Build a -map flag from a StreamSpecifier or raw string.
mapStream(ss(0, 'v', 0)) → ['-map', '0:v:0']mapStream('0:a:1') → ['-map', '0:a:1'] Copy
mapStream(ss(0, 'v', 0)) → ['-map', '0:v:0']mapStream('0:a:1') → ['-map', '0:a:1']
Build a -map flag from a StreamSpecifier or raw string.