Do not leak all the temp buffers.

Do not leak the x/y expressions.

Do not overwrite the variable set through AVOptions.

Do not overwrite the variables set through AVOptions.

Frame number should be incremented normally even if the link properties
change.

It should not be reinitialized if the link properties change.

Do not leak the initialized filter instance.

Do not leak the expressions.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

This is shorter and consistent across filters.

Currently it would incorrectly trigger on a string that contains a '='
but does not contain a ':', e.g. flags=<flags>.

There is now no need to explicitly pass 0:0 as width/height to scale,
those are the defaults.

The C code treats the data as arrays of uint16_t so strides must not
be in bytes but in pixels.

Signed-off-by: Anton Khirnov <anton@khirnov.net>

Always use the special filter for the first and last 3 columns (only).

Changes made in 64ed3976 slowed the filter to just under 3/4 of what it
was.  This commit restores the speed while maintaining identical output.

For reference, on my Athlon64:
1733222 decicycles in old
2358563 decicycles in new
1727558 decicycles in this

Signed-off-by: Anton Khirnov <anton@khirnov.net>

delta is in samples, not bytes. Also the sample format is not guaranteed
to be planar.

CC:libav-stable@libav.org