Budget: 2500 UAH Deadline: 3 days
The task is not entirely clear.
"Single pass" — FFmpeg in any case breaks tasks into separate jobs. Not everything can truly be implemented in multiple threads, if I understand you correctly. And it does not always improve performance — it all depends on your "hardware" (particularly, the number of cores).
And sometimes it is better to intentionally divide processing into parts. For example, if it is a stream and you need to run processing of multiple videos in parallel, this approach can allow processing significantly more simultaneously within an acceptable time.