aulevel_performance.c

#include <re.h>
#include <rem.h>
#include <stdint.h>

enum {
	SILENCE_Q = 1024 * 1024, /* Quadratic sample value for silence */
};


static bool auframe_silence(struct auframe *af)
{
	const int16_t *v;
	int32_t sum = 0;
	size_t i;

	v = af->sampv;
	for (i = 0; i < af->sampc; i++) {
		sum += v[i] * v[i];

		if (sum > (int32_t)(i + 1) * SILENCE_Q)
			return false;
	}

	return true;
}


static bool auframe_silence2(struct auframe *af)
{
	return auframe_level(af) < -30.;
}


int main(void)
{
	uint64_t start, end;
	int16_t testv[1920] = {0, 0};
	struct auframe af;
	bool ret;
	int cnt = 0;

	auframe_init(&af, AUFMT_S16LE, testv, ARRAY_SIZE(testv), 48000, 2);

	for (int j = 0; j < 2; j++) {
		cnt   = 0;
		start = tmr_jiffies_usec();
		for (int i = 0; i < 2000; i++) {
			ret = auframe_silence(&af);
			if (ret)
				cnt++;
			af.level = AULEVEL_UNDEF;
		}
		end = tmr_jiffies_usec();

		re_printf("auframe_silence %d usecs (%d)\n", end - start, cnt);

		cnt   = 0;
		start = tmr_jiffies_usec();
		for (int i = 0; i < 2000; i++) {
			ret = auframe_silence2(&af);
			if (ret)
				cnt++;
			af.level = AULEVEL_UNDEF;
		}
		end = tmr_jiffies_usec();

		re_printf("auframe_silence2 %d usecs (%d)\n", end - start,
			  cnt);
	}
	return 0;
}

We found that the example code has to be compiled also with same optimization level like rem. But anyway your silence detection is slightly faster:

auframe_silence2 1713 usecs (2000)
auframe_silence 2318 usecs (2000)
auframe_silence2 683 usecs (2000)
auframe_silence 2341 usecs (2000)

Also I tried with this code:

bool auframe_silence(struct auframe *af)
{
	const int16_t *v;
	int32_t sum = 0;
	int64_t b = SILENCE_Q;
	size_t i;
	size_t len = af->sampc;

	v = af->sampv;
	for (i = 0; i < len; i++) {
		sum += v[i] * v[i];
		b += SILENCE_Q;

		if (sum > b)
			return false;
	}

	return true;
}

Here b += SILENCE_Q; and if (sum > b) leads to the performance loss.