Subtitles not found on Red Bull TV

[fhcwcsy]

• [x] I'm reporting a broken site support
• [x] I've verified that I'm running youtube-dl version 2021.12.17
• [x] I've checked that all provided URLs are alive and playable in a browser
• [x] I've checked that all URLs and arguments with special characters are properly quoted or escaped
• [x] I've searched the bugtracker for similar issues including closed ones

Verbose log

$ youtube-dl -v https://www.redbull.com/int-en/episodes/reel-rock-s8-e6 --list-sub
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-v', 'https://www.redbull.com/int-en/episodes/reel-rock-s8-e6', '--list-sub']
[debug] Encodings: locale UTF-8, fs utf-8, out utf-8, pref UTF-8
[debug] youtube-dl version 2021.12.17
[debug] Python version 3.9.12 (CPython) - Linux-5.15.0-56-generic-x86_64-with-glibc2.35
[debug] exe versions: ffmpeg 4.4.2, ffprobe 4.4.2
[debug] Proxy map: {}
[RedBull] reel-rock-s8-e6: Downloading JSON metadata
[RedBullEmbed] rrn:content:episode-videos:c038ad0f-7ce7-4825-b47e-5c5de25ff2c6:en-INT: Downloading JSON metadata
[RedBullEmbed] AANUZR8HLR8731PQKS82: Downloading access token
[RedBullEmbed] AANUZR8HLR8731PQKS82: Downloading video information
[RedBullEmbed] AANUZR8HLR8731PQKS82: Downloading m3u8 information
AANUZR8HLR8731PQKS82 has no subtitles

Description

It doesn't seems to be correctly finding subtitles on Red Bull TV. For example, the following video has many subtitles but they were not found by youtube-dl:

https://www.redbull.com/int-en/episodes/reel-rock-s8-e6

[dirkf]

Whatever subtitles might be available (the video gives an endless redirect to my "UK content" in my browser), they aren't listed in the non-JS webpage, nor in the data returned by the APIs that the extractor uses, nor in the M3U8 manifests. Also the page contains this JSON fragment for the video:

"subtitlesLanguages":[]

However, this similar yt-dlp issue was resolved by extracting VTT subtitles from the M3U8 manifest. The same fix can be applied in the yt-dl extractor once the common _extract_m3u8_formats_and_subtitles() method has been back-ported.