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Panasonic LUMIX G / GF / GH / GX Series
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Old May 13th, 2013, 04:29 PM   #1
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GH3, advantages of 50 MBPS and timecodes

Hi, been wondering about this for a while so thought I would ask here.

50 MBPS

OK, I get ti, higher bandwidth = more video info which is good but was wondering what this means practically. I ask because I just did an edit that was delivered as a DCP and shown on a cinema screen (shot on GH2) and it looked glorious. So is it less noise is introduced when expanding contrast in grading? What are the other real world, noticeable, advantages.

Timescodes

One thing I have noticed with the GH2 is that the video/audio is generally 1 frame out of sync. I am guessing this is because it takes longer to process the video than audio so the video is written slightly later. With the GH3 there are timescodes. Does this mean that the video/audio will be in sync frame perfect always? Just to clarify I am talking about audio from and external mic (but also wonder if it is the same of internal mic).

The other question concerns syncing timecodes between multiple GH3s/GH3 and external audio devices. Can this been done.

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Ben
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Old May 14th, 2013, 07:06 AM   #2
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Re: GH3, advantages of 50 MBPS and timecodes

50mbps? You answered the question mostly. Over a stock GH2 (no hacks), the GH3 delivers a more robust image that has lower compression artifacts which is important for grading and scenes with movement (water, trees in the wind, hand-held). The 72mbps mode is even better but you have to be ready with lots of quality SD cards. The interesting part of your post is about the DCP. I make DCPs all the time and test them at various screening facilities, I find that depending on the theater that the process of projecting softens the image in a pleasing way that can mask some of the compression artifacts of the GH2. Not all, aliasing gets more noticeable on the big screen.

Regarding the audio sync issue: I have not encountered this problem on either camera. Does this occur during playback on your computer only, or is it present when you output to DVD, BluRay or DCP? Also some theaters have a one frame audio delay in their speaker systems if they have a microphone in the theater.
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Old May 14th, 2013, 02:15 PM   #3
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Re: GH3, advantages of 50 MBPS and timecodes

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Originally Posted by William Hohauser View Post
The 72mbps mode is even better but you have to be ready with lots of quality SD cards.
72mbps is the all-i I believe. From my research I came to the conclusion 72 was not nearly enough for all intraframe so the image quality is actually worse.

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Originally Posted by William Hohauser View Post
Regarding the audio sync issue: I have not encountered this problem on either camera. Does this occur during playback on your computer only, or is it present when you output to DVD, BluRay or DCP? Also some theaters have a one frame audio delay in their speaker systems if they have a microphone in the theater.
I noticed it when I was syncing non-sync audio. If you have a clap (slate) and sync the non-sync audio the waveform of the scratch audio is one frame out. A friend of mine also noticed this.
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Old May 14th, 2013, 03:43 PM   #4
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Re: GH3, advantages of 50 MBPS and timecodes

Which program are you using to sync the wild audio track to the video?

Regarding the 72mbps Intra-frame recording, while I can accept that somehow the camera doesn't record it well in certain circumstances, are you implying that 50mbps has a higher quality I frame for each GOP than the constant 72mbps I frames? I have not used 72mbps except for some brief tests in low light situations. Those tests showed me a slight improvement over the 50mbps files (less compression blocking, smoother gradients) but not enough to warrant me using it except in extraordinary circumstances therefore I have little practical experience with it. Certainly I find that 50mbps of the GH3 compares very well with 35mbps XDCam footage from my other camera where the stock 24mbps of the GH2 doesn't.
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Old May 15th, 2013, 10:34 PM   #5
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Re: GH3, advantages of 50 MBPS and timecodes

Having no GOP frames means you need a lot more data for each frames. I believe the data-rate people are using for all intraframe on GH2 hack is over 150 mbps. It seems GOP frames save a LOT of datarate so you really need to really crank it up. If you dont have the data-rate all frames will simply not be encoded well. Your test results are interesting, sounds like more research would be good. In terms of using lost of cards its not as if you are using double the space. If it really works it seems like a very good idea.
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Old May 16th, 2013, 02:15 PM   #6
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Re: GH3, advantages of 50 MBPS and timecodes

Standard ProRes HD 24p hovers around 120Mbit/s so it makes sense that the high end hacks are aiming higher.

For important jobs I rather use an external ProRes recorder via the HDMI and record back-up standard AVCHD on the camera. Unfortunately the GH series doesn't make using external recorders easy. I have not been able to record 24p out of my GH3's HDMI yet (although the external monitor takes it OK) and none of the external recorders on the market currently advertise that they work properly with the GH3 (at least the last time I checked about a month ago).
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Old May 19th, 2013, 04:41 PM   #7
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Re: GH3, advantages of 50 MBPS and timecodes

William,
I record gh3 hdmi out signal on Convergent Design's Nanoflash flowlessly.
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Old May 19th, 2013, 07:42 PM   #8
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Re: GH3, advantages of 50 MBPS and timecodes

24p? My Blackmagic Designs UltraRecorder can only do 60i from the GH3 even if the camera is recording 24p on the SD cards.
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Old May 20th, 2013, 01:33 AM   #9
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Re: GH3, advantages of 50 MBPS and timecodes

True, I've never tried 24P. I am usually shooting 720P50 and 1080P25.
I'll give it a try tomorrow and come back to you.
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Old May 27th, 2013, 10:17 PM   #10
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Re: GH3, advantages of 50 MBPS and timecodes

Quote:
Originally Posted by William Hohauser View Post
...none of the external recorders on the market currently advertise that they work properly with the GH3 (at least the last time I checked about a month ago).
Atomos seems to think the Ninja 2 works with the GH3: H2 - Ninja Tested with popular DSLR cameras - ATOMOS


Cheers,

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Old May 28th, 2013, 03:21 PM   #11
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Re: GH3, advantages of 50 MBPS and timecodes

Yes 30p or 25p works fine but what about 24p? This is the answer I haven't been able to get.

As I have experienced, my BlackMagic UltraStudio Thunderbolt Record adaptor works fine when the GH3 is set at 30p or 60i but something about the UltraStudio causes the GH3 to still output 30 fps when it's recording 24p to the SD card. No pulldown on the 30p clips the UltraStudio makes on my laptop, just straight 30fps, every frame different. The same clips on the SD card are true 24p. How this is possible I don't know. My Lilliput monitor, however, receives true 24p from the GH3 and says so on the screen. It's easy to see the frame rate is correct just by panning back and forth.
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