Official Low GOP topic

driftwood

@All Here's a GOP3 test to keep you up. videobitrate 24H = 200mbps. Pappas death chart stable.

stoney

@stefanos You got it.

@driftwood 200Mbps sound scary!!! 110Mbps gave something close to 115Mbps average video rate.

I did some motion test. When a camera is stable and taking detailed scene, I-frame stayed around 9Mb. As soon as it began moving, I-frame size dropped and B-frame got beefed up where the size of I-frame kept above B-frame. Max B-frame size stayed around 5Mb. As soon as the camera was stabilized and focused on a detailed scene, the I-frame size restored to 9Mb and B-frame size got tamed to little above 3Mb.

The codec worked beautifully. I'll get some beer and celebrate. Gotta order Rokinon 35mm, too. Double celebration WooHoo!!!!

cbrandin

@driftwood

well... if you are going to go that far try upping FB1 FB2 and frame limit to 3x.

Chris

stoney

Cheers!!!

driftwood

@cbrandin trying it right now...

bwhitz

Great work people!!! Been waiting for 1 GOP!!!

peterdv_dot_com

@driftwood Sorry if this is a dumb question, but do your recordings using these settings play in camera?

I just did a quick test using your settings (3 gop) outdoors in fading daylight (shrubbery of death) with lumix 20mm lens, 24H, full manual, SanDisk Extreme 8GB.

My cam will show 1st frame of each clip in cam's playback mode, but not play it. However the clips play on my Mac and look very good so far. As expected, or ?

Thanks to Vitaliy, Chris, & all.

stoney

Mistakenly 132Mbps was set. Wow. Still stable. Yielding 129Mbps average bitrate. Graph looks great, but too high...

110Mbps makes 1GB clip in a minute. 16GB card can record 16mins.

driftwood

GOP 3 , 200mbps, FB1/FB2/FBL x 3 multiplier. Death Chart stable at 2 minutes still. Your thoughts?

bdegazio

Where's all that extra bitrate going? The I-frame sizes are not that much bigger than your 100 mps test. The b-frames are noticeably larger, but I don't think they could account for an extra 100 mbps.

edit - I notice that the effective bitrate is actually "only" around 115 mbs, despite your setting of 200 mbs. Perhaps you've hit a limit here? Maybe you could push it by setting AQ higher?

plasmasmp

This will only work with a card that can write as fast as a Sandisk Extreme Pro. 176mb has the unstable issue, but 24L produces perfectly stable 134mb average video. All other GOP settings are unstable. I went 4x multiplier and AQ 4. Maybe finding the sweet spot for the buffers will fix the b-frame issue at 176

driftwood

@peterdv_dot_com playback fine on my 'around the room' recordings. However, death chart wont playback.

driftwood

@cbrandin 3 x multiplier on the FBs seems hardly worth it. Your thoughts?

peterdv_dot_com

@driftwood Thanks for that confirmation.

VLC reports a playback stream bitrate of ~95mbs for my static & moving shrubbery of death clip. This is the first time my GH2 has recorded this "scene" w/o what I call "buzzy" compression artifacts along the edges of all the leaves, twigs, etc. The video looks really good -- relatively clean & natural -- which is saying a lot. Cheers.

Edit: My clips log & transfer & edit into FCP 7, too.

Here's a sample:

cbrandin

@driftwood

Yeah, I agree. I think you've maxed out I frames - no reason to go above 1.5x. Actually, I'd try maybe going to AQ=3 and see if I frames get bigger. You may actually max out at 88M. I think you have about hit the limit. Past where you are I think all you'll get is artificially big B frames.

Chris

driftwood

I'm leaving this short GOP 3 at 140mbps for now as anything above this (like 200mbps) appears to be a waste of bitrate. Multiplier for FB1 FB2 and limit has been currently left at x 2 (though 1.5 has been suffice). AQ left at 2 as 3 kept dying on pappas chart after 30 seconds. T4 = T1 seems to cure the cadence. More tests tomoz.

cosimo_bullo

You go out dancing for a few hours and then come back to this! Holy crap!!! Well done all. @driftwood - your enthusiastic posts are high in value (!) and it's just delightful to see the community come together like this and break limits. Great.

Vitaliy_Kiselev

@driftwood

randolfo

It will come to a final setting? and in what post? Too many posts.

Vitaliy_Kiselev

@randolfo
This is why you need reading skills :-) Don't be lazy.

danyyyel

What are the pros and cons of having a lower AQ 2 and higher bitrate rather than 4 for gradients etc

Mihuel

@driftwood
Good job !!! Thanks !!!!

lenuisible

@dirftwood (and all), what particular parameter in your settings fixed the different problems everyone else had ? I suppose it doesn't span, does it ?

Thanks all !

bkmcwd

@driftwood
@V&C&all
Thank you for your great works!
This post is first of mine.

I cannot understand detailed logic, but can do test.

This is just a motion test footage with driftwood's 100Mbps,3GOP setting.

Stray

@bkmcwd Looks like the cadence problem happened around frame 580 or so, I frames drop a lot in size there in some of it. Did the focus change or was the shot mostly static in that section ?

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