videodecoder: Add API to allow subclasses to specify that they needs caps before any buffers

docs/libs/gst-plugins-base-libs-sections.txt

@@ -2536,6 +2536,8 @@ gst_video_decoder_set_estimate_rate
 gst_video_decoder_set_output_state
 gst_video_decoder_set_max_errors
 gst_video_decoder_set_packetized
+gst_video_decoder_get_needs_format
+gst_video_decoder_set_needs_format
 gst_video_decoder_merge_tags
 <SUBSECTION Standard>
 GST_IS_VIDEO_DECODER

gst-libs/gst/video/gstvideodecoder.c

@@ -336,6 +336,7 @@ struct _GstVideoDecoderPrivate
   gboolean had_output_data;
   gboolean had_input_data;
 
+  gboolean needs_format;
   gboolean do_caps;
 
   /* ... being tracked here;
@@ -558,6 +559,7 @@ gst_video_decoder_init (GstVideoDecoder * decoder, GstVideoDecoderClass * klass)
   decoder->priv->input_adapter = gst_adapter_new ();
   decoder->priv->output_adapter = gst_adapter_new ();
   decoder->priv->packetized = TRUE;
+  decoder->priv->needs_format = FALSE;
 
   gst_video_decoder_reset (decoder, TRUE, TRUE);
 }
@@ -1981,6 +1983,9 @@ gst_video_decoder_chain (GstPad * pad, GstObject * parent, GstBuffer * buf)
     decoder->priv->do_caps = FALSE;
   }
 
+  if (G_UNLIKELY (!decoder->priv->input_state && decoder->priv->needs_format))
+    goto not_negotiated;
+
   GST_LOG_OBJECT (decoder,
       "chain PTS %" GST_TIME_FORMAT ", DTS %" GST_TIME_FORMAT " duration %"
       GST_TIME_FORMAT " size %" G_GSIZE_FORMAT,
@@ -3446,6 +3451,50 @@ gst_video_decoder_get_max_errors (GstVideoDecoder * dec)
   return dec->priv->max_errors;
 }
 
+/**
+ * gst_video_decoder_set_needs_format:
+ * @dec: a #GstVideoDecoder
+ * @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.
+ *
+ * Since: 1.4
+ */
+void
+gst_video_decoder_set_needs_format (GstVideoDecoder * dec, gboolean enabled)
+{
+  g_return_if_fail (GST_IS_VIDEO_DECODER (dec));
+
+  dec->priv->needs_format = enabled;
+}
+
+/**
+ * gst_video_decoder_get_needs_format:
+ * @dec: a #GstVideoDecoder
+ *
+ * Queries decoder required format handling.
+ *
+ * Returns: TRUE if required format handling is enabled.
+ *
+ * Since: 1.4
+ */
+gboolean
+gst_video_decoder_get_needs_format (GstVideoDecoder * dec)
+{
+  gboolean result;
+
+  g_return_val_if_fail (GST_IS_VIDEO_DECODER (dec), FALSE);
+
+  result = dec->priv->needs_format;
+
+  return result;
+}
+
 /**
  * gst_video_decoder_set_packetized:
  * @decoder: a #GstVideoDecoder

gst-libs/gst/video/gstvideodecoder.h

@@ -316,6 +316,11 @@ void     gst_video_decoder_set_max_errors (GstVideoDecoder * dec,
 
 gint     gst_video_decoder_get_max_errors (GstVideoDecoder * dec);
 
+void     gst_video_decoder_set_needs_format (GstVideoDecoder * dec,
+                                             gboolean enabled);
+
+gboolean gst_video_decoder_get_needs_format (GstVideoDecoder * dec);
+
 void     gst_video_decoder_set_latency (GstVideoDecoder *decoder,
 					GstClockTime min_latency,
 					GstClockTime max_latency);

win32/common/libgstvideo.def

@@ -95,6 +95,7 @@ EXPORTS
 	gst_video_decoder_get_latency
 	gst_video_decoder_get_max_decode_time
 	gst_video_decoder_get_max_errors
+	gst_video_decoder_get_needs_format
 	gst_video_decoder_get_oldest_frame
 	gst_video_decoder_get_output_state
 	gst_video_decoder_get_packetized
@@ -107,6 +108,7 @@ EXPORTS
 	gst_video_decoder_set_estimate_rate
 	gst_video_decoder_set_latency
 	gst_video_decoder_set_max_errors
+	gst_video_decoder_set_needs_format
 	gst_video_decoder_set_output_state
 	gst_video_decoder_set_packetized
 	gst_video_encoder_allocate_output_buffer