Our conference.conf.xml had: 

      <param name="comfort-noise" value="false"/>  

and no auto-gain-level. I changed it:

      <param name="comfort-noise" value="0"/>
      <param name="auto-gain-level" value="-2000"/>

And there's now clipping only during the loudest parts. But I think this gain setting is already extreme and I'd like to know if there's a less brute-force way to eliminate clipping.

On Wed, Sep 9, 2020 at 9:33 AM David P <davidswalkabout@gmail.com> wrote:
When we configure FSv10.4 to transcode Opus to PCMA/U, the output stream always has clipping (peak amplitude is always -0.17dB, 0.99 linear when measured in Audacity).

I tried configuring opus.conf.xml as suggested in https://serverfault.com/a/807070 (with restart via: fs_cli -x 'fsctl shutdown elegant restart') but it makes no difference.

When we simultaneously record the session with Audacity clientside, less than half the available range is used, so the user mic doesn't have gain too high.

How can we avoid clipping when transcoding?