Compression artifact or does my camera have a problem?

thisisapocalypse

thisisapocalypse

Well-known member
Hi everyone - so I've had this particular issue with my GH1 that I haven't been sure was related to the codec itself, or whether or not my camera might just have an issue.

So, my issue is particular. At the bottom of my 1080/24p footage I get a "band" all the way across the very bottom of the image that is about 8 pixels tall where there is a serious drop in detail, and also vertical lines of color, not in a fixed way, but in a way that almost looks like noise, it's in every bit of footage I have with varying degrees, but it's always 8px tall and always the same symptoms. All of these shots were taken locked down.

I can't tell if I've just got too much detail in the image for the codec to handle, or what it is exactly.

All of the above images were shot locked down on a tripod. All shot at 1080/24 on a Class 6 Patriot 16gb card and transcoded in Cineform (the artifacts show up both in Cineform and the straight AVCHD footage).

I've attached several images here, these are screengrabs from Vegas, full 1920x1080 - you'll have to pull them up and zoom all the way in and then scroll across, but if you do, you should see what I mean.

Anyone else experienced this? In preperation for the Feature film I'm about to shoot, I've been doing camera tests and while I noticed this problem when I got the camera, I thought maybe it was just that I was underexposing the area too much or it was just that I taxed the codec too much - in scenes that are light in color, you don't notice the band as much, but when it gets dark it gets nasty, especially if I do any grading, and it also seems like I'm seeing more compression artifacts overall than I'm noticing in other user's GH1 footage, and I've always felt like the footage didn't look quite as sharp either. I've gotten some good stuff, no doubt, but I'm wondering if something is not working all the way here.

I'm on Firmware 1.1

These happens at all ISOs, and I'm using various Canon FD lenses, I don't have the kit lens.

Take a look. Thanks everyone!
 

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I have never seen this before or heard of it before on the forums so my first inclination would be to say the camera is faulty. However, I would advise you to wait until some of the more experienced people on the forum, who may have a better idea of what this is and what's causing it, get a look at this.

You know, in all but the first shot, I had to look really hard to even notice it.

If you don't want to deal with sending the camera in for warranty you could always put some tape on the LCD and crop your film to anamorphic in post? :D
 
I took several second to really see it. I dont know butt seeing all this problems I´m kind of regretting buying GH1, and it id not even arrive.
 
Hi T.I.A.: I don't know what troubleshooting you've already tried, but here are some suggestions:

- Have you determined whether or not the issue is visible on a high-quality 1080p HDMI monitor directly connected to your GH1 during playback? If it's not visible direct from the cam on playback, then the issue is somehow getting introduced during NLE import, transcoding or other post process.

- If playback direct from cam does show the issue, have you tried recording & playing back new test clips using at least one other different SDHC Class 6 card to determine if your current card has a problem?

- If the above doesn't address your issue, have you tried resetting the cam (RESET in SETUP menu)?

- If still no joy, you should seriously consider updating your GH1 to the current firmware version. No guarantee this will address your issue, but worth a shot. Note: The firmware requires use of Panasonic brand batteries or fully-compatible 3rd party batteries.

Let us know what you find out.

P.S.: Cute dog!
 
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Thanks everyone, I went ahead and updated to v1.2 but I still have the problem. I have done a sensor cleaning and a pixel refresh, have not "reset" the camera yet.

As far as cards, I have two 16gb cards, one a Class 2 and one a Class 6, they both show the same problem. For what it is worth, when I click on the raw AVCHD files in Windows 7, it shows the "total bitrate" for each file, and I get numbers ranging from 10593 kbps to 16090 kbps and most of the files fall somewhere in the middle, which would make me think that I'm not killing the codec since it's not maxing out...but I don't know how variable it really is and if its recording too low either.

I have not tried playback straight from the HDMI, however the artifacts appear in the Panasonic player, the Windows 7 built in AVCHD compatible player, when playing the cineform files through the cineform decoder, and also in my NLE, so it does seem to have the issues right up front.

Honestly my concern isn't so much about the 8pxl band as I can crop that off if that is the only problem, but my concern is that it may be indicative of something not being right with my camera -- I know this is not a pro cam and has its issues, I just want to make sure that I'm living with the right issues and not the wrong ones.

Can any else speak to what bitrate range they are seeing on their recorded files with the GH1? The fact that I'm averaging around 12000kbps and I've never been higher than 16000kbps and yet I'm having the same issue in all the footage is a concern.

Anyone also recommend an SDHC card that they know works without issues on the GH1?
I read good reviews of the Patriot Class 6 card, which is why I bought it.
 
Anyone think it could be a function of noise reduction?

Everything above shot on the Smooth setting, -2 Contrast, - 2 Saturation, +2 Sharpness, - 2 Noise Reduction - Possible that the combination of the +2 Sharpness and the -2 NR is causing the issue?

I will test more today.
 
