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Official Low GOP topic, series 3
  • 1008 Replies sorted by
  • @CraftyClown
    My experience has been that patching the camera to pack more than 1920 pixels into each horizontal line puts excessive stress on the MJPEG encoder. This forces you to reduce the MJPEG bitrate to preserve stability, and that lowers the image quality.

    With the GH2 in VGA mode, a 2x anamorphic will produce an image that has a native 2.67:1 aspect ratio. Since this is wider than the desired widescreen frame, you have to crop the sides accordingly. In HD mode it's even more mismatched - a 2x anamorphic produces a native aspect ratio of 3.56:1.

    In VGA mode, 2160x810 would be the ideal frame size for a 2x anamorphic, allowing you to produce a 1920x810 cropped frame without any frame-stretching in post. My 100Mbps MJPEG patch does work reliably at this resolution:

    http://www.personal-view.com./talks/discussion/479/gh2-mjpeg-100mbps-low-light-1080p-patch/p1
  • @driftwood - *** Driftwood 'Quantum' ver 2 BETA ***

    The SH mode 720p60 GOP-3 mode uses P-frames. Is there some reason it can't use B-frames instead?
  • @Sage

    That looks good. I had a tweak myself, hope you don't mind. Was going for a look inspired by "Musgo".

    Cheers
    Sam
    Quantum102_00000.png
    1920 x 816 - 2M
  • @lpowell Encoder settings need to be switched for B frames. Problem is 720p 50 is fine on Intra but the shared settings for 720p60 result in 9 seconds recording on Intra hence Gop3 - im afraid we cant have it both ways. Oh how Ive tried! If you prefer b frames youll affect 50p on Intra. But theres no harm changing them both to gop3 and b frames.

    Thanks for your advice on anamorphic stuff. Im away shooting this wknd up north so not at 'pute to continue tests.
  • I still don't understand the advantages of shooting these specialty anamorphic settings. Someone enlighten me. Would it not be best to just shoot the best quality currently possible from the sensor (INTRA or other), and do stretching (horizontally) or compressing (vertically) in post? Is the only benefit of these specialty settings that it is pre-converted from squashed anamorphic state right off the camera? what gives? I don't get it. What's on the LVF shouldn't matter, there are monitors that can desqueeze for your live viewing benefit if that's what you're after. If you shoot full 1920x1080 and stretch horizontally with good software, you should get a very good, very large image, no? If 2x is too wide, lop a bit off either side of the bastard, or even use it to pan and scan a bit . . . but why these settings that compromise vertical resolution? Seems backwards to me. Am I missing something?
  • @driftwood
    Thanks for the inside scoop on B-frames in SH mode. In the case where we'd have GOP-3 in both 720p60 and 720p50, are there encoder settings 1-4 you'd recommend?
  • @B3Guy
    MJPEG mode is currently the only way to shoot at a 30p frame rate with synced audio. I find it very useful for conforming down the footage 20% to 24p, producing a very subtle effect that doesn't look like obvious slow motion. Plus, it's inherently Intra, which is all to the good.

    When shooting anamorphic, it is very helpful to see your exact framing in the viewfinder. With a 1920x810 image in the LCD, I can judge exactly how to frame each scene without guessing. In addition, when the camera does the scaling, it works on uncompressed data from the sensor, rather than the compressed 4:2:0 data stored in the file.
  • @LPowell Just so I understand, does this imply that one can currently actually hack the GH2 to shoot 1920x810 so the image is pre-cropped in camera and viewable that way on the LCD for framing purposes too?

    If so, that would mean that the people shooting 2.40:1 with tape marks on their LCD and intending to apply the correct aspect ratio/letterboxing in post (i.e. those not shooting with anamorphic lenses) could crop in-camera and monitor correctly too.

    So, could we take driftwood's AVCHD Intra settings and modify to shoot and display 1920x800 for example? Is this actually possible?
  • @ka00
    Yes, but it only works in MJPEG mode.
  • at 30fps. No 24. And it squeezes the vertical dimension, which technically lowers your vertical resolution. But yes, I see your point about it doing the conversion straight from the sensor. For Blu-Ray (other than the 30p), this is actually ideal, as B-Ray cannot go wider than 1920 anyhow.
  • My feeling about 2x Anamorphic is that the lower resulting resolution in the stretched dimension gives that anamorphic film feel. Likewise, the explanation that de-squeezing the image off the sensor before the compression, is a better option than doing it in post after running through compression.
  • I do not know if this is possible.
    With a 2x adapter, could a hack be developed that would make the GH2 record only a central section (I would put tape on my monitor) such that It records a ~2.4 or ~2.65 image? That is throw away the extra width before recording.

    And if I can help with any testing, I have 1.33x 1.5x and 2x adapters
  • @driftwood. No issues with both 24p H and L modes on Quantum V2 today.

