@lalitjindal it's a problem with ffmpeg codec. You can try to do this on terminal:
curl -L -O https://github.com/iteufel/nwjs-ffmpeg-prebuilt/releases/download/0.47.2/0.47.2-linux-x64.zip
unzip 0.47.2-linux-x64.zip
sudo mkdir /usr/lib/x86_64-linux-gnu/opera/lib_extra
sudo mv libffmpeg.so /usr/lib/x86_64-linux-gnu/opera/lib_extra
After that, it should work.