Ozpeter
08-24-2009, 10:01 PM
I downloaded the tool mentioned elsewhere that checks the GH1 footage for missing frames (not that I felt I had a problem) and ran it over about 100 '720' format clips recently shot at a family event.
Most were fine but in three clips it reported huge number of dropped frames.
I played back those clips (in NeroVision on a PC) and could see nothing wrong.
Then I noticed that the places where the missing frames were reported were at a certain point in the clip right through to the end of the clip.
Then I noticed that in the clips, the point at which the missing frames were reported as having started corresponded with someone walking right in front of the camera, which was (apart from hand held wobble...) static at those points, just showing groups of people talking in a room.
Then I stepped through frame by frame, and at the point where the person walks in front of the camera, to the end of the clip, every frame is duplicated so in effect, the effective frame rate halves from 50 (PAL) to 25. What I mean is, in Nero, every time you press "t" it goes forward one frame. So I press ttttttt... and each time I see a change in picture content - but once someone passes across the camera, and the tool reports missing frames, I have to press tt tt tt tt... to see a difference in frame content.
I was shooting with shutter priority, shutter at 50th second, in CMPM (to the best of my knowledge and belief).
It's as if, faced with a major change in picture content (something filling the frame and moving quickly across it), the GH1 is panicing and only reading off the sensor at half rate right through to the end of the clip
Maybe this accounts for some of the comments about mud or jerking or whatever??
I guess I should now try to reproduce this under controlled and documented conditions.
Most were fine but in three clips it reported huge number of dropped frames.
I played back those clips (in NeroVision on a PC) and could see nothing wrong.
Then I noticed that the places where the missing frames were reported were at a certain point in the clip right through to the end of the clip.
Then I noticed that in the clips, the point at which the missing frames were reported as having started corresponded with someone walking right in front of the camera, which was (apart from hand held wobble...) static at those points, just showing groups of people talking in a room.
Then I stepped through frame by frame, and at the point where the person walks in front of the camera, to the end of the clip, every frame is duplicated so in effect, the effective frame rate halves from 50 (PAL) to 25. What I mean is, in Nero, every time you press "t" it goes forward one frame. So I press ttttttt... and each time I see a change in picture content - but once someone passes across the camera, and the tool reports missing frames, I have to press tt tt tt tt... to see a difference in frame content.
I was shooting with shutter priority, shutter at 50th second, in CMPM (to the best of my knowledge and belief).
It's as if, faced with a major change in picture content (something filling the frame and moving quickly across it), the GH1 is panicing and only reading off the sensor at half rate right through to the end of the clip
Maybe this accounts for some of the comments about mud or jerking or whatever??
I guess I should now try to reproduce this under controlled and documented conditions.