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| rjisinspired |
| Posted: Sep 5 2010, 01:44 PM |
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I just got done reading about how analog camcorders lie about black levels and DV video can come out a little on the bright side in the shadows when viewed on TVs. I had it happen a few times before in the past when burning files made from DV cameras that the TV image would come out a bit bright though this didn't happen all the time it seemed. Maybe it depends on the subject matter that is being shot also?
I just got done reading this:
http://www.signvideo.com/dv-black-levels-d...eg-2-part-1.htm
One recommendation is not to use software to adjust the black levels. I don't have a proc amp nor do I know anybody who does. I am tempted to go the filter route though because, well, I want to be done with my project, lol.
Is there a Vdub filter that can change the black level downward at the edit step so that the resulting video shown on TV will look normal?
I'm also at a loss on how an mpeg2 encoder can influence brightness though I do notice some settings when I used MJPEG that had sliders for luminance and chroma quality.
I do notice that as you lower the quality factor down in MJPEG, the Luma and chroma levels increase. They are all at "0" at the highest quality level of "20". I'm taking it that mpeg2 has something similar to brightness settings as MJPEG does
I have read not long ago that luminance and brightness are not the same, so maybe luma is responsible or maybe it's not? I'll have to get back on that one. This is getting confusing. I thought luma was the black and white channel "(Y)" and was related to brightness?
I have left MJPEG because I have noticed that re-encoding to MJPEG a second time, forget it. Not only do you get the fuzzies but you also get this posterized, moving, effect with solid colors, like non-textured with walls. It's pretty gross looking actually.
I'll be looking up some stuff more in the time being. I don't like asking a lot of questions all the time and it can drive people crazy but I do look up what I'm trying to find. Sometimes I am successful, sometimes not so. I try to get as much as I can cram in and then I totally lose it.
I did get Lagarith working but only in RGB mode. According to the text: Having the "prevent upscaling from decoding" while having RBG is suppose to do no color space conversion. Either I read that part wrong or it is a typo? Because for me it outputs RGB
I was able to use lagarith a while back and was able to use any color space without problem until I started using Vegas and I have an email where Ben told me to enable the "not to upsample" part for Vegas because if not Vegas will not be able to use lagarith compression at all. This was at version 8 of Vegas though, I will have to try this out in version 9 and see if I get a "no compressor" message in the video preview window like I did last year
As I end this post, I am using the info() command in avisynth on a file just processed as a test and the video file is coming out as BFF when all three sections in Vegas: Project properties, video properties and rendering properties are all set on NONE, progressive scan.
Is it me? is it my system? Is it my programs? Might be all of the above. It's been almost two days and I'm pretty much back where I first started with almost half of a full drive of garbage files. This has kept me up. Think some rest is in order. |
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| dloneranger |
| Posted: Sep 5 2010, 03:54 PM |
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Something wrong with your system... oh yeah, that there is... lot's of bits that should work seem to have trouble on your pc
Even the normal, 'built into windows' stuff like colourspace converters
The only time I've seen a pc like that was after someone had installed a 'codec-pack' that replaced bits of windows files
Then, when they uninstalled the pack, nothing worked properly again, as it uninstalled the files, but didn't put back the standard windows ones
Black levels
Ahh, they are so much fun
RGB uses levels from 0 to 255 for each colour, with all 3 at 0 for full black
But that's not how tv works
Think about the black bars on a widescreen clip show on a 4:3 tv, the black of the bars is much blacker than the darkest black of the film itself
So they needed a way to say blacker-than-black
TV etc use YUV, and the standard for that is to use levels from 16-235 for the brightness
0-15 means blacker-than-black, and 236-255 is whiter-than-white
Everything's fine as long as they everything agrees on using 0-255 or 16-235
Trouble is, some things use YUV with 0-255
And all hell breaks out
There's a filter 'alias format' that you can add to say 'look I know it should be 16-235, but it's not, heres what it really is'
Or in MultiAdjust, you can untick 'levels 16-239'
Then it'll read 0-255, but output 16-239
(I'm using 235 and 239 interchangeably here as Y uses 16-235, but UV uses 16-239)
Luma pretty much is the brightness
It's the channel that's adjusted in YUV filters that alter the brightness
It's not a linear scale though, so a value of 20 isn't twice as bright as 10
Colour and brightness is a more complicated system than you'd think at first look
There's hardware limits to work around, and adjustments for the ways our eyes work involved
There's two things you can do with that, either read until your eyes bleed and brains start dripping from your ears, or take a pragmatic approach and go with what looks best
(after all, all the maths and hardware are there to give a final result of what-looks-best)
See, in the end, no matter how good you think your video looks, you're relying on your eyes
And no two people see exactly the same due to differences in our eyeballs and brains
So you go for the 'average person approach'
Here's an interesting fact
About 20% of women have an extra colour detector in their eyeballs
They can distinguish extra colours that normal people can't
So from their point of view, we have the same problem as red/green colour blinds do to us
Now, how on earth can you adjust/check video for that
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| rjisinspired |
| Posted: Sep 5 2010, 06:04 PM |
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I haven't been to bed yet, lol.
