[FFmpeg-user] A query on the nofillin flag

[Dennis Mungai]

Hey there,

I’ve had (specific) UDP streams that will fail to encode properly without
the +igndts +genpts flags, and even then, I’d occasionally get issues with
stuttery playback on the final encode after about 24 hours.

What fixed it was +genpts+nofillin fflags, but with one caveat: CPU load
went up significantly, by a factor of up to 10x on some streams and RAM
utilization per ffmpeg process went from about 2.5 GB to 6 GB. However, the
streams are quite stable to this point, with no playback issues encountered.

Which brings me to the query: What is it about +nofillin fflag that incurs
so much CPU and RAM usage overhead?