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GH2 Stutter/Judder/Strobe issues discussion
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  • I still am using making money with my GH13 hacked riggs... they look very film like and don't get the 'judder' thing. This is editing in vegas 10d and Edius 6 set to 23.97

    The GH2, when I tried to mix it in with GH13 footage.... at same shutter and light settings and then even slightly corrected... looked weird to me and it would not inter cut very well.... has anyone else noticed this or fixed this?

    I have a standard 60p LCD LG monitor (images look beautiful from GH13 and look very good from GH2 but motion cadence is just different and I can't figure out why. The motion blur doesn't look right, almost like the shutter is shooting faster than the setting it's set at.



  • Try hdtv natively supporting 24p display. That is 23.976 fps display. BTW I don't own such tv.
  • I have a projector that supports that.... but still there is a slight difference...
    I don't get why there would be a difference as the GH13 is at 23.976 and so is the GH2 right? It's not at exactly 24.00p is it?

    Anyway the hacked footage is looking sweet.... just wish it integrated better with my current gh13s... I'm probably going to have to shoot something all on GH13s or all on GH2H (i have no idea what the acronym for the hacked GH2 is so that's what I'll call it for now.)

    I've just returned to this news from a shoot so I have to catch up and go download and watch some footage. Is there much out there yet or only a few people have done it?
  • Go for all GH23s or whatever u call it. 24p is stable.
  • Looked at some more footage shot today by a friend of mine. He took the gh2 out on his break and shot using a shoulder rig. He's good at that kind of stuff since he shoots some of those CSI type shows. Anyway, we burnt a Blu- Ray and watched it on the projecter at the studio. The footage really did not look good. Static shots rock! Anything with a bit of movement looks terrible. My friend swore I made a mistake with the frame rate so we went back in and made two more discs. One at 23.976 and another at 24p. Both still looked strange. He thought it looked like the image jumped back and forth and appeared to almost vibrate. Some shots of the trees outside would strobe so badly that you actually did feel sick after looking at it for a while. I asked one of the guys from Universal to come take a look at it. He agreed it looked terrible. So, while I do agree that acting and story make the movie, I think this issue could cause you problems when trying to sell your film. I know for a fact that ligitimate movie companies do look at the quality of the overall product. I'm at a loss at this point and have thrown in the towel. I know some of you will make awesome movies with this camera. You'll probably end up selling them to Lucas or something. Noones word is the gospel. So take my posts with a grain of salt. Maybe I'm just a picky dickhead. My buddy did thank me for saving him $800.00 bucks, though. Cheers.....for now.......
  • Oh, just to clarify, he used a 23.976 timeline and a 24 timeline. Okay, I'm out.
  • @Dalefpf

    Great that you did the test, but am highly surprised at the results. Can you ask your friend EXACTLY what his settings were? Did he hack the GH2? If so what .ini did he use, etc.? This is critical info as you're laying some pretty damning pronouncements on us. I'm hoping it's 'shooter error' ;-) Maybe we can suggest some ini mods that may get him better results. Also, if you 'burnt' a blu-ray you transcoded it, so could you post exactly what program you used and the settings? I've totally hosed my GH1/GH2 footage on a blu-ray burn by having just one setting wrong and it wasn't necessarily the frame rate.
  • ...um...is it me or does it seem strange that all of these claims of judder don't have any accompanying videos for us to look at? I sincerily have no idea what Dalefpf is talking about. I've heard of these judder claims before with the GH-1. But I've yet to see someone show an example of this "judder" (that is supposedly different from any every other 24p camera).

    Now if one is referring to the "tearing" that we see in panning etc.,....then yeah...I always wondered why that happens (in GH-1, GH-2 and really....most CMOS footage I've seen). I don't see that kind of "tearing" in Apple movie trailers that originated on film. But I have to say...the GH-2 looks no different from any other HD camera (when it comes to motion).

    Dalefpf please post an example of what you are talking about. I've watched a ton of GH-2 videos with lots and lots of motion in them and understanding that your "terrible" opinion, in regards to its motion cadence, is purley subjective mine is nowhere as extreme. Seeing is believing.

    EDIT: What also comes to mind is how some folks with higher end cameras (like Red, AF100 etc.) have been seamlessy intermixing their footage with this camera. If there was that much of a difference it would (or should) have reared its ugly head by now....don't you think? But now that the hack is in full swing then......
  • I think that judder in gh2 24p is way more evident that in all others cameras. You can check it without pixel peeping, it is really obvious to my eyes. It would be fun to solve this issue (because it IS an issue), now when i've to shoot scenes with movements i use 720p and then frame skipping to get 25, or 80% slower (it helps much).
  • @Elenion

    After more panning tests with a pro kine tripod & head, I still can't tell if it's something in the camera or just the nature of 24 fps viewed on a 60p display. Shooting at 1080i60 or 720p60 are both MUCH better at smoothness, but so is shooting at 24H 80% and conforming back to 30. Unfortunately I don't have any other 24p DSLR footage to compare to.

