aplay: place hard limits on resampler conversions

Allow time for each rate ratio adjustment to have an effect on
the delay before making another ajustment.

Do not allow the resampler to modify the rate ratio beyond fixed
limits above and below the nominal rate ratio.

If the delay changes too rapidly, or the delay goes too far away
from the target value, then reset the rate ratio to its nominal
value and update the target delay value.

Author: borine

utils/aplay/aplay.c

@@ -601,8 +601,8 @@ static void *io_worker_routine(struct io_worker *w) {
 #if WITH_LIBSAMPLERATE
 					if (use_resampler)
 						resampler_reset(resampler);
-#endif
 				}
+#endif
 			}
 
 			ssize_t ret;
@@ -725,7 +725,9 @@ static void *io_worker_routine(struct io_worker *w) {
 						w->ba_pcm.rate,
 						w->alsa_pcm.format,
 						w->alsa_pcm.rate,
-						read_buffer.nmemb / w->ba_pcm.channels);
+						w->alsa_pcm.start_threshold,
+						w->alsa_pcm.start_threshold + w->alsa_pcm.period_frames,
+						read_buffer.nmemb );
 
 				if (resampler == NULL)
 					goto fail;
@@ -826,9 +828,6 @@ static void *io_worker_routine(struct io_worker *w) {
 #if WITH_LIBSAMPLERATE
 		size_t resample_delay_frames;
 		if (use_resampler) {
-			if (!alsa_pcm_is_running(&w->alsa_pcm) || w->alsa_pcm.underrun)
-				resampler_reset(resampler);
-
 			resample_delay_frames = ffb_len_out(write_buffer) / w->ba_pcm.channels;
 			resample_delay_frames /= resampler_current_rate_ratio(resampler);
 		}
@@ -845,8 +844,14 @@ static void *io_worker_routine(struct io_worker *w) {
 		}
 
 #if WITH_LIBSAMPLERATE
-		if (use_resampler && alsa_pcm_is_running(&w->alsa_pcm)) {
-			bool rate_changed = resampler_update_rate_ratio(resampler, dr.avg_value);
+		if (use_resampler) {
+			bool rate_changed = false;
+			if (w->alsa_pcm.underrun) {
+				resampler_reset(resampler);
+				rate_changed = true;
+			}
+			if (alsa_pcm_is_running(&w->alsa_pcm))
+				rate_changed = resampler_update_rate_ratio(resampler, read_samples / w->ba_pcm.channels, dr.avg_value);
 			if (verbose >= 5 && rate_changed)
 				debug("new rate ratio %.6f", resampler_current_rate_ratio(resampler));
 		}