Scene clip in VSE affecting the image strip above it #38344

New Issue

Garrett · 2014-01-24T00:04:12+01:00

Garrett commented

2014-01-24 00:04:12 +01:00

System Information
OS: Ubuntu 13.10
Linux kernel: 3.11.0-15-generic

Graphics:
VGA compatible controller: Intel Corporation 4th Gen Core Processor Integrated Graphics Controller (rev 06)
3D controller: NVIDIA Corporation GK107M [GeForce GT 750M] (rev a1)

Blender Version
Broken: 2.69-linux-glibc211-x86_64 (r60991) and 2.69-c700103-linux-glibc211-x86_64

Short description of error
In the Video Sequence Editor, I have a scene clip and above it, an .jpg image strip, set to Alpha Over with Opacity: 100. Since the opactiy is 100, the scene clip underneath it should have no effect on it, but it causes it to be more dim.

I was unable to reproduce the error from a new file, but the attached file demonstrates the bug.

Exact steps for others to reproduce the error
Here is a folder with the .blend file and the .jpg image used in the VSE: problem_with_alphaOver.tar.gz

To see the error:

open the file, make sure it's at frame 21, then hit F12 to render.
now go to frame 22 and hit F12 to render

Notice the difference - frame 21 is more dim than frame 22. (I've included .pngs of these frames). If you do not immediately see the difference, then open the resultant rendered .png images in Gimp and go to pixel (664, 34). In frame21.png, it has RGB value (22,22,22), while in frame22.png, it has RGB value (111,111,111).

**System Information** OS: Ubuntu 13.10 Linux kernel: 3.11.0-15-generic Graphics: VGA compatible controller: Intel Corporation 4th Gen Core Processor Integrated Graphics Controller (rev 06) 3D controller: NVIDIA Corporation GK107M [GeForce GT 750M] (rev a1) **Blender Version** Broken: 2.69-linux-glibc211-x86_64 (r60991) and 2.69-c700103-linux-glibc211-x86_64 **Short description of error** In the Video Sequence Editor, I have a scene clip and above it, an .jpg image strip, set to Alpha Over with Opacity: 100. Since the opactiy is 100, the scene clip underneath it should have no effect on it, but it causes it to be more dim. I was unable to reproduce the error from a new file, but the attached file demonstrates the bug. **Exact steps for others to reproduce the error** Here is a folder with the .blend file and the .jpg image used in the VSE: [problem_with_alphaOver.tar.gz](https://archive.blender.org/developer/F74615/problem_with_alphaOver.tar.gz) To see the error: - open the file, make sure it's at frame 21, then hit F12 to render. - now go to frame 22 and hit F12 to render Notice the difference - frame 21 is more dim than frame 22. (I've included .pngs of these frames). If you do not immediately see the difference, then open the resultant rendered .png images in Gimp and go to pixel (664, 34). In frame21.png, it has RGB value (22,22,22), while in frame22.png, it has RGB value (111,111,111).

Garrett commented

2014-01-24 00:04:12 +01:00

Changed status to: 'Open'

Garrett commented

2014-01-24 00:04:12 +01:00

Added subscriber: @Garrett-8

Sergey Sharybin self-assigned this 2014-01-24 08:51:20 +01:00

Sergey Sharybin commented

2014-01-24 09:38:21 +01:00

Changed status from 'Open' to: 'Resolved'

Sergey Sharybin closed this issue

2014-01-24 09:38:21 +01:00

Sergey Sharybin commented

2014-01-24 09:38:21 +01:00

This isn't actually a bug, rather a specific of render pipeline with color management disabled (Display = None disables color management).

It leads to displaying image buffers as as on the display. And what's happening is:

Sequencer Preview sends image which is always in sequencer space (which is sRGB regardless to whether it's float or byte image) to display without color management. This makes it looking properly on your sRGB display.
On the frame 21 there's a scene strip under the jpeg strip. Scene is being rendered to linear float buffer and hence implies conversion of byte jpeg image to float buffer as well. Then sequencer applies Alpha Over (which basically does nothing because of opacity). And sequencer outputs float buffer back to render pipeline. Render pipeline converts this float buffer to linear space to match the rest of pipeline. Image editor displays this image as-is, and viewing linear buffer on sRGB screen will make image darker.
On the frame 22 there's nothing under the image strip and it's being output as-is to the render pipeline as byte buffer in sRGB space. Render pipeline does nothing in this case with render result (because it's a final point actually and linearizing byte buffer is lossy). This makes it so image editor displays sRGB byte buffer displayed on sRGB space which makes it look as it's expected.

This might sound complicated, but disabled color management is confused on it's own and it's only left there for compatibility issues. You're not actually supposed to use such a pipeline in modern environments.

Thanks for the report, but it's just a specific of color management in blender..

This isn't actually a bug, rather a specific of render pipeline with color management disabled (Display = None disables color management). It leads to displaying image buffers as as on the display. And what's happening is: * Sequencer Preview sends image which is always in sequencer space (which is sRGB regardless to whether it's float or byte image) to display without color management. This makes it looking properly on your sRGB display. * On the frame 21 there's a scene strip under the jpeg strip. Scene is being rendered to linear float buffer and hence implies conversion of byte jpeg image to float buffer as well. Then sequencer applies Alpha Over (which basically does nothing because of opacity). And sequencer outputs float buffer back to render pipeline. Render pipeline converts this float buffer to linear space to match the rest of pipeline. Image editor displays this image as-is, and viewing linear buffer on sRGB screen will make image darker. * On the frame 22 there's nothing under the image strip and it's being output as-is to the render pipeline as byte buffer in sRGB space. Render pipeline does nothing in this case with render result (because it's a final point actually and linearizing byte buffer is lossy). This makes it so image editor displays sRGB byte buffer displayed on