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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 <sys/time.h>
#include <math.h>
#include <chrono>
static unsigned char header[4] = { 0xff, 0xff, 0xff, 0xff };
const char *pdevice = "hw:0,0";
@ -53,7 +53,7 @@ int block = 0; /* block mode */
int use_poll = 0;
int resample = 1;
unsigned long loop_limit;
uint64_t end_to_end_latency = 0;
double end_to_end_latency = 0;
uint64_t end_to_end_samples = 0;
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 =
std::chrono::duration_cast<std::chrono::milliseconds>(
std::chrono::system_clock::now().time_since_epoch()).count();
timespec tp;
if (clock_gettime(CLOCK_MONOTONIC, &tp) != 0) {
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++) {
if (!memcmp(buf + i, header, 4)) {
memcpy(&sentMs, buf + i + 4, 8);
//printf("elpased %lu ms\n", recvMs - sentMs);
if ((recvMs - sentMs) < 1000) {
end_to_end_latency += recvMs - sentMs;
if ((recvMs - sentMs) < 1000000) {
end_to_end_latency += ((double)recvMs - (double)sentMs) / 1000;
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;
}
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;
int frame_bytes = (snd_pcm_format_width(format) / 8) * channels;
uint64_t ms =
std::chrono::duration_cast<std::chrono::milliseconds>(
std::chrono::system_clock::now().time_since_epoch()).count();
if (add_ts) {
timespec tp;
if (clock_gettime(CLOCK_MONOTONIC, &tp) != 0) {
printf("Cannot read monotonic clock\n");
exit(1);
}
memcpy(buf, header, 4);
memcpy(buf + 4, &ms, sizeof(ms));
uint64_t ms = tp.tv_sec * 1000000 + tp.tv_nsec / 1000;
memcpy(buf, header, 4);
memcpy(buf + 4, &ms, sizeof(ms));
}
while (len > 0) {
r = snd_pcm_writei(handle, buf, len);
@ -664,11 +672,11 @@ int main(int argc, char *argv[])
fprintf(stderr, "silence error\n");
break;
}
if (writebuf(phandle, buffer, latency, &frames_out) < 0) {
if (writebuf(phandle, buffer, latency, &frames_out, false) < 0) {
fprintf(stderr, "write error\n");
break;
}
if (writebuf(phandle, buffer, latency, &frames_out) < 0) {
if (writebuf(phandle, buffer, latency, &frames_out, false) < 0) {
fprintf(stderr, "write error\n");
break;
}
@ -698,7 +706,7 @@ int main(int argc, char *argv[])
else {
if (effect)
applyeffect(buffer,r);
if (writebuf(phandle, buffer, r, &frames_out) < 0)
if (writebuf(phandle, buffer, r, &frames_out, true) < 0)
ok = 0;
}
}
@ -735,7 +743,7 @@ int main(int argc, char *argv[])
}
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
printf("End to end latency: no samples collected\n");
snd_pcm_close(phandle);