GH1 video stutter

Hi all,

I've taken a number of videos using my GH1 and I've been very impressed in general with the clarity and performance. However, I've had 2 with problems:

1. I was taking a video of 2 people quickly capturing a moment, but behind them was a glass wall with a lot of light. In the areas with movement, there were some very strange artifacts - not just blockiness, but quite strange effects. I attributed this to the light background.

2. The second I had just yesterday taking a video of our little one attempting to crawl. There was not a lot of movement in this (!), but several times during the 2 minute video there was clearly some sort of brief freeze/stutter again with some artifacts. Playing this back directly from the AVCHD file in VLC showed it very badly - frames appeared to repeat. After import into iMovie it was not so bad, but clearly there was some freezing and a minor jump to a subsequent frame. I wondered if iMovie was doing some adjustment on the import to limit the effects.

I've been taking these on FHD (1920 x 1200), and using a 4GB SanDisk Extreme III card rated class 6 (30MB/s) and with plenty of space on it.

Is this likely a storage card problem or something more fundamental? I've taken many other videos in the same format - some with more movement - and not noticed this before. Obviously I'm concerned that something may need fixing under warranty.

I'm happy to share samples of the videos in whatever format is best and load them somewhere suitable (my dotmac gallery?) if anyone has any interest in this?

Many thanks
Ian

I may have missed this in your post, what mode was the camera in? If you're using one of the modes where the shutter speed isn't locked (such as aperture priority) it can lead to problems like you've mentioned where the video stutters and jumps because the camera is varying the shutter speed.

If you're not using a fixed shutter speed I'd try using either S mode or tje manual film mode and lock the shutter at double the framerate. The luminous landscape look at the GH1 explains this issue in more detail.

John

They playback studdering I suspect is the playback software. Even on my i7 12GB system I get playback issues with a lot (not all) videos. I don't think it is the camera, but the playback software. Try playing back the videos on the camera and see if you see it there (I haven't done this myself.)

As for the other things I can't help you there. Can you post a sample of what you are talking about?

Video is not an easy thing. It is far harder to deal with than still images.

Robert
--
Ketchup is just over loved tomatoes.

JohnMcL7 said:

I may have missed this in your post, what mode was the camera in? If you're using one of the modes where the shutter speed isn't locked (such as aperture priority) it can lead to problems like you've mentioned where the video stutters and jumps because the camera is varying the shutter speed.

If you're not using a fixed shutter speed I'd try using either S mode or tje manual film mode and lock the shutter at double the framerate. The luminous landscape look at the GH1 explains this issue in more detail.

John

Click to expand...

Hi JohnMcL7
Many thanks for your input.

I took these in iA mode which is how I usually leave the camera, so not sure what shutter speed was selected by the camera.

When I review these in vlc, it does look to me like it's dropped frames that are happening as the effect is quite severe and makes the video unusable in this format. It is visible when I play it back on the camera but there it appears to be more just a quick freeze followed by a jump. I've now posted 2 mts files on my public iDisk folder at mobileme. Anyone can access these (though the larger file at 280MB may be frustrating). The smaller file (00003.MTS) shows the artifacts I got when taken with a glass wall behind. The second larger file (00006.MTS) shows the much more severe effects (there's also a strange optical effect on the mats - is this what's called moire?).

I can't use either video as is, and don't want to make any more mistakes!

My idisk public folder is http://public.me.com/ian.hobson

Thanks for any further tips!
ian

RobertBarnett said:

They playback studdering I suspect is the playback software. Even on my i7 12GB system I get playback issues with a lot (not all) videos. I don't think it is the camera, but the playback software. Try playing back the videos on the camera and see if you see it there (I haven't done this myself.)

As for the other things I can't help you there. Can you post a sample of what you are talking about?

Video is not an easy thing. It is far harder to deal with than still images.

Robert
--
Ketchup is just over loved tomatoes.

Click to expand...

Hi Robert

Many thanks for your suggestions. I don't think it's the computer though as I see some of the effects on the camera display (though vlc seems to handle it worse).

I've posted 2 sample files (unfortunately the primary one 00006.mts is very large). You're welcome to look at these and give your wisdom! 0003.mts is the smaller one taken agains a glass wall background to the outside.

http://public.me.com/ian.hobson

Thanks for looking (if you have time).

Ian

Hi, Ian. I could only now quickly view these with VLC on my work laptop. VLC does a pretty bad job decompressing the MTS files as you've noticed and in the first video I couldn't see anything that I wouldn't attribute to VLC in normal circumstances. Maybe the iA mode with varying aperture and continuous AF causes things to go in and out of focus so quickly that the codec can't quite handle it.

The stutters on the second one though had to be something else. It might have something to do with the shutter speed changing and maybe somehow the camera isn't able to feed the frames to the compressor (etc. scientific I don't know enough about), but it definitely looks like the data isn't ok. The card spec should easily be enough, but maybe they can have defective units as well causing failing writes and rewrites and subsequent stalling of the stream. So I can't say what the cause is but whatever it is I haven't encountered it myself. I would at least try with fixing the shutter speed as mentioned and trying another card before going for the warranty fix with the camera. And of course let us know if you find out what the cause was...

The effect on the carpet would be moire, yes. That might be something you could have only helped by less sharpening or getting the carpet completely OOF. Anyway it's difficult to predict and you can't probably even see it on the camera screen. Probably just something one has to live with on those rare occasions.

Ian Hobson said:

JohnMcL7 said:

I may have missed this in your post, what mode was the camera in? If you're using one of the modes where the shutter speed isn't locked (such as aperture priority) it can lead to problems like you've mentioned where the video stutters and jumps because the camera is varying the shutter speed.

If you're not using a fixed shutter speed I'd try using either S mode or tje manual film mode and lock the shutter at double the framerate. The luminous landscape look at the GH1 explains this issue in more detail.

John

Click to expand...

Hi JohnMcL7
Many thanks for your input.

I took these in iA mode which is how I usually leave the camera, so not sure what shutter speed was selected by the camera.

Click to expand...

I suspect iA will vary the shutter speed which will lead to stuttering and what appears to be dropped frames. I'd try using the video function with the shutter speed locked to see if the problem still occurs.

John