/test/latency.c

Shows the measuring of minimal latency between capture and playback devices.

/*
 *  Latency test program
 *
 *     Author: Jaroslav Kysela <perex@perex.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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

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

#ifndef CLOCK_MONOTONIC_RAW
#define CLOCK_MONOTONIC_RAW CLOCK_MONOTONIC
#endif

#if defined(__OpenBSD__)
#define sched_getparam(pid, parm) (-1)
#define sched_setscheduler(pid, policy, parm) (-1)
#endif

typedef struct timespec timestamp_t;

char *sched_policy = "rr";
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 use_poll = 0;
int usleep_val = 0;
int resample = 1;
int sys_latency = 0;        /* data I/O: use system timings instead driver wakeups */
int pos_dump = 0;       /* dump positions */
int realtime_check = 0;
unsigned long loop_limit;
snd_pcm_uframes_t playback_buffer_size;

snd_output_t *output = NULL;

static inline long long frames_to_micro(size_t frames)
{
    return (long long)((frames * 1000000LL) + (rate / 2)) / rate;
}

void timestamp_now(timestamp_t *tstamp)
{
    if (clock_gettime(CLOCK_MONOTONIC_RAW, tstamp))
        printf("clock_gettime() failed\n");
}

long long timestamp_diff_micro(timestamp_t *tstamp)
{
    timestamp_t now, diff;
    timestamp_now(&now);
    if (tstamp->tv_nsec > now.tv_nsec) {
        diff.tv_sec = now.tv_sec - tstamp->tv_sec - 1;
        diff.tv_nsec = (now.tv_nsec + 1000000000L) - tstamp->tv_nsec;
    } else {
        diff.tv_sec = now.tv_sec - tstamp->tv_sec;
        diff.tv_nsec = now.tv_nsec - tstamp->tv_nsec;
    }
    /* microseconds */
    return (diff.tv_sec * 1000000) + ((diff.tv_nsec + 500L) / 1000L);
}

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;
    }
    /* we do not want driver wakeups */
    if (sys_latency > 0 && snd_pcm_hw_params_can_disable_period_wakeup(params)) {
        err = snd_pcm_hw_params_set_period_wakeup(handle, params, 0);
        if (err < 0) {
            printf("Cannot disable period wakeups for %s\n", id);
            return err;
        }
    }
    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;

    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;
    }
    if (!block)
        val = 4;
    else
        snd_pcm_hw_params_get_period_size(params, &val, NULL);
    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;
    }
    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;
    unsigned int val;

    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);
    playback_buffer_size = p_size;
    if (p_psize * 2 < p_size) {
                snd_pcm_hw_params_get_periods_min(p_params, &val, NULL);
                if (val > 2) {
            printf("playback device does not support 2 periods per buffer\n");
            exit(0);
        }
        goto __again;
    }
    snd_pcm_hw_params_get_buffer_size(c_params, &c_size);
    if (c_psize * 2 < c_size) {
                snd_pcm_hw_params_get_periods_min(c_params, &val, NULL);
        if (val > 2 ) {
            printf("capture device does not support 2 periods per buffer\n");
            exit(0);
        }
        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;
    int policy = SCHED_RR;
    const char *spolicy = "Round Robin";

    if (strcasecmp(sched_policy, "fifo") == 0) {
        policy = SCHED_FIFO;
        spolicy = "FIFO";
    } else if (strcasecmp(sched_policy, "other") == 0) {
        policy = SCHED_OTHER;
        spolicy = "OTHER";
    }
    if (sched_getparam(0, &sched_param) < 0) {
        printf("Scheduler getparam failed...\n");
        return;
    }
    sched_param.sched_priority = sched_get_priority_max(policy);
    if (!sched_setscheduler(0, policy, &sched_param)) {
        printf("Scheduler set to %s with priority %i...\n", spolicy, sched_param.sched_priority);
        fflush(stdout);
        return;
    }
    printf("!!!Scheduler set to %s with priority %i FAILED!!!\n", spolicy, 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 = 1000000 + 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_physical_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;
    int frame_bytes = (snd_pcm_format_physical_width(format) / 8) * channels;

    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 * frame_bytes;
        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];
        }
    }
}

static ssize_t get_avail(snd_pcm_t *pcm)
{
    ssize_t avail;

    while (1) {
        avail = snd_pcm_avail(pcm);
        if (avail == -EAGAIN)
            continue;
        break;
    }
    return avail;
}

