Under linux ubuntu exporting the video with ffmpeg doesn't works

Hello, I have this problem.

When I start exporting my animation into a video in ffmpeg format it doesn’t work: The compress steps works but absolutely no files are created in my folder.

I tried to export it using the command line:
synfigstudio.synfig ./mémoire.sifz -v 3 -t ffmpeg -a 3 -o ./zoom.avi

and it reports me some errors:
firsts are:
synfig(9895) [20:23:27] avertissement: Cannot open ./synfig_modules.cfg
synfig(9895) [20:23:27] avertissement: Cannot open /home/bourdon/snap/synfigstudio/1/.local/share/synfig/synfig_modules.cfg
synfig(9895) [20:23:27] avertissement: Cannot open /usr/etc/synfig_modules.cfg

last are:
ffmpeg: error while loading shared libraries: libflite_cmu_us_awb.so.1: cannot open shared object file: No such file or directory
synfig(9895) [20:23:28] avertissement: Broken Pipe…
synfig(9895) [20:23:28] avertissement: Broken Pipe…
synfig(9895) [20:23:28] avertissement: Broken Pipe…
synfig(9895) [20:23:28] avertissement: Broken Pipe…
synfig(9895) [20:23:28] avertissement: Broken Pipe…

and it repeats lot of times : synfig(9895) [20:23:28] avertissement: Broken Pipe…

and at the end not files are created.

I thought the library libflite_cmu_us_awb.so.1is missing in my system but apparently, it’s here because
the command"ldconfig -v |grep libflite_cmu_us_awb.so.1" return me somethiing.

In dv format it works!

Do you know where the problem come from?

Thanks for your answer

Nicolas