GH4 video judder/strobing - a solution

d3xmeister wrote:

To be honest I haven't noticed anything disturbing on the camera's lcd while filming but I wasn't really looking for it so I can't say for sure that it does or doesn't judder, all I can say is I haven't noticed.

At 25fps (and 24fps) when panning EVF judder makes me feel sick, the rear LCD isn't much better.  At 30fps the EVF and LCD pan smoothly, and are a joy.

I just sold my GH4 and went with lighter Panasonic GX85. So after reading this I've looked at 24p footage from the GH4 and from the GX85 on my 60p HP professional monitor, and to my surprise there is no judder on any of the footage. I don't have anything like sports or very fast movements but footage with my kids playing is looking smooth from both cameras.

Generally you wont notice stutter/judder if the camera has a mostly fixed viewpoint, anything or anybody moving in the frames probably wont be moving that quickly or that smoothly. Judder/Stutter is mostly evident when smoothly panning - even slowly.

However, I was shocked to see the outdoor 30p footage from the GX85 does have some stuttering. GH4 30p footage that I have looks smooth. How can that be ? 30p footage I always shoot at 1/60. It does stutter from time to time. Playing on TV player, or nvidia shield media center, also stutters.

Curious. Was the GH4 footage that played smoothly 1080p and the GX85 footage 4K?

4K places 4x the load on your processor and graphics card, not many can play 4K smoothly for that reason, generally the footage needs to be re-encoding at a lower bitrate - which usually happens after editing.

Arh, just saw later you say both GH4 and GX85 were C4K.

So what I did was playing the same portion of the scene over and over again in VLC and I noticed something strange: the stutter happens randomly, never on the exact same frames, and once in a while it plays without stuttering at all.

Ok so it's not recorded in the footage (i.e. due to the new IBIS) which is good news, it must be a playback/display issue.

The judder I see is 3:2 pulldown. To render 25fps on a fixed 30/60Hz display, ever 6 frames the frame is doubled (this is the judder), like this,

1:1:1:1:2:1:1:1:1:2:1:1:1:1:2:1:1:1:1:2:1:1:1:1:2:  etc (that's slotting 25fps into 30Hz)

depending on exactly which frame I start playing, the doubling will occur at a different frame.

But I don't see how the files from the GH4 and GX85 can be different - in terms of playback.  Panasonic haven't bumped up the bit-rate have they?

That is unexpected, no stutter or judder on 24p on GH4 (C4K) or GX85 footage but stutter on GX85 30p.

This I do not understand.  Of course it's not just the display that has to support the correct refresh-rate, but also the graphics card delivering the signal.  Many laptops due to using 60Hz screens, have graphics-cards fixed at that refresh rate - even when connecting them to an external monitor capable of other refresh rates.

I'm thinking you should also try my experiment with your GH4 video and see if it stutters randomly or on same frames.

24 and 25fps stutters at different frames, as I described above, though only on my fixed 60Hz screen, on a TV 24 and 25fps plays back fine.

Let me know if you get to the bottom of the GX85 playback issue.