PAL GH2 First Impressions

Phil Rhodes said:
What of this speculation that the 50i is reweaved 25p frames?
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It was wishful thinking, and incorrect. http://www.dvxuser.com/V6/showthrea...25PsF-or-not&p=2176630&viewfull=1#post2176630 That thread contains links to 50i footage.

Edit: Apologies, I read your post in haste and thought you were asking about the speculation about 25PsF, but I realize you may have been referring to my own comment about 'reweaving', in that same thread. In which case I of course hope my own earlier comment isn't incorrect.
 
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What of this speculation that the 50i is reweaved 25p frames?
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The 1080i is definitely just that - interlaced. I've downloaded the footage from the thread that Graham H linked to and had a play with it. So as a combo with another GH1/13 or any other 25p camera in europe, it means there will be a workaround of either de interlacing or shooting in 24p and retiming, neither of which I'm really up for.
As a great little 24p cam though, it looks fine.
 
but I realize you may have been referring to my own comment about 'reweaving', in that same thread. In which case I of course hope my own earlier comment isn't incorrect.
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OK, so we have established you -can- get 25p out of the damned thing, but only if you're willing to turn AB-BC-CD-DE into BB-CC-DD?

Oh how I'd love to hear Jan Crittenden's explanation of how this is a good idea, if only for comedy value.
 
Phil Rhodes said:
OK, so we have established you -can- get 25p out of the damned thing, but only if you're willing to turn AB-BC-CD-DE into BB-CC-DD?

Oh how I'd love to hear Jan Crittenden's explanation of how this is a good idea, if only for comedy value.
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Why would Jan Crittenden want to make a comedic comment about a product from a completely different division of the company than the one she represents? She has no reason to need explain anything about the GH2. The comedic value is contained in your own comment. :)
 
Wishful thinking, I'm afraid. Ms Crittenden and I have, ahem, discussed Panasonic's decision-making in the past.

Of course, the disconnected thinking inherent in situations like this is in many ways caused by internal divisions in a corporate structure. Canon has always claimed that the 5D lacked useful frame rates simply because the people who built it were stills and not video camera specialists. I think it's a poor excuse, to be honest - how do you even get to be in charge of a development project like the GH2 or 5D without having at least enough general knowledge of your area to understand why certain things are necessary?
 
Phil,


Please forgive my stills shooter ignorance, but can you explain this or provide a link, and what software do you need to do this ?


Phil Rhodes said:
OK, so we have established you -can- get 25p out of the damned thing, but only if you're willing to turn AB-BC-CD-DE into BB-CC-DD?

Oh how I'd love to hear Jan Crittenden's explanation of how this is a good idea, if only for comedy value.
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What we're talking about is interlaced video, which is a technique developed early in the history of television as a way of regulating the bandwidth demands of broadcast TV. You can read about it in detail on Wikipedia, but the upshot as far as we're concerned is that you end up with the odd pixel rows of the image captured at one point in time, and the even rows at another point in time, producing pronounced discontinuities ("combing") where there's motion in the frame.

The conjecture is that in some circumstances, a PAL-region GH2 simulates this by splitting a single 25p frame into two fields (comprising, respectively, its odd and even lines), then combines the second field of one frame with the first field of the following frame. The result is that each frame appears to be interlaced, but two consecutive frames contain all of the rows required to build a single progressive frame. This will simulate the artifacts of interlaced capture without really simulating the motion rendering very well, and it's a very odd thing to do. They do seem absolutely desperate to provide either 50i or at least something that looks a bit like it. You could argue, by the letter of the rules, if they're taking the position that AVCHD doesn't have a 25p mode, that they're already putting something in a 50i AVCHD data stream that isn't really 50i.

If this were the case it would be possible to recover true 25p video using software such as AVIsynth, among other techniques, but it's a pain in the neck.
 
Murph100, the letters are a reference to my post in the "PsF" thread linked to above. In that thread, we determined that if you shoot in 50i with a shutter speed of less than 1/50, then successive fields are identical in a sequence ABBCCDDEEFFGGHHII. Because each frame consists of a pair of fields, the footage plays frame by frame as AB BC CD DE and thus still looks interlaced.

Using a scripting software such as avisynth (which have have to warn you has a bit of a learning curve), one could clip off the "A" and reweave as BB CC DD EE etc. However I suspect that footage, although now properly progressive, likely has 540 rather than 1080 resolution - that would need to be investigated further.
 
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Phil,


Thanks a mill for that, the haze is beginning to lift :beer:

So basically from what I've read so far here, the best way to get 25p from the Pal version is to speed up the 24p Cinema mode but shoot at 1/50 to sync with the grid ... am I right or will I get me coat :huh:
 
GrahamH, all I can say is thank God I found this forum before I ventured down the motion route, its like a daily blast of real life info which is invaluable. Thanks for the replies, and I'll try and limit the dumb questions :)
 
Why Can you just transcod ( modify) 24p to 25p in avid you have that option or do you loose some quality?

I just orderd gh2 maybe à misstake:( if Its not working like above. But shuld i shoot in 1/50? ( 24 p mode) Will that be correct?

Hoping for your help
 
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the best way to get 25p from the Pal version is to speed up the 24p Cinema mode but shoot at 1/50 to sync with the grid ...
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God knows. I hate to try and predict what they may or may not have been up to with regard to the relationship between shutter speed and frame rate, but theoretically yes, since (24 / 50) / 24 = 0.02 = 1/50s.
 
kainekainekaine said:
Only mode that has the option of 24p 24mbs is creative movie mode all other modes record in maximum 1080i. Intelligent auto, scene modes ect. You cannot select 24p mode for them. Also "auto" modes on 24p suffers from flicker, so only auto mode thats any good in 24p mode is shutter and manual, as aperture and program suffer from flicker. They could do with adding anti flicker mode, so you can have point and shoot 24mbs without worrying about flicker. The rest of the modes dont suffer from flicker as they are all 1080i 50, 720p 50 etc.
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Wait a minute...
so you can´t set shutter at 50, Iso at e.g. 160 and aperture on auto because the picture starts to flicker?
That´s unbelievably bad news! Makes the 14-140 Lens´ seamless aperture completely useless...
 
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Phil Rhodes said:
OK, so we have established you -can- get 25p out of the damned thing, but only if you're willing to turn AB-BC-CD-DE into BB-CC-DD?
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Someone with avisynth-scripting chops (i.e., not me) could easily write a script that would unweave, remove first field, and reweave. But what I'm not sure about is whether doing that will give a true 1080 image ... or a half-vertical res image. If the latter, it would be easier (but equally low-quality) to simply bob-deinterlace to 50P then decimate half the frames to get back to 25P.
 
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