It was ported to a native libavfilter filter.

Partially based on the port by Niel van der Westhuizen
<nielkie@gmail.com>, done for GCI 2010. Same output as the original
filter and as fast.

See thread:
Subject: [FFmpeg-devel] [PATCH] Port MPlayer 2xSaI filter to libavfilter
Date: Thu, 25 Nov 2010 01:31:24 +1000

The header is part of the public API, in particular is used by
doc/examples/filtering_audio.c.

Fixes Ticket1184
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signal that it can output a frame when there are frames on the main
input and EOF on the overlay input, but a frame is buffered -- e.g.
single picture overlay.

Since those are pseudo-palette formats, swscale does not write
into data[1], swscale must initialize the palette properly itself.
This lead to frames that actually decoded as all-gray before.
Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

This fixes that the GIF encoder crashes with it because
it has no palette.
And the arguments for the pseudopalette apply to gray8 as
much as to RGB8 etc.
In addition the changes required in lavfi should be needed anyway
when adding support for RGB8 etc.
Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

We can't use whether the input format is paletted to decide that
the output format has a palette in data[1], too, that makes no sense.
Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

removelogo has been ported to libavfilter, and the wrapper was not
working.

The code is based on the remove-logo filter in MPlayer/libmpcodecs, by
Robert Edele, relicensed to LGPL with consent of the author.

Address trac issue #249.

the overwrite flag became unused when merging support for buffering
multiple frames.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

This will simplify future code.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Ported by: Baptiste Coudurier
cleanup+fate by ubitux
For detailed authorship of the original code please see avisynth

This fixes the following warning:
libavfilter/vf_unsharp.c:106: warning: initialization discards qualifiers from pointer target type

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

15k->10k cpu cycles
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

19k -> 15k cpu cycles
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

2500 -> 1900 cpu cycles
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

I.e. just pass the buffer along when src parameters == dst parameters.

Current code, with a filterchain such as
(input - yuv411) -> (scale - any) -> (sink - any)
will result in yuv420 being chosen for the second link, which is clearly
not right.

This commit attempts to improve in the following way:
repeat until convergence:
  loop over all filters
    find input link with exactly one format
    force this format on all output links of the same type (if possible)