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-   -   The XAVC-L 4K (Long GOP) gotcha (https://www.dvinfo.net/forum/general-hd-720-1080-acquisition/526861-xavc-l-4k-long-gop-gotcha.html)

Jack Zhang February 13th, 2015 11:17 AM

The XAVC-L 4K (Long GOP) gotcha
As most FS7 owners have found out by now, the FS7 only does non-broadcast compliant 4:2:0 in it's 150mbps Long GOP mode. It's likely the F5, F55 and Z100 also don't have 10bit 4:2:2 Long GOP in 4K specifically. At the moment this thread doesn't fit into a specific camera thread so I'm posting it here.

With the big broadcasters trying to future proof their acquisition by mandating 4K 60p at 10bit 4:2:2 for major productions, XAVC-I at 600mbps is not space efficient and can be a real pain for long-form stuff like concerts. ProRes at 4K 60p is higher than XAVC-I, so it isn't any better.

I understand hardware limitations may make it impossible to compress Long GOP in real time and still maintain 4K 10bit 4:2:2 at the moment. HEVC is not mature enough to be a broadcast acquisition codec. So this begs the question: For productions that need storage efficency, does everyone think now's not the right time? The F5 and F55 may get new ASICs to support it combined with a new firmware update, but it looks like the FS7 is the only cam that won't be broadcast compliant in 4K Long GOP.

The other argument is, does color subsampling matter at that high resolutions? To the broadcasters, I'm willing to bet so, but to the "YouTube" generation of vloggers that like to hold a FS700 selfie style with a single hand (They exist, and it's quite shocking to see that) they don't care. However, the FS7 is not a Youtuber camera in any sense, so the exclusion of Long GOP 4K 4:2:2 is baffling.

Sony, get on it. Make XAVC-L 4K 10bit 4:2:2 possible.

If I got the F5 and F55 parts wrong (if they already support Long GOP 10bit 4:2:2 at 4K) please let me know.

I also made this thread because I could find nothing on Google about the subject matter.

Monday Isa February 14th, 2015 01:07 PM

Re: The XAVC-L 4K (Long GOP) gotcha
According to this pdf XAVC-L 4K 422 10-bit is possible as the highest operating point in XAVC-L.

"To add with, 4:2:2 10bit for 4K Long GOP will be added as the highest operating point in
XAVC 4K profile to enhance the picture quality even further."


It mentions it's coming to the FS7. I use Vegas Pro 13 and XAVC-L has been useless to me as it won't ingest the footage properly. It's not only Vegas but Final Cut as well. Till this is resolved what benefit is 10-bit LongGop in 4K to other FS7 users? I've been stuck with Intra and Mpeg422 which is not what I purchased the camera for. :/

Jack Zhang February 15th, 2015 04:17 AM

Re: The XAVC-L 4K (Long GOP) gotcha
Sony wasn't clear that it would/would not come in a future firmware update. This white paper was made before the camera was released, implying it would be available at launch. It was not.

Even the F5 and F55 upgrade timelines don't indicate this.

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