From: Mike Brady <mikebrady@eircom.net>
Date: Mon, 17 Dec 2018 16:31:03 +0000 (+0000)
Subject: Don't send silence into the alsa device within the scanner's sleep time of the last... 
X-Git-Tag: 3.3RC0~83
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cb17fb263ada0907152fdee884d7701c042c8747;p=thirdparty%2Fshairport-sync.git

Don't send silence into the alsa device within the scanner's sleep time of the last legitimate write to it. This is to stop the scanner inserting silent frames while the player is flushing fames.
---

diff --git a/audio_alsa.c b/audio_alsa.c
index 8cb96e05..17fc672a 100644
--- a/audio_alsa.c
+++ b/audio_alsa.c
@@ -133,6 +133,8 @@ static uint64_t frames_played_at_measurement_start_time;
 static uint64_t measurement_time;
 static uint64_t frames_played_at_measurement_time;
 
+static uint64_t most_recent_write_time;
+
 static uint64_t frames_sent_for_playing;
 static uint64_t frame_index;
 static int measurement_data_is_valid;
@@ -956,6 +958,7 @@ static int init(int argc, char **argv) {
       die("Could not open the alsa device with the settings given.");
   }
 
+	most_recent_write_time = 0; // could be used by the alsa_buffer_monitor_thread_code
   pthread_create(&alsa_buffer_monitor_thread, NULL, &alsa_buffer_monitor_thread_code, NULL);
 
   return response;
@@ -1079,7 +1082,7 @@ int delay(long *the_delay) {
           debug(2, "delay not available -- state is SND_PCM_STATE_XRUN");
         } else {
 
-          debug(2, "Error -- ALSA delay(): bad state: %d.", dac_state);
+          debug(1, "Error -- ALSA delay(): bad state: %d.", dac_state);
         }
         if ((derr = snd_pcm_prepare(alsa_handle))) {
           debug(1, "Error preparing after delay error: \"%s\".", snd_strerror(derr));
@@ -1175,7 +1178,7 @@ static int play(void *buf, int samples) {
         debug(1, "empty buffer being passed to pcm_writei -- skipping it");
       if ((samples != 0) && (buf != NULL)) {
         // debug(3, "write %d frames.", samples);
-
+				most_recent_write_time = get_absolute_time_in_fp();
         err = alsa_pcm_write(alsa_handle, buf, samples);
 
         stall_monitor_frame_count += samples;
@@ -1457,6 +1460,10 @@ void *alsa_buffer_monitor_thread_code(void *arg) {
   debug(1, "alsa: dither will %sbe added to inter-session silence.", use_dither ? "" : "not ");
 
   int sleep_time_ms = 80;
+  uint64_t sleep_time_in_fp = sleep_time_ms;
+  sleep_time_in_fp = sleep_time_in_fp << 32;
+  sleep_time_in_fp = sleep_time_in_fp / 1000;
+  debug(1,"alsa: sleep_time: %d ms or 0x%" PRIx64 " in fp form.",sleep_time_ms,sleep_time_in_fp);
   int frames_of_silence = desired_sample_rate * sleep_time_ms / 1000;
   size_t size_of_silence_buffer = frames_of_silence * frame_size;
   // debug(1,"Silence buffer length: %u bytes.",size_of_silence_buffer);
@@ -1469,24 +1476,25 @@ void *alsa_buffer_monitor_thread_code(void *arg) {
     int reply;
     while (1) {
     	if (config.keep_dac_busy != 0) {
-				if (buffer_size < (((int)desired_sample_rate * sleep_time_ms) / (1000))) {
-					if ((hardware_mixer == 0) && (config.ignore_volume_control == 0) && (config.airplay_volume != 0.0))
-						use_dither = 1;
-					else
-						use_dither = 0;
-					dither_random_number_store = generate_zero_frames(
-							silence, frames_of_silence, config.output_format, use_dither, // i.e. with dither
-							dither_random_number_store);
-					play(silence, frames_of_silence);
+    		uint64_t present_time = get_absolute_time_in_fp();
+    		if ((most_recent_write_time == 0) || ((present_time - most_recent_write_time) > sleep_time_in_fp)) {
+					reply = delay(&buffer_size);
+					if (reply != 0)
+						buffer_size = 0;
+					if (buffer_size < (((int)desired_sample_rate * sleep_time_ms) / (1000))) {
+						if ((hardware_mixer == 0) && (config.ignore_volume_control == 0) && (config.airplay_volume != 0.0))
+							use_dither = 1;
+						else
+							use_dither = 0;
+						dither_random_number_store = generate_zero_frames(
+								silence, frames_of_silence, config.output_format, use_dither, // i.e. with dither
+								dither_random_number_store);
+						play(silence, frames_of_silence);
+					}
 				}
-      	usleep((sleep_time_ms * 1000) / 2);
-      	reply = delay(&buffer_size);
-      	if (reply != 0)
-        	debug(1, "error %d during buffer monitoring of delay", reply);
-      } else {
-      	usleep(sleep_time_ms * 1000);      
-      }      
-      pthread_testcancel();
+      }   
+      usleep((sleep_time_ms * 1000) / 2); // has a cancellation point in it
+//      pthread_testcancel();
     }
   }
   pthread_cleanup_pop(1);