GH2 How to avoid "digtial rain"?

GHKAM

GHKAM

Well-known member
I shot some indoor footage where the subject was properly exposed (with lights at the front).

There weren't any additional lights filling the background. The footage exhibits streaks/"rain" of varying brightness going across diagonally in the background. This can only be seen when playing/not if paused.

I do have Flow Motion installed, but I don't think this is the issue because I had this before the hack and it seems this kind of specific shot (bright up front/dark in back) only has this issue.

I had the ISO set to 320; I raised higher, than lower as suggested here to avoid the ISO bug. But I did turn on/off the camera without doing this again/leaving it at 320. (Perhaps this was a mistake?) I shot something fairly important recently and I feel discouraged that the subject otherwise looked great, except for the rain.

Is this a symptom of the GH2 ISO bug, some inherent defect of the camera or this a matter of placing fill lighting in the background?
 
You don't mention what NLE you are using, but I'm going to guess that it is Adobe Premiere. This is a bug with how Premiere decodes AVCHD from the GH2 (I have never seen this behavior with AF100 or Canon C100 footage, but if anyone else has, I'd like to hear about it). The way around it is to transcode your footage using something else besides Adobe products (like 5DtoRGB for example).

As an aside, this does not occur with hacks like Sedna and Apocalypse Now. I would assume this would have something to do with them being Intra hacks.
 
I've fixed all of my Flow Motion footage by transcoding to DNxHD. I noticed the rain all over the place and transcoded the affected clips and replaced the footage in Premiere.

I guess to actually address your question about avoiding it in the first place, don't shoot with Flow Motion if you edit in Premiere without transcoding first. I use 5DtoRGB (on Windows).
 
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Gary Huff said:
You don't mention what NLE you are using, but I'm going to guess that it is Adobe Premiere. This is a bug with how Premiere decodes AVCHD from the GH2 (I have never seen this behavior with AF100 or Canon C100 footage, but if anyone else has, I'd like to hear about it). The way around it is to transcode your footage using something else besides Adobe products (like 5DtoRGB for example).

As an aside, this does not occur with hacks like Sedna and Apocalypse Now. I would assume this would have something to do with them being Intra hacks.
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Chris Adler said:
I've fixed all of my Flow Motion footage by transcoding to DNxHD. I noticed the rain all over the place and transcoded the affected clips and replaced the footage in Premiere.
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Thanks for the replies. I am using Sony Vegas Pro 12. Do I render out of Vegas uncompressed using the DNxHD codec and then import back in? I installed DNxHD on my PC, but it's not showing in any of the Vegas render drop-down dialogues.

I thought I had the same kind of digital rain pre-hack.
I have stuck with Flow Motion mainly because I have a bunch of the Sandisk 30MB cards. Would changing to a different hack remove the possibility of the rain?
 
Chris Adler said:
I use 5DtoRGB to make DNxHD versions of all of my MTS files before I edit.
Click to expand...

Thanks a lot, I'll check it out.
So, did you stay with Flow Motion and just incorporate the transcoding into your workflow?

edit: I converted an mts file to DNxHD using 5DtoRGB and Vegas rejected it, as well as rejecting a converted ProRes file in the same program.
Vegas accepted Lagarith and Sony YUV files, created in Vegas from the original mts, but it didn't address the rain. Even if a lossless codec did work, it's not practical being the files sizes are already big to begin with.

I watched the original, unedited mts files in Windows Media Player and there is no rain at all, which means this isn't an issue with Flow Motion.

I wonder if a script could be written in Vegas to address this...
 
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So, I used Vegas to convert the mts to DNxHD and replaced the mts in the project with DNxHD.

The rain is still there. Is my only option to go with a hack like Sedna and the 95MB/s cards?

Someone suggested that the NLE is bringing out a consequence of using a higher bitrate, possibly overriding the GH2's noise reduction. I'm pretty sure this symptom was there before the hack, did others also see this in the stock firmware?

