ABCDEFGHIJKMM pattern of frames in 1080 PAL

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Ozpeter

Well-known member
I think I've described the pattern correctly...

Scenario - test video on PAL 1080 with cars passing through the static frame. Shutter priority in Creative Motion Picture mode, various shutter speeds (can't see a difference in reported behaviour if shutter speed is low or fairly high).

I've tried stepping through it frame by frame on three simple editors.

Frame A = car in first position
Frame B = car in next position, let's say one foot further ahead.
Frame C = car in next position, another foot ahead.

etc etc

Frame K = car in next correct position, one foot ahead of frame J
Frame M = car two feet ahead of frame K - there's no frame L
Frame M = car in same position, frame is a repeat.

Then the cycle repeats.

In fact, in two out of the three editors, after 12 frames the car jumps twelve frames ahead then stays there for the next twelve frames, then moves forward frame by frame as expected, then 'jumps and jams' again for another 12 frames, though this only seems to happen when going forward frame by frame - normal replay looks smooth enough.

Given that it's PAL and a 25fps timeline displaying (in theory) 25 reads from the sensor, why the skip every 12 frames? It's like as if the sensor is 24 frames per second and a frame is being duplicated to create the 25 frames per second - or something. Anyone care to venture an explanation? Is this some consequence of interlacing being removed? I'm admittedly weak on that stuff, though I have been reading through links to theoretical discussions posted in various places here.
 
You answered your own question mate... The sensor is 24p and the PAL camera uses this hack to achieve 25p.

A Japanese camera company isn't going to manufacturer two totally different sets of hardware to cater for the international market, much easier to do it with software (and then lock it down so you get Japanese flickering lights when on holiday :kali:)

Small things though... a bit of a none issue. The GH1 is still a great camera whatever version you get and wherever you use it. I won't be swapping my NTSC for a PAL model in the UK - not while the RRP is £1299 anyway.
 
Hmmm.... having now rendered the timeline to HDV2 format, the duplicated frames are removed as if by magic and going through that render frame by frame reveals nothing amiss (that I can spot).

Which again goes to show that what you see from the GH1 depends on how you are seeing it.

Funny stuff, video.
 
This drove me batty for a while; I was seeing "duplicate frames" in Premiere Pro CS4.1 when scrubbing the timeline. So I made specific timecode notations as to where the duplicate frames were occurring, so I could see if there was a pattern.

And there wasn't. In fact, when I went back to verify my findings, the duplicate frames were no longer there -- they were moved!

Which just means -- YOUR FOOTAGE IS FINE. It is being recorded fine. But NLEs are still in their infancy in working with this format, and sometimes they get the wrong frame.

Seems to be only a problem during scrubbing; during playback it's fine, and in conversion through Voltaic or NeoScene it's fine.
 
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