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IGNORING THE FOLLOWING TEMPLATE WILL RESULT IN ISSUE CLOSED AS INCOMPLETE
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## Checklist
<!--
Carefully read and work through this check list in order to prevent the most common mistakes and misuse of youtube-dl:
- First of, make sure you are using the latest version of youtube-dl. Run `youtube-dl --version` and ensure your version is 2020.12.05. If it's not, see https://yt-dl.org/update on how to update. Issues with outdated version will be REJECTED.
- Make sure that all provided video/audio/playlist URLs (if any) are alive and playable in a browser.
- Make sure that all URLs and arguments with special characters are properly quoted or escaped as explained in http://yt-dl.org/escape.
- Search the bugtracker for similar issues: http://yt-dl.org/search-issues. DO NOT post duplicates.
- Read bugs section in FAQ: http://yt-dl.org/reporting
- Finally, put x into all relevant boxes (like this [x])
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- [x] I'm reporting a broken site support issue
- [x] I've verified that I'm running youtube-dl version **2020.12.05**
- [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 bug reports including closed ones
- [x] I've read bugs section in FAQ
## Verbose log
<!--
Provide the complete verbose output of youtube-dl that clearly demonstrates the problem.
Add the `-v` flag to your command line you run youtube-dl with (`youtube-dl -v <your command line>`), copy the WHOLE output and insert it below. It should look similar to this:
[debug] System config: []
[debug] User config: []
[debug] Command-line args: [u'-v', u'http://www.youtube.com/watch?v=BaW_jenozKcj']
[debug] Encodings: locale cp1251, fs mbcs, out cp866, pref cp1251
[debug] youtube-dl version 2020.12.05
[debug] Python version 2.7.11 - Windows-2003Server-5.2.3790-SP2
[debug] exe versions: ffmpeg N-75573-g1d0487f, ffprobe N-75573-g1d0487f, rtmpdump 2.4
[debug] Proxy map: {}
<more lines>
-->
```
$ youtube-dl -v --list-subs https://www.youtube.com/watch?v=48sCx-wBs34
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-v', '--list-subs', 'https://www.youtube.com/watch?v=48sCx-wBs34']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2020.12.05
[debug] Python version 3.7.1 (CPython) - Darwin-20.1.0-x86_64-i386-64bit
[debug] exe versions: ffmpeg 4.3.1, ffprobe 4.3.1, rtmpdump 2.4
[debug] Proxy map: {}
[youtube] 48sCx-wBs34: Downloading webpage
[youtube] 48sCx-wBs34: Looking for automatic captions
WARNING: Couldn't find automatic captions for 48sCx-wBs34
48sCx-wBs34 has no automatic captions
Available subtitles for 48sCx-wBs34:
Language formats
zh vtt, ttml, srv3, srv2, srv1
en-US vtt, ttml, srv3, srv2, srv1
$ youtube-dl -v --list-subs https://www.youtube.com/watch?v=48sCx-wBs34
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-v', '--list-subs', 'https://www.youtube.com/watch?v=48sCx-wBs34']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2020.12.05
[debug] Python version 3.7.1 (CPython) - Darwin-20.1.0-x86_64-i386-64bit
[debug] exe versions: ffmpeg 4.3.1, ffprobe 4.3.1, rtmpdump 2.4
[debug] Proxy map: {}
[youtube] 48sCx-wBs34: Downloading webpage
[youtube] 48sCx-wBs34: Looking for automatic captions
Available automatic captions for 48sCx-wBs34:
Language formats
af vtt, ttml, srv3, srv2, srv1
sq vtt, ttml, srv3, srv2, srv1
am vtt, ttml, srv3, srv2, srv1
ar vtt, ttml, srv3, srv2, srv1
hy vtt, ttml, srv3, srv2, srv1
...
yo vtt, ttml, srv3, srv2, srv1
zu vtt, ttml, srv3, srv2, srv1
Available subtitles for 48sCx-wBs34:
Language formats
zh vtt, ttml, srv3, srv2, srv1
en-US vtt, ttml, srv3, srv2, srv1
```
## Description
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Hi, I think there is a bug in the way that youtube-dl retrieves if a youtube video has auto captions because if you run `--list-subs` on any video with automatic captions, the output is inconsistent. This is also probably related to atleast #27306 and #27292.