X-Git-Url: https://git.videolan.org/?p=ffmpeg.git;a=blobdiff_plain;f=doc%2Fhooks.texi;h=15013547ca25b2c389de2d309c1036055c708b86;hp=fff226f28d82c0a9e8c40d3ca2e9e3a21cf13262;hb=abc7202f45b61ae586972618b90fe613f6d76720;hpb=79cc8267f4f91e8f86b2e5120c137fef9d1baf3b diff --git a/doc/hooks.texi b/doc/hooks.texi index fff226f28d..15013547ca 100644 --- a/doc/hooks.texi +++ b/doc/hooks.texi @@ -18,7 +18,7 @@ Any number of hook modules can be placed inline, and they are run in the order that they were specified on the ffmpeg command line. Three modules are provided and are described below. They are all intended to -be used as a base for your own modules. +be used as a base for your own modules. Modules are loaded using the -vhook option to ffmpeg. The value of this parameter is a space separated list of arguments. The first is the module name, and the rest @@ -41,9 +41,73 @@ colors than would an RGB cuboid. @section imlib2.c -This allows a caption to be placed onto each frame. It supports inserting the -time and date. By using the imlib functions, it would be easy to add your own -graphical logo, add a frame/border, etc. - +This module implements a text overlay for a video image. Currently it +supports a fixed overlay or reading the text from a file. The string +is passed through strftime so that it is easy to imprint the date and +time onto the image. + +You may also overlay an image (even semi-transparent) like TV stations do. +You may move either the text or the image around your video to create +scrolling credits, for example. + +Text fonts are being looked for in a FONTPATH environment variable. + +Options: +@multitable @columnfractions .2 .8 +@item @option{-c } @tab The color of the text +@item @option{-F } @tab The font face and size +@item @option{-t } @tab The text +@item @option{-f } @tab The filename to read text from +@item @option{-x } @tab X coordinate of text or image +@item @option{-y } @tab Y coordinate of text or image +@item @option{-i } @tab The filename to read a image from +@end multitable + +Expresions are functions of these variables: +@multitable @columnfractions .2 .8 +@item @var{N} @tab frame number (starting at zero) +@item @var{H} @tab frame height +@item @var{W} @tab frame width +@item @var{h} @tab image height +@item @var{w} @tab image width +@item @var{X} @tab previous x coordinate of text or image +@item @var{Y} @tab previous y coordinate of text or image +@end multitable + +You may also use the constants @var{PI}, @var{E}, and the math functions available at the +FFmpeg formula evaluator at (@url{ffmpeg-doc.html#SEC13}), except @var{bits2qp(bits)} +and @var{qp2bits(qp)}. + +Usage examples: + +@example + # Remember to set the path to your fonts + FONTPATH="/cygdrive/c/WINDOWS/Fonts/" + FONTPATH="$FONTPATH:/usr/share/imlib2/data/fonts/" + FONTPATH="$FONTPATH:/usr/X11R6/lib/X11/fonts/TTF/" + export FONTPATH + + # Bulb dancing in a Lissajous pattern + ffmpeg -i input.avi -vhook \ + 'vhook/imlib2.dll -x W*(0.5+0.25*sin(N/47*PI))-w/2 -y H*(0.5+0.50*cos(N/97*PI))-h/2 -i /usr/share/imlib2/data/images/bulb.png' \ + -acodec copy -sameq output.avi + + # Text scrolling + ffmpeg -i input.avi -vhook \ + 'vhook/imlib2.dll -c red -F Vera.ttf/20 -x 150+0.5*N -y 70+0.25*N -t Hello' \ + -acodec copy -sameq output.avi +@end example + +@section ppm.c + +It's basically a launch point for a PPM pipe, so you can use any +executable (or script) which consumes a PPM on stdin and produces a PPM +on stdout (and flushes each frame). + +Usage example: + +@example +ffmpeg -i input -vhook "/path/to/ppm.so some-ppm-filter args" output +@end example @bye