[FFmpeg-user] showvolume filter

[Moritz Barsnick]

On Sun, Apr 03, 2016 at 01:14:47 +1100, Nisar Ahmed wrote:
> I am using ffmpeg to capture audio/video from a decklink card and producing
> 2 outputs from it, one is the captured movie file on disk and the other one
> is mpegts stream for monitoring. The monitoring stream should have audio
> bars for audio monitoring as well.
> 
> ffmpeg -f decklink -i "DeckLink Intensity" -vcodec libx264 -acodec
> libmp3lame -preset ultrafast -crf 30 output.mp4 -vf scale=640:-1 -f mpegts
> udp://127.0.0.1:1234
> 
> It would be best if I could overlay showvolumne filter or pipe it to ffplay
> or both.

For the monitoring output, use a comples filter as such:
  [...] -filter_complex "[0:a]showvolume[vol]; [0:v][vol]overlay[v]" -map "[v]" -map 0:a <output>

Perhaps adda box around the volume display, because it's not obvious it's there due to its transparency:
  [...] -filter_complex "[0:a]showvolume,drawbox=w=iw:h=ih[vol]; [0:v][vol]overlay[v]" -map "[v]" -map 0:a <output>

You may want to also force the width of the bars to your output width
(and I forgot to scale your monitoring stream):
  [...] -filter_complex "[0:a]showvolume=w=640,drawbox=w=iw:h=ih[vol]; [0:v]scale=640:-1[scaled]; [scaled][vol]overlay[v]" -map "[v]" -map 0:a <output>

Moritz