Youtube-dl downloads all formats instead of mp3 only.

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[ ] Site support request (request for adding support for a new site)
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If the purpose of this issue is a bug report, site support request or you are not completely sure provide the full verbose output as follows:

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 here. It should look similar to one below (replace it with your log inserted between triple ```):

[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'--ignore-errors', u'-v', u'-x', u'--audio-format', u'mp3', u'-continue', u'-o', u'%(autonumber)02d-%(title)s.%(ext)s', u'--add-metadata', u'https://deboned.bandcamp.com/album/deboned-existench']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2017.09.02
[debug] Python version 2.7.9 - Linux-3.16.0-4-amd64-x86_64-with-debian-8.9
[debug] exe versions: avconv 11.9-6, avprobe 11.9-6, ffmpeg 3.3.2, ffprobe 3.3.2
[debug] Proxy map: {}
[Bandcamp:album] deboned-existench: Downloading webpage
[download] Downloading playlist: Deboned / Existench
[Bandcamp:album] playlist Deboned / Existench: Collected 5 video ids (downloading 5 of them)
[download] Downloading video 1 of 5
[Bandcamp] fuckin-melt: Downloading webpage
[Bandcamp] 1986026118: Downloading free downloads page
[Bandcamp] 1986026118: Downloading alac JSON
[Bandcamp] 1986026118: Downloading aac-hi JSON
[Bandcamp] 1986026118: Downloading mp3-v0 JSON
[Bandcamp] 1986026118: Downloading mp3-320 JSON
[Bandcamp] 1986026118: Downloading flac JSON
[Bandcamp] 1986026118: Downloading wav JSON
[Bandcamp] 1986026118: Downloading vorbis JSON
[Bandcamp] 1986026118: Downloading aiff-lossless JSON
[debug] Invoking downloader on u'http://popplers5.bandcamp.com/download/track?enc=aiff-lossless&fsig=02f69c297eb8c15c521b8e115ee5a525&id=1986026118&ts=1504412186.1030003688'
[download] Destination: 01-Deboned - Fuckin Melt!.aiff
[download] 100% of 11.16MiB in 00:28
[debug] avconv command line: avprobe -show_streams 'file:01-Deboned - Fuckin Melt!.aiff'
[ffmpeg] Destination: 01-Deboned - Fuckin Melt!.mp3
[debug] ffmpeg command line: avconv -y -i 'file:01-Deboned - Fuckin Melt!.aiff' -vn -acodec libmp3lame '-q:a' 5 'file:01-Deboned - Fuckin Melt!.mp3'
Deleting original file 01-Deboned - Fuckin Melt!.aiff (pass -k to keep)
[ffmpeg] Adding metadata to '01-Deboned - Fuckin Melt!.mp3'
[debug] ffmpeg command line: avconv -y -i 'file:01-Deboned - Fuckin Melt!.mp3' -c copy -metadata 'purl=https://deboned.bandcamp.com/track/fuckin-melt' -metadata 'artist=Deboned' -metadata 'title=Fuckin Melt!' 'file:01-Deboned - Fuckin Melt!.temp.mp3'
[download] Downloading video 2 of 5
[Bandcamp] decaying-rotten-insides: Downloading webpage
[Bandcamp] 1108131875: Downloading free downloads page
[Bandcamp] 1108131875: Downloading alac JSON
[Bandcamp] 1108131875: Downloading aac-hi JSON
[Bandcamp] 1108131875: Downloading mp3-v0 JSON
[Bandcamp] 1108131875: Downloading mp3-320 JSON
[Bandcamp] 1108131875: Downloading flac JSON
[Bandcamp] 1108131875: Downloading wav JSON
[Bandcamp] 1108131875: Downloading vorbis JSON
[Bandcamp] 1108131875: Downloading aiff-lossless JSON
[debug] Invoking downloader on u'http://popplers5.bandcamp.com/download/track?enc=aiff-lossless&fsig=ac85da38eb46066a7c7dbf3adeeb3c2b&id=1108131875&ts=1504412221.3505618781'
[download] Destination: 02-Deboned - Decaying Rotten Insides.aiff
[download]   4.7% of 10.72MiB at 685.82KiB/s ETA 00:15^C
ERROR: Interrupted by user

...
<end of log>

Description of your issue, suggested solution and other information

I run a script using youtube-dl, which I will post below. The issue is the fact that youtube-dl announces a download of every file format even though I limit it to mp3, as can be seen in the script. The file size is of course way larger than it would be when only downloading a single mp3. I do end up with only the mp3. So I'm wandering if youtube-dl is actually first downloading all these different file formats or that it produces the output above for other reasons.

Script

echo $1 | awk -F / '{print $3.$5 }' | sed 's/.bandcamp.com/./' | xargs mkdir

cd `echo $1 | awk -F / '{print $3.$5 }' | sed 's/.bandcamp.com/./'`

youtube-dl --ignore-errors -v -x --audio-format mp3 -continue -o "%(autonumber)02d-%(title)s.%(ext)s" --add-metadata "${1}"

ytdl-org / youtube-dl