PCM decoder: Correct the end of audio stream handling. It was not being detected before so that logic was not examining the WAV header in the first buffer of the next audio file

audio/pcm_decode.c

@@ -785,6 +785,10 @@ static int pcm_shutdown(FAR struct audio_lowerhalf_s *dev)
 
   DEBUGASSERT(priv);
 
+  /* We are no longer streaming audio */
+
+  priv->streaming = false;
+
   /* Defer the operation to the lower device driver */
 
   lower = priv->lower;
@@ -851,6 +855,10 @@ static int pcm_stop(FAR struct audio_lowerhalf_s *dev)
 
   DEBUGASSERT(priv);
 
+  /* We are no longer streaming */
+
+  priv->streaming = false;
+
   /* Defer the operation to the lower device driver */
 
   lower = priv->lower;
@@ -1026,6 +1034,14 @@ static int pcm_enqueuebuffer(FAR struct audio_lowerhalf_s *dev,
   if (priv->streaming)
     {
       /* Yes, we are streaming */
+      /* Check for the last audio buffer in the stream */
+
+      if ((apb->flags & AUDIO_APB_FINAL) != 0)
+        {
+          /* Yes.. then we are no longer streaming */
+
+          priv->streaming = false;
+        }
 
 #ifndef CONFIG_AUDIO_EXCLUDE_FFORWARD
       audvdbg("Received: apb=%p curbyte=%d nbytes=%d\n",
@@ -1062,9 +1078,15 @@ static int pcm_enqueuebuffer(FAR struct audio_lowerhalf_s *dev,
         {
           struct audio_caps_s caps;
 
-          /* Now we are streaming */
+          /* Now we are streaming.  Unless for some reason there is only one
+           * audio buffer in the audio stream.  In that case, this will be
+           * marked as the final buffer
+            */
 
-          priv->streaming = true;
+          if ((apb->flags & AUDIO_APB_FINAL) == 0)
+            {
+              priv->streaming = true;
+            }
 
           /* Configure the lower level for the number of channels, bitrate,
            * and sample bitwidth.
@@ -1110,6 +1132,18 @@ static int pcm_enqueuebuffer(FAR struct audio_lowerhalf_s *dev,
 
           return lower->ops->enqueuebuffer(lower, apb);
         }
+
+      /* Return the unhandled buffer to the previous level with an error
+       * indication.
+       */
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+      priv->export.upper(priv->export.priv, AUDIO_CALLBACK_DEQUEUE, apb,
+                         -EINVAL, NULL);
+#else
+      priv->export.upper(priv->export.priv, AUDIO_CALLBACK_DEQUEUE, apb,
+                         -EINVAL);
+#endif
     }
 
   /* This is not a WAV file! */