[File format] srt, vtt, ass

[Thomasssb1]

Describe the file format
Subtitle formats, used to render and style subtitles in videos.

• .srt.: plain-text format, containing only sequence numbers, timestamps and unformatted text
• .vtt: used in HTML5 video so includes extra metadata on top of SRT and supports CSS styling
• .ass: advanced typsetting and styling, including vector graphics, font styling, text effects (e.g. karaoke) and precise text positioning

Describe the expected behavior

• To SRT/VTT: When converting from ASS, complex styling should be stripped or simplified to basic tags to maintain readability on simpler players.
• To ASS: When converting from SRT/VTT, the tool should wrap the text in a default style template so it can be further edited in subtitle software (e.g. in Aegisub)
• To TXT: The subtitle format should be able to convert to text-based documents by extracting the text itself without styling and meta-tags but including the timestamps.

Provide reference implementations

• https://github.com/ffmpegwasm/ffmpeg.wasm

Do you plan on implementing this yourself?
Yes

Additional context
Reason: Users often need to convert VTT from web streams into SRT for local playback, or convert ASS to SRT for compatibility with older smart TVs.

[ConnorTippets]

ffmpeg can do this? interesting