@@ -3,10 +3,10 @@

 Filtering in FFmpeg is enabled through the libavfilter library.

-In libavfilter, it is possible for filters to have multiple inputs and

-multiple outputs.

-To illustrate the sorts of things that are possible, we can

-use a complex filter graph. For example, the following one:

+In libavfilter, a filter can have multiple inputs and multiple

+outputs.

+To illustrate the sorts of things that are possible, we consider the

+following filtergraph.

 @example

 input --> split ---------------------> overlay --> output

@@ -15,25 +15,32 @@ input --> split ---------------------> overlay --> output

             +-----> crop --> vflip -------+

 @end example

-splits the stream in two streams, sends one stream through the crop filter

-and the vflip filter before merging it back with the other stream by

-overlaying it on top. You can use the following command to achieve this:

+This filtergraph splits the input stream in two streams, sends one

+stream through the crop filter and the vflip filter before merging it

+back with the other stream by overlaying it on top. You can use the

+following command to achieve this:

 @example

-ffmpeg -i input -vf "[in] split [T1], [T2] overlay=0:H/2 [out]; [T1] crop=iw:ih/2:0:ih/2, vflip [T2]" output

+ffmpeg -i INPUT -vf "split [main][tmp]; [tmp] crop=iw:ih/2:0:0, vflip [flip]; [main][flip] overlay=0:H/2" OUTPUT

 @end example

 The result will be that in output the top half of the video is mirrored

 onto the bottom half.

-Filters are loaded using the @var{-vf} or @var{-af} option passed to

-@command{ffmpeg} or to @command{ffplay}. Filters in the same linear

-chain are separated by commas. In our example, @var{split,

-overlay} are in one linear chain, and @var{crop, vflip} are in

-another. The points where the linear chains join are labeled by names

-enclosed in square brackets. In our example, that is @var{[T1]} and

-@var{[T2]}. The special labels @var{[in]} and @var{[out]} are the points

-where video is input and output.

+Filters in the same linear chain are separated by commas, and distinct

+linear chains of filters are separated by semicolons. In our example,

+@var{crop,vflip} are in one linear chain, @var{split} and

+@var{overlay} are separately in another. The points where the linear

+chains join are labelled by names enclosed in square brackets. In the

+example, the split filter generates two outputs that are associated to

+the labels @var{[main]} and @var{[tmp]}.

+

+The stream sent to the second output of @var{split}, labelled as

+@var{[tmp]}, is processed through the @var{crop} filter, which crops

+away the lower half part of the video, and then vertically flipped. The

+@var{overlay} filter takes in input the first unchanged output of the

+split filter (which was labelled as @var{[main]}), and overlay on its

+lower half the output generated by the @var{crop,vflip} filterchain.

 Some filters take in input a list of parameters: they are specified

 after the filter name and an equal sign, and are separated from each other