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GH2 Stutter/Judder/Strobe issues discussion
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  • @bueller
    I believe this is 720P, which I find does not have the same effect
  • @Elenion:"I think it is quite incredible that no one here can see the effect ..... just take a medium-wide lens, go outside in the garden..."

    OK, I did just that. I strapped an HMC40 onto the tripod along with my GH2, and went outside in the garden. What I see from both cameras is simply what I would expect to see from 24P from any camera. But judge for yourself:

    24P comparison.jpg
    826 x 1402 - 141K
  • OK, here are the tech notes, since those dont show up if you watch the embedded version of the Vimeo clip: A Panasonic GH2 and a HMC40 were mounted together on a pan-head tripod. Both were set to shoot 1080p23.976 at 1/50 shutter. The resulting MTS files were converted to Cineform avi 1080P23.976. These clips were overlayed in a 23.976 timeline in Premiere CS5.5 and exported to .MP4 for upload to Vimeo using H.264 720p23.976. Watch with HD on.
  • For what it's worth, we haven't had this problem on our GH2 any more then we do on our non MX'd RED. Progressive cameras create this effect, and the sharper the image, the worse it gets, or so had been our experience.

    Have people done an AVCHD vs MJPEG at 1080 comparison with this?
  • @CobyD: I just don't see 'it' in that example. Thank you for doing the test.
  • Hi there, one of the samples posted from above is from me (Gunther). Regarding strobing, while I haven't noticed anything wrong with the 1080p24 mode from GH2 (also compared to GH13) as can be seen in my comparison video above, what I have noticed is something strange: I always use the main trigger (release button) to start filming (the one used for photos normally). When I use the dedicated video button, the GH2 seems to switch and use the automatic 1080i50 mode (I have a PAL model). Could this be one of the main reasons for the observed problems, i.e. people not using the main trigger in creative movie mode and then getting shutter speeds, etc. messed up?
  • i've uploaded three test videos to my vimeo account (please excuse the salsa videos...). hopefully the content is what is required to most clearly show any problems.

    these are all raw MTS files which you can download from vimeo.

    filmed at 24H mode
    standard film mode 0 0 0 0
    i.resolution off
    i.dynamic off
    shutter 1/50
    iso 320
    WB incandescent
    lens is voigtlander 25mm f.95 at F2.8. focus is on the tape holding up the middle black object.
    video head is a manfrotto 701hdv
    I live in PAL land so lighting is 50hz.
    firmware is hacked to 32000000 24H mode (don't believe this will make any difference as bitrate doesn't get anywhere near 20Mbps in any of the videos).

    first video is a pan with the left edge of the middle black object on the right edge of frame, taking 7 seconds to get to the left edge of frame.



    second video is about twice as fast



    third video is much slower



    i have used ffdshow tryouts rev3914 (with no post-processing) to frame grab 50 frames (so about 2 seconds) of the first video to PNG format which you can download from here http://www.mediafire.com/?mseg7gma6dd0avv if you want to look at every single frame pixel by pixel as raw as it can get


  • @Bezerk
    don't you think that the strobe is evident even in a simple scene like this?
  • @Elenion
    Yes, I can see strobing in all three versions, but by far the worst in version #2. Although some strobing is present Version #3, it's is quite acceptable, depending on your presenetation medium. Internet would be OK, large screen projection I would have to check.

    @bezerk55
    If I can get your original files I can check them on a 40' screen with a Christie 2K projector later this week. I'd like to see for myself.

    BTW, I like the police siren effect as the black box "speeds by" in #3 ;-)
  • Watching the vids above, I have downloaded the middle (fastest / worst) one and stepped through it in VLC and can't see frame-by-frame what's wrong. But the fast motion does look a bit unpleasant and it reminded me of something I've seen recently, connected with motion and dark / light transitions.

    On a shoot I did that there is a REALLY strange effect where there's a "persistence" to black objects which looks odd - this video shows you an upload of part of the offending shot (otherwise untouched and only shortened and transcoded to mp4 for Vimeo as the original is 5 mins long). Recorded originally in 1080 50i but I'm wondering if there's some weird GH2 processing thing going on and that it's related to strobing in some way? Never seen this in my other cameras:

  • @Mark_the_Harp

    Not sure what to look at in your clip. Seems OK to me.
  • @bdegazio Have a look at the funny three-sided hole above the strings (it's the same shape as the one bottom of frame), as the hand crosses it from time to time during the clip. Do you see it apparently sitting "on top of" the hand as it sweeps past? If not maybe it's my monitor! That might explain why some of us are seeing these things and some aren't.
  • @bdegazio Just looked on another machine and it looks fine - the effect isn't there at all. So maybe if anyone else is seeing judder, have a look at my clip above and if you see the 'black hole effect' it might be a monitor and / or video card thing.
  • @Mark_the_Harp

    Downloaded the mp4 file, single-stepped though it and it looks OK. Just the normal superimposition you would expect from a certain amount of motion blur. The effect must be in your monitor, or maybe it's a perceptual thing like those "figure/ground" reversal tricks.
  • Could be. I couldn't see it (particularly) on stepping through either. Could it be that something in the GH2 is making these effects more noticeable on certain monitors (shutter speed not being what it says, for example)?
  • @Mark_the_Harp
    As a result of the various tests and discussion in this thread, I've come to the conclusion that the strobing is a combination of:

    1) common 24 fps strobing
    2) irregular decoding in playback (i.e sometime a frame is decoded a field or two late)
    3) interference in playback with 60 fps monitors
    4) possibly some exaggeration due to highly detailed GH2 image or absence of motion-blur
  • @elenion

    i don't see anything so offensive about it that dalefpf is saying, definitely not what his friend sees "as if the image paused every 1/2 second or so". having looked at the frame grabs of every single frame, it literally looks like a perfectly linear translation from right to left with constant movement from frame to frame across the entire sequence. there is no frame that is doubled up or shows more or less movement or more or less motion blur than any other. it literally looks like the scene was copied and pasted x number of pixels to the left from frame to frame. this is exactly what i would expect from a motion picture recording (or even an animation) of an object moving linearly from right to left.

