[FFmpeg-cvslog] doc/filters: mention required compile options for some filters

[Lou Logan]

ffmpeg | branch: master | Lou Logan <lou at lrcd.com> | Mon Jun  4 16:38:20 2018 -0800| [1f75756c719442280590b97bf17f3eed7d6aa93d] | committer: Lou Logan

doc/filters: mention required compile options for some filters

Signed-off-by: Lou Logan <lou at lrcd.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=1f75756c719442280590b97bf17f3eed7d6aa93d
---

 doc/filters.texi | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/doc/filters.texi b/doc/filters.texi
index 9f8fb74090..256ab42b00 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -3893,6 +3893,9 @@ not meant to be used directly.
 @section rubberband
 Apply time-stretching and pitch-shifting with librubberband.
 
+To enable compilation of this filter, you need to configure FFmpeg with
+ at code{--enable-librubberband}.
+
 The filter accepts the following options:
 
 @table @option
@@ -11739,7 +11742,9 @@ Pass the video source unchanged to the output.
 @section ocr
 Optical Character Recognition
 
-This filter uses Tesseract for optical character recognition.
+This filter uses Tesseract for optical character recognition. To enable
+compilation of this filter, you need to configure FFmpeg with
+ at code{--enable-libtesseract}.
 
 It accepts the following options:
 
@@ -17143,7 +17148,8 @@ zoompan=z='min(max(zoom,pzoom)+0.0015,1.5)':d=1:x='iw/2-(iw/zoom/2)':y='ih/2-(ih
 @anchor{zscale}
 @section zscale
 Scale (resize) the input video, using the z.lib library:
-https://github.com/sekrit-twc/zimg.
+ at url{https://github.com/sekrit-twc/zimg}. To enable compilation of this
+filter, you need to configure FFmpeg with @code{--enable-libzimg}.
 
 The zscale filter forces the output display aspect ratio to be the same
 as the input, by changing the output sample aspect ratio.