FS7: XAVC -L long gop

L

Lenilenapi

Carbonite Member
Has anyone played with 4K XAVC-L Long Gop yet?
Seems like it might be very useful in the field when long record times are happening in 4K - especially interviews. Get you off the set faster when downloading footage.
I'm curious if there is any loss of quality and whether it needs to be transcoded in post back to an Intra codec for editing.

BTW - Whoever is maintaining this forum - at the very least add FS7 to the list of prefixes.
 
Haven't done any yet, but the long-GOP doesn't mean inferiour quality than all-I.
It's just another way of compression , that is very CPU hungry when encoding/decoding.
Maybe fast motion can be better on all-I, but the difference shouldn't be that big.

If you really want to safe space and don't need every penny in compression quality you
can use the long-GOP codec without a hassle.
When it comes to editing - it can be a pain. The long GOP codecs are not edit friendly.
If they work for you or your clients - there you go.

With my iMac late 2012 i7 3,4GHz with 24GB Ram and 2GB VideoRAM it'S possible to
edit natively when not using to much FX. The all-I codec just runs better here.
I will choose the all-I variant whenever it's possible in the first place. Even if it means
to buy bigger XQDs along the way. I never liked the long-GOP codecs for editing and
had them changed to ProRes before editing. This means more time and work for the
project.

You need to try it out for yourself. It'S more a question of workflow than a matter of
picture quality.
 
Whether it needs to be transcoded to intra frame is purely down to your compiter system's power. It's perfectly fine to edit Long GOP compressed omages, but yes it does take quite a bit more computer power. The computer needs to make complex decoding during editing, while it's not as complex when each frame is compressed individually (ALL-I).

In all the cameras I've used Long GOP was not visually inferior to All i, or perhaps I am not that picky in compression quality anyway. I would try it first and compare as this is a new camera and it will be hard to find tests/information out there now.
 
It terms of image quality, long gop can produce excellent results when motion in the frame is slow. Long gop will suffer the most when there are very sudden changes in the frame. For instance, I personally wouldn't use long gop when shooting with strobes or other rapid stage lighting.

I haven't tested out these XAVC codecs very much yet though.
 
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