Fix a problem with audio not starting on a list of short files

Forced audio start was left out when a third codec attempts to
start a second track transition. Only one pending transition is
allowed at a time. There wouldn't be enough PCM in the buffer to
trigger audio playback and audio would just return without giving
the pcm buffer a kick.

Fixes FS#13100 - Player failed on short tracks

Change-Id: I338b0b12022c591930451fd5ed26a2a73008835f

apps/pcmbuf.c

@@ -204,6 +204,13 @@ extern void audio_pcmbuf_sync_position(void);
 
 /**************************************/
 
+/* start PCM if callback says it's alright */
+static void start_audio_playback(void)
+{
+     if (audio_pcmbuf_may_play())
+        pcmbuf_play_start();
+}
+
 /* Return number of commited bytes in buffer (committed chunks count as
    a full chunk even if only partially filled) */
 static size_t pcmbuf_unplayed_bytes(void)
@@ -492,8 +499,8 @@ void * pcmbuf_request_buffer(int *count)
         trigger_cpu_boost();
 
         /* If pre-buffered to the watermark, start playback */
-        if (!pcmbuf_data_critical() && audio_pcmbuf_may_play())
+        if (!pcmbuf_data_critical())
-            pcmbuf_play_start();
+            start_audio_playback();
     }
 
     void *buf;
@@ -672,15 +679,22 @@ void pcmbuf_monitor_track_change(bool monitor)
 
 void pcmbuf_start_track_change(enum pcm_track_change_type type)
 {
+    /* Commit all outstanding data before starting next track - tracks don't
+       comingle inside a single buffer chunk */
+    commit_if_needed(COMMIT_ALL_DATA);
+
+    if (type == TRACK_CHANGE_AUTO_PILEUP)
+    {
+        /* Fill might not have been above watermark */
+        start_audio_playback();
+        return;
+    }
+
 #ifdef HAVE_CROSSFADE
     bool crossfade = false;
 #endif
     bool auto_skip = type != TRACK_CHANGE_MANUAL;
 
-    /* Commit all outstanding data before starting next track - tracks don't
-       comingle inside a single buffer chunk */
-    commit_if_needed(COMMIT_ALL_DATA);
-
     /* Update position key so that:
        1) Positions are keyed to the track to which they belong for sync
           purposes
@@ -695,9 +709,8 @@ void pcmbuf_start_track_change(enum pcm_track_change_type type)
     {
         crossfade_cancel();
 
-        /* If end of all data, force playback */
+        /* Fill might not have been above watermark */
-        if (audio_pcmbuf_may_play())
+        start_audio_playback();
-            pcmbuf_play_start();
     }
 #ifdef HAVE_CROSSFADE
     /* Determine whether this track change needs to crossfaded and how */

apps/pcmbuf.h

@@ -43,6 +43,7 @@ enum pcm_track_change_type
     TRACK_CHANGE_NONE = 0,     /* No track change pending */
     TRACK_CHANGE_MANUAL,       /* Manual change (from user) */
     TRACK_CHANGE_AUTO,         /* Automatic change (from codec) */
+    TRACK_CHANGE_AUTO_PILEUP,  /* Auto change during pending change */
     TRACK_CHANGE_END_OF_DATA,  /* Expect no more data (from codec) */
 };
 void pcmbuf_monitor_track_change(bool monitor);

apps/playback.c

@@ -2376,9 +2376,16 @@ static void audio_on_codec_complete(int status)
            Skipping: There was already a skip in progress, remember it and
                      allow no further progress until the PCM from the previous
                      song has finished
+
+           This function will be reentered upon completing the existing
+           transition in order to do the one that was just tried (below)
          */
         codec_skip_pending = true;
         codec_skip_status = status;
+
+        /* PCM buffer must know; audio could still be filling and hasn't
+           yet reached the play watermark */
+        pcmbuf_start_track_change(TRACK_CHANGE_AUTO_PILEUP);
         return;
     }