Several encoders were multiplying the buffer size by 8, in order to get
a bit size. However, the buffer_size argument is for the byte size of
the buffer. We had experienced crashes encoding prores (Anatoliy) at
size 4096x4096.
(cherry picked from commit 50833c9f7b4e1922197a8955669f8ab3589c8cef)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
