webvtt | Parse WEBVTT files with Ruby | Parser library

Negative lookaheads may be a solution.

The following replaces sequences of a single . with .\n but only when it's not followed by any of . or new line (\n), and not followed by an end-of-sequence ($):

Off the top of my head; one way of going about doing it is to make a div for your subtitles area and the arrange everything in it using flex with wrap and justify-center. This div will contain ... tags for your words.

Then, you can dynamically fill up this template for each word in each timestamp.

Here's what I mean:

I've posted this answer purely to document what I used to get the positioning working but I'll be glad to accept an answer from anyone who's better than me at figuring out what the specs say, and in doing so can explain exactly how positioning in WebVTT works.

Since first writing up this question, and after a lot of reading the specs and testing against them, I managed to stumble on the right permutation of code needed to solve this issue, with some caveats.

For the most part:

align:left position:0% size:50% works to left-align captions

align:right position:100% size:50% works to right-align them

...at least in my particular case. However, this approach seems to fail completely on longer lines, which fall back to being centre-aligned.

I also don't understand why, but the size directive needed to be around 50% in my video: setting it to too low or too high a value - including 100%, as would be the case in CSS - also seems to fail.

Using re.sub we can try first removing the unwanted repetitive text. Then, do a second replacement to replace remaining newlines with single spaces:

You can shorten the first 4 replace statements under Remove noisy punctuation from the transcript. to use a single character class using re.sub.

To keep the dots in the timestamps, you can for example match a dot if no directly followed by a digit.

As all the statements replace the match with an empty string, you can use an alternation | to combine them.

The update line could look like:

After a deep search I found what I asked for in an underrated Github repo online named subsrt, can be found here for whoever encounters the same request or similar. it transforms between the following subtitles formats :

MicroDVD SUB (.sub), SubRip (.srt), SubViewer (.sbv), WebVTT (.vtt), SubStation Alpha (.ssa and .ass), SAMI (.smi) aka Synchronized Accessible Media Interchange, LRC (.lrc) aka LyRiCs, JSON (.json)

I find it hard to believe that there's no support for exporting an mp3 file

Overcome your difficulty and believe it. Due to a complex of copyright issues, Apple has no license to provide any native capacity to create MP3 files. You might find some third party library that can do it, but you won't do it with AVAssetWriter.

Since, no one answered my question I found answer myself.

• first thing is .vtt and .srt are slightly different.
  in .vtt the first line is a text WEBVTT check this
  in .srt there is no such thing

• secondly, very important thing is MimeTypes in subtitleFormat it should be MimeTypes.APPLICATION_SUBRIP for .srt and MimeTypes.TEXT_VTT for .vtt

• If you rename .srt to .vtt and added that first line WEBVTT manually some parsing exception will come. So, better check webvtt file whether it is proper or not.

That's all now things are working fine.

See my previous answer:

Ffmpeg burnt in subtitles out of sync when converting to hls

For some reason FFMPEG adds about 1.4 seconds to the presentation time of the MPEG-2 Transport Stream when writing. So your video and audio are late. If you add -muxdelay 0 to your FFMPEG command line the sync issue should be resolved.