VideoHelp Forum
+ Reply to Thread
Page 2 of 2
FirstFirst 1 2
Results 31 to 44 of 44
Thread
  1. If anyone cares, here's a 10 second test video (MPEG 2, DVD compatible) with superblacks and superbrights, Y all the way from 0 to 255. The background behind the dark bars is Y=16, IRE=0, black. The bars behind the bright bars are Y=235, IRE=100, white. When viewed on a TV you should not be able to see the dark bars below 16 (ie, they should be the same shade of black as the background), or the bright bars over 235. The background behind the dark bars should be as dark as your TV can display. The dark bar labeled 30 becomes RGB=17 after conversion to RGB with a rec.601 matrix. You should easily be able to see that bar on just about any TV.
    Image Attached Files
    Quote Quote  
  2. Originally Posted by themaster1 View Post

    I need to use pc>tv otherwise my encoder will encode at up to double the required bitrate due to the red part of this text:

    Code:
    ColorYUV(cont_y=-20,gamma_y=100, off_y=-32)
    If you have an alternative to that red text or to pc>tv then please let me know.

    I don't understand histograms and stuff like the image you showed me so I don't know what that's supposed to mean to me. I looked at my video with and without the pc>Tv line on my TV and it looked near identical so I don't see any problem. This is the code I used:

    Code:
    # ColorYUV(levels="PC->TV") 
    ColorYUV(off_u=10, off_v=-2)
    ColorYUV(gamma_y=100, off_y=-32) # Add cont_y=-20 when not using PC-TV
    I don't seem to need the cont_y=-20 when not using PC-TV.

    Also guys I believe you guys CAN see a difference with the following line but I can't on my TV (I watched 2 clips with and without that line) so I'm reluctant to use something where it seems like it's not doing anything.
    Code:
    org=last Overlay(org,last,0,0,GreyScale(org).ColorYUV(cont_y=100))
    Quote Quote  
  3. Banned
    Join Date
    Oct 2004
    Location
    New York, US
    Search Comp PM
    We've surmised for some time that neither your PC monitor nor your tv are properly calibrated. On monitors and tv at factory settings, everything looks pretty much alike.
    Quote Quote  
  4. Most people don't use calibration tools for their TV and it's those people who I'm making videos for. My TV's default HDMI settings look perfectly fine to me. I tried adjusting the settings of it but they didn't give any better results than the default settings.
    Last edited by VideoFanatic; 14th Feb 2013 at 13:22.
    Quote Quote  
  5. Originally Posted by VideoFanatic View Post
    I need to use pc>tv otherwise my encoder will encode at up to double the required bitrate due to the red part of this text:

    Code:
    ColorYUV(cont_y=-20,gamma_y=100, off_y=-32)
    I don't believe that. I just tried it with the video that's currently in your first post and the difference was only about 10 percent. Without the off_y adjustment the video is totally washed out (lower contrast --> lower bitrates with CRF encoding).
    Quote Quote  
  6. Banned
    Join Date
    Oct 2004
    Location
    New York, US
    Search Comp PM
    You don't adjust a monitor by eye. Not ever. Period. There are tools and software for that.

    No, most people don't adjust their monitors. They look no better than the cheap CRT's they used for years. They can tell no difference at all, so I just ignore it when they claim their new hardware is "better". I've seen new LCD's that look worse than the old CRTs their owners threw away.

    Monitors and TV are adjusted to known standards. There is plenty of guidance, tools, and software for doing it. For those who don't see the improvements, or don't care, it's a waste of time. If my TV looked like theirs, I'd never watch TV.
    Last edited by sanlyn; 25th Mar 2014 at 12:42.
    Quote Quote  
  7. That's why I said "up to double the bitrate". Yes on this particular video the bitrate difference is 10%. But on other videos I've seen it use double the bitrate. I don't know what encoder you used but in Simple x264 Launcher at CRF 17.0 setting what I said is true.

