Merge remote-tracking branch 'qatar/master'

* qatar/master:
  doc: Add section about AviSynth support

Conflicts:
	doc/general.texi

Merged-by: Michael Niedermayer <michaelni@gmx.at>

diff --cc doc/general.texi
index 079b3ff9d20b86d8020a9c4b9b0793b964477c34,8c0cb1b2e67b2ed5b6b2574f9a94827f994bc607..28ea12fdbe657dde721d67236df2359db3d43b79
--- 1/doc/general.texi
--- 2/doc/general.texi
+++ b/doc/general.texi
@@@ -147,23 -126,41 +147,57 @@@ Go to @url{https://github.com/dekkers/l
  installing the library. Then pass @code{--enable-libilbc} to configure to
  enable it.
  
 -Libav can read AviSynth scripts as input. To enable support you need a
 +@section libzvbi
 +
 +libzvbi is a VBI decoding library which can be used by FFmpeg to decode DVB
 +teletext pages and DVB teletext subtitles.
 +
 +Go to @url{http://sourceforge.net/projects/zapping/} and follow the instructions for
 +installing the library. Then pass @code{--enable-libzvbi} to configure to
 +enable it.
 +
 +@float NOTE
 +libzvbi is licensed under the GNU General Public License Version 2 or later
 +(see @url{http://www.gnu.org/licenses/old-licenses/gpl-2.0.html} for details),
 +you must upgrade FFmpeg's license to GPL in order to use it.
 +@end float
 +
+ @section AviSynth
+ 
 -updated to support AviSynth 2.6. AviSynth 2.5 is not supported by Libav.
++FFmpeg can read AviSynth scripts as input. To enable support you need a
+ suitable @file{avisynth_c.h} header to compile against. The header in
+ classic AviSynth's CVS repository is not compatible as it has not been
 -AviSynth and AvxSynth are loaded dynamically.  Distributors can build Libav
++updated to support AviSynth 2.6. AviSynth 2.5 is not supported by FFmpeg.
+ Once you have the appropriate header, pass @code{--enable-avisynth} to
+ configure to enable AviSynth support.
+ 
+ For Windows, supported AviSynth variants are
+ @url{http://avisynth.nl, AviSynth 2.6} for 32-bit builds and
+ @url{http://avs-plus.net, AviSynth+ 0.1} for 32-bit and 64-bit builds.
+ The necessary @file{avisynth_c.h} header is the variant in the @file{extras/}
+ directory of the @url{https://www.videolan.org/developers/x264.html, x264}
+ source tree. For convenience, this header is also available from a
+ @url{https://github.com/qyot27/avisynth_headers, temporary repository}
+ along with an installation routine.
+ 
+ For Linux and OS X, the supported AviSynth variant is
+ @url{https://github.com/avxsynth/avxsynth, AvxSynth}.
+ @file{avxsynth_c.h} is installed as part of the normal
+ build routine, as illustrated on
+ @url{https://github.com/avxsynth/avxsynth/wiki/System-Setup, AvxSynth's wiki}.
+ (the instructions for compiling its prerequisites are outdated, as FFMS 2.18
+ or higher is now needed; the list of dependencies to be downloaded from the
+ repositories is still the same, though).
+ 
+ @float NOTE
 -@chapter Supported File Formats and Codecs
++AviSynth and AvxSynth are loaded dynamically.  Distributors can build FFmpeg
+ with @code{--enable-avisynth}, and the binaries will work regardless of the
+ end user having AviSynth or AvxSynth installed - they'll only need to be
+ installed to use AviSynth scripts (obviously).
+ @end float
+ 
 +
 +@chapter Supported File Formats, Codecs or Features
  
  You can use the @code{-formats} and @code{-codecs} options to have an exhaustive list.