spelling cosmetics

[ffmpeg] / doc / hooks.texi

diff --git a/doc/hooks.texi b/doc/hooks.texi
index ea1051ca9751aa0a0312d5cd13f003ed38636b48..c410f1cb0545e9c1b1655c79051bbf6c35b4a05d 100644 (file)
--- a/doc/hooks.texi
+++ b/doc/hooks.texi
@@ -10,6 +10,12 @@
 
 @chapter Introduction
 
+@var{Please be aware that vhook is deprecated, and hence its development is
+frozen (bug fixes are still accepted).
+The substitute will be 'libavfilter', the result of our 'Video Filter API'
+Google Summer of Code project. You may monitor its progress by subscribing to
+the ffmpeg-soc mailing list at
+@url{http://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-soc}.}
 
 The video hook functionality is designed (mostly) for live video. It allows
 the video to be modified or examined between the decoder and the encoder.
@@ -67,7 +73,7 @@ with the full path to the font file, as in:
 @end example
 where 20 is the point size.
 
-You can specify the filename to read RGB color names from. If none are
+You can specify the filename to read RGB color names from. If it is not
 specified, these defaults are used: @file{/usr/share/X11/rgb.txt} and
 @file{/usr/lib/X11/rgb.txt}
 
@@ -81,6 +87,10 @@ Options:
 @item @option{-x <expression>}@tab x coordinate of text or image
 @item @option{-y <expression>}@tab y coordinate of text or image
 @item @option{-i <filename>}  @tab The filename to read a image from
+@item @option{-R <expression>}@tab Value for R color
+@item @option{-G <expression>}@tab Value for G color
+@item @option{-B <expression>}@tab Value for B color
+@item @option{-A <expression>}@tab Value for Alpha channel
 @end multitable
 
 Expressions are functions of these variables:
@@ -147,8 +157,24 @@ Usage examples:
      'vhook/imlib2.so -C rgb.txt -c CustomColor1 -F VeraBd.ttf/16 -x 100 -y -1.0*N -f credits.txt' \
      -sameq output.avi
 
-   This example does the same as the one above, but specifies an rgb.txt file
-   to be used, which has a custom made color in it.
+     This example does the same as the one above, but specifies an rgb.txt file
+     to be used, which has a custom-made color in it.
+
+   # Variable colors
+   ffmpeg -i input.avi -vhook \
+     'vhook/imlib2.so -t Hello -R abs(255*sin(N/47*PI)) -G abs(255*sin(N/47*PI)) -B abs(255*sin(N/47*PI))' \
+     -sameq output.avi
+
+     In this example, the color for the text goes up and down from black to
+     white.
+
+   # Text fade-out
+   ffmpeg -i input.avi -vhook \
+     'vhook/imlib2.so -t Hello -A max(0,255-exp(N/47))' \
+     -sameq output.avi
+
+     In this example, the text fades out in about 10 seconds for a 25 fps input
+     video file.
 
    # scrolling credits from a graphics file
    ffmpeg -sameq -i input.avi \