I'm wondering if not everybody is seeing this because perhaps there is a defect in some camera batches, that others don't have?
 
You cannot use Vegas to transcode because it's just going to embed the "rain" in the footage as you have seen. Do you have QuickTime installed and updated to the latest version? Vegas will not decode transcoded footage without QuickTime installed for ProRes and the the Avid codecs have to be installed separately on top of that for DNxHD.

Unhacked footage can exhibit the same behavior.
 
Gary Huff said:
You cannot use Vegas to transcode because it's just going to embed the "rain" in the footage as you have seen. Do you have QuickTime installed and updated to the latest version? Vegas will not decode transcoded footage without QuickTime installed for ProRes and the the Avid codecs have to be installed separately on top of that for DNxHD.

Unhacked footage can exhibit the same behavior.
Click to expand...

Once I changed the install order, it worked and removed the rain.

Does anyone know of a batch script I could use with 5DtoRGB instead of converting one-by-one? (Windows 7/64)

Thanks all for the help.
 
Gary, have you seen the "Rain" with non-flow motion footage? I switched to Sanity and haven't experienced it since then, but I'll probably go back to Flow Motion and just keep transcoding.
 
Another thing you can try that works for me is, right click on the media on the time line, click properties and disable forced resampling. See if that works.
 
MBPRODUCTS said:
Another thing you can try that works for me is, right click on the media on the time line, click properties and disable forced resampling. See if that works.
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Still there either way with Smart Resample or Disable Resample, although I always disable resample in Vegas.

It's good there's a solution to this with the transcoding, but between stitching for example a one hour spanned event into a single mts file, then tanscoding to DNxHD, this is a lot of time and storage space. I guess I'll work out something where I'll trancode overnight, I just need to find a good batch script for Windows.

The image quality of the GH2 is superior to any consumer camcorder footage I've seen, but working with camcorders I've never seen this kind of background noise.
 
Gary Huff said:
You can avoid it by shooting with Sedna instead of Flowmotion too.
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Thanks, either way I need to buy more HDD space for transcoded Flow Motion or SDXC cards with Sedna. Any lockups shooting with Sedna 24H or 24L?

I would be horrified if shooting something important and the GH2 locked. I had a few lock-ups with 24H Flow Motion shooting with trees in the background outside but not when spanning with 24L.
 
One last thought on this. Since the rain shows up only under certain shooting conditions and only appears in rendered files, Flow Motion could be used and later do a quick render of all the clips from the NLE timeline/inspect the rendered file for signs of rain/instead of first transcoding all the files. If it's there, transcode.

Another option; with Vegas, and perhaps other editors, a file in a project can be replaced. After viewing a final rendered file even with fx; if only some of the files have rain and need to transcoded, then it would need to be considered if the quality of a DNxHD image can be matched to the original mts through tweaking.

Otherwise, the better cards/higher hacks.
 
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Gary Huff said:
This is a bug with how Premiere decodes AVCHD from the GH2
Click to expand...

It's not a bug with PP, the artifacts are in the footage itself. I and others have seen them outside of PP as well. (And apparently now even Vegas shows them.)

I really think this is a camera problem, seemingly affecting only some models. Users affected by this may want to investigate a repair process, because not one of my clips has ever shown the artifact. Yet I do see it on samples uploaded to the web.
 
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Guys, I have used Flowmotion 2.02 to shoot a lot of projects and have never had any problems like the "rain" you suggest. However, when I first started experimenting with hacks I did experience the "rain" as you call it. I found this to be velocity errors. Caused by either a slow or faulty flash card or a slow processor in your computer. Once I started using San Disk Extreme and Extreme Pro cards the problem went away. I believe I read that these cards are recommended especially if you are shooting anything above 50mbs. Also, Once I upgraded my computer with a faster processor and more ram, I have had no acquisition problems at all. I edit with Premiere Pro 5.5 Hope this helps.
 
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