Repository: youtube-dl
Issue: Question about operation of "--write-auto-sub"
Labels: question

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## Checklist

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## Question

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What should result from the following examples ?

> youtube-dl -v --write-auto-sub --write-sub "https://www.youtube.com/watch?v=F5Y7BniaRXg"
> youtube-dl -v --write-auto-sub --write-sub --all-subs "https://www.youtube.com/watch?v=F5Y7BniaRXg"

I get the following from both forms:

> youtube-dl -v --write-auto-sub --write-sub --all-subs "https://www.youtube.com/watch?v=F5Y7BniaRXg"
> [debug] System config: []
> [debug] User config: []
> [debug] Custom config: []
> [debug] Command-line args: [u'-v', u'--write-auto-sub', u'--write-sub', u'--all-subs', u'https://www.youtube.com/watch?v=F5Y7BniaRXg']
> [debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
> [debug] youtube-dl version 2020.12.05
> [debug] Python version 2.7.16 (CPython) - Darwin-19.6.0-x86_64-i386-64bit
> [debug] exe versions: ffmpeg 4.3.1-tessus, ffprobe 4.3.1-tessus
> [debug] Proxy map: {}
> [youtube] F5Y7BniaRXg: Downloading webpage
> WARNING: video doesn't have subtitles
> [youtube] F5Y7BniaRXg: Looking for automatic captions
> WARNING: Couldn't find automatic captions for F5Y7BniaRXg
> 

That result seems correct as using --list-subs also returns a warning that there are no subtitles:

> youtube-dl -v --list-subs "https://www.youtube.com/watch?v=F5Y7BniaRXg"      
> [debug] System config: []
> [debug] User config: []
> [debug] Custom config: []
> [debug] Command-line args: [u'-v', u'--list-subs', u'https://www.youtube.com/watch?v=F5Y7BniaRXg']
> [debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
> [debug] youtube-dl version 2020.12.05
> [debug] Python version 2.7.16 (CPython) - Darwin-19.6.0-x86_64-i386-64bit
> [debug] exe versions: ffmpeg 4.3.1-tessus, ffprobe 4.3.1-tessus
> [debug] Proxy map: {}
> [youtube] F5Y7BniaRXg: Downloading webpage
> WARNING: video doesn't have subtitles
> [youtube] F5Y7BniaRXg: Looking for automatic captions
> WARNING: Couldn't find automatic captions for F5Y7BniaRXg

However, when this form is used, auto generated subtitles ARE downloaded:

> youtube-dl -v --write-auto-sub "https://www.youtube.com/watch?v=F5Y7BniaRXg" 
> [debug] System config: []
> [debug] User config: []
> [debug] Custom config: []
> [debug] Command-line args: [u'-v', u'--write-auto-sub', u'https://www.youtube.com/watch?v=F5Y7BniaRXg']
> [debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
> [debug] youtube-dl version 2020.12.02
> [debug] Python version 2.7.16 (CPython) - Darwin-19.6.0-x86_64-i386-64bit
> [debug] exe versions: ffmpeg 4.3.1-tessus, ffprobe 4.3.1-tessus
> [debug] Proxy map: {}
> [youtube] F5Y7BniaRXg: Downloading webpage
> [youtube] F5Y7BniaRXg: Looking for automatic captions
> [debug] Default format spec: bestvideo+bestaudio/best
> [info] Writing video subtitles to: How to recover data from a hard drive (stuck heads - buzzing, clicking, etc)-F5Y7BniaRXg.en.vtt

Other than testing for a warning, is there a way of finding auto generated subtitles ?

Why does combining _--write-auto-sub_ and _--write-sub_ return the warning that there are no auto generated subtitles when there clearly are ?

Should _--list-subs_ return info on auto generated subtitles ?