Parse expression only when a new value is explicitly specified.
In particular, avoid double free in case an old expression value is
cached, it is set in the context, it is freed as the old value, and
finally the pointer stored in the context is freed again when the filter
is released.
This allows dynamic reconfiguration of the filter.
The callback uses some code that was in the init function. Hence this code
has been moved in its own function.
Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
This is a port of the MPlayer hue filter (libmpcodecs/vf_hue.c) by
Michael Niedermayer.
Signed-off-by: Jérémy Tran <tran.jeremy.av@gmail.com>
Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
