That is exactly what I expect, or did I misread you? I expect its text output on stderr, and stdout being reserved for its video (or whatever) output.

Maybe the name “stderr” is a bit misleading. It’s totally common for non-error output to be in stderr as well, like verbose/debug logging.

I've just checked the man page for ffmpeg and they have a `-report` flag to capture the log. There should be no need to redirect stderr.