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I frame vs Long GOP for sports

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John Castelli
I frame vs Long GOP for sports
on Apr 25, 2013 at 7:33:47 pm

Any editors out there working on sports or fast paced content? If you do, do you prefer I frame only or long GOP? I worry I frame only will be a bit choppy bc of the speed of the sports but I am really just assuming- so if you have had any experience with this I would truly appreciate your thoughts and feedback!

Thanks!

_____________

John Castelli
Editor


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Shane Ross
Re: I frame vs Long GOP for sports
on Apr 25, 2013 at 7:48:49 pm

They'd better SHOOT I-Frame...or the damage is already done. GOP formats consist of just a few real frames in one second (typically 3 frames) and the rest are a group of pictures that make up the image. So with sports, and fast movement, you can end up with a lot of blur. I-Frame cameras shoot real frames per second...so they are far better to shoot with.

So the answer is...SHOOT I-Frame...don't even shoot with GOP formats like HDV or AVCHD. XDCAM is better of the formats, but still not the best. Or...use those cameras but record to external recorder that takes the feed of the sensor but records I Frame, like the KiPro, KiPro Mini, Ninja recorders. or direct feed to production trucks.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Alex Gerulaitis
Re: I frame vs Long GOP for sports
on Apr 25, 2013 at 9:35:22 pm

As long as camera's long GOP codec doesn't "break" under pressure of fast motion, the picture quality will always be better vs. the same camera encoding into an i-frame-only codec. GOP codecs are simply way more efficient vs. i-frame ones.

I-frame doesn't get choppy in fast motion - it's the GOP codec that can "break" (fail) in extreme circumstances, when the amount of information (fast motion, lots of picture details) exceeds its capacity for processing - but like I said, this mostly applies to old, cheap, V.1 cameras. The only reasons for i-frame (vs. GOP) in cameras are: (a) camera's brain not powerful enough to encode into GOP, (b) easier to work with in post. Both of these reasons may have been valid, say, five years ago - not so much anymore.

Alex Gerulaitis
Systems Engineer
DV411 - Los Angeles, CA


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Pat Horridge
Re: I frame vs Long GOP for sports
on Apr 26, 2013 at 9:08:17 am

If you record direct to proves or dnx then you are effectively doing frame based recording and these are proven codes. Long GOP has its place but lots of motion stretches its ability. But to avoid it you have to start non long GOP.

Pat Horridge
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Fred Gasc
Re: I frame vs Long GOP for sports
on Apr 26, 2013 at 9:33:29 am

I'd avoid long GOP like the plague. It's not going to make anything "smoother" in fast action. All it does is that it degrades the gop and makes post operations more chalenging, particularly critical in higher isos. Instead of film grain it's an huggly soupe of artefacts.
I hacked My gh2 with I.frame and it's way better. But you'd need at least 100 Mb/s. File size is about the double of a longGOP hack at the same bitrate, but image is of better robustness.

There are IMO 2 things that
Should be removed by law
From the workflows: One is
Quicktime, and the other is
Long GOP.

Fred.


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