how to fix these warnings

[kernelpanic1]

sudo youtube-dl -v -F http://www.youtube.com/watch?v=C1vzxjOx7xQ

[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'-v', u'-F', u'http://www.youtube.com/watch?v=C1vzxjOx7xQ']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2019.06.08
[debug] Python version 2.7.12 (CPython) - Linux-4.4.0-150-generic-x86_64-with-Ubuntu-16.04-xenial
[debug] exe versions: ffmpeg 4.1.3-0york1, ffprobe 4.1.3-0york1
[debug] Proxy map: {}
[youtube] C1vzxjOx7xQ: Downloading webpage
[youtube] C1vzxjOx7xQ: Downloading video info webpage
[youtube] {18} signature length 105, html5 player vflyUY2ev
[youtube] {137} signature length 105, html5 player vflyUY2ev
[youtube] {248} signature length 105, html5 player vflyUY2ev
[youtube] {136} signature length 101, html5 player vflyUY2ev
[youtube] {247} signature length 101, html5 player vflyUY2ev
[youtube] {135} signature length 105, html5 player vflyUY2ev
[youtube] {244} signature length 105, html5 player vflyUY2ev
[youtube] {397} signature length 101, html5 player vflyUY2ev
WARNING: Unknown codec unknown
[youtube] {134} signature length 101, html5 player vflyUY2ev
[youtube] {243} signature length 105, html5 player vflyUY2ev
[youtube] {396} signature length 101, html5 player vflyUY2ev
WARNING: Unknown codec unknown
[youtube] {133} signature length 105, html5 player vflyUY2ev
[youtube] {242} signature length 105, html5 player vflyUY2ev
[youtube] {395} signature length 105, html5 player vflyUY2ev
WARNING: Unknown codec unknown
[youtube] {160} signature length 105, html5 player vflyUY2ev
[youtube] {278} signature length 105, html5 player vflyUY2ev
[youtube] {394} signature length 105, html5 player vflyUY2ev
WARNING: Unknown codec unknown
[youtube] {140} signature length 101, html5 player vflyUY2ev
[youtube] {171} signature length 101, html5 player vflyUY2ev
[youtube] {249} signature length 101, html5 player vflyUY2ev
[youtube] {250} signature length 105, html5 player vflyUY2ev
[youtube] {251} signature length 105, html5 player vflyUY2ev
[info] Available formats for C1vzxjOx7xQ:

WARNING: Unknown codec unknown ??
what does it mean?

[hedii]

Related to #21381

[dstftw]

Youtube serves invalid codecs metadata.