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"
"-U,--updates   I/O updates in milliseconds (0 = off)\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"
"-p,--poll      use poll (wait for event - reduces CPU usage)\n"
"-y,--usleep    sleep for the specified amount of microseconds between\n"
"               stream updates (default 0 - off)\n"
"-e,--effect    apply an effect (bandpass filter sweep)\n"
"-x,--posdump   dump buffer positions\n"
"-X,--realtime  do a realtime check (buffering)\n"
"-O,--policy    set scheduler policy (RR, FIFO or OTHER)\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\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'},
        {"updates", 1, NULL, 'U'},
        {"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'},
        {"poll", 0, NULL, 'p'},
        {"usleep", 1, NULL, 'y'},
        {"effect", 0, NULL, 'e'},
        {"posdump", 0, NULL, 'x'},
        {"realtime", 0, NULL, 'X'},
        {"policy", 1, NULL, 'O'},
        {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, cap_avail, cap_avail_max, pbk_fill, pbk_fill_min;
    size_t frames_in, frames_out, in_max;
    timestamp_t tstamp_start;
    int effect = 0;
    morehelp = 0;
    while (1) {
        int c;
        if ((c = getopt_long(argc, argv, "hP:C:m:M:U:F:f:c:r:B:E:s:y:O:bpenxX", 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 'U':
            err = atoi(optarg);
            sys_latency = err <= 0 ? 0 : 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 'p':
            use_poll = 1;
            break;
        case 'y':
            usleep_val = atoi(optarg);
            break;
        case 'e':
            effect = 1;
            break;
        case 'n':
            resample = 0;
            break;
        case 'x':
            pos_dump = 1;
            break;
        case 'X':
            realtime_check = 1;
            break;
        case 'O':
            sched_policy = optarg;
            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 * 2 * snd_pcm_format_physical_width(format) / 8) * channels);

    /* I/O updates based on a system timer */
    if (sys_latency > 0) {
        block = 0;
        use_poll = 0;
    }

    setscheduler();

    printf("Playback device is %s\n", pdevice);
    printf("Capture device is %s\n", cdevice);
    printf("Parameters are %iHz, %s, %i channels, %s mode, use poll %s\n",
            rate, snd_pcm_format_name(format),
            channels, block ? "blocking" : "non-blocking",
            use_poll ? "yes" : "no");
    printf("Loop limit is %lu frames, minimum latency = %i, maximum latency = %i",
            loop_limit, latency_min * 2, latency_max * 2);
    if (sys_latency > 0)
        printf(", I/O updates %ims", sys_latency);
    else if (!block && !use_poll)
        printf(", I/O usleep %ius", usleep_val);
    printf("\n");

    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));     
    }

    cap_avail_max = 0;
    pbk_fill_min = latency * 2;
              
    while (1) {
        frames_in = frames_out = 0;
        if (setparams(phandle, chandle, &latency) < 0)
            break;
        showlatency(latency);
        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 (realtime_check)
            timestamp_now(&tstamp_start);
        if ((err = snd_pcm_start(chandle)) < 0) {
            printf("Go error: %s\n", snd_strerror(err));
            exit(0);
        }
        if (realtime_check)
            printf("[%lldus] Stream start\n", timestamp_diff_micro(&tstamp_start));
        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) {
            cap_avail = latency;
            if (sys_latency > 0) {
                poll(NULL, 0, sys_latency);
                cap_avail = get_avail(chandle);
                if (cap_avail < 0) {
                    printf("Avail failed: %s\n", snd_strerror(cap_avail));
                    ok = 0;
                    break;
                }
            } else if (use_poll) {
                /* use poll to wait for next event */
                snd_pcm_wait(chandle, 1000);
            } else if (!block && usleep_val > 0) {
                usleep(usleep_val);
            }
            if (pos_dump || realtime_check) {
                if (sys_latency <= 0)
                    cap_avail = get_avail(chandle);
                pbk_fill = get_avail(phandle);
                if (pbk_fill >= 0)
                    pbk_fill = playback_buffer_size - pbk_fill;
                if (cap_avail > cap_avail_max)
                    cap_avail_max = cap_avail;
                if (pbk_fill >= 0 && pbk_fill < pbk_fill_min)
                    pbk_fill_min = pbk_fill;
                if (realtime_check) {
                    long long diff = timestamp_diff_micro(&tstamp_start);
                    long long cap_pos = frames_to_micro(frames_in + cap_avail);
                    long long pbk_pos = frames_to_micro(frames_out - pbk_fill);
                    printf("[%lldus] POS: p=%zd (min=%zd, rt=%lldus) c=%zd (max=%zd, rt=%lldus)\n",
                            diff, pbk_fill, pbk_fill_min, pbk_pos - diff,
                            cap_avail, cap_avail_max, cap_pos - diff);
                } else if (pos_dump) {
                    printf("POS: p=%zd (min=%zd), c=%zd (max=%zd)\n",
                            pbk_fill, pbk_fill_min, cap_avail, cap_avail_max);
                }
            }
            if ((r = readbuf(chandle, buffer, cap_avail, &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 == c_tstamp.tv_sec &&
            p_tstamp.tv_usec == c_tstamp.tv_usec)
            printf("Hardware sync\n");
        if (realtime_check) {
            long long diff = timestamp_diff_micro(&tstamp_start);
            long long mtime = frames_to_micro(frames_in);
            printf("Elapsed real time: %lldus\n", diff);
            printf("Elapsed device time: %lldus\n", mtime);
            printf("Test time diff (device - real): %lldus\n", mtime - diff);
        }
        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",
                   (long)p_tstamp.tv_sec,
                   (int)p_tstamp.tv_usec,
                   (long)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);
    snd_output_close(output);
    snd_config_update_free_global();
    free(buffer);
    free(pdevice);
    free(cdevice);
    return 0;
}