", 0, NULL, 'b'},
            {"time", 1, NULL, 't'},
            {"poll", 0, NULL, 'p'},
            {"effect", 0, NULL, 'e'},
            {NULL, 0, NULL, 0},
      };
      snd_pcm_t *phandle, *chandle;
      char *buffer;
      int err, latency, morehelp;
      int ok;
      snd_timestamp_t p_tstamp, c_tstamp;
      ssize_t r;
      size_t frames_in, frames_out, in_max;
      int effect = 0;
      morehelp = 0;
      while (1) {
            int c;
            if ((c = getopt_long(argc, argv, "hP:C:m:M:F:f:c:r:s:bt:pen", long_option, NULL)) < 0)
                  break;
            switch (c) {
            case 'h':
                  morehelp++;
                  break;
            case 'P':
                  pdevice = strdup(optarg);
                  break;
            case 'C':
                  cdevice = strdup(optarg);
                  break;
            case 'm':
                  err = atoi(optarg) / 2;
                  latency_min = err >= 4 ? err : 4;
                  if (latency_max < latency_min)
                        latency_max = latency_min;
                  break;
            case 'M':
                  err = atoi(optarg) / 2;
                  latency_max = latency_min > err ? latency_min : err;
                  break;
            case 'f':
                  format = snd_pcm_format_value(optarg);
                  if (format == SND_PCM_FORMAT_UNKNOWN) {
                        printf("Unknown format, setting to default S16_LE\n");
                        format = SND_PCM_FORMAT_S16_LE;
                  }
                  break;
            case 'c':
                  err = atoi(optarg);
                  channels = err >= 1 && err < 1024 ? err : 1;
                  break;
            case 'r':
                  err = atoi(optarg);
                  rate = err >= 4000 && err < 200000 ? err : 44100;
                  break;
            case 'B':
                  err = atoi(optarg);
                  buffer_size = err >= 32 && err < 200000 ? err : 0;
                  break;
            case 'E':
                  err = atoi(optarg);
                  period_size = err >= 32 && err < 200000 ? err : 0;
                  break;
            case 's':
                  err = atoi(optarg);
                  loop_sec = err >= 1 && err <= 100000 ? err : 30;
                  break;
            case 'b':
                  block = 1;
                  break;
            case 't':
                  tick_time = atoi(optarg);
                  tick_time = tick_time < 0 ? 0 : tick_time;
                  break;
            case 'p':
                  use_poll = 1;
                  break;
            case 'e':
                  effect = 1;
                  break;
            case 'n':
                  resample = 0;
                  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;
      }

      loop_limit = loop_sec * rate;
      latency = latency_min - 4;
      buffer = malloc((latency_max * snd_pcm_format_width(format) / 8) * 2);

      setscheduler();

      printf("Playback device is %s\n", pdevice);
      printf("Capture device is %s\n", cdevice);
      printf("Parameters are %iHz, %s, %i channels, %s mode\n", rate, snd_pcm_format_name(format), channels, block ? "blocking" : "non-blocking");
      printf("Wanted tick time: %ius, poll mode: %s\n", tick_time, use_poll ? "yes" : "no");
      printf("Loop limit is %li frames, minimum latency = %i, maximum latency = %i\n", loop_limit, latency_min * 2, latency_max * 2);

      if ((err = snd_pcm_open(&phandle, pdevice, SND_PCM_STREAM_PLAYBACK, block ? 0 : SND_PCM_NONBLOCK)) < 0) {
            printf("Playback open error: %s\n", snd_strerror(err));
            return 0;
      }
      if ((err = snd_pcm_open(&chandle, cdevice, SND_PCM_STREAM_CAPTURE, block ? 0 : SND_PCM_NONBLOCK)) < 0) {
            printf("Record open error: %s\n", snd_strerror(err));
            return 0;
      }

      /* initialize the filter sweep variables */
      if (effect) {
            fs = (float) rate;
            BW = FILTER_BANDWIDTH;

            lfo = 0;
            dlfo = 2.*M_PI*FILTERSWEEP_LFO_FREQ/fs;

            x[0] = (float*) malloc(channels*sizeof(float));       
            x[1] = (float*) malloc(channels*sizeof(float));       
            x[2] = (float*) malloc(channels*sizeof(float));       
            y[0] = (float*) malloc(channels*sizeof(float));       
            y[1] = (float*) malloc(channels*sizeof(float));       
            y[2] = (float*) malloc(channels*sizeof(float));       
      }
                    
      while (1) {
            frames_in = frames_out = 0;
            if (setparams(phandle, chandle, &latency) < 0)
                  break;
            showlatency(latency);
            if (tick_time_ok)
                  printf("Using tick time %ius\n", tick_time_ok);
            if ((err = snd_pcm_link(chandle, phandle)) < 0) {
                  printf("Streams link error: %s\n", snd_strerror(err));
                  exit(0);
            }
            if (snd_pcm_format_set_silence(format, buffer, latency*channels) < 0) {
                  fprintf(stderr, "silence error\n");
                  break;
            }
            if (writebuf(phandle, buffer, latency, &frames_out) < 0) {
                  fprintf(stderr, "write error\n");
                  break;
            }
            if (writebuf(phandle, buffer, latency, &frames_out) < 0) {
                  fprintf(stderr, "write error\n");
                  break;
            }

            if ((err = snd_pcm_start(chandle)) < 0) {
                  printf("Go error: %s\n", snd_strerror(err));
                  exit(0);
            }
            gettimestamp(phandle, &p_tstamp);
            gettimestamp(chandle, &c_tstamp);
#if 0
            printf("Playback:\n");
            showstat(phandle, frames_out);
            printf("Capture:\n");
            showstat(chandle, frames_in);
#endif

            ok = 1;
            in_max = 0;
            while (ok && frames_in < loop_limit) {
                  if (use_poll) {
                        /* use poll to wait for next event */
                        snd_pcm_wait(chandle, 1000);
                  }
                  if ((r = readbuf(chandle, buffer, latency, &frames_in, &in_max)) < 0)
                        ok = 0;
                  else {
                        if (effect)
                              applyeffect(buffer,r);
                        if (writebuf(phandle, buffer, r, &frames_out) < 0)
                              ok = 0;
                  }
            }
            if (ok)
                  printf("Success\n");
            else
                  printf("Failure\n");
            printf("Playback:\n");
            showstat(phandle, frames_out);
            printf("Capture:\n");
            showstat(chandle, frames_in);
            showinmax(in_max);
            if (p_tstamp.tv_sec == p_tstamp.tv_sec &&
                p_tstamp.tv_usec == c_tstamp.tv_usec)
                  printf("Hardware sync\n");
            snd_pcm_drop(chandle);
            snd_pcm_nonblock(phandle, 0);
            snd_pcm_drain(phandle);
            snd_pcm_nonblock(phandle, !block ? 1 : 0);
            if (ok) {
#if 1
                  printf("Playback time = %li.%i, Record time = %li.%i, diff = %li\n",
                         p_tstamp.tv_sec,
                         (int)p_tstamp.tv_usec,
                         c_tstamp.tv_sec,
                         (int)c_tstamp.tv_usec,
                         timediff(p_tstamp, c_tstamp));
#endif
                  break;
            }
            snd_pcm_unlink(chandle);
            snd_pcm_hw_free(phandle);
            snd_pcm_hw_free(chandle);
      }
      snd_pcm_close(phandle);
      snd_pcm_close(chandle);
      return 0;
}

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