Replace some arrays with variables
Revert "Replace some arrays with variables"

- ffmpeg sees each of the array's items as a one big argument

This reverts commit 159fb1b24b25e131ab760c6b64f5fea26b948c87.
Revert "Use array sizes to assign map_{a,v}, assign filter_v earlier"

- ffmpeg sees each of the array's items as a one big argument

This reverts commit e6d34b56eab3824048c848a6e259c8a95909a20e.
Assign filter_v earlier so that $blind can unset it