lavfi: port tinterlace filter from MPlayer

Port MPlayer tinterlace filter from MPlayer, with some ideas taken
from the FFmbc/libavfilter port, with the following main differences:

* added support for full-scale YUVJ formats
* added support for YUVA420P
* request_frame() on the filter is forced to return a frame
* some code factorization (related to the copy_picture_fields() function)
* fixed black padding values for mode 3

1 files changed, 34 insertions, 0 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index da36e8b1b8..387a05e6a7 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -2433,6 +2433,40 @@ Complete example of a thumbnail creation with @command{ffmpeg}:
 ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
 @end example
 
+@section tinterlace
+
+Perform various types of temporal field interlacing.
+
+Frames are counted starting from 1, so the first input frame is
+considered odd.
+
+This filter accepts a single parameter specifying the mode. Available
+modes are:
+
+@table @samp
+@item 0
+Move odd frames into the upper field, even into the lower field,
+generating a double height frame at half framerate.
+
+@item 1
+Only output even frames, odd frames are dropped, generating a frame with
+unchanged height at half framerate.
+
+@item 2
+Only output odd frames, even frames are dropped, generating a frame with
+unchanged height at half framerate.
+
+@item 3
+Expand each frame to full height, but pad alternate lines with black,
+generating a frame with double height at the same input framerate.
+
+@item 4
+Interleave the upper field from odd frames with the lower field from
+even frames, generating a frame with unchanged height at half framerate.
+@end table
+
+Default mode is 0.
+
 @section transpose
 
 Transpose rows with columns in the input video and optionally flip it.