Black pixel row at the bottom

R

Ruzo

Well-known member
Hi,
I am not a pro so I'm just reporting something that came to my attention. After using cgipro's script to fix the stair-stepping on a file, I used InstantHD to convert it to 1080p and that's when I saw a grayed line across the bottom:

1229883752.jpg



After further investigation, I realized that it happened because of a row of black pixels at the bottom which is also found in the original footage. InstantHD must be trying to blend the doubled black row into the expanded image, creating the grayed row. If I crop this last row out, it gives me a clean image at 1080.

So, my D90 seems to produce a 1280x719 image plus a row of black pixels at the bottom. Here is a frame over a blue background:

1229893167.jpg



I was thinking that cgipro's script (and other Stair-Stepping removal scripts) could be modified to include a crop of this last row in order to have a clean footage. I'm not sure how much the ratio becomes an issue but I could not see a real difference when going from 1280x800 to 1920x1080 compared to 1280x801. However, if there is a way to keep the ratio intact, I would prefer it.

If I knew a bit about AviSynth script syntax, I'm sure it would be as simple as adding one line of code.

I hope I'm not seen as "anal" after this :)
 
isnt the footage already in HD? and cant you just export as 1920X1080 with an editing program? why the need for InstantHD?
 
NJ3118 said:
isnt the footage already in HD? and cant you just export as 1920X1080 with an editing program? why the need for InstantHD?
Click to expand...

The footage is at 1280x720. The Stair-Stepping removal method increases the size to 1280X801. Instead of resizing to 1280x720, I wanted to go to 1920x1080. With InstantHD, it's supposed to give better results than just a direct export. Also, the instantHD process was just something that brought my attention to the strange black row. It wasn't my main point.
 
Last edited:
okay, maybe I confused everyone with too much information at one time. It's just that my whole experience brought me to discover the fact that the last bottom row of pixels of my D90 movies is totally black.
The up-scaling artifact is caused by this black row which is in all the original movie files.

Could anyone check one of their D90 files to see if the last bottom row is black?

Thanks.
 
I just opened one of my original .AVI files in Photoshop Extended and zoomed in very far. There is no black line either at the top or bottom. Are you 100% sure this isn't caused by upscaling or the stair step fix? I get a black line by using the displacement map method in After Effects though. Some displacement map filters have a "wrap around" checkbox to avoid this I think.
 
Martin Koch said:
I just opened one of my original .AVI files in Photoshop Extended and zoomed in very far. There is no black line either at the top or bottom. Are you 100% sure this isn't caused by upscaling or the stair step fix? I get a black line by using the displacement map method in After Effects though. Some displacement map filters have a "wrap around" checkbox to avoid this I think.
Click to expand...

Thanks for checking, Martin. I see the black row just by adding a new uncompressed file in a new 720p project/composition in Premiere and AE without any other processes. It may have to do with these particular softwares. I'll check one out in Photoshop and see if I get the same result.
 
Alright...I understand one more thing about this strange problem. It has to do with Premiere Pro and After Effects. Most D90 videos edited with PP have the same black line at the bottom. I say "most" because I've found some without this problem. Here are a few links to some of the movies with the black line. You can actually see the tiny black line while playing them on the browser's page (not fullscreen). It's easier to see if you compare the top and bottom borders. If downloaded, you should watch them without a black border like in window mode on Quicktime):

http://vimeo.com/2365765
http://www.vimeo.com/2430695
http://www.vimeo.com/2007364

I'm still trying to find the source of the problem so if anyone has a theory, don't hesitate to share it.
 
okay, i think i know what you're talking about. it's not video...it's nothing. i saw this when the d90 wasn't released and seen that the video didn't "fit" or was off center. if you move the video and center it in correctly it should fix it. It's your X,Y adjustments and I think that's what the problem is.

i'm almost sure this is a premiere pro problem, because it did this with my dvx footage from time to time. it hasn't done it for a while. dunno what could cause it either.

in premiere you just click on the video in your preview window and move it with the keyboard arrows.
 
it could be a field order issue. if your footage is interpreted as lower first and you drop it in an upper first sequence many nle's, like fcp, will shift it one row automatically. if this is the case make sure both are set to none/progressive.

/matt
 
Thanks for the replies guys.
In After Effects, if I move the footage's position, the black line moves with it so I'm not sure that it has nothing to do with video. Also, I'm pretty sure that I choose none/progressive for the project. As far as the interpretation of the footage, I'll have to check it out.

P.S. I don't know why but this forum will not notify me of new posts, no matter what settings I have.
 
Found the source of the problem!

It has nothing to do with position or fields, it's just a codec problem. For some reason, without the proper codec, the black line becomes part of the video as soon as it's imported in most softwares. After installing new codecs, it disappears.

Now, the Mainconcept codec (http://www.mainconcept.com/site/prosumer-products-4/motion-jpeg-codec-785/information-797.html) worked with Premiere and After Effects but the black line was still showing in VirtualDub which I need to run the stair-stepping script. I unstalled this codec and used the Morgan (http://www.morgan-multimedia.com/) one instead and there are no black lines anywhere.

However, now I seem to have some "crushed blacks" problems. Where could I find some info about how codecs behave in my system:

Which codecs affect realtime editing or not?
Why do they seem to affect an exported movie even if I choose another codec in the export settings?
Which codec is actually being used at a certain time or task?
Can I use something like Edius HQ codec for RT editing in Premiere?

So many questions, so little time... :(
 
yes i believe the d90 produces zero black, while many codecs clip at 16. the picvideo codec, which i've successfully used for 10 years, has a setting for it, maybe morgan has it too.

/matt
 
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