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Changes to latency test apllication:

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- used monotonic clock instead of system clock
- precision increased to report micro senconds
- timestamp info is not added to pre-buffering samples
This commit is contained in:
Andrea Bondavalli 2021-12-06 12:10:46 +01:00
parent 9221deaf39
commit 7def2411c0
1 changed files with 25 additions and 17 deletions
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42
test/latency.cc
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@ -36,7 +36,7 @@
#include <alsa/asoundlib.h> #include <alsa/asoundlib.h>
#include <sys/time.h> #include <sys/time.h>
#include <math.h> #include <math.h>
#include <chrono>
static unsigned char header[4] = { 0xff, 0xff, 0xff, 0xff }; static unsigned char header[4] = { 0xff, 0xff, 0xff, 0xff };
const char *pdevice = "hw:0,0"; const char *pdevice = "hw:0,0";
@ -53,7 +53,7 @@ int block = 0; /* block mode */
int use_poll = 0; int use_poll = 0;
int resample = 1; int resample = 1;
unsigned long loop_limit; unsigned long loop_limit;
uint64_t end_to_end_latency = 0; double end_to_end_latency = 0;
uint64_t end_to_end_samples = 0; uint64_t end_to_end_samples = 0;
snd_output_t *output = NULL; snd_output_t *output = NULL;
@ -381,17 +381,20 @@ long readbuf(snd_pcm_t *handle, char *buf, long len, size_t *frames, size_t *max
} }
uint64_t sentMs, recvMs = timespec tp;
std::chrono::duration_cast<std::chrono::milliseconds>( if (clock_gettime(CLOCK_MONOTONIC, &tp) != 0) {
std::chrono::system_clock::now().time_since_epoch()).count(); printf("Cannot read monotonic clock\n");
exit(1);
}
uint64_t sentMs, recvMs = tp.tv_sec * 1000000 + tp.tv_nsec / 1000;
for (int i = 0; i < (r - 12); i++) { for (int i = 0; i < (r - 12); i++) {
if (!memcmp(buf + i, header, 4)) { if (!memcmp(buf + i, header, 4)) {
memcpy(&sentMs, buf + i + 4, 8); memcpy(&sentMs, buf + i + 4, 8);
//printf("elpased %lu ms\n", recvMs - sentMs); //printf("elpased %lu ms\n", recvMs - sentMs);
if ((recvMs - sentMs) < 1000) { if ((recvMs - sentMs) < 1000000) {
end_to_end_latency += recvMs - sentMs; end_to_end_latency += ((double)recvMs - (double)sentMs) / 1000;
end_to_end_samples++; end_to_end_samples++;
} }
} }
@ -401,17 +404,22 @@ long readbuf(snd_pcm_t *handle, char *buf, long len, size_t *frames, size_t *max
return r; return r;
} }
long writebuf(snd_pcm_t *handle, char *buf, long len, size_t *frames) long writebuf(snd_pcm_t *handle, char *buf, long len, size_t *frames, bool add_ts)
{ {
long r; long r;
int frame_bytes = (snd_pcm_format_width(format) / 8) * channels; int frame_bytes = (snd_pcm_format_width(format) / 8) * channels;
uint64_t ms = if (add_ts) {
std::chrono::duration_cast<std::chrono::milliseconds>( timespec tp;
std::chrono::system_clock::now().time_since_epoch()).count(); if (clock_gettime(CLOCK_MONOTONIC, &tp) != 0) {
printf("Cannot read monotonic clock\n");
exit(1);
}
memcpy(buf, header, 4); uint64_t ms = tp.tv_sec * 1000000 + tp.tv_nsec / 1000;
memcpy(buf + 4, &ms, sizeof(ms)); memcpy(buf, header, 4);
memcpy(buf + 4, &ms, sizeof(ms));
}
while (len > 0) { while (len > 0) {
r = snd_pcm_writei(handle, buf, len); r = snd_pcm_writei(handle, buf, len);
@ -664,11 +672,11 @@ int main(int argc, char *argv[])
fprintf(stderr, "silence error\n"); fprintf(stderr, "silence error\n");
break; break;
} }
if (writebuf(phandle, buffer, latency, &frames_out) < 0) { if (writebuf(phandle, buffer, latency, &frames_out, false) < 0) {
fprintf(stderr, "write error\n"); fprintf(stderr, "write error\n");
break; break;
} }
if (writebuf(phandle, buffer, latency, &frames_out) < 0) { if (writebuf(phandle, buffer, latency, &frames_out, false) < 0) {
fprintf(stderr, "write error\n"); fprintf(stderr, "write error\n");
break; break;
} }
@ -698,7 +706,7 @@ int main(int argc, char *argv[])
else { else {
if (effect) if (effect)
applyeffect(buffer,r); applyeffect(buffer,r);
if (writebuf(phandle, buffer, r, &frames_out) < 0) if (writebuf(phandle, buffer, r, &frames_out, true) < 0)
ok = 0; ok = 0;
} }
} }
@ -735,7 +743,7 @@ int main(int argc, char *argv[])
} }
if (end_to_end_samples) if (end_to_end_samples)
printf("End to end latency: %lu ms\n", end_to_end_latency / end_to_end_samples); printf("End to end latency: %.3f msecs\n", end_to_end_latency / end_to_end_samples);
else else
printf("End to end latency: no samples collected\n"); printf("End to end latency: no samples collected\n");
snd_pcm_close(phandle); snd_pcm_close(phandle);