On Sat, Jul 13, 2019, 23:54 Paul B Mahol <onemda@gmail.com> wrote: That is very vague and unspecific wording to claim such feature. And specification is misleading you. Anyway NUT specification was written much before introduction of frame metadata as we know it. So what you actually pointed out have nothing to do with frame metadata, but with updating stream metadata within new packet side data. It's of course very likely that I can be mislead by that specification. If so, I would call it a problem of the specification itself to name something "per frame side and metadata" and not refer precisely to further data that has 1:1 relationship with frame. Look at the Matroska proposal because IMO they understood exactly this (referring for example to camera real-time parameters, e.g zoom/iris). I would love to hear a word from Michael about this feature and possible implementation in NUT but in the mean time I will consider it as missing from all formats. Cheers, Francesco