diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 3007f814ce..a5d2dd9d2b 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -198,6 +198,10 @@
  *   be set to the timebase that the caller desires to use for this stream (note
  *   that the timebase actually used by the muxer can be different, as will be
  *   described later).
+ * - It is advised to manually initialize only the relevant fields in
+ *   AVCodecContext, rather than using @ref avcodec_copy_context() during
+ *   remuxing: there is no guarantee that the codec context values remain valid
+ *   for both input and output format contexts.
  * - The caller may fill in additional information, such as @ref
  *   AVFormatContext.metadata "global" or @ref AVStream.metadata "per-stream"
  *   metadata, @ref AVFormatContext.chapters "chapters", @ref