Error converting downloaded from youtube on Ubuntu

[ceduliocezar]

I'm trying to download and convert some audio from youtube, but when pyjam tries to convert something goes wrong.
Here it says that there is some lib missing but, I checked on apt and it is already installed.

I'm running pyjam on: Ubuntu 16.04 - 64-bit

23:56:46 INFO: Python 3.4.2 (default, Oct  8 2014, 10:47:48) 
[GCC 4.9.1] on linux
23:56:46 INFO: uname_result(system='Linux', node='game-ubuntu', release='4.4.0-42-generic', version='#62-Ubuntu SMP Fri Oct 7 23:11:45 UTC 2016', machine='x86_64', processor='x86_64')
23:56:46 INFO: pyjam version 1.2.9
23:56:46 INFO: Generating track list with path audio/csgo
23:58:31 INFO: Beginning download
23:58:31 INFO: All songs were downloaded succesfully!
23:59:39 INFO: 
23:59:39 CRITICAL: FFmpeg converter: Couldn't convert /home/gameuser/Desktop/music.webm
23:59:39 CRITICAL: FFmpeg converter: Error output log
/usr/bin/ffmpeg: /tmp/_MEIfbxQy7/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by /usr/lib/x86_64-linux-gnu/libjack.so.0)
/usr/bin/ffmpeg: /tmp/_MEIfbxQy7/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by /usr/lib/x86_64-linux-gnu/libzmq.so.5)
/usr/bin/ffmpeg: /tmp/_MEIfbxQy7/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by /usr/lib/x86_64-linux-gnu/libopencv_core.so.2.4)
/usr/bin/ffmpeg: /tmp/_MEIfbxQy7/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by /usr/lib/x86_64-linux-gnu/libopencv_imgproc.so.2.4)
/usr/bin/ffmpeg: /tmp/_MEIfbxQy7/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by /usr/lib/x86_64-linux-gnu/libsnappy.so.1)
/usr/bin/ffmpeg: /tmp/_MEIfbxQy7/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by /usr/lib/x86_64-linux-gnu/libtbb.so.2)

23:59:43 CRITICAL: Error converting these files
/home/gameuser/Desktop/music.webm
23:59:43 INFO: Songs converted with 1 error(s)
23:59:44 INFO: Generating track list with path audio/csgo

[10se1ucgo]

It's a problem with your FFmpeg install. Try running sudo apt-get install libstdc++6

[ceduliocezar]

I did run the command that you suggested.

But I'm still getting the same error.