    The GH2 strobing reminds me of screening rushes at IMAX in 24 fps back in the 90s. The giant screen really exaggerates the strobing problem. IMAX experimented with a 48 fps format to try to solve the it, but the stock costs were prohibitive. And of course Doug Trumball had Showscan running at 48 fps and now talks about 60 and 120 fps as future standards. 120 would be great because 24, 30 and 60 could all be derived from it without artifacts and of course it would produce fabulous slow motion .

    Strobing is also pretty visible sometimes in regular 24 fps theatrical movies when viewed on on a big screen.

    For now I'm satisfied with the motion quality of both the conformed 24H 80% and 720p60. Both options are slightly problematic though - the 24H-80% has no sound, and it pushes the codec very hard so there are often "card too slow" errors (with kae's 60m settings). And the 720p though very good IQ looks a little soft when up-resed to 1080.

    As a third option, I'm hoping that someone will pick up the ball to get the 1080 interleaved>progressive patch working properly, to give us a full-HD option without strobing.

  • @Ian_t

    There are already examples of this with footage posted on other websites. Do a search for gh2 strobe / stutter. Maybe you could lead me towards some gh2 footage with some actual moving camera work? I'm sure it's out there but most stuff is static.

    @kae
    The camera was not hacked. I had reverted it back. It was set to nostalgic.-2-2-2. In 24h mode with Nikon lenses. He used his dp6 monitor which he said looked as if the image paused every 1/2 second or so. I didn't get to see that. Keep in my I didn't tell him I was having any issues with the camera and he was excited to check it out. He dropped it into two different time lines in Vegas then just used the template settings for burning in DVD Arch. I wasn't looking over his shoulder but I trust he knows what he's doing. Looks the same with FCP as well.

    I'm not trying to rain on anyone's parade here. Sorry, if you feel that way. You could totally inter-cut GH2 footage with any camera out there. It is a great looking camera. But it doesn't have the same 24p look as most cameras. Work within this limitation and you'll have a great looking movie. Once again, this is just my opinion. If you're happy, then this thread was not for you. Last thing I want to do is make anyone second guess their camera. I was just looking for a possible answer for what I perceived as a problem.
  • @Dalefpf

    I think that it would only be fair if you did allow us to see the footage that you are seeing the problem with so that others can chime in with their individual observations. It's not about raining on anyone's parade - there are lots of experienced people here as well, wouldn't it be helpful to open up the dialogue with direct obervation of the footage in question?
  • If you use standard DVD rendering, which is 60i, you'll get the telecine artifacts. One way to test the cadence would be to use a turntable. Put a visible line on a record and spin it at 33rpm. If cadence is good the line should change by the same angle (8.25 degrees at 24p, if my math is correct) in each frame. Checking a rendered file (unless it is rendered at 23.xxx progressive) won't work. It also won't work if your project isn't set to 23.xxx as well. Single stepping should reveal the angle change between frames. If your timeline is actual 24p, you'll see a skipped frame every now and then. The width of the blurred line should give you the shutter angle as well - if it is 4.125 degrees, for example, the angle is 180. At 1/50 shutter you would see something like 4 degrees.

    Chris
  • @Dalefpf:

    Ok, since I'm a bit ignorant on what people are calling strobing I'll post some examples that I've come accross.


    I remember the following video from a few months back by Gunther Machu. This was a side by side test with a hacked GH-1 vs GH-2. To me...there was no difference in motion between the two. I see Blackout's request for him to film a more crowded area like a beach etc., but... a motion difference is not evident in this video (IMO).:



    Or... does strobing mean what PC CHongor mentions in this very recent video (where there is noise and pixelation in the dark areas)?:



    Or.... is strobing the effect we see in the following video @ 1:47 - 1:55? This is the type of strobing I am very much familiar with. This happens in every kind of video camera when it comes to using the wrong shutter speed while viewing monitors or around flourescent/street lights etc.:




    The following is a video test done by Mr. Barry Green displaying the effects of LED lights used with ALL CMOS cameras (including Red, F3, FS100 etc., etc.). It just so happens he is using a GH-2 for this test. I'll quote Barry's statement in this test:

    "This was a sample video to show what effect a dimmable LED light will show, when used with a rolling-shutter CMOS camera (in this case a GH2). The more you dim the light, the more prevalent these scrolling bands become.

