Repository: yt-dlp
Issue: [Mediasite] Transcript and subtitle downloading
Labels: site-enhancement,triage

### DO NOT REMOVE OR SKIP THE ISSUE TEMPLATE

- [X] I understand that I will be **blocked** if I *intentionally* remove or skip any mandatory\* field

### Checklist

- [X] I'm requesting a site-specific feature
- [X] I've verified that I have **updated yt-dlp to nightly or master** ([update instructions](https://github.com/yt-dlp/yt-dlp#update-channels))
- [X] I've checked that all provided URLs are playable in a browser with the same IP and same login details
- [X] I've searched [known issues](https://github.com/yt-dlp/yt-dlp/issues/3766) and the [bugtracker](https://github.com/yt-dlp/yt-dlp/issues?q=) for similar issues **including closed ones**. DO NOT post duplicates
- [X] I've read the [guidelines for opening an issue](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#opening-an-issue)
- [ ] I've read about [sharing account credentials](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#are-you-willing-to-share-account-details-if-needed) and I'm willing to share it if required

### Region

_No response_

### Example URLs

https://events7.mediasite.com/Mediasite/Play/a7812390a2d44739ae857527e05776091d

### Provide a description that is worded well enough to be understood

Mediasite often offers captioning on the videos or presentations it hosts. yt-dlp can already download videos but it cannot download their captions. Mediasite stores the information for videos in a json file called GetPlayerOptions. The available caption tracks will be found under the key `Presentation.Transcripts`. Inside `Presentation.Transcripts`, the language code can be found in the key `LanguageCode` or `DetailedLanguageCode` and the URL of the captions file will be in the key `CaptionsUrl`.

For some reason, it also has a key called `Presentation.TranscriptUrl` which will give, as it sounds, a transcript of the entire video in plain text, despite of this option not normally being exposed to the user. For the example URL, this is at https://events7.mediasite.com/Mediasite/FileServer/Presentation/a7812390a2d44739ae857527e05776091d/transcript.txt.

If I have missed out anything, please let me know and thank you in advance.

### Provide verbose output that clearly demonstrates the problem

- [X] Run **your** yt-dlp command with **-vU** flag added (`yt-dlp -vU <your command line>`)
- [ ] If using API, add `'verbose': True` to `YoutubeDL` params instead
- [X] Copy the WHOLE output (starting with `[debug] Command-line config`) and insert it below

### Complete Verbose Output

```shell
yt-dlp -vU -f - https://events7.mediasite.com/Mediasite/Play/a7812390a2d44739ae857527e05776091d --list-subs
[debug] Command-line config: ['-vU', '-f', '-', 'https://events7.mediasite.com/Mediasite/Play/a7812390a2d44739ae857527e05776091d', '--list-subs']
[debug] Encodings: locale UTF-8, fs utf-8, pref UTF-8, out utf-8, error utf-8, screen utf-8
[debug] yt-dlp version nightly@2024.06.30.232744 from yt-dlp/yt-dlp-nightly-builds [24f3097ea] (darwin_exe)
[debug] Python 3.12.4 (CPython arm64 64bit) - macOS-14.5-arm64-arm-64bit (OpenSSL 3.0.13 30 Jan 2024)
[debug] exe versions: ffmpeg 7.0.1 (setts), ffprobe 7.0.1, rtmpdump 2.4
[debug] Optional libraries: Cryptodome-3.20.0, brotli-1.1.0, certifi-2024.06.02, curl_cffi-0.5.10, mutagen-1.47.0, requests-2.32.3, sqlite3-3.45.3, urllib3-2.2.2, websockets-12.0
[debug] Proxy map: {}
[debug] Request Handlers: urllib, requests, websockets, curl_cffi
[debug] Loaded 1824 extractors
[debug] Fetching release info: https://api.github.com/repos/yt-dlp/yt-dlp-nightly-builds/releases/latest
Latest version: nightly@2024.06.30.232744 from yt-dlp/yt-dlp-nightly-builds
yt-dlp is up to date (nightly@2024.06.30.232744 from yt-dlp/yt-dlp-nightly-builds)
[Mediasite] Extracting URL: https://events7.mediasite.com/Mediasite/Play/a7812390a2d44739ae857527e05776091d
[Mediasite] a7812390a2d44739ae857527e05776091d: Downloading webpage
[Mediasite] a7812390a2d44739ae857527e05776091d: Downloading JSON metadata
[Mediasite] a7812390a2d44739ae857527e05776091d: Downloading m3u8 information
[debug] Formats sorted by: hasvid, ie_pref, lang, quality, res, fps, hdr:12(7), vcodec:vp9.2(10), channels, acodec, size, br, asr, proto, vext, aext, hasaud, source, id
a7812390a2d44739ae857527e05776091d has no subtitles
```