Changes between Version 47 and Version 48 of FilteringGuide

Timestamp:

Feb 24, 2018, 4:00:58 AM (8 years ago)

Author:

Jim DeLaHunt

Comment:

Add description of filter syntax, especially filter options.

FilteringGuide

@@ -7 +7 @@
 
 Refer to the [http://ffmpeg.org/ffmpeg-filters.html FFmpeg filters documentation] for more information and examples for each filter. This wiki page is for user contributed examples and tips, and contributions to this page are encouraged.
+
+== Filter syntax ==
+
+When documentation refers to "filter options", or says the "filter accepts the following options", the syntax to use for the options is as described in '''FFmpeg Filters''', section ''4.1 [http://ffmpeg.org/ffmpeg-filters.html#Filtergraph-syntax-1 Filtergraph] syntax''. Briefly, that syntax is to add, after the name of the filter, an `=` character, then the name of the first filter option, an `=` character, and the value of that option. If you want to specify further filter options, you delimit them with `:`, then append the name of the next filter option, an `=` character, and the next value. 
+
+For instance, to apply the [http://ffmpeg.org/ffmpeg-filters.html#loudnorm loudnorm filter] to an audio stream, the basic syntax is:
+{{{
+ffmpeg -i input -filter:a loudnorm  output
+}}}
+To add the `print_format` and `linear` filter options, use the syntax:
+
+{{{
+ffmpeg -i input -filter:a loudnorm=print_format=summary:linear=true  output
+}}}
+
+As described in section ''4.1 [http://ffmpeg.org/ffmpeg-filters.html#Filtergraph-syntax-1 Filtergraph] syntax'', you can omit the option names and `=` characters, supplying just the values, delimited by `:` characters. For example, in this invocation:
+{{{
+ffmpeg -i input -vf scale=iw/2:-1 output
+}}}
+FFmpeg assumes the option names in the order they are declared in the source code.  For instance, in this use of the [http://ffmpeg.org/ffmpeg-filters.html#scale scale filter], FFmpeg assumes the option name `width` for the value `iw/2`, and the name `height` for the value `-1`. 
 
 == Examples ==