Your right: reading all the tech text does make my eyes bleed. I get a good deal of it then comes along a link to some place which leads to more text of something related which provides even more links to other related.......... Then I forgot where I was in the first place.
If things were broken down and didn't branch apart so much, I wouldn't be taken on as much different things all at once. Just that one article is interesting then something else is interesting and then I'm gone.
You explained levels and techniques simply. I'm going to play around with the alias and your filter with the levels.
I like that pre-reduction feature. There was a building that was blown out in one of my videos and when I adjusted the sliders I got it to where the color of the building almost showed through, peach colored but with no detail but it didn't go gray at all which was really cool. After the slight tinge of peach it would gray-out if you moved a little ahead with the slider but backing off a little helped out.
I do have this burning feeling that installing that Flipshare application suite last month, on the 10th, might had done something. It's all bloat with little niceties that nobody probably uses anyway and I found that if you transfer say 20 video files through Flipshare software and don't delete them from the camera, you can't transfer those 20 files again. They are somehow marked from transferring again. You have to go into My Computer and get them from there. This could be a safety in case the Flip resets its video counter and one could accidentally erase a past file but sometimes I back files up, put them away, and don't empty the camera right away and maybe I want to get back to a past file which is on the camera.
One interesting mishap that occurred about 2 weeks ago was that my ogg audio collection showed up with Haali icons in-place of the xmplayer icons and when I went to open one of them, mediainfo utility popped right up as the app to open ogg files.  I think I have some association issues with a few media files it looks like.
I think I will have to some time soon redo the system again. After this project since there are huge files and I would need to split up work files if I was to back them up. I would rather get the project finished then get these big files out of the way so after I'm done with them I can just delete them.
Have Blu-Ray burners gone down in price yet? Boy what I would give to get one of those. Disks are still an arm and a leg from what I hear though, still.
I think I will try to rest now. |
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| dloneranger |
| Posted: Sep 5 2010, 06:29 PM |
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You can fix all these problems
But honestly - if there are many problems, it's nearly always faster to reinstall the os and programs
And you get the 'wow, its so fast now' effect after all the crud that has built up over the years has been removed
With my own systems, after installing an os, I only install what-i-need-when-i-need-it
Testing things or I-ll-only-need-this-once programs get run in a virtual machine
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| dloneranger |
| Posted: Sep 5 2010, 06:34 PM |
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One of the reasons I did that filter was a levels problem, but the other way around to yours
A filter I was using produced 0-255 levels for YUV, and I hadn't noticed
This was fine when watching on the pc
But, when I came to watch them on the tv, levels smaller than 16 came out as jet black
It was awful
eg a black dress or jacket would have jet black blocks moving over the surface
Had to redo the lot
Heres an example - the same video in virtualdub, and mpc(with the brightness turned up to show it clearly)
On a tv, the blocks are always visible
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| brucefield |
 Posted: Nov 15 2010, 04:11 PM |
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Hi there,
I just rode your message with a lot of attention. I feel like I have the same issue as yours but I still can't figure it out.
Without compressing or processing a video, it appears darker as it should be in VirtualDub. I believe that Dloneranger is definitly right about the "offset level theory" 
In my sense, the most important thing is to recover the exact same range of details. Thus I thought that I could get those details just by adding a gamma/offset filter but it just fail! If you have a look at the picture2, the black turned gray but still details no in here.
Ideally we would need an option just right at the open dialog windows in order to get the correct value INPUT. 
By the way, I could not find "alias format" filter. If someone has a link, I will appreciate for sure, Thx!
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| phaeron |
| Posted: Nov 22 2010, 01:12 AM |
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The brightness/contrast filter can push blacker-than-black and whiter-than-white details into visible range, if you maintain a YCbCr pipeline up to that point. The levels filter currently cannot due to mapping restrictions (the gamma curve is not well defined).
The output in your video players is likely being influenced by the settings in your video driver. Unfortunately, on many systems this is set to a setting that gives washed out blacks and whites for videos (0-255), and more importantly, is inconsistent with software rendering. You know if you have this problem if you change the video acceleration setting in your player to No Acceleration and you get the higher contrast level. |
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| Loadus |
| Posted: Nov 24 2010, 03:56 PM |
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| QUOTE (brucefield @ Nov 15 2010, 10:11 AM) | Without compressing or processing a video, it appears darker as it should be in VirtualDub. If you have a look at the picture2, the black turned gray but still details no in here.
By the way, I could not find "alias format" filter. If someone has a link, I will appreciate for sure, Thx! |
If you want to view the full tonality, keep the video in it's native
YUV format (YV12, or YUY2), so set the Video > Color Depth ...
to "auto" or "YUY2".
The lower 16 levels is not supposed to be visible in [CRT] television,
user needs to set the Brightness (Black Level) to comply with SMPTE
standards (there are calibration DVD's available for that).
The TV (again, CRT) should also be set to it's maximum power output,
with the Contrast (Power) adjustment - then the highest 236-255 levels
will clamp to high.
When you open YUV video in VirtualDub, use the Alias Format filter to
view all the tones (Alias Format comes with the latest VirtualDub version)
using the Full Component Range.
Also, when posting screenies, resize the image width to about 650, so
the board doesn't get stretched. Thx. : )
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