Update documentation for r20435 (which added the -fpre option).

Originally committed as revision 20753 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/ffmpeg-doc.texi

@@ -833,13 +833,17 @@ awkward to specify on the command line. Lines starting with the hash
 ('#') character are ignored and are used to provide comments. Check
 the @file{ffpresets} directory in the FFmpeg source tree for examples.
 
-Preset files are specified with the @code{vpre}, @code{apre} and
-@code{spre} options. The options specified in a preset file are
+Preset files are specified with the @code{vpre}, @code{apre},
+@code{spre}, and @code{fpre} options. The @code{fpre} option takes the
+filename of the preset instead of a preset name as input and can be
+used for any kind of codec. For the @code{vpre}, @code{apre}, and
+@code{spre} options, the options specified in a preset file are
 applied to the currently selected codec of the same type as the preset
 option.
 
-The argument passed to the preset options identifies the preset file
-to use according to the following rules.
+The argument passed to the @code{vpre}, @code{apre}, and @code{spre}
+preset options identifies the preset file to use according to the
+following rules:
 
 First ffmpeg searches for a file named @var{arg}.ffpreset in the
 directories @file{$HOME/.ffmpeg}, and in the datadir defined at
@@ -854,11 +858,6 @@ the preset file options will be applied. For example, if you select
 the video codec with @code{-vcodec libx264} and use @code{-vpre max},
 then it will search for the file @file{libx264-max.ffpreset}.
 
-Finally, if the above rules failed and the argument specifies an
-absolute pathname, ffmpeg will search for that filename. This way you
-can specify the absolute and complete filename of the preset file, for
-example @file{./ffpresets/libx264-max.ffpreset}.
-
 @anchor{FFmpeg formula evaluator}
 @section FFmpeg formula evaluator