i'm reopening an old bug segnalation (i opened a bug on the ffmpeg site but seems not related to ffmpeg)

this is the starting video: http://www.wcn.it/blacktest.zip


and this is an horizontal image to better see the contrast issue: (this on a Nvidia 9500GT)
http://www.wcn.it/contrast-issues.jpg

usually on 17.04.3 to fix the contrast issue i have to add manually the "mlt_image_format=yuv420p" option... but now adding this.. i have a GREEN output. (image 3)

this is a closeup to a random spot :


i've not checked the contrast on 17.08.1 .. but on 17.08.2 (not -2) the contarst was wrong (checked now)
i tried with 2 different footages from 2 different quadcopters... ( .mp4 extension)

this was an old image (17.04.3) with the Yuv420p correction: (720p AVI source - YUV 30FPS Mjpeg codec) on Radeon HD6670


on the 3rd image the contrast is good after rendering.. using DIVX ( MPEG-4-ASP ) and YUV420P on the 720p file


these are properties of source files

if someone whould try to fix the issue .. this is a minimal video (720p) with a black background to test renderings: http://www.wcn.it/blacktest.zip

and this is what happens from 17.04 to 17.8.2-2 releases when rendering:

original video black is from 0 to 8 ... and on rendered is from 14 to 22

[EDIT] SOLVED replacing the VGA card with a Nvidia GT610 ( ) and removing YUV parameters [/EDIT]

Maybe …

> "usually on 17.04.3 to fix the contrast issue i have to add manually the "mlt_image_format=yuv420p" option... but now adding this.. i have a GREEN output. (image 3)"

> "mlt_image_format the image format to request in rendering threads, defaults to yuv422"
https://www.mltframework.org/doxygen/properties.html

Figure 1 looks like the typical blur (flatten) to provide better compression. Have you tried another codec?

blacktest.avi: f=matroska vcodec=libx265 crf=%quality x265-params=:me=star:subme=3 (quality=16) … Minimal differences due to compression (3,1M / 1,6M).

Hello,
Isn't it linked to a Rec 601 / Rec 709 colorspace not properly recognized?
I'm far from an expert in the topic, but looking for these keywords would bring you some explanations, on WP or this forum
=> In clip properties, you have the "Force properties" tab, try checking Colorspace and/or "Full luma range"?

vpinon wrote:Hello,
Isn't it linked to a Rec 601 / Rec 709 colorspace not properly recognized?
I'm far from an expert in the topic, but looking for these keywords would bring you some explanations, on WP or this forum
=> In clip properties, you have the "Force properties" tab, try checking Colorspace and/or "Full luma range"?

tried the Full luma range, but nothing changes...

Stetsbequem wrote:Maybe …
Figure 1 looks like the typical blur (flatten) to provide better compression. Have you tried another codec?
blacktest.avi: f=matroska vcodec=libx265 crf=%quality x265-params=:me=star:subme=3 (quality=16) … Minimal differences due to compression (3,1M / 1,6M).

tried now with your rendering line (matroska) .. good compresison.. but background still GRAY... and not BLACK
have you used my blacktest.avi source?

what filters/effects do you use in your KDENLiVE project?

humanbeing wrote:what filters/effects do you use in your KDENLiVE project?

nothing just placed the clip on the timeline..

but.. today i replaced the Nvidia 9500GT with aNvidia GT610 .. and now renderings are well-contrasted... black is black
no idea about this... can't understand what this have to do with ffmpeg...

i've used same project of yesterday.. without any YUV parameter..


is this a "reproduction" effect? is the rendered video wrong .. but Nvidia GT610 play it using full scale color?
i've tried VLC / WMP / Windows10MoviePlayer and all 3 apps are displaying the right contrast.

This may also be due to the color management. Maybe it uses a different profile now?

Stetsbequem wrote:This may also be due to the color management. Maybe it uses a different profile now?

i haven't changed anything from default settings... i find also that to see the real black on VLC i've to disable the YUV RGB hardware converison.


because on 2 different VGA cards this conversion is different...

the Windows 10 Movie player display a real black... but with the Radeon HT6770/9500GT i have wrong contrast also on Windows Movie player. (arghhh)

going crazy with this thing... can't uderstand if a Video was rendered correctly .. or NOT... i don't want that is the final player to "FIX" a wrong conversion.. or a wrong color range...
this mean that maybe i can distribuite a Video... and other users can't see real colors.

P.S. the option [2] has nothing to do with the issue.. (i think)

I don't want to ride on it, but VLC can only support sRGB, color management is not supported. As long as only simple sRGB monitors are used, this shouldn't matter. However, continuous (and even calibrated) color management is common in image processing. The video editor, playback and monitor should be synchronized. The same applies to programs for determining the color values of screen shots. If you don't have a color management, at least the lowest common denominator should be found, here sRGB (compatible to BT.709). But I don't know Windows and my language skills are not sufficient to deepen it.

- https://en.wikipedia.org/wiki/Color_management