    @bdegazio
    you can download the raw MTS files from vimeo

    i'm sorry if i sound argumentative, but i sincerely don't get it. if the GH2 is recording motion incorrectly in 24H mode, surely it would be evident in frame by frame analysis where the motion is non-linear from one frame to the next? a "pause every 1/2 second" should show up as less (or no) movement every 12 frames, but i can't see anything at all like that.

    edit: i removed a paragraph with my math which was totally wrong :)
  • @bdegazio: "2) irregular decoding in playback (i.e sometime a frame is decoded a field or two late) 3) interference in playback with 60 fps monitors"

    I agree about these kinds of playback issues; I find my footage looks different on my various different computer systems, but once I finally edit it to an HD clip for playback on a widescreen TV via a TViX, it becomes consistent and OK. One test I did for myself - and the one that convinced me that my raw GH2 footage was OK - was to transcode the .mts file to a format with intraframe compression (e.g. Cineform) and add manual 3:2 pulldown as I did so. My computer systems all play 24P packaged within a pure 60P intraframe footage very consistently.
  • @bdegazio I think 4) is a strong possibility. Maybe influenced by the unnatural way I'm in love with the GH2!
  • @bezerk55 There is nothing different about your 3 videos that I don't already see in every other HD video on the Web from any camera. If anything what I see is "tearing"...which I've already mentioned is a sort of pet peeve of mine with ALL HD videos I've come accross (No matter how cheap or expensive the camera). The faster the pan...the easier it tears. This is not GH-2 specific.

    With that said...I challenge any of you making these "strobing" claims to post footage like bezerk55's with a camera YOU think doesn't display ....um....strobing.

    Oh...@CobyD thanks for your footage. I see no difference in it either.
  • To my eye, this "strobing" effect is the same effect seen in any theater where a feature film is being exhibited. Features are shot and projected at 24 fps, as we all know. But, as I say, "to my eye".
  • @ian_t

    don't know if you have explored this tearing problem on your computer much, but if it is the type of tearing i am familiar with, it could very well be a problem of your video renderer not vsyncing properly or at all. on windows xp there are many video renderers depending on your video card capabilities and drivers, from the standard "video renderer" to "video overlay", VMR7 and VMR9. All have varying ability to vsync properly. On Vista and Win7, EVR renderer generally solves the vsync problem. the best way to find out would be to play with media player classic home cinema which gives you access to many different renderers including evr and evr sync and d3d9 fullscreen with many different vsync options. most importantly it has a "tearing test" to show vsync problems (it draws a red line travelling across the video to see if it doesn't line up properly).

    another very useful tool in mpc-hc that everyone here should probably check out before blaming the gh2 is the playback graph which shows you in real-time graph form the timing difference between what the video decoder requests of the frame timing, vs what is actually displayed on screen (jitter). See here for example of detailed statistics: http://imageshack.us/photo/my-images/827/capturestat.jpg/
  • +1 on the last comment. Almost certainly the machine not the GH2. I see tearing on one of my PCs and not the other.
  • The type of strange strobing I've noticed on my GH2 is due to sharpening, when you're viewing on LCD monitors.

    The LCD monitor issue hasn't been mentioned, and isn't widely understood - LCD pixels respond slowly, much slower than the specs lead you to believe. To get the faster response times, they are optimised for low-contrast transitions. The worst-case scenario for an LCD pixel is having to switch from black to white (or the other way). So when a lot of pixels have to change contrast quickly, LCDs do a really nasty pixel-level flickering that you wouldn't see on another display technology (even old CRTs).

    The worst example is a 1:1 black and white checkerboard pattern like this: http://protie.sweb.cz/checkerboard_1920_1080.gif . Be sure to view it at 100% without any scaling - now scroll the image slowly in your browser. LCD screens will flicker like crazy (but some screens are worse than others).

    (@Vitaliy_Kiselev, links break when they end in a full stop. http://protie.sweb.cz/checkerboard_1920_1080.gif. doesn't work http://protie.sweb.cz/checkerboard_1920_1080.gif . does (space between URL and full stop)).

    What that means for footage is that any moving high contrast edges, and especially where there is a lot of small contrast detail like grass, tree branches etc, will flicker on an LCD screen - but it's the screen causing it, not the footage. I see this effect quite clearly in the last video @Ian_T posted, in the earlier tree shots (especially around the grass blades), and I've seen it on my own 24p GH2 footage.

    That's partly why I'd like a hack that can disable sharpening altogether, -2 isn't fully disabled. It would also give a more smooth cinematic image and allow better post sharpening.
  • @_gl Contrast / LCD issues - totally makes sense. Would be nice to disable sharpening completely I agree.