Averaging brightness?

[Skul 9]

I have some time lapse video where the auto-iris was not consistant resulting in the brightness jumping up and down from frame to frame. It's a minor amount but it is noticeable.

What filter should I use that will analyse the brightness of each frame and adjust it so that all frames have the same level, preferably one that I can set or at least be able to average it over the entire video?

[Leo 69]

http://forum.doom9.org/showthread.php?s=&threadid=93571

Play with its settings a bit ;-) I hope it helps

[Skul 9]

I've tried HDR-AGC but I can't get it to average the entire frame.

Ideally I would like a filter where you could specify by x\y coordinates a small area in the frame that stays static, like a wall, and use it to evaluate the luminance level.

That way, things like a big white truck driving by won't skew the overall luminance in a filter that might judge the overall frame.

[sh0dan]

Something like this perhaps:

global compensate = 0 #Will be overridden by conditional filter
global areamedian = 128 #Adjust to fit your images 0->255

v = avisource("...")
analyzeMe = Crop(v,0,0,64,64) # Area to analyze. Adjust 0,0 to a uniform colored area.
v = scriptclip(v, "Coloryuv(off_y=compensate)")
v = v.FrameEvaluate("compensate = areamedian - YPlaneMedian(analyzeMe)")


(Not tested at all)

[Skul 9]

I ran it but it's giving me an error that's hard to read. I'm a newb so I hope I am doing the right thing. When I first ran it it said "the scripts return value was not a video clip. I added "return(v)" (hope that's right?) and now virtualmod displays the video in the preview window but at the top it says something like this "E\MinMax:image must be planar!" with something else written underneath it so it hard to read. Below this line it reads "([ScriptClip], Line 1)"

[Wilbert]

Scriptclip needs YV12. Try


...
v = avisource("...").ConvertToYV12
...

[Skul 9]

That did it. Script worked perfect. Thanks everyone!

[Skul 9]

Video (http://rapidshare.de/files/1767386/TL_side_by_side.wmv.html)

Here's a side by side comparison of before and after the filter was applied. Scroll to bottom of the page and click the "free" button, scroll to bottom again and wait for link to video.

[FredThompson]

Whoa, this looks really cool. I've got some NTSC DV shot at a trade show in Paris 2 years ago. Some of the light is natural, some is flourescent. The flourescent pulses at 50 Hz. From looking at the sample video, there just might be a way to "rescue" the video. Boy! This is wonderful!

[HighInBC]

It truly amazes me how new video technology is forming so fast... I am sure there are large end production companies that don't know this one yet.

[FredThompson]

OK, I'm stumped. This isn't working with my DV at all. Why the heck does the script puke with a report that the returned argument is not a clip?

global compensate = 0
global areamedian = 128
v = AVISource("flicker.avi").ConvertToYV12()
analyzeMe = Crop(v,528,42,34,34)
v = scriptclip(v, "Coloryuv(off_y=compensate)")
v = v.FrameEvaluate("compensate = areamedian - YPlaneMedian(analyzeMe)")

actually, this will make it puke:

v = AVISource("flicker.avi")

huh?

[Wilbert]

It pukes, because no clip is returned in the last line, try


global compensate = 0
global areamedian = 128
v = AVISource("flicker.avi").ConvertToYV12()
analyzeMe = Crop(v,528,42,34,34)
v = scriptclip(v, "Coloryuv(off_y=compensate)")
v = v.FrameEvaluate("compensate = areamedian - YPlaneMedian(analyzeMe)")
return v

[FredThompson]

Oh, geez, what an obvious thing to miss. Think I'll slinnnk off now and get some sleep.http://home.mindspring.com/~fredthompson/Smiley-HeadSlap.gif