bug#43418: ffprobe/avprobe and ffmpeg/avconv should be added as dependencies of youtube-dl so it will function correctly

[raingloom <raingloom@riseup.net>]

On Tue, 15 Sep 2020 14:06:11 +0200
Tobias Geerinckx-Rice via Bug reports for GNU Guix <bug-guix@gnu.org>
wrote:

> Hi Nathan,
> 
> Nathan Dehnel 写道：
> > bash-5.0$ youtube-dl -x 
> > https://www.youtube.com/watch?v=7Ijd_iN9Blk
> > [youtube] 7Ijd_iN9Blk: Downloading webpage
> > [download] Deadmau5 - Hit Save-7Ijd_iN9Blk.webm has already been 
> > downloaded
> > [download] 100% of 15.45MiB
> > ERROR: ffprobe/avprobe and ffmpeg/avconv not found. Please 
> > install one.  
> 
> It works fine without ‘-x’:
> 
>   λ youtube-dl https://www.youtube.com/watch?v=7Ijd_iN9Blk
>   [youtube] 7Ijd_iN9Blk: Downloading webpage
>   [download] Destination: Deadmau5 - Hit Save-7Ijd_iN9Blk.mp4
>   [download] 100% of 37.09MiB in 00:02
> 
> This *is* functioning correctly in my view: that advanced options 
> optionally require run-time dependencies is not a bug but a 
> feature.  The programme clearly explains which package could be 
> installed to continue, and the user can chose which one they 
> prefer - including neither, which suffices for the majority of 
> youtube-dling.
> 
> Matters would be different if the error message were less clear, 
> or perhaps if ffmpeg weren't so insanely great:
> 
>   λ guix size youtube-dl | tail -n1
>   total: 186.9 MiB
>   λ guix size youtube-dl ffmpeg | tail -n1
>   total: 811.2 MiB
> 
> (!)
> 
> Kind regards,
> 
> T G-R

Maybe it's time we added an "optional dependencies" field?
There seems to be a bug report or help request like every week that
just boils down to "this package has an undocumented dependency".