diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 479f1f51c1..21b0e3103b 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -2369,6 +2369,61 @@ int av_read_play(AVFormatContext *s);
  */
 int av_read_pause(AVFormatContext *s);
 
+/**
+ * Command IDs that can be sent to the demuxer
+ *
+ * The following commands can be sent to a demuxer
+ * using ::avformat_send_command.
+ */
+enum AVFormatCommandID {
+    /**
+     * Send a RTSP `SET_PARAMETER` request to the server
+     *
+     * Sends an SET_PARAMETER RTSP command to the server,
+     * with a data payload of type ::AVRTSPCommandRequest,
+     * ownership of it and its data remains with the caller.
+     *
+     * A reply retrieved is of type ::AVRTSPResponse and it
+     * and its contents must be freed by the caller.
+     */
+    AVFORMAT_COMMAND_RTSP_SET_PARAMETER,
+};
+
+/**
+ * Send a command to the demuxer
+ *
+ * Sends the specified command and (depending on the command)
+ * optionally a command-specific payload to the demuxer to handle.
+ *
+ * @param s     Format context, must be allocated with
+ *              ::avformat_alloc_context.
+ * @param id    Identifier of type ::AVFormatCommandID,
+ *              indicating the command to send.
+ * @param data  Command-specific data, allocated by the caller
+ *              and ownership remains with the caller.
+ *              For details what is expected here, consult the
+ *              documentation of the respective ::AVFormatCommandID.
+ */
+int avformat_send_command(AVFormatContext *s, enum AVFormatCommandID id, void *data);
+
+/**
+ * Receive a command reply from the demuxer
+ *
+ * Retrieves a reply for a previously sent command from the muxer.
+ *
+ * @param s         Format context, must be allocated with
+ *                  ::avformat_alloc_context.
+ * @param id        Identifier of type ::AVFormatCommandID,
+ *                  indicating the command for which to retrieve
+ *                  the reply.
+ * @param data_out  Pointee is set to the command reply, the actual
+ *                  type depends on the command. This is allocated by
+ *                  the muxer and must be freed with ::av_free.
+ *                  For details on the actual data set here, consult the
+ *                  documentation of the respective ::AVFormatCommandID.
+ */
+int avformat_receive_command_reply(AVFormatContext *s, enum AVFormatCommandID id, void **data_out);
+
 /**
  * Close an opened input AVFormatContext. Free it and all its contents
  * and set *s to NULL.
diff --git a/libavformat/demux.h b/libavformat/demux.h
index c0c2164e92..f09afc849f 100644
--- a/libavformat/demux.h
+++ b/libavformat/demux.h
@@ -53,6 +53,16 @@ enum FFInputFormatStreamState {
      FF_INFMT_STATE_PAUSE,
  };
 
+/**
+ * Command handling options
+ * Different options influencing the behaviour of
+ * the FFInputFormat::handle_command callback.
+ */
+enum FFInputFormatCommandOption {
+    FF_INFMT_COMMAND_SUBMIT,
+    FF_INFMT_COMMAND_GET_REPLY,
+};
+
 typedef struct FFInputFormat {
     /**
      * The public AVInputFormat. See avformat.h for it.
@@ -130,9 +140,33 @@ typedef struct FFInputFormat {
                           enum FFInputFormatStreamState state);
 
     /**
-     * Currently unused.
+     * Handle demuxer commands
+     * This callback is used to either send a command to a demuxer
+     * (FF_INFMT_COMMAND_SUBMIT), or to retrieve the reply for
+     * a previously sent command (FF_INFMT_COMMAND_GET_REPLY).
+     *
+     * Demuxers implementing this must return AVERROR(ENOTSUP)
+     * if the provided \p id is not handled by the demuxer.
+     * Demuxers should return AVERROR(EAGAIN) if they can handle
+     * a specific command but are not able to at the moment.
+     * When a reply is requested that is not available yet, the
+     * demuxer should also return AVERROR(EAGAIN).
+     *
+     * Depending on \p opt, the \p data will be either a pointer
+     * to the command payload structure for the specified ID, or
+     * a pointer to the buffer for the command reply for the
+     * specified ID.
+     *
+     * When a command is submitted, before a previous reply
+     * was requested from the demuxer, the demuxer should discard
+     * the old reply.
+     *
+     * @see avformat_send_command()
+     * @see avformat_receive_command_reply()
      */
-    int (*unused)(void);
+    int (*handle_command)(struct AVFormatContext *,
+                          enum FFInputFormatCommandOption opt,
+                          enum AVFormatCommandID id, void *data);
 
     /**
      * Seek to timestamp ts.
diff --git a/libavformat/demux_utils.c b/libavformat/demux_utils.c
index 34b6ba4ac7..639fed35fd 100644
--- a/libavformat/demux_utils.c
+++ b/libavformat/demux_utils.c
@@ -188,6 +188,20 @@ int av_read_pause(AVFormatContext *s)
     return AVERROR(ENOSYS);
 }
 
+int avformat_send_command(AVFormatContext *s, enum AVFormatCommandID id, void *data)
+{
+    if (ffifmt(s->iformat)->handle_command)
+        return ffifmt(s->iformat)->handle_command(s, FF_INFMT_COMMAND_SUBMIT, id, data);
+    return AVERROR(ENOSYS);
+}
+
+int avformat_receive_command_reply(AVFormatContext *s, enum AVFormatCommandID id, void **data_out)
+{
+    if (ffifmt(s->iformat)->handle_command)
+        return ffifmt(s->iformat)->handle_command(s, FF_INFMT_COMMAND_GET_REPLY, id, data_out);
+    return AVERROR(ENOSYS);
+}
+
 int ff_generate_avci_extradata(AVStream *st)
 {
     static const uint8_t avci100_1080p_extradata[] = {