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Still interlacing artefacts after DeInterlacing ?!?
Hello 🙂
Thats something I have to fight often. But this time somehow I would like to understand it 🙂
I have fast motion interlaced material. I simply deinterlace it but then I still have that so called “mice teeth” in the chroma channel, that become visible in the whole picture. I use footage from a Sony Z1, both 1080i and downconverted SD. The same for both.
I am aware of the chroma channel and its reduced resolution but isn’t that chroma generated in the camera AFTER the interlaced frame is captured ? I thought the full frame is captured (consisting of 2 Fields) of course uncompressed and then it’s going to be compressed … but by writing this explanation I find that I wrote part of my desired answer 🙂
There is chroma information that relates half to each field, but compressed in one pixel color-information.Is it that or could someone please explain it better. And maybe suggest solutions to compensate that.
Maybe heavy blurring of the chroma channel ? I tried that before and it made it sometimes a little better. But not all the time.Thanks for any idea or solution 🙂
Peter
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9 Replies
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I’m not sure I follow exactly but generally A camera’s CCD captures the image uncompressed, (perfect luma and chroma) then the recording format compresses the signal for the medium. In this case 4:2:0 Which will certainly cause some interlace artifacting.
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I don’t see how 4:2:0 could cause interlacing artifacts. Perhaps you are thinking of encoding signal processing time, but this affects odd and even fields equally.
Interlace artifacts are caused by trying to capture images of objects in fast motion, with the odd lines being recorded 1/30th or 1/25th of a second apart from the even lines.
Even if you capture uncompressed, you still have the physical reality of being unable to match the odd and even lines.
You need a better deinterlacer than what’s in the AE box.
The Re:VisionFX Fieldskit AE plug-in (around $90) could do it, as could Magic Bullet Suite.
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If you interpreted the footage as having fields (“separating fields”), you will see no teeth. AE doubles each field in draft quality, and interpolates in high quality.
I can only imagine that somewhere in the workflow, the interlaced video was scaled up or down without separating fields. This can happen even when scaling from 486 to 480 or 540. If this is true, you’ll see “teeth” of varying width, and you’re out of luck. Nothing can fix that if you don’t have access to the original unscaled footage.
Just to make sure, do you have a screengrab?
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There is no artifacting when viewed properly (without doubling or interpolating) but you better believe it’s there if you deinterlace without a high quality method.
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“In this case 4:2:0 Which will certainly cause some interlace artifacting. ”
Meaning when de-interlaced. As per the context of the original post.
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Hmm … by “viewed properly”, what do you mean? On an interlaced monitor?
Otherwise there’s always doubling or some kind of interpolation, since there are no complete frames when interlaced material has been shot.
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Artifacting meaning undesired side effects of deinterlacing and excessive chromatic noise beyond that which is expected from HDV.
Now, on say an LCD display if I were looking at a full frame of 1080i, I would see 2 fields, the HDV compression in this frame would be what is expected when viewed unaffected pixel for pixel or as a full frame. (“properly” may not be the best term – Perhaps the frame as a whole)
Interlace artifacting is a fact, weather the footage is HD 4:4:4 or HDV 4:2:0. However when interpolating (deinterlacing) an image with already less than perfect chroma sampling, the results arn’t going to improve.
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Ah – I see.
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Very clear, Andrew.
Viewing interlaced footage on a progressive display such as an LCD is rarely pretty if there’s motion involved. Old problem that’s getting much bigger as CRTs are discreetly disappearing out the back door.
Better deinterlacing algorithms make a big difference.
And for looking at pixel level blowups, it would be helpful to do some chroma smoothing, too.
If outputting to MPEG-2 for DVD or broadcast, chroma smoothing won’t have that impact on the 4:2:0 output though, because the HDV source is also 4:2:0.
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