From 136071a62180c5d5215678d6d00638240f1321bd Mon Sep 17 00:00:00 2001
From: Mike Brady <4265913+mikebrady@users.noreply.github.com>
Date: Fri, 26 Nov 2021 15:17:27 +0000
Subject: [PATCH] change stats to report non-zero if output has just opened or
 if there has been any discontinuity in play from previous time.

---
 audio_alsa.c | 46 +++++++++++++++++-----------------------------
 1 file changed, 17 insertions(+), 29 deletions(-)

diff --git a/audio_alsa.c b/audio_alsa.c
index caaad899..0910b9e7 100644
--- a/audio_alsa.c
+++ b/audio_alsa.c
@@ -248,8 +248,12 @@ static snd_pcm_uframes_t period_size_requested, buffer_size_requested;
 static int set_period_size_request, set_buffer_size_request;
 
 static uint64_t frames_sent_for_playing;
-static int output_error_occurred; // set to true if an underrun or similar has occurred since last
-                                  // requested
+
+ // set to true if there has been a discontinuity between the last reported frames_sent_for_playing
+ // and the present reported frames_sent_for_playing
+ // Not that it will be set when the device is opened, as any previous figures for frames_sent_for_playing
+ // (which Shairport Sync might hold) would be invalid.
+static int frames_sent_break_occurred;
 
 static void help(void) {
   printf("    -d output-device    set the output device, default is \"default\".\n"
@@ -1632,13 +1636,10 @@ int delay(long *the_delay) {
 int stats(uint64_t *the_time, uint64_t *the_delay, uint64_t *frames_sent_to_dac) {
   // returns 0 if the device is in a valid state -- SND_PCM_STATE_RUNNING or
   // SND_PCM_STATE_PREPARED
-  // or SND_PCM_STATE_DRAINING
-  // and returns the actual delay if running or 0 if prepared in *the_delay
-
-  // otherwise return an error code
-  // the error code could be a Unix errno code or a snderror code, or
-  // the sps_extra_code_output_stalled or the
-  // sps_extra_code_output_state_cannot_make_ready codes
+  // or SND_PCM_STATE_DRAINING.
+  // returns the actual delay if running or 0 if prepared in *the_delay
+  // returns the present value of frames_sent_for_playing
+  // otherwise return a non-zero value
   int ret = 0;
   *the_delay = 0;
 
@@ -1657,8 +1658,10 @@ int stats(uint64_t *the_time, uint64_t *the_delay, uint64_t *frames_sent_to_dac)
     ret = delay_and_status(&state, &my_delay, NULL);
   }
   if (ret == 0)
-    ret = output_error_occurred; // will be zero unless an error like an underrun occurred
-  output_error_occurred = 0;     // reset it.
+    ret = frames_sent_break_occurred; // will be zero unless an error like an underrun occurred
+  else
+    ret = 1; // just indicate there was some kind of a break
+  frames_sent_break_occurred = 0;     // reset it.
   if (frames_sent_to_dac != NULL)
     *frames_sent_to_dac = frames_sent_for_playing;
   debug_mutex_unlock(&alsa_mutex, 0);
@@ -1668,22 +1671,6 @@ int stats(uint64_t *the_time, uint64_t *the_delay, uint64_t *frames_sent_to_dac)
   *the_delay = hd;
   return ret;
 }
-
-int get_frames_sent_for_output(__attribute__((unused)) uint64_t *elapsed_time,
-                               uint64_t *frames_sent_to_dac) {
-  int ret = 0;
-  pthread_cleanup_debug_mutex_lock(&alsa_mutex, 10000, 0);
-  *frames_sent_to_dac = frames_sent_for_playing;
-  if (alsa_handle == NULL)
-    ret = ENODEV;
-  else
-    ret = output_error_occurred; // will be zero unless an error occurred
-  output_error_occurred = 0;     // reset it.
-  debug_mutex_unlock(&alsa_mutex, 0);
-  pthread_cleanup_pop(0);
-  return ret;
-}
-
 /*
 int get_rate_information(uint64_t *elapsed_time, uint64_t *frames_played) {
   // elapsed_time is in nanoseconds
@@ -1728,7 +1715,7 @@ int do_play(void *buf, int samples) {
         stall_monitor_frame_count += samples;
         frames_sent_for_playing += samples;
       } else {
-        output_error_occurred = -ret; // note than an output error has occurred
+        frames_sent_break_occurred = 1; // note than an output error has occurred
         if (ret == -EPIPE) {          /* underrun */
 
           // It could be that the DAC was in the SND_PCM_STATE_XRUN state before
@@ -1802,7 +1789,8 @@ int do_open(int do_auto_setup) {
                           // set accordingly
         // do_mute(0); // complete unmute
       }
-      output_error_occurred = 0;
+      frames_sent_break_occurred = 1; // there is a discontinuity with
+      // any previously-reported frame count      
       frames_sent_for_playing = 0;
       alsa_backend_state = abm_connected; // only do this if it really opened it.
     }