Subtitles on Chromecast

[mderazon]

New subtitles feature works really well, thank you very much for that!

You think it's technically possible to have them show in Cast mode, at least for Chromecast ? From what I see the underlying lib should support it, right? (https://github.com/mafintosh/chromecasts#playersubtitlestrack-cb)

[feross]

Yep, we can support this.

[mderazon]

Started digging a little bit to see if I can implement this easily and found out the following:

1. Only .vtt is supported - Need to convert srt to vtt
2. Subtitles would have to be loaded up front when the cast initializes and not "hot loaded" while the movie is playing on chromecast - see play() doc: https://github.com/mafintosh/chromecasts#playerplayurl-opts-cb. subtitles() is only used to switch between active tracks. This means that users will have to first load subtitles and then cast. Not a deal breaker IMO
3. Passing a subtitle file to chromecast through node-castv2-client is not as straight forward as passing a buffer. It expects a file url instead, sitting on a server with CORS enabled. see - https://github.com/thibauts/node-castv2-client/wiki/How-to-use-subtitles-with-the-DefaultMediaReceiver-app. Probably doable, not sure how as i'm not very familiar with Electron. Looks like it has been done before: mafintosh/playback@968b985#diff-168726dbe96b3ce427e7fedce31bb0bcR343

Thoughts?

[feross]

1. We already have code to convert .srt to .vtt. This is pretty straightforward.
2. This is no problem! We have the torrent file list upfront so we can pass all files that are .vtt into player.play().
3. We are already running a server using torrent.createServer() that supports CORS. So we can reference any file in the torrent by URL. We can pass the .vtt ones directly into player.play(), but we'll need to extend the server to convert .srt files into .vtt on the fly.

[mderazon]

we'll need to extend the server to convert .srt files into .vtt on the fly

Are you talking about extending it from within webtorrent's server ? Or do you want to extend it from webtorrent-desktop ?

I can probably do something like

server.prependListener('request', (req, res) => {
  // try to convert srt here ?
})