    One interesting late day find was no issues with Sandisk 45/mbs card and a quick test on a 32 gb/ class 10 Sandisk. Then found that my blue label Class 10 16gb Transcend card worked in 24p H mode, but my 3 yellow labeled Transcend class 10 16gb cards got fairly quick write errors. Also, 2 clips from 16-20 clips on the Transcend 16gb class 10 blue card, show the clip length to be much longer than actual clip and playback is jumpy, but does show proper length in editor although play back isn't smooth. Can be rendered out and is ok.....

    More testing tomorrow on some other modes.
  • @kavadni, that's been #1 on my wishlist for a long time. I would love a 4x3 mode for AVCHD. Even to shoot native 4x3 for aesthetic reasons, sometimes. The closest thing we have right now is VGA mode but it's not very interesting to me at 30p.
  • @driftwood @LPowell

    I second LPowell on shooting 2x anamorphic VGA at 2160x810. I like it. If higher res would be possible, then fine, but i suspect not much gain from higher resolutions, so this in-camera solution would be great if optimized.

    Like @Oedipax says 30p isn't really interesting for VGA mode. So it would be nice if there could be changes made to the frame rate. Right now i just slow it down to 24p, but of course that isn't a very workable solution when shooting anything else than leaves. :)
    Now maybe the new firmware might make something like this possible? Anyone know already?
  • Hi guys!
    Although I was pressed with work last month, I could take slight time to adjust my patches recently. :-)

    @driftwood
    Although I could not participate in the test of your patch, I was seeing you doing uncanny work pleasantly.
    Since I understand the meaning of much of your advice recently, I make again the patch which is different from you according to my friend's request from now on.
    Thanks always!

    @soru
    Since I repaired the Q18 former patch, please try.
    In order to keep the I-frame size of 1M also at the time of high stress, I had to set Q value to 18.

    NOTE:
    In this patch, it is ignored except 24p(24H).


    bkmcwd 3GOP Test Patch 11.12.05.zip
    620B
    bkmcwd 3GOP Test Patch 11.12.05.JPG
    1297 x 633 - 194K
    q18_forest_sp.JPG
    1296 x 633 - 200K
    3GOP_SHINJUKU.JPG
    1295 x 634 - 177K
  • @driftwood
    Just bought a 2nd GH2 body for a cheap price so I can start testing your awesome patches again. Going to try out Quantum V2 the coming days.

    Do I need to use TerrAQuake on Transcend Ultra 32GB class 10 or can I use Quantum/SeAQuake as well?
  • @sohus glad youre back in action mate. Quantum2 held up on a commercial shoot up north this weekend - and the L setting wasnt bad at all too if you want long durations and spanning. 80% mode in L seemed fine too. But I got to take a look at the graphs to check now... ;-) So in effect you could try out Quantum v2. :-)
  • I did some further testing with bitrates and SD cards today outdoors in daylight shooting freeway traffic and golf course. I used SeaQuake 24H at 166mbs and 24L at 100mbs recording on a Transcend 64GB SDXC class 10 card. Both 24H and 24L spanned with no problems. However, the 80% slomo failed. I also tested the same scenarios with a Sandisk 32GB Extreme HD 30mbs class 10 card and the results were just the opposite. 24H and 24L recordings did not span and stopped at 4GB limit but the 80% slomo at 24L 100mbs worked fine. At least for the time being, I can cover all shooting variations using these two cards. Cheers,
  • I just tested quantum2 and quality in 24h is same to seaquake. 24L span on Sandisk 30mbs. The mjep I changed to resolution 1920X720 for work on anamorphic lens. But It show weird remaining time on the display screen. Show 2:11 remaining time on an empty 16gb SDHC. But remaining time increases as you go keep recording down to 48sec. Finally it stop recording when video reaches over 2GB. One major thing I think we need to fix is the noise level. iso 1600 is almost unusable. If it is clean noise, then I would be fine but this is unacceptable noise.
  • @driftwood - did some testing with your latest 'Quantum' ver 2 BETA settings @ 24L this night.
    Now there is intra below 80mbs i am in! Streamparser showed a significant drop in framerate after 12 frames with the 24L settings. Footage looks amazing though - very clean @ 800 iso with my Leica 1.4!
    Thanks again mate!
  • @ishvar it is intentional and dont worry about the drop after a second. It doesnt underrun/overflow and is on par in terms of quality with AQuamotion 2. By reducing the bitrate in the L setting (but not touching the H best quality setting) will drop down to a lower i frame size for spanning and long recording times but still retaining excelent quality and of course INTRA. This finding by @balazer is beginning to prove its worth it seems. :-) Well done to him.
  • @driftwood
    Yes now intra GOP1 is available @ a lower bitrates i am in! I have two GH2's - one with cbrandins 44mbs/2fps mjpeg settings and one with your latest's GOP1. This is videoheaven!
    The weakest point of the GH2 for me is the drop of sharpness @ 24p when doing slow horizontal panning/steadicam. Many times i shoot these @ 50fps. I am very curious what follows here after the new Panny firmware update!
  • @bkmcwd
    thanks! I'll try it.
  • Where can i find "cbrandins 66mbs/2fps mjpeg settings" ?
    Or any that allows 2fps for timelapse ?
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