[gegl] docs: add notes about simple commandline video filtering

[Øyvind Kolås <ok src gnome org>]

commit 9e04f26ccf4b135049858c47e1bd85e20500f63a
Author: Øyvind Kolås <pippin gimp org>
Date:   Wed Apr 12 17:51:38 2017 +0200

    docs: add notes about simple commandline video filtering

 docs/commandline.txt |    3 +--
 docs/gegl-chain.txt  |   11 ++++++++++-
 2 files changed, 11 insertions(+), 3 deletions(-)
---
diff --git a/docs/commandline.txt b/docs/commandline.txt
index 604c5e3..cf82fef 100644
--- a/docs/commandline.txt
+++ b/docs/commandline.txt
@@ -8,8 +8,7 @@ during development of GEGL operations.
 Some examples:
 
 Render a composition to a PNG file, the composition can be in GEGLs XML format
-or the terser link:gegl-chain.html[gegl-chain] gegl-chain one-liner friendly
-format.
+or the one-liner friendly terser link:gegl-chain.html[gegl-chain] format.
 
  $ gegl composition -o composition.png
 
diff --git a/docs/gegl-chain.txt b/docs/gegl-chain.txt
index 87cd439..9a87e31 100644
--- a/docs/gegl-chain.txt
+++ b/docs/gegl-chain.txt
@@ -26,10 +26,19 @@ The format treats input and output pads as explicitly linked when they follow ea
 
  $ gegl in.jpg -- noise-reduction iterations=2 over aux=[ text string='hello there' color=white size=32 
translate x=100 y=100 dropshadow radius=2 x=1.5 y=1.5 ]
 
-And finally, it is possible to create links in the chain, reusing permitting
+And it is also possible to create reference in the chain, reusing permitting
 creating masks for color adjustments based on image content, for instance the
 following example, which uses a blurred version of an image as a threshold mask
 - which thus becomes a local content dependent thresholding filter.
 
  $ gegl in.jpg -- id=a threshold aux=[ ref=a gaussian-blur std-dev-x=0.1rel std-dev-y=0.1rel ]
 
+If gegl have working gegl:ff-load and gegl:ff-save ops, The gegl binary also
+permits simple forms of video processing, like the following:
+
+ $ gegl input.mp4 -o output.ogv -- scale-size x=160 y=120 newsprint period=4
+
+If you want to create a GIF as the final output, it is recommended to create a
+temporary video file, and use for instance ffmpeg to create a high quality GIF
+with a two pass approach.
+