basetransform: refactor metadata modifications

Check when we need to touch the metadata of the output buffer after selecting
the output buffer so that we have everything in one place.
Also take flags and timestamp modifications into account.

libs/gst/base/gstbasetransform.c

@@ -1168,8 +1168,8 @@ gst_base_transform_prepare_output_buffer (GstBaseTransform * trans,
   GstBaseTransformPrivate *priv;
   GstFlowReturn ret = GST_FLOW_OK;
   guint outsize, newsize, expsize;
-  gboolean discard;
+  gboolean discard, setcaps, copymeta;
-  GstCaps *incaps, *oldcaps, *newcaps;
+  GstCaps *incaps, *oldcaps, *newcaps, *outcaps;
 
   bclass = GST_BASE_TRANSFORM_GET_CLASS (trans);
 
@@ -1340,7 +1340,10 @@ gst_base_transform_prepare_output_buffer (GstBaseTransform * trans,
     }
   }
 
-  /* try to make a final output buffer, make sure the metadata is writable */
+  /* these are the final output caps */
+  outcaps = GST_PAD_CAPS (trans->srcpad);
+
+  copymeta = FALSE;
   if (*out_buf == NULL) {
     if (!discard) {
       GST_DEBUG_OBJECT (trans, "make default output buffer of size %d",
@@ -1351,12 +1354,7 @@ gst_base_transform_prepare_output_buffer (GstBaseTransform * trans,
           GST_BUFFER_COPY_FLAGS | GST_BUFFER_COPY_TIMESTAMPS);
     } else {
       GST_DEBUG_OBJECT (trans, "reuse input buffer");
-      /* we can reuse the input buffer if it's writable else we take a
-       * subbuffer. Note that we can't unref in_buf. */
-      if (gst_buffer_is_metadata_writable (in_buf))
       *out_buf = in_buf;
-      else
-        *out_buf = gst_buffer_create_sub (in_buf, 0, GST_BUFFER_SIZE (in_buf));
     }
   } else {
     if (trans->passthrough && in_buf != *out_buf) {
@@ -1369,35 +1367,59 @@ gst_base_transform_prepare_output_buffer (GstBaseTransform * trans,
     if (discard) {
       GST_DEBUG_OBJECT (trans, "discard buffer, reuse input buffer");
       gst_buffer_unref (*out_buf);
-      /* we can reuse the input buffer if it's writable else we take a
-       * subbuffer. Note that we can't unref in_buf. */
-      if (gst_buffer_is_metadata_writable (in_buf))
       *out_buf = in_buf;
-      else
-        *out_buf = gst_buffer_create_sub (in_buf, 0, GST_BUFFER_SIZE (in_buf));
     } else {
       GST_DEBUG_OBJECT (trans, "using allocated buffer in %p, out %p", in_buf,
           *out_buf);
-      /* we need a metadata writable output buffer. Note that we can't unref
+      /* if we have different buffers, check if the metadata is ok */
-       * in_buf. */
+      if (*out_buf != in_buf) {
+        guint mask;
+
+        mask = GST_BUFFER_FLAG_PREROLL | GST_BUFFER_FLAG_IN_CAPS |
+            GST_BUFFER_FLAG_DELTA_UNIT | GST_BUFFER_FLAG_DISCONT |
+            GST_BUFFER_FLAG_GAP | GST_BUFFER_FLAG_MEDIA1 |
+            GST_BUFFER_FLAG_MEDIA2 | GST_BUFFER_FLAG_MEDIA3;
+        /* see if the flags and timestamps match */
+        copymeta =
+            (GST_MINI_OBJECT_FLAGS (*out_buf) & mask) ==
+            (GST_MINI_OBJECT_FLAGS (in_buf) & mask);
+        copymeta |=
+            GST_BUFFER_TIMESTAMP (*out_buf) != GST_BUFFER_TIMESTAMP (in_buf) ||
+            GST_BUFFER_DURATION (*out_buf) != GST_BUFFER_DURATION (in_buf) ||
+            GST_BUFFER_OFFSET (*out_buf) != GST_BUFFER_OFFSET (in_buf) ||
+            GST_BUFFER_OFFSET_END (*out_buf) != GST_BUFFER_OFFSET_END (in_buf);
+      }
+    }
+  }
+
+  /* check if we need to make things writable. We need this when we need to
+   * update the caps or the metadata on the output buffer. */
+  newcaps = GST_BUFFER_CAPS (*out_buf);
+  setcaps = (newcaps != outcaps) && (!gst_caps_is_equal (newcaps, outcaps));
+  /* we need to modify the metadata when the element is not gap aware,
+   * passthrough is not used and the gap flag is set */
+  copymeta |= !trans->priv->gap_aware && !trans->passthrough
+      && (GST_MINI_OBJECT_FLAGS (*out_buf) & GST_BUFFER_FLAG_GAP);
+
+  if (setcaps || copymeta) {
+    GST_DEBUG_OBJECT (trans, "setcaps %d, copymeta %d", setcaps, copymeta);
     if (!gst_buffer_is_metadata_writable (*out_buf)) {
+      GST_DEBUG_OBJECT (trans, "buffer metadata %p not writable", *out_buf);
       if (in_buf == *out_buf)
-          *out_buf =
+        *out_buf = gst_buffer_create_sub (in_buf, 0, GST_BUFFER_SIZE (in_buf));
-              gst_buffer_create_sub (in_buf, 0, GST_BUFFER_SIZE (in_buf));
       else
         *out_buf = gst_buffer_make_metadata_writable (*out_buf);
     }
+    /* when we get here, the metadata should be writable */
+    if (setcaps)
+      gst_buffer_set_caps (*out_buf, outcaps);
+    if (copymeta)
       gst_buffer_copy_metadata (*out_buf, in_buf,
           GST_BUFFER_COPY_FLAGS | GST_BUFFER_COPY_TIMESTAMPS);
-    }
+    /* clear the GAP flag when the subclass does not understand it */
-  }
+    if (!trans->priv->gap_aware)
-  /* when we get here, the metadata should be writable */
-  gst_buffer_set_caps (*out_buf, GST_PAD_CAPS (trans->srcpad));
-
-  /* clear the GAP flag when the subclass does not understand it
-   * and passthrough mode is not used */
-  if (!trans->priv->gap_aware && !trans->passthrough)
       GST_BUFFER_FLAG_UNSET (*out_buf, GST_BUFFER_FLAG_GAP);
+  }
 
   return ret;