When playing mkv movie by vlc media player, sometimes I only get the video not the audio

I have VLC media player installed on Ubuntu 14.04 64 bit.

The problem is when I play movies that are in .mkv format using VLC it sometimes cannot play the sound of the movie and I only see the video. This problem occurs in the middle of the movie when I click on the progress bar to go forward or backward.

Is there a solution for this?

If VLC shows following error:

No suitable decoder module VLC does not support the audio or video format hevc. Unfortunately there is no way for you to fix this.

Then try to install libde265 via PPA.

sudo apt-add-repository ppa:strukturag/libde265 
sudo apt-get update 
sudo apt-get upgrade
sudo apt-get install vlc

VLC should now play these media files after installation has been completed successfully.