    I never said anything about not using theoff_y=-32 text. See the quoted passage in your last post.
    Quote Quote  
  8. Sanlyn - I'm certainly happy to try and use tools to configure my monitor and TV. Could you please give some links to those tools?
    Quote Quote  
  9. Banned
    Join Date
    Oct 2004
    Location
    New York, US
    Search Comp PM
    The tools aren't cheap. We're talking $220-$250 USD. And that's one of the cheaper ones. There are cheaper ones. They're a waste of money. There are also $1000-plus versions -- again, a waste of $$$ for a PC monitor. Fortunately, for a typical PC monitor it's mostly automated -- follow a couple of opening screen prompts, and the software and hardware do the rest. The major cost isn't the software (you can even downlaod the software for free), but in the precision hardware device. They are difficult to manufacture. Here's the current EODIS3 product: http://www.amazon.com/Xrite-EODIS3-i1Display-Pro/dp/B0055MBQOW/ref=sr_1_1?s=electronic...+i1Display+Pro

    Here's an older article on what the screen shots look like and what's involved. This is for the older EyeOne Display 2 model, but the new process is similar: http://www.tftcentral.co.uk/reviews/eye_one_display2.htm

    TV is more difficult. Very much so. It would likely take a couple of days just to study the instructions. There's no automated way to do it, it's totally manual. Some TV's have no means of accurate calibration; they were not designed for it. Common brands that are equipped with extra controls for a proper calibration are SONY, LG, and Samsung. You use the same hardware device used for PC monitors, but you need some free software called HCFR on your computer. Run HCFR on the computer, connect the hardware colorimeter device to your USB input, place the colorimeter on your TV screen, and run the program. The software reads what your TV is doing and gives you several bar graphs and readouts to tell you what's happening. Then you adjust the TV and run the tests again. It usually takes several rounds and a couple of hours to run this stuff. Not for the faint of heart.

    Better yet, for TV you could get a popular TV calibration disc that's greatly simplified and guides you thru the whole process. It uses common TV controls like Brightness, Tint, etc., so you don't have to know anything about gamma curves, Blue bias, Red gain, and all that. The DVE disc has been around for years and is very popular (but the new one is for BluRay players only): http://www.amazon.com/Digital-Video-Essentials-Basics-Blu-ray/dp/B00ADJG56Q/ref=pd_cp_mov_1
    There's an older non-BD edition around, but I couldn't readily find one.

    Anyway, save this info for later. It took me a while to get into this stuff myself, I spent months investigating. And as I said...for many users, it really doesn't make much difference.
    Last edited by sanlyn; 25th Mar 2014 at 12:43.
    Quote Quote  
  10. It's hard to see subtle differences when you play one video after another. It's much easier when they are both visible at the same time. Use something like:

    Code:
    StackHorizontal(Crop(video1, 0, 0, width/2, height),  Crop(video2, width/2, 0, width/2, height))
    to get side by side views.
    Last edited by jagabo; 15th Feb 2013 at 08:31.
    Quote Quote  
  11. By the way, ColorYUV(Levels="PC>TV") is a contrast reduction (of all three channels). It's about the same as

    Code:
     ColorYUV(cont_y=-36, off_y=-2, cont_u=-32, cont_v=-32)
    or

    Code:
     Tweak(cont=0.86, bright=14, sat=0.86)
    Note that Tweak's cont argument is really gain, not contrast. Hence the need to add to the brightness.

    Code:
    gain: Y = Y * gain
    cont: Y = (Y - 128) * cont + 128
    Knowing that we can also use gain_y in ColorYUV to approximate Tweak:

    Code:
    ColorYUV(gain_y=-36, off_y=16, cont_u=-32, cont_v=-32)
    Last edited by jagabo; 15th Feb 2013 at 08:58.
    Quote Quote  
  12. Banned
    Join Date
    Oct 2004
    Location
    New York, US
    Search Comp PM
    Those would work. Squishing darks and brights into a more useable range is the idea, IMO.
    Last edited by sanlyn; 25th Mar 2014 at 12:43.
    Quote Quote  
  13. I know that my original script with the original video left lots of pixels with Y outside the 16-235 range, but they were mostly oversharpening halos and the black borders, not really parts of the picture. If you want to eliminate them you can use opt=coring in ColorYUV().

    One way of seeing where all the superblacks are is:

    Code:
    ColorYUV(off_y=240).Invert().ColorYUV(gain_y=2560)
    Click image for larger version

Name:	superblacks.png
Views:	395
Size:	55.4 KB
ID:	16276
    Last edited by jagabo; 15th Feb 2013 at 09:13.
    Quote Quote  
  14. Banned
    Join Date
    Oct 2004
    Location
    New York, US
    Search Comp PM
    Wow, those are pretty big numbers. I didn't think one could set gain that high, but I see that the spec doesn't state a limit. Guess you can. Nice demo.

    BTW, thanks for your levels.mpg posted earlier. Added it to my jagabo collection and will give it a run.
    Quote Quote  



Similar Threads

Visit our sponsor! Try DVDFab and backup Blu-rays!