diff --git a/libavcodec/internal.h b/libavcodec/internal.h
index a681329f20d0f63e724f8923f980cb0be551b599..5aa77129a2354e2ba3f8cc2f2a549c8f99e90622 100644
--- a/libavcodec/internal.h
+++ b/libavcodec/internal.h
@@ -34,11 +34,16 @@
 #include "config.h"
 
 /**
- * Codec is thread safe.
+ * The codec does not modify any global variables in the init function,
+ * allowing to call the init function without locking any global mutexes.
  */
 #define FF_CODEC_CAP_INIT_THREADSAFE        (1 << 0)
 /**
- * Codec cleans up memory on init failure.
+ * The codec allows calling the close function for deallocation even if
+ * the init function returned a failure. Without this capability flag, a
+ * codec does such cleanup internally when returning failures from the
+ * init function and does not expect the close function to be called at
+ * all.
  */
 #define FF_CODEC_CAP_INIT_CLEANUP           (1 << 1)