Update - the problem does seem less severe if I set exposure the "Hot Rod" exposure metering method - Sekonic incident meter set at ASA 640 for the GH1's ISO 100, and this time I properly lit this "scene" at least from an overall exposure standpoint (something I have not been doing in my other around the house testing as I was shooting with such fast lenses and the built in meter was reading proper exposure).

There are still artifacts in that bottom 8 pixels (always those bottom eight - like clockwork). I'm going to be shooting with the Panasonic Anamorphic adapter (for the DVX100) and so when the image is squeezed and put in a 1920x1080 timeline it becomes less noticable as those bottom eight pixels are shrunk - for the non anamorphic footage I'm going to shoot, I'm going to crop - so I think in the end even if I do have a problem it's going to be okay.

This image was done with the "Hot Rod Cameras" exposure setting advice - the meter on the camera reads this as 3 stops too low but it has given me one of the cleanest images so far with the fewest artifacts.
 

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The last image has trees with horrible teal trunks, unless they were painted like this in reality. The GH1 seems to have problems with (1) green and (2) lots of detail. Most of its "mud" images involve grass or trees or leaves or similar sort of thing. The last image as a whole is pretty soft.
 
What's the probability that 3 different samples, from 3 different cameras, would show the same problem?

This is a 2x zoom (using nearest neighbor) and cropped to the lower edge to show more clearly what's going on here, for those with "bad eyes"

2ur4byw.png


A full frame .png of each can be downloaded here
http://www.mediafire.com/?zlwkgq0oeyj

Sample 1 is from Barry's Chroma Key Smackdown
http://www.dvxuser.com/V6/showthread.php?t=190061

Sample 2 is from a GH1 review
http://www.imaging-resource.com/PRODS/DMCGH1/DMCGH1VIDEO.HTM
http://www.imaging-resource.com/PRODS/DMCGH1/FULLRES/zvid_AVCHD_1920x1080_00008.MTS

Sample 3 is from
http://sss1.sakura.ne.jp/download/20090424_205752.m2ts

Pulldown removal was done by avisynth, TIVTC.

It's unlikely to be decoder issue or pulldown removal issue, because the artifacts are there even when switching various decoders, or using different pulldown removal techniques. The artifacts are there even when viewing separate fields in the raw elementary stream

This doesn't look like compression artifacts; compression artifacts for h.264 look like "mud" and oversmoothing (as in sample #2 if you download the full frame)
 
Maybe its the thing with the greens that was the problem and so now Panasonic is fixing it with these new sensors that were rumored that have different exposure to red green and blue

"The green pixels are exposed 4 times longer than the red and blue, thus achieving the sensitivity gain"
 
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PDR said:
What's the probability that 3 different samples, from 3 different cameras, would show the same problem?

This is a 2x zoom (using nearest neighbor) and cropped to the lower edge to show more clearly what's going on here, for those with "bad eyes"

2ur4byw.png


A full frame .png of each can be downloaded here
http://www.mediafire.com/?zlwkgq0oeyj

Sample 1 is from Barry's Chroma Key Smackdown
http://www.dvxuser.com/V6/showthread.php?t=190061

Sample 2 is from a GH1 review
http://www.imaging-resource.com/PRODS/DMCGH1/DMCGH1VIDEO.HTM
http://www.imaging-resource.com/PRODS/DMCGH1/FULLRES/zvid_AVCHD_1920x1080_00008.MTS

Sample 3 is from
http://sss1.sakura.ne.jp/download/20090424_205752.m2ts

Pulldown removal was done by avisynth, TIVTC.

It's unlikely to be decoder issue or pulldown removal issue, because the artifacts are there even when switching various decoders, or using different pulldown removal techniques. The artifacts are there even when viewing separate fields in the raw elementary stream

This doesn't look like compression artifacts; compression artifacts for h.264 look like "mud" and oversmoothing (as in sample #2 if you download the full frame)
Click to expand...

Thank you for the excellent post highlighting this issue - I'm honestly relieved that it's not just my camera, I don't know how big an issue this really is but I'm curious that I have not seen anyone else post about this as of yet.
 
Car3o said:
i don't think that anyone has really looked at 8pixels out of 1080. i still don't see it from those images you posted.
Click to expand...

It's a band exactly 8 pixels tall across the entire bottom row where the artifacts occur, it happens to varying degrees but to some extent it is always there and highly visible actually in dark scenes - it may only be 8pxl tall but it can be in wide areas and it pops up in very bright colors - the images posted by PDR in this thread show it better than mine but it's the same problem.
 
I looked at some stuff I've done and I don't see it on my camera.

The only pic I sort of noticed it in, in this thread, is the one with the guitar. I really can't see it in the other pics.
 
this is truly pixel peeping at it's finest! Honestly, I don't see it in the examples either. When my face is 3 inches from the screen and I'm squinting to find it, but still having trouble, that's when I don't worry about it.
 
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