    Certain lights (like the CN126) can be dimmed without these scrolling bars showing up, but some lights (like the YN160) cannot. The YN160 dims in discrete steps, it has a +/- button set that you press to move the light to the next dim stage. The CN126 has an analog wheel that you turn to progressively increase or decrease brightness.

    The YN160 works great and strobe-free at 100% brightness, but at any dim level the scrolling bars show up. You can try to chase them away by changing the shutter speed, but if you were using two of these lights you would probably soon find it impossible to get a strobe-free look. Unless you used them always at 100% brightness.

    Note -- this issue only affects CMOS camcorders; I tried the same test with the HMC150 CCD camera and there was no issue whatsoever. But any CMOS camcorder with a rolling shutter will show these same scrolling bars."



    Now this last video is something I would probably consider the closest to what you guys are talking about. It is a video with lots of dolly movements and one could really see a very ugly "strobe-like" effect in many of the shots. I've never seen this effect in my camera...but if this is what you are referring to then yes...that is a problem. This is one of only a few videos from the GH-2 I've seen it in. Then again...there are a lot of other things wrong in this video (Vimeo compression is one). I also remember early on seeing it in other cameras (especially GH-1) but folks called it "pulsing effect.":






    As you can see these examples are different from one another. Now you can hopefully understand why I asked what I asked in my last post. With that said...I'm not even sure if everyone here is referring to the same thing. So...when it comes to the subject of this thread it goes back to you Dalefpf. Can you point out in any of the linked videos above what you are referring to... or maybe provide your own example? I really want to learn more. Thanks.
  • By the way, the little record player test can tell you a lot about what your render settings are doing as well.

    Chris
  • Without one-to-one comparisons, it will be hard to say. It seems every new video camera goes through the same question regarding overall motion and judder.

    Grab another video camera and set the frame rate and shutter to the exact same settings. Next, carefully setup your shots so they are as close as possible in capturing the same motion and speed across the sensor.
  • @Ian_T Thank you for such a fantastic post, with the various examples. I think you're totally right when you say they are different - there are different things happening which we might / might not be seeing as the same effect (and that's leaving aside the differences in what equipment we're using to view the videos, our own individual tolerance and sensitivity to judder, and our powers of description)!

    Just using one example of a potential contributory factor, sharpening could well have an effect on perceived "judder" as it tends to make stuff really leap out at us, and the effect of sharpening varies frame-to-frame according to movement / compression / focus / shutter speed. I know I had a lot of issues with sharpening moving footage shot on my Canon XHA1s (HDV codec at a cbr of 25mbps).

    I'm not presenting that as an answer, rather suggesting it as one of many factors which could be individually or collectively causing this. There are probably so many potential things going on with this judder issue, I hope we all get to the bottom of this and arrive at some useful conclusions / settings / test procedures.
  • surely if this issue is so prevalent and obvious, it should be pretty easy to point to any number of vimeo videos with this problem. there must be heaps of 1080p24 videos with panning where it would be visible.

    i look back at all the 24H video i've taken and i can't see a problem at all, all pans are nice and smooth. the only big thread i read about this and after 9 pages it turned out to be a playback problem.

    there are so many variables here:
    shutter speed
    panning rate
    in-camera adjustments
    as well as playback variables:
    playing back on computer? is it the raw mts or transcoded? what decoder (ffdshow/ffmpeg, internal vlc, mpc-hc w/dxva, coreavc, ...)?, what renderer (evr, evr sync, haali, madvr, vmr-9, opengl, ...)? tried using ReClock?
    output device (lcr, crt, projector)? refresh rate of output device (50/60hz, 23.976hz, 120hz)?

    i might even go and shoot a quick pan tomorrow and upload the raw mts so we can all be looking at the same source footage as a comparison.

    i am genuinely curious as to what this issue is, mostly because i don't have any other raw footage to compare it to so i'm worried there is a problem here that i don't perceive but would be visible for others.
  • @DouglasHorn Hmmm.... I'm afraid I'm not going to be a terrible help on that -- unfortunately don't know much about final cut workflow -- I'm just importing directly into the bin at dnxhd 175 x. I know before avid got the avchd import bugs fixed, a lot of people were converting with external converters before bringing it in not sure if that would help.

