Broken codec concern, maybe me

P

Park Edwards

Veteran
I'm not much of a pixel peeper, but I did notice more than anything the codec breaking up in underexposed area's on the GH2. I've attached a screengrab for others to see. Is it my monitor? Or is this something that's a potential problem? I shot this at ISO 160 28mm 2.0. The corner in the back is really blocky. The avg bitrate was 18Mb.

http://imgur.com/ntAWI


here's a .tif in case people say it's the jpeg compression

http://imgur.com/YoIlM

well i guess imgur changes it into a jpeg image. so nevermind.
 
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Are you talking about the blocks on the far wall? I see compression blocks on my monitor, but could it be the jpeg compression more than anything else?
 
yes, the blocks on the wall. and no, it's not the .jpeg. I'll have to upload the .tif. I tried to through imgur, but it just changed it to another .jpeg. I knew that would be one of the first responses I would get.
 
I'm just curious if anyone else has experienced this. Maybe it was a bad setting in the camera. I was a little surprised that underexposed area's was breaking the codec up that bad.
 
stoneinapond said:
Tiresome.
Click to expand...

Yet true.

There are issues with the codec. Even with the production release. And that's just that. Everyone said I was a nutcase and must be seeing things. Yes, I was seeing things, and they were exactly what is shown here. It doesn't always happen, but when it does it tends to happen in the shadow areas, that is where the codec is taking away detail, and it's ugly. This is not an attack on GH2ers. I will still be buying it. But the codec issue is real. Basically, you have to work around it. Get some more light in that shadow area and it should go away.
 
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lets try to veer away from whether or not anyone was right or wrong, but rather if they can recreate what i see. putting more light in shadows isn't really going to solve anything. some things aren't meant to be lit.
 
Then you're only option is to re-frame a bit until you 'trick' the codec into analyzing the data differently. The ** cough ** was just a lil bit of sarcasm I'm not trying to be an ass... seriously, that's what the gh2 does to shadow areas sometimes and I saw it then and I still see it now - SOMETIMES. Also remember that there is variance in sensor quality from camera to camera I am assuming.. that's how it was on the GH1 so I doubt it will be any different with the GH2. Some people will have cleaner ones than others. Regardless of that, the codec on the firmware should all be the same, so I am saying the issue is there on ALL GH2s.. some people just haven't hit the bad spot yet and are not seeing it. try re-framing just a little bit and it might go away.
 
Workflow? Looks like a decoding issue. Wouldn't jump to conclusions. If you can upload a raw file I'm sure people can get to the bottom of it.
 
Nah, not a workflow issue. Straight from the .mts file on a Premiere timeline. I'll upload something tomorrow. Regarding framing: It's not that simple. The gh1's codec wouldn't break up this badly in under exposed area's, so I can't understand why this is happening the Gh2. Banding, sure, shoot a few stops underexposed and that's what you got, but this is was from an evenly exposed clip and in one portion of the image, the shadows, just breaks up. Reminds me a lot of how the d90's codec reacted to under exposed areas.
 
first, what camera are we talking about? I haven't actually seen anyone mention what camera we are talking about..


second, I'm not seeing the compression blocks. I just see codec noise.
 
Gh2. If you say it's codec noise, then we'll call it codec noise. I'm not sure what lingo people use for various problems. It's just an issue in an under exposed area. Also, want to make sure people know this was shot at 160 ISO.
 
Car3o said:
Nah, not a workflow issue. Straight from the .mts file on a Premiere timeline. I'll upload something tomorrow. Regarding framing: It's not that simple. The gh1's codec wouldn't break up this badly in under exposed area's, so I can't understand why this is happening the Gh2. Banding, sure, shoot a few stops underexposed and that's what you got, but this is was from an evenly exposed clip and in one portion of the image, the shadows, just breaks up. Reminds me a lot of how the d90's codec reacted to under exposed areas.
Click to expand...

I noticed this as well. It appears to me that the original GH1 would zap detail out of the black areas (pre hack) and so mud would occur in under exposed areas but it was a bit more muddy.. or smoother smooshy artifacts while the GH2 looks kinda blocky artifacts. It appears it is trying to keep the scene exposed , yet it's taking away detail data from that specific area and hence the ugliness. Again we'd all need to see the actual clip in motion but that's what I see in your frame grab.
 
Car3o said:
Gh2. If you say it's codec noise, then we'll call it codec noise. I'm not sure what lingo people use for various problems. It's just an issue in an under exposed area. Also, want to make sure people know this was shot at 160 ISO.
Click to expand...

well It's not blocking like what we were seeing with the GH1. it looks like gradations where the codec has to make a decision between boundaries of color and brightness. It's always worse in areas that are dark. I see it more in the yellow wall next to the bricks. Heck, on my GH1 I still see a little bit of blocking on brick walls even after being hacked with C settings.
 
We really need to see a side by side with a GH13 and a GH2 taking the same clip with the same settings. Yeah that's noticeable though.
 
Pretty sure that avchd codecs in consumer cams give preferential treatment to mid tones/ highlights in accordance with perceptual psych models
-There is a pretty good work around though.
 
Just curious, which Film Mode was this shot with? Cinema? Smooth? What were the contrast settings. I ask because "Cinema" pushes midtones and shadows down lower into the blacks compared to "Smooth". I'm trying to figure out which mode is best for low light and conrasty shooting.
 
I had a GH2 for 2 weeks and tested it against my GH13. The GH2 had noise issues in the blacks as well, where my GH13 did not. The ETC had strange artifacts as well . Too bad I really liked some of the new features it had. It just wasn't on par with my hacked GH1.
 
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