diff --git a/DOCS/man/en/mplayer.1 b/DOCS/man/en/mplayer.1
index 103757a274..972e3bbc90 100644
--- a/DOCS/man/en/mplayer.1
+++ b/DOCS/man/en/mplayer.1
@@ -4479,8 +4479,21 @@ This is not a bug, but a side effect of not decoding at full resolution.
 If <w> is specified lowres decoding will be used only if the width of the
 video is major than or equal to <w>.
 .RE
-.IPs "o\ \ \ \ "
-FIXME: undocumented
+.B o=<key>=<value>[,<key>=<value>[,...]]
+Pass AVOptions to libavcodec decoder
+Note, a patch to make the o= unneeded and pass all unknown options through
+the AVOption system is welcome.
+A full list of AVOptions can be found in FFmpeg manual.
+Note that some options may conflict with MEncoder options.
+.sp 1
+.RS
+.I EXAMPLE:
+.RE
+.RSs
+.PD 0
+.IPs o=debug=pict
+.PD 1
+.RE
 .IPs "sb=<number> (MPEG-2 only)"
 Skip the given number of macroblock rows at the bottom.
 .IPs "st=<number> (MPEG-2 only)"
@@ -7632,9 +7645,11 @@ Read the source for full details.
 .
 .TP
 .B o=<key>=<value>[,<key>=<value>[,...]]
-Pass AVOptions to libavcodec
+Pass AVOptions to libavcodec encoder
 Note, a patch to make the o= unneeded and pass all unknown options through
 the AVOption system is welcome.
+A full list of AVOptions can be found in FFmpeg manual.
+Note that some AVOptions may conflict with MEncoder options.
 .sp 1
 .RS
 .I EXAMPLE:
@@ -9077,9 +9092,6 @@ FIXME: Document this.
 .B skip_threshold=<0\-1000000>
 FIXME: Document this.
 .
-.TP
-.B "o\ \ \ \ \ \ "
-FIXME: undocumented
 .
 .
 .SS nuv (\-nuvopts)
@@ -10475,8 +10487,21 @@ Maximum length in seconds to analyze the stream properties.
 Force a specific libavformat demuxer.
 .
 .TP
-.B "o\ \ \ \ \ \ "
-FIXME: undocumented
+.B o=<key>=<value>[,<key>=<value>[,...]]
+Pass AVOptions to libavformat demuxer
+Note, a patch to make the o= unneeded and pass all unknown options through
+the AVOption system is welcome.
+A full list of AVOptions can be found in FFmpeg manual.
+Note that some options may conflict with MPlayer/MEncoder options.
+.sp 1
+.RS
+.I EXAMPLE:
+.RE
+.RSs
+.PD 0
+.IPs o=ignidx
+.PD 1
+.RE
 .
 .TP
 .B probesize=<value>
@@ -10545,8 +10570,21 @@ currently it is meaningful only for MPEG[12].
 Sometimes raising it is necessary in order to avoid "buffer underflows".
 .
 .TP
-.B "o\ \ \ \ \ \ "
-FIXME: undocumented
+.B o=<key>=<value>[,<key>=<value>[,...]]
+Pass AVOptions to libavformat muxer
+Note, a patch to make the o= unneeded and pass all unknown options through
+the AVOption system is welcome.
+A full list of AVOptions can be found in FFmpeg manual.
+Note that some options may conflict with MEncoder options.
+.sp 1
+.RS
+.I EXAMPLE:
+.RE
+.RSs
+.PD 0
+.IPs o=packetsize=100
+.PD 1
+.RE
 .
 .TP
 .B packetsize=<size>