Add new vf_tiltandshift filter

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

1 files changed, 63 insertions, 0 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index 6d00ba2c3f..1d1634bf06 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -23186,6 +23186,69 @@ tile=3x2:nb_frames=5:padding=7:margin=2
 @end example
 @end itemize
 
+@section tiltandshift
+
+What happens when you invert time and space?
+
+Normally a video is composed of several frames that represent a different
+instant of time and shows a scence that evolves in the space captured by the
+frame. This filter is the antipode of that concept, taking inspiration by
+tilt and shift photography.
+
+A filtered frame contains the whole timeline of events composing the sequence,
+and this is obtained by placing a slice of pixels from each frame into a single
+one. However, since there are no infinite-width frames, this is done up the
+width of the input frame, and a video is recomposed by shifting away one
+column for each subsequent frame. In order to map space to time, the filter
+tilts each input frame as well, so that motion is preseved. This is accomplished
+by progressively selecting a different column from each input frame.
+
+The end result is a sort of inverted parralax, so that far away objects move
+much faster that the ones in the front. The ideal conditions for this video
+effect are when there is either very little motion and the backgroud is static,
+or when there is a lot of motion and a very wide depth of field (eg. wide
+panorama, while moving on a train).
+
+The filter accepts the following parameters:
+
+@table @option
+
+@item tilt
+Tilt video while shifting (default). When unset, video will be sliding a
+static image, composed of the first column of each frame.
+
+@item start
+What to do at the start of filtering (see below).
+
+@item end
+What to do at the end of filtering (see below).
+
+@item hold
+How many columns should pass through before start of filtering.
+
+@item pad
+How many columns should be inserted before end of filtering.
+
+@end table
+
+Normally the filter shifts and tils from the very first frame, and stops when
+the last one is received. However, before filtering starts, normal video may
+be preseved, so that the effect is slowly shifted in its place. Similarly,
+the last video frame may be reconstructed at the end. Alternatively it is
+possible to just start and end with black.
+
+@table @samp
+@item none
+Filtering is starts immediately and ends when the last frame is received.
+
+@item frame
+The first frames or the very last frame are kept intact during processing.
+
+@item black
+Black is padded at the beginning or at the end of filtering.
+
+@end table
+
 @section tinterlace
 
 Perform various types of temporal field interlacing.