avconv version and youtube-dl

I have youtube-dl version 2015.07.04. While downloading a video, I see this message:

Your copy of avconv is outdated and unable to properly mux separate video and audio files, youtube-dl will download single file media. Update avconv to version 10-0 or newer to fix this.

Apparently, the drawback of an outdated avconv is that youtube-dl won't be able to download bestvideo and bestaudio separately and mux them together into a single file giving the best overall quality available.

How can I find my currently installed avconv's version number? How can I get a newer version than what is provided by libav-tools 6:9.18-0ubuntu0.14.04.1?

Is there a ppa available for 14.04 with avconv version 10.0 or higher?

ppa can be found here

sudo add-apt-repository ppa:mc3man/trusty-media
sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install ffmpeg

The following command will add an alias to your bashrc file so your user can execute youtube-dl and bash will execute youtube-dl --prefer-ffmpeg automatically to eliminate unnecessary typing in the future:

echo "alias youtube-dl='youtube-dl --prefer-ffmpeg'" | tee -a ~/.bashrc; . ~/.bashrc

You can also add extra flags to the command by editing your ~/.bashrc file with your favorite text editor like gedit, vim, or nano; just keep in mind that you do not need to and should not use sudo to edit this file as it should be under your current user profile and needs to maintain your user permissions, not that of sudo or root. Just add extra flags within the quoted command for youtube-dl. Also, after editing ~/.bashrc you will need to source the file or open a new terminal to use the new alias. Source the file by running the following command:

. ~/.bashrc

To view the currently installed version of libav-tools, run the following command:

dpkg -l | grep libav

Also, to view what is available from apt-get, run the following command:

apt-cache show libav-tools | grep Version:

All available versions will be listed. The newest version will be installed by default when you run sudo apt-get upgrade or 'dist-upgrade or you can just sudo apt-get install it and it will install the newest available version unless otherwise specified.

To do a search for related packages, use apt-cache search like so:

apt-cache search libav

To narrow the search, you can use grep to only print results containing a keyword like so:

apt-cache search libav | grep libav

Avconv-11 is still available for Ubuntu Trusty in the heyarje ppa:

sudo add-apt-repository ppa:heyarje/libav-11 && sudo apt-get update
sudo apt-get upgrade
sudo apt-get install libav-tools