GH1 Stereoscopic Rig Collaboration

David Cole said:
The LANC Shepherd manual says.... A sync offset greater than 0.50 msec will produce just noticeable disparity for an average city street corner with wind, people walking, and slow moving cars. Action video with considerably faster motion and shorter shutter speeds, needs to have a sync proportionally better.
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LANC Shepher manual says it for STILL or VIDEO? I believe it says it for stills when you are using proportionally faster shutter speeds (so as that the photographed subject remains sharp). On the other way, it was also written somewhere (read the manual for LANC Shepherd) that it is enough to have 10-times better synch than the shutter speed. If the shutter speed is 1/50s, it is usually enough to have synchronisation within 1/500s. Why? Faster objects are blurred, so 10% difference in blurred object is not so distracting. Of course, it's always better to have tightly synched cameras, but in my opinion we should not exaggerate too much. Note that I am usually quite picky about synchs:

http://dsc.ijs.si/damir.vrancic/personal/TRV900/Sync/default.htm

There I've got less than 100ns (0.1 microsecond!) missynch. :happy:
 
Sync disparity is a sticky problem. It's nearly impossible to discern "good enough" without a large audience viewing the material for a prolonged length of time. Motion-blur actually doesn't cure this ill for negative-parallax content. The problem is that the loss of edge cues (occlusion) rivals the parallax cues... and the result is world-class headache-vision.

Also, differential encoders (such as MVC for 3D Blu-ray) are not efficient at encoding material with any temporal disparity. This may be an important consideration for some 3D shooters out there.
 
David Cole said:
The problem is that the loss of edge cues (occlusion) rivals the parallax cues... and the result is world-class headache-vision.
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You are right. If the clips have many fast moving objects (which are located close to the camera) there might be problems even if synch is slightly better than 1/10 of the shutter speed. However, by graduate improvement of synch the problems should vanish, since small missynch which is seen only for a couple of frames should not be noticed. Of course, if you have many fast scenes it might be problematic.

David Cole said:
Also, differential encoders (such as MVC for 3D Blu-ray) are not efficient at encoding material with any temporal disparity. This may be an important consideration for some 3D shooters out there.
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Good to know! I thought that encoding is made for both files (views) separately. I did not know that the encoding is made for one view and then additional encoding for differences between both views in Blu-Ray 3D. How does it work? Does it decode the difference between both pictures (like left minus right)?
 
crunchy said:
How does it work? Does it decode the difference between both pictures (like left minus right)?
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Both the left and right image streams are decomposed into macroblocks (same as MPEG2, H.264, etc). However, the MVC encoder can re-use macroblocks from either eye - eliminating the need to re-code and store picture elements that are shared in both eye views. Depending on parallax, out of phase elements will either require motion vectors to map them from one eye to the other - or - they will not be seen as the same element and the encoder will have to store both macroblock sets. In either case, encoder QP drops and consumes precious bandwidth.
 
David Cole said:
However, the MVC encoder can re-use macroblocks from either eye - eliminating the need to re-code and store picture elements that are shared in both eye views. Depending on parallax, out of phase elements will either require motion vectors to map them from one eye to the other - or - they will not be seen as the same element and the encoder will have to store both macroblock sets. In either case, encoder QP drops and consumes precious bandwidth.
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Interesting! Are specifications available somewhere? I would never guess that they are using such kind of decoding in BluRay 3D. I am wondering if BluRay 3D can also use separate macroblocks/pictures for each view.
 
Crunchy:

MVC is an addition to the H.264, MPEG spec, documented in ISO/IEC 14496. It's not generally available for free (have to buy the doc from ISO, but, you'll find some decent info floating around on MVC if you google it. For instance, http://en.wikipedia.org/wiki/Multiview_Video_Coding.

When you encode MVC, you can tell the encoder NOT to re-use macroblocks between eye-views. This is a worst-case scenario for this encoder, however. It will drop QP to the sub-basement.
 
David Cole said:
It's not generally available for free (have to buy the doc from ISO, but, you'll find some decent info floating around on MVC if you google it. For instance, http://en.wikipedia.org/wiki/Multiview_Video_Coding.

When you encode MVC, you can tell the encoder NOT to re-use macroblocks between eye-views. This is a worst-case scenario for this encoder, however. It will drop QP to the sub-basement.
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Thank you very much on that info (Wiki is not working, but it might be some kind of glitch...).
So, for home 3D movies, if we would like to have the same quality out of the BluRay 3D, it would be enough to code each view separately and the final size would be almost two times higher than when using motion-vectors? It does not bother me much. However, the question is how to author such BluRay 3D? I suppose that some low-cost solution should appear soon.

