avfilter/dualinput: remove unused variable

Signed-off-by: Paul B Mahol <onemda@gmail.com>
avformat/vfq: fix deadlock in vqf_read_header()

Fixes #3010.
Reported-by: Piotr Bandurski <ami_stuff@o2.pl>
Signed-off-by: Paul B Mahol <onemda@gmail.com>
avformat/utils: factor find_decoder() out

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