    Good to know that you are having fcp7 problems though -- I've just moved over to a final cut shop and was actually going to get them to pull in some test files because we're going to be trying to match (as close as possible) a gh2 with f800 so I'll be fiddling with the cameras settings. But I'll look out for strobe now too. How are you monitoring the fcp7 footage?
  • I think it is quite incredible that no one here can see the effect. Obviously in the clips posted by Ian_T this effect is not evident because movements are minimal, most with tele, blurred with low dof, vintage lenses with few definition. And they are in most cases clips that want to be beautiful, then bad shoots are out.
    If you want to check the effect just take a medium-wide lens, go outside in the garden, close the diaphram and move the camera quite fast around the garden. You can see 24p strobe effect that in gh2 is way more evident than elsewhere. If you can't make this test i'll make a clip tomorrow or the day after.
    But, again, i think that the effect is obvious and i can't believe that you never noticed it.
  • lpowell explained this issue some time ago where high contrast vertical subjects were strobing in video because the GH2/GH1 is optimized as a stills camera not a video camera.

    posted by lpowell

    image

    Judging from the high-contrast vertical edges in the GH2_Strobe_issue.MTS frame shot, I think it's likely this strobing phenomenom is the same as the AF100 issue discussed in recent thread

    I analyzed a sample video with a similar type of pan-induced flickering, contributed by one of the posters in that thread:

    Quote Originally Posted by nugat View Post
    What we need to see is is really slow movement of an object across the frame for more than 7 seconds...

    I downloaded the MP4 file from Vimeo and imported it into a Premiere Pro CS5 25p sequence. At 100% magnification, I saw a prominent flicker on the edges of the potted plant as it scrolls across the frame, both at 25p and single-stepping through the frames. I've seen this distracting effect numerous times on high-contrast scrolling shots I've taken in daylight, particularly when shooting at high shutter speeds.

    As an experiment, I displayed the video at 200% magnification in Premiere Pro (with Full Playback Resolution). This dramatically reduced the flickering effect, though I could still detect small traces of flickering on the edges of the plant stalks. It's obvious to my eyes that Premiere uses a smoothing filter at 200% magnification that reduces the contrast on sharp edges.

    I believe this flicker is a side-effect of the sharpening filter used in the demosaicing algorithm the camera uses to convert the RAW Bayer Filter output into RGB pixels. When an object with a high-contrast edge moves across the frame, its alignment with the image sensor RGBG grid varies slightly with each frame. As a result, the calculated RGB values of the pixels on the edges can vary noticeably from frame to frame. In the early days of low-resolution 3D computer animation, we used to call these edge effects "farkle" to distinguish them from the flicker due to low frame rates.

    If you single-step through the video, you'll see that this edge flickering is only apparent in the instant that one frame is replaced by the next - it does not persist for the entire duration of each frame. In addition to the sharpening filter in the camera, the response time of the video monitor will have an effect on the flicker. Unfortunately, hi-res displays with faster response times (such as LCD's designed for gaming) will make the flicker appear more prominent. Slower displays will tend to smooth the high-contrast edges and minimize the flickering.

    There are two approaches that may help suppress this flickering effect. When shooting high-contrast moving subjects, using slow shutter speeds and minimum in-camera sharpening should help smooth out the sharp edges. In addition, post-production smoothing filters can be used to selectively blend problematic edges into the background. I'm sure the gross improvement I saw using Premiere's 200% magnification could be done with far more skill and subtlety.

    lpowell
    GH2_strobe.jpg
    841 x 478 - 127K
  • @Rambo

    I suggest to use high bitrate MJPEG for testing of any such issues.
    As it is simple intra encoder, so all motion artefacts can be caused by sensor only.
  • While not disagreeing with lpowell about the pixel-level stuff he's commenting on, let's not lose sight of the bigger issue being highlighted by those two side-by-side screengrabs (which I posted way back when on DVXUser). The original GH2_Strobe_issue.MTS was supposed to have been shot at ~1/48 (i.e. "180 degree shutter" for a 24P clip). But if that were so it should have had motion blur similar to that seen in the right-hand clip, which was a screengrab from a very similar pan I did on my GH2 camera . So clearly GH2_Strobe_issue.MTS was shot at a much higer shutter speed, for whatever reason, and so yes it strobed badly, as would be expected.
  • Question for those having the strobe problem: What filters are you using? I was shooting a bunch of panning b-roll on my 701 head today and had zero strobe, even in similar situations to above, even in hdmi playback. I almost always have a nd filter on, and often a black frost. Could that be softening or diffusing the strobe perhaps? Have people still experienced strobe with a strong nd filter?
  • Does anyone see the "Stutter" in this hacked GH2 clip from mpgxsvcd.