generate documentation from config.sample.php

admin_manual/configuration_server/config_sample_php_parameters.rst

@@ -1383,6 +1383,14 @@ Use this if LibreOffice/OpenOffice requires additional arguments.
 
 Defaults to ``''`` (empty string)
 
+::
+
+	'preview_ffmpeg_path' => '/usr/bin/ffmpeg',
+
+custom path for ffmpeg binary
+
+Defaults to ``null`` and falls back to searching ``avconv`` and ``ffmpeg`` in the configured ``PATH`` environment
+
 ::
 
 	'preview_imaginary_url' => 'http://previews_hpb:8088/',