Repository: yt-dlp
Issue: [youtube] auto-generated subtitles from livestreams
Labels: site-enhancement

### Checklist

- [X] I'm reporting a feature request
- [X] I've verified that I'm running yt-dlp version **2021.12.01**. ([update instructions](https://github.com/yt-dlp/yt-dlp#update))
- [X] I've searched 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)

### Description

Link to video: https://www.youtube.com/watch?v=9Auq9mYxFEE
Dumps: https://gist.github.com/445200e4b8b1d0596faa0891f4c555b1

Some livestreams contain (real-time) subtitles in both HLS and DASH manifests. This isn't actually a feature request, but may be better to be able to grab them too?

![image](https://user-images.githubusercontent.com/10355528/146641911-6c3458df-2956-43ca-ac2e-68b8d764c00b.png)

```
$ yt-dlp -sv --write-page --extractor-args youtube:include_live_dash 9Auq9mYxFEE
[debug] Command-line config: ['-sv', '--write-page', '--extractor-args', 'youtube:include_live_dash', '9Auq9mYxFEE']
[debug] Encodings: locale UTF-8, fs utf-8, out utf-8, err utf-8, pref UTF-8
[debug] yt-dlp version 2021.12.01 [91f071af6]
[debug] Python version 3.9.9 (CPython 64bit) - Linux-5.11.0-34-generic-x86_64-with-glibc2.33
[debug] exe versions: ffmpeg 4.3.2-0, ffprobe 4.3.2-0
[debug] Optional libraries: Crypto, sqlite
[debug] Proxy map: {}
[debug] [youtube] Extracting URL: 9Auq9mYxFEE
[youtube] 9Auq9mYxFEE: Downloading webpage
[youtube] Saving request to 9Auq9mYxFEE_https_-_www.youtube.com_watchv=9Auq9mYxFEE_bpctr=9999999999_has_verified=1.dump
[youtube] 9Auq9mYxFEE: Downloading android player API JSON
[youtube] Saving request to 9Auq9mYxFEE_https_-_www.youtube.com_youtubei_v1_playerkey=AIzaSyAO_FJ2SlqU8Q4STEHLGCilw_Y9_11qcW8.dump
[youtube] 9Auq9mYxFEE: Downloading m3u8 information
[youtube] Saving request to 9Auq9mYxFEE_https_-_manifest.googlevideo.com_api_manifest_hls_variant_expire_1639853541_ei_hdm9YcizH9_cs8IP5Jqa8Ao_ip_2401%3Ac080%3A1000%3A4d16%3A5400%3A3ff%3Afe8b%3Ad04e_id_9Auq9mYxFEE.2_source_yt_live_br_eec3fa89cdd8e63948036ce1d1f45c67.dump
WARNING: [youtube] Ignoring subtitle tracks found in the HLS manifest; if any subtitle tracks are missing, please report this issue on  https://github.com/yt-dlp/yt-dlp . Make sure you are using the latest version; see  https://github.com/yt-dlp/yt-dlp  on how to update. Be sure to call yt-dlp with the --verbose flag and include its complete output.
[youtube] 9Auq9mYxFEE: Downloading MPD manifest
[youtube] Saving request to 9Auq9mYxFEE_https_-_manifest.googlevideo.com_api_manifest_dash_expire_1639853541_ei_hdm9YcizH9_cs8IP5Jqa8Ao_ip_2401%3Ac080%3A1000%3A4d16%3A5400%3A3ff%3Afe8b%3Ad04e_id_9Auq9mYxFEE.2_source_yt_live_broadcast_dd1e9667dae36b55495a49e42df498ed.dump
WARNING: [youtube] Ignoring subtitle tracks found in the DASH manifest; if any subtitle tracks are missing, please report this issue on  https://github.com/yt-dlp/yt-dlp . Make sure you are using the latest version; see  https://github.com/yt-dlp/yt-dlp  on how to update. Be sure to call yt-dlp with the --verbose flag and include its complete output.
[youtube] 9Auq9mYxFEE: Downloading m3u8 information
[youtube] Saving request to 9Auq9mYxFEE_https_-_manifest.googlevideo.com_api_manifest_hls_variant_expire_1639853541_ei_hNm9Yf6qOomz4gK57YCYCQ_ip_2401%3Ac080%3A1000%3A4d16%3A5400%3A3ff%3Afe8b%3Ad04e_id_9Auq9mYxFEE.2_source_yt_live_bro_1c332574933a44dda526a5c50d71fdcf.dump
[youtube] 9Auq9mYxFEE: Downloading MPD manifest
[youtube] Saving request to 9Auq9mYxFEE_https_-_manifest.googlevideo.com_api_manifest_dash_expire_1639853541_ei_hNm9Yf6qOomz4gK57YCYCQ_ip_2401%3Ac080%3A1000%3A4d16%3A5400%3A3ff%3Afe8b%3Ad04e_id_9Auq9mYxFEE.2_source_yt_live_broadcast_fa046104a8ba40c76055834f7faada71.dump
[debug] Sort order given by extractor: quality, res, fps, hdr:12, source, codec:vp9.2, lang, proto
[debug] Formats sorted by: hasvid, ie_pref, quality, res, fps, hdr:12(7), source, vcodec:vp9.2(10), acodec, lang, proto, filesize, fs_approx, tbr, vbr, abr, asr, vext, aext, hasaud, id
[debug] Default format spec: bestvideo*+bestaudio/best
[info] 9Auq9mYxFEE: Downloading 1 format(s): 248+140
```

P.S. I don't mind exposing IP addresses in dumps, since it's not from my home.