20210605:
- libass: back to 0.15.1, enable asm optimization
- xysubfilter: fix scale between subtitle and video on CWord
- add missing delay and speed when rendering
- default "loading" to "always"
20210517:
- fix: pixel aspect
- fix: occasional messy text
- fix bug libass/libass#509
20210508:
- commits from Cyberbeing#16
- process srt and external ssa
- using unicode ass/ssa path & detect bom before parse