audiodecoder: add some properties to tweak baseclass behaviour

... so subclass can also rely upon never being bothered with some NULL buffer
it can't do any interesting with, or with any data before it received
any format configuration (and setup properly).

gst-libs/gst/audio/gstaudiodecoder.c

@@ -181,6 +181,8 @@ enum
 #define DEFAULT_LATENCY    0
 #define DEFAULT_TOLERANCE  0
 #define DEFAULT_PLC        FALSE
+#define DEFAULT_DRAINABLE  TRUE
+#define DEFAULT_NEEDS_FORMAT  FALSE
 
 typedef struct _GstAudioDecoderContext
 {
@@ -262,6 +264,8 @@ struct _GstAudioDecoderPrivate
   GstClockTime latency;
   GstClockTime tolerance;
   gboolean plc;
+  gboolean drainable;
+  gboolean needs_format;
 
   /* pending serialized sink events, will be sent from finish_frame() */
   GList *pending_events;
@@ -395,6 +399,8 @@ gst_audio_decoder_init (GstAudioDecoder * dec, GstAudioDecoderClass * klass)
   dec->priv->latency = DEFAULT_LATENCY;
   dec->priv->tolerance = DEFAULT_TOLERANCE;
   dec->priv->plc = DEFAULT_PLC;
+  dec->priv->drainable = DEFAULT_DRAINABLE;
+  dec->priv->needs_format = DEFAULT_NEEDS_FORMAT;
 
   /* init state */
   gst_audio_decoder_reset (dec, TRUE);
@@ -1024,6 +1030,10 @@ gst_audio_decoder_push_buffers (GstAudioDecoder * dec, gboolean force)
     } else {
       if (!force)
         break;
+      if (!priv->drainable) {
+        priv->drained = TRUE;
+        break;
+      }
       buffer = NULL;
     }
 
@@ -1344,6 +1354,9 @@ gst_audio_decoder_chain (GstPad * pad, GstBuffer * buffer)
 
   dec = GST_AUDIO_DECODER (GST_PAD_PARENT (pad));
 
+  if (G_UNLIKELY (!GST_PAD_CAPS (pad) && dec->priv->needs_format))
+    goto not_negotiated;
+
   GST_LOG_OBJECT (dec,
       "received buffer of size %d with ts %" GST_TIME_FORMAT
       ", duration %" GST_TIME_FORMAT, GST_BUFFER_SIZE (buffer),
@@ -1381,6 +1394,15 @@ gst_audio_decoder_chain (GstPad * pad, GstBuffer * buffer)
   GST_AUDIO_DECODER_STREAM_UNLOCK (dec);
 
   return ret;
+
+  /* ERRORS */
+not_negotiated:
+  {
+    GST_ELEMENT_ERROR (dec, CORE, NEGOTIATION, (NULL),
+        ("decoder not initialized"));
+    gst_buffer_unref (buffer);
+    return GST_FLOW_NOT_NEGOTIATED;
+  }
 }
 
 /* perform upstream byte <-> time conversion (duration, seeking)
@@ -2461,3 +2483,105 @@ gst_audio_decoder_get_tolerance (GstAudioDecoder * dec)
 
   return result;
 }
+
+/**
+ * gst_audio_decoder_set_drainable:
+ * @enc: a #GstAudioDecoder
+ * @enabled: new state
+ *
+ * Configures decoder drain handling.  If drainable, subclass might
+ * be handed a NULL buffer to have it return any leftover decoded data.
+ * Otherwise, it is not considered so capable and will only ever be passed
+ * real data.
+ *
+ * MT safe.
+ *
+ * Since: 0.10.36
+ */
+void
+gst_audio_decoder_set_drainable (GstAudioDecoder * dec, gboolean enabled)
+{
+  g_return_if_fail (GST_IS_AUDIO_DECODER (dec));
+
+  GST_OBJECT_LOCK (dec);
+  dec->priv->drainable = enabled;
+  GST_OBJECT_UNLOCK (dec);
+}
+
+/**
+ * gst_audio_decoder_get_drainable:
+ * @enc: a #GstAudioDecoder
+ *
+ * Queries decoder drain handling.
+ *
+ * Returns: TRUE if drainable handling is enabled.
+ *
+ * MT safe.
+ *
+ * Since: 0.10.36
+ */
+gboolean
+gst_audio_decoder_get_drainable (GstAudioDecoder * dec)
+{
+  gboolean result;
+
+  g_return_val_if_fail (GST_IS_AUDIO_DECODER (dec), 0);
+
+  GST_OBJECT_LOCK (dec);
+  result = dec->priv->drainable;
+  GST_OBJECT_UNLOCK (dec);
+
+  return result;
+}
+
+/**
+ * gst_audio_decoder_set_needs_format:
+ * @enc: a #GstAudioDecoder
+ * @enabled: new state
+ *
+ * Configures decoder format needs.  If enabled, subclass needs to be
+ * negotiated with format caps before it can process any data.  It will then
+ * never be handed any data before it has been configured.
+ * Otherwise, it might be handed data without having been configured and
+ * is then expected being able to do so either by default
+ * or based on the input data.
+ *
+ * MT safe.
+ *
+ * Since: 0.10.36
+ */
+void
+gst_audio_decoder_set_needs_format (GstAudioDecoder * dec, gboolean enabled)
+{
+  g_return_if_fail (GST_IS_AUDIO_DECODER (dec));
+
+  GST_OBJECT_LOCK (dec);
+  dec->priv->needs_format = enabled;
+  GST_OBJECT_UNLOCK (dec);
+}
+
+/**
+ * gst_audio_decoder_get_needs_format:
+ * @enc: a #GstAudioDecoder
+ *
+ * Queries decoder required format handling.
+ *
+ * Returns: TRUE if required format handling is enabled.
+ *
+ * MT safe.
+ *
+ * Since: 0.10.36
+ */
+gboolean
+gst_audio_decoder_get_needs_format (GstAudioDecoder * dec)
+{
+  gboolean result;
+
+  g_return_val_if_fail (GST_IS_AUDIO_DECODER (dec), 0);
+
+  GST_OBJECT_LOCK (dec);
+  result = dec->priv->needs_format;
+  GST_OBJECT_UNLOCK (dec);
+
+  return result;
+}

gst-libs/gst/audio/gstaudiodecoder.h

@@ -293,6 +293,16 @@ void              gst_audio_decoder_set_tolerance   (GstAudioDecoder * dec,
 
 gint64            gst_audio_decoder_get_tolerance   (GstAudioDecoder * dec);
 
+void              gst_audio_decoder_set_drainable (GstAudioDecoder * dec,
+                                                   gboolean enabled);
+
+gboolean          gst_audio_decoder_get_drainable (GstAudioDecoder * dec);
+
+void              gst_audio_decoder_set_needs_format (GstAudioDecoder * dec,
+                                                      gboolean enabled);
+
+gboolean          gst_audio_decoder_get_needs_format (GstAudioDecoder * dec);
+
 G_END_DECLS
 
 #endif /* _GST_AUDIO_DECODER_H_ */