Build the -var_stream_map value for a set of variants.
Each entry is v:0,a:0,name:1080p — video stream 0 paired with audio
stream 0 of the same split. Returns the joined map and the per-variant
stream indices, which the caller needs to know how many streams to create.
Build the
-var_stream_mapvalue for a set of variants.Each entry is
v:0,a:0,name:1080p— video stream 0 paired with audio stream 0 of the same split. Returns the joined map and the per-variant stream indices, which the caller needs to know how many streams to create.