Using ffmpeg to convert files to OVG (libtheora) on Windows 10 results in corrupted Video Files
According to this thread: https://old.reddit.com/r/ffmpeg/comments/fy2618/need_someone_to_test_libtheora_encoder_on_64bit/
The theora encoder is currently broken in the 64bits versions.
I tried this with the 32bits version and it now works as expected.  

32bits builds can be found here: https://ffmpeg.zeranoe.com/builds/win32/static/

Greetings