title: Error installing ffmpeg on ubuntu: opus not found using pkg-config
body: <p>When I try to install ffmpeg on my ubuntu 14.10 machine, I keep getting this: </p>
  
  <blockquote>
    <p>ERROR: opus not found using pkg-config</p>
  </blockquote>
  
  <p>at this <a href="https://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu#ffmpeg" rel="noreferrer">step</a>:</p>
  
  <pre><code>PATH="$HOME/bin:$PATH" PKG_CONFIG_PATH="$HOME/ffmpeg_build/lib/pkgconfig" ./configure \
    --prefix="$HOME/ffmpeg_build" \
    --extra-cflags="-I$HOME/ffmpeg_build/include" \
    --extra-ldflags="-L$HOME/ffmpeg_build/lib" \
    --bindir="$HOME/bin" \
    --enable-gpl \
    --enable-libass \
    --enable-libfdk-aac \
    --enable-libfreetype \
    --enable-libmp3lame \
    --enable-libopus \
    --enable-libtheora \
    --enable-libvorbis \
    --enable-libvpx \
    --enable-libx264 \
    --enable-nonfree
  </code></pre>
  
  <p>I've followed all the previous installation steps and it went all successful. I'm really new to Ubuntu. Could anybody give me a hint? </p>