alsa-lib/test/latency.c

#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>

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 latency_min = 32;		/* in frames */
int latency_max = 2048;		/* in frames */
int loop_sec = 30;		/* seconds */
unsigned long loop_limit;

snd_output_t *output = NULL;

#if 0
static char *xitoa(int aaa)
{
	static char str[12];

	sprintf(str, "%i", aaa);
	return str;
}
#endif

/*
 *  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.
 *
 *  Used format is 44100Hz, Signed Little Endian 16-bit, Stereo.
 */

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

	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_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;
	}
	err = snd_pcm_hw_params_set_rate_near(handle, params, rate, 0);
	if (err < 0) {
		printf("Rate %iHz not available for %s: %s\n", rate, id, snd_strerror(err));
		return err;
	}
	if (err != 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,
		      int bufsize,
		      const char *id)
{
	int size;
	int err, periodsize;

	snd_pcm_hw_params_copy(params, tparams);
	size = (bufsize * (snd_pcm_format_width(format) * channels)) / 8;
	err = snd_pcm_hw_params_set_buffer_size_near(handle, params, size);
	if (err < 0) {
		printf("Unable to set buffer size %i for %s: %s\n", size, id, snd_strerror(err));
		return err;
	}
	periodsize = snd_pcm_hw_params_get_buffer_size(params) / 2;
	err = snd_pcm_hw_params_set_period_size_near(handle, params, periodsize, 0);
	if (err < 0) {
		printf("Unable to set period size %i 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;

	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;
	}
	err = snd_pcm_sw_params_set_avail_min(handle, swparams, 4);
	if (err < 0) {
		printf("Unable to set avail min for %s: %s\n", id, snd_strerror(err));
		return err;
	}
	err = snd_pcm_sw_params_set_xfer_align(handle, swparams, 4);
	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_buf_size = *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_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);
	}

      __again:
      	if (last_buf_size == *bufsize)
		*bufsize += 4;
	last_buf_size = *bufsize;
	if (*bufsize > latency_max)
		return -1;
	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);
	}
	if (snd_pcm_hw_params_get_buffer_size(p_params) !=
	    snd_pcm_hw_params_get_buffer_size(c_params)) {
	    	int size;
	    	size = (snd_pcm_hw_params_get_buffer_size(p_params) * 8) / (snd_pcm_format_width(format) * channels);
	    	if (size > *bufsize)
			*bufsize = size;
	    	size = (snd_pcm_hw_params_get_buffer_size(c_params) * 8) / (snd_pcm_format_width(format) * channels);
	    	if (size > *bufsize)
			*bufsize = 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 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)
{
	long r;
	
	do {
		r = snd_pcm_readi(handle, buf, len);
	} while (r == -EAGAIN);
	if (r > 0)
		*frames += r;
	// printf("read = %li\n", r);
	// 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;
}

void help(void)
{
	int k;
	printf("\
Usage: latency [OPTION]... [FILE]...
-h,--help      help
-P,--pdevice   playback device
-C,--cdevice   capture device
-m,--min       minimum latency in frames
-M,--max       maximum latency in frames
-F,--frames    frames to transfer
-f,--format    sample format
-c,--channels  channels
-r,--rate      rate
");
        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");
}

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'},
		{NULL, 0, NULL, 0},
	};
	snd_pcm_t *phandle, *chandle;
	char *buffer;
	int err, latency, morehelp;
	int size, ok;
	snd_timestamp_t p_tstamp, c_tstamp;
	ssize_t r;
	size_t frames_in, frames_out;

	morehelp = 0;
	while (1) {
		int c;
		if ((c = getopt_long(argc, argv, "hP:C:m:M:F:f:c:r:", 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);
			latency_min = err >= 4 ? err : 4;
			if (latency_max < latency_min)
				latency_max = latency_min;
			break;
		case 'M':
			err = atoi(optarg);
			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;
		}
	}

	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\n", rate, snd_pcm_format_name(format), channels);
	printf("Loop limit is %li frames, minimum latency = %i, maximum latency = %i\n", loop_limit, latency_min, latency_max);

	if ((err = snd_pcm_open(&phandle, pdevice, SND_PCM_STREAM_PLAYBACK, 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, SND_PCM_NONBLOCK)) < 0) {
		printf("Record open error: %s\n", snd_strerror(err));
		return 0;
	}
	  
	while (1) {
		frames_in = frames_out = 0;
		if (setparams(phandle, chandle, &latency) < 0)
			break;
		printf("Trying latency %i frames...\n", 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*channels, &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;
		size = 0;
		while (ok && frames_in < loop_limit) {
			if ((r = readbuf(chandle, buffer, latency, &frames_in)) < 0)
				ok = 0;
			else if (writebuf(phandle, buffer, r, &frames_out) < 0)
				ok = 0;
		}
		printf("Playback:\n");
		showstat(phandle, frames_out);
		printf("Capture:\n");
		showstat(chandle, frames_in);
		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, 1);
		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;
}