On the other way it is surprising that I haven't found any NMT or similar player which can send stereoscopic information through the HDMI cable (for separate left/right files or parallel, over/under pairs) by using frame sequential technique (similar to the BlueRay 3D players). NMTs are only capable of sending squeezed parallel format.
 
Here is a link to short stereoscopic clip (X-View, but separate left and right files are uploaded as well) made from parallel GH1s on a sliding bar synched by 3DSLR Master. The clips are synched to about 1.5ms or less.

http://vimeo.com/21907496

I am just making half-mirror setup and will post clips when I finish it...

Setup_1r.jpg
pencil.png
 
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Good news: after a long battle, the store that took my GH2 bodies order 3 months ago is finally about to honour them... well, I'll celebrate if they actually turn up, but they're due this week.

Bad news: apparently the GH2's ETC (1:1 cropping) mode that gives you a 2.6x zoom multiplier, as well as 720p recording, are reported not to work if anything is connected to HDMI - so no monitoring with either of those!

A pain for me as I wanted the zoom with my primes, now I'll have to frame the shots zoomed out and then watch zoomed on the built-in LCDs instead (doable I guess).
 
g.l said:
Good news: after a long battle, the store that took my GH2 bodies order 3 months ago is finally about to honour them... well, I'll celebrate if they actually turn up, but they're due this week.

Bad news: apparently the GH2's ETC (1:1 cropping) mode that gives you a 2.6x zoom multiplier, as well as 720p recording ...
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Finally you'll get them! This is great! Don't forget to buy external power supply module ("battery" with a plug). I think it is not supplied with GH2.
Why do you need so high zoom? You might end up with "cardboard" effect in stereoscopic image.
 
They've just told me they shipped : ). Now I have to find the lenses.

crunchy said:
Don't forget to buy external power supply module ("battery" with a plug). I think it is not supplied with GH2.
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Right, I can't even find them listed anywhere in the UK. A few stores in Europe are listing them, but only on backorder.

Why do you need so high zoom? You might end up with "cardboard" effect in stereoscopic image.
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I plan to only use the 14mm Panny primes, to keep the entire rig ultra portable, and also because with primes I don't have to worry about matching zooms manually. So the 2.6x zoom option is great because it gives me another choice without needing to swap lenses. On the GH2 you can even map this function to a dedicated button.

My rig will also have an adjustable interaxial, so I can avoid cardboarding.
 
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I have my GH2 bodies too - but - AC adapters remain on terminal backorder!! Anyone having luck finding them?

Thx,

David
 
crunchy said:
Here is a link to short stereoscopic clip (X-View, but separate left and right files are uploaded as well) made from parallel GH1s on a sliding bar synched by 3DSLR Master.
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On a quick view, looking good crunchy. There's an interesting colour shift on the 1st scene, was that shot on the bar, or your mirror rig?
 
g.l said:
There's an interesting colour shift on the 1st scene, was that shot on the bar, or your mirror rig?
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I also noticed it. The problem was that I used auto WB. Later clips had better colour matching. It seems that WB needs some time to get right colours.
 
g.l said:
I plan to only use the 14mm Panny primes, to keep the entire rig ultra portable, and also because with primes I don't have to worry about matching zooms manually. So the 2.6x zoom option is great because it gives me another choice without needing to swap lenses.
My rig will also have an adjustable interaxial, so I can avoid cardboarding.
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I see.

Adjustable interaxial cannot always avoid cardboarding if using too exaggerated tele lenses (you can brake 1/30 rule easily). However, in your case it's only about 2 times more "tele" than usual (73mm equivalent), so it should not be a problem when using it with care. It's good to have ETC.
 
DL'ed the side-by-side AVI and played it on 63" Sammy 3D plasma w/ Stereoscopic player. Awesome stereo, crunchy! Just awesome.

-- David
 
What the hell? I asked Panny UK about the DC coupler, this is their reply:

"The DC coupler and AC adaptor for this model are not marketed in the United Kingdom unfortunately."

??? Of course after the earthquake and tsunami all delays & plan changes are expected, but they obviously never planned to sell them here at all. Are they insane?


EDIT: confirmed, spoke to their parts dept., 'not enough demand in the UK, people tend to buy 2nd batteries instead'. That's fine for compacts, but for a high-end 'enthusiast' film maker's camera??

On the Earthquake front, asked if there are going to be exceptional supply problems or price rises. The guy claimed that all Japanese Panny factories are up and running now, but he did say that they need to look into supply issues with components they buy in.
 
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