capsfeatures: Add documentation about ANY GstCapsFeatures

diff --git a/docs/design/part-caps.txt b/docs/design/part-caps.txt
index b65a940..ed129bf 100644 (file)
--- a/docs/design/part-caps.txt
+++ b/docs/design/part-caps.txt
@@ -33,7 +33,8 @@ that makes most sense for the media format by the element or pad
 implementation and afterwards every remaining unfixed fields is set to
 an arbitrary value that would be a subset of the unfixed field value.
 
-EMPTY caps are fixed caps, ANY caps are not fixed.
+EMPTY caps are fixed caps, ANY caps are not fixed. Caps with ANY caps
+features are not fixed.
 
 Subset
 ------

diff --git a/gst/gstcapsfeatures.c b/gst/gstcapsfeatures.c
index ab0d4ca..b64240e 100644 (file)
--- a/gst/gstcapsfeatures.c
+++ b/gst/gstcapsfeatures.c
@@ -30,7 +30,12 @@
  * structures with different feature sets to the caps.
  *
  * Empty #GstCapsFeatures are equivalent with the #GstCapsFeatures that only
- * contain #GST_CAPS_FEATURE_MEMORY_SYSTEM_MEMORY.
+ * contain #GST_CAPS_FEATURE_MEMORY_SYSTEM_MEMORY. ANY #GstCapsFeatures as
+ * created by gst_caps_features_new_any() are equal to any other #GstCapsFeatures
+ * and can be used to specify that any #GstCapsFeatures would be supported, e.g.
+ * for elements that don't touch buffer memory. #GstCaps with ANY #GstCapsFeatures
+ * are considered non-fixed and during negotiation some #GstCapsFeatures have
+ * to be selected.
  *
  * Examples for caps features would be the requirement of a specific #GstMemory
  * types or the requirement of having a specific #GstMeta on the buffer. Features