title: ffmpeg transparent waveform and solid background
body: <p>Im trying to create waveform image with transparent wave and solid background color. Im find the similar topic here:</p>
  
  <p><a href="https://stackoverflow.com/questions/37149739/ffmpeg-waveform-transparent-background-solid-color">FFMPEG waveform transparent, background solid color</a></p>
  
  <p>but the answer not working for me :( 
  Maybe do you know why this code suspend the program in console command.</p>
  
  <pre><code>ffmpeg -i input.mp3 -filter_complex \    "[0:a]aformat=channel_layouts=mono,compand=gain=-6, \
      showwavespic=s=600x120:colors=white,negate[a]; \
      color=red:600x120[c]; \
      [c][a]alphamerge"  -vframes 1 output.png
  </code></pre>