30 march 2023

	30 march 2023
	catdeer haven - Downloading Albums, from Youtube


	So, for the geekier people out there, there's a really neat tool to
	download youtube videos and do a whole bunch of fancy formatting
	from the command line: `youtube-dl`. This, however, tends to break
	every now and then and is slow to update. In comes `yt-dlp`, a fork
	that gets more frequent updates, does some fancy User-Agent stuff
	to not get throttled, and probably has some other features over
	it's predecesor.

	One neat function these tools have is to wrangle downloaded videos
	into mp3s, even adding metadata it can find.

	This is nice and all, but it only really comes together when you
	realize one thing: Youtube Music is just a frontend for Youtube.
	You can notice that easily by just looking at the URL when you're
	viewing an album on Youtube Music: It's just a playlist, nothing
	more, and `yt-dlp` can download all videos in a playlist.

	However, getting all the options right for `yt-dlp` to download an
	album's worth of music and add in the right metadata including the
	cover art is a bit of an ordeal, considering that tool is meant to
	be much more general purpose. So, I've spent a day or two getting
	it mostly right:


	```
	yt-dlp \
	--replace-in-metadata uploader ' - Topic' '' \
	--parse-metadata '%(playlist_index)s:%(meta_track)s' \
	--parse-metadata '%(uploader)s:%(meta_album_artist)s' \
	--embed-metadata \
	--embed-thumbnail --ppa "EmbedThumbnail+ffmpeg_o:-c:v mjpeg -vf \
	crop=\"'if(gt(ih,iw),iw,ih)':'if(gt(iw,ih),ih,iw)'\"" \
	--yes-playlist --format 'bestaudio/best' --extract-audio \
	--audio-format mp3 --audio-quality 0 \
	--windows-filenames --force-overwrites -o \
	'%(uploader)s/%(album)s/%(playlist_index)s - %(title)s.%(ext)s' \
	--print '%(uploader)s - %(album)s - %(playlist_index)s %(title)s' \
	--no-simulate "$@"
	```

	You can just stuff this overly long command into a shell script and
	give it the link to a playlist (read: youtube music album) and
	it'll download, convert and tag everything for you. It'll even
	store everything in a neat folder structure that coincidentally is
	perfect for media servers like Jellyfin: `<album
	artist>/<album>/<track nr> - <title>.mp3`


	# Cool, but what does that wall of options actually do?

	```
	--replace-in-metadata uploader ' - Topic' '' \
	```

	This first line of options uses a pretty neat function: Using
	yt-dlp, you can basically run `sed` over any metadata `yt-dlp`
	managed to extract. Since for some reason youtube likes to add " -
	Topic" to the end of artist's channels, this line simply removes
	that.


	```
	--parse-metadata '%(playlist_index)s:%(meta_track)s' \
	--parse-metadata '%(uploader)s:%(meta_album_artist)s' \
	--embed-metadata \
	```

	This one does some further metadata-magic: It tells `yt-dlp` to use
	the playlist index as the track number and the uploader (which we
	previously "fixed") as the album artist, since Youtube basically
	never sets that one like ever. This does break sometimes, I've
	noticed it choke on DMC5's and Metal Gear Rising's soundtrack. With
	that last option, `yt-dlp` actually embeds the metadata into the
	finished files.


	```
	--embed-thumbnail --ppa "EmbedThumbnail+ffmpeg_o:-c:v mjpeg -vf \
	crop=\"'if(gt(ih,iw),iw,ih)':'if(gt(iw,ih),ih,iw)'\"" \
	```

	This line is pure magic: the first option simply embeds the
	thumbnail, which unfortunately isn't square, as cover art should
	be, but the second option fixes just that. I'm not nearly
	well-versed enough in `ffmpeg`'s cryptic options to understand
	what's going on, I'm just glad it works.


	```
	--yes-playlist --format 'bestaudio/best' --extract-audio \
	--audio-format mp3 --audio-quality 0 \
	```

	Here's just some basic format selection. Basically, if you give it
	a link to a video in a playlist, it'll download the whole playlist
	instead of just the one video. Also it's told to get the best audio
	it can and that you want to end up with an mp3 file.


	```
	--windows-filenames --force-overwrites -o \
	'%(uploader)s/%(album)s/%(playlist_index)s - %(title)s.%(ext)s' \
	```

	This is where the fancy folder structure happens. I've chosen to
	force yt-dlp to use windows compatible filenames, just for a little
	extra compatibility.


	```
	--print '%(uploader)s - %(album)s - %(playlist_index)s %(title)s' \
	--no-simulate "$@"
	```

	Now this line exists to fix the horribly verbose output of yt-dlp.
	This way, you'll only see errors, warnings, and one line per
	downloaded video, allowing you to preview the folder structure in
	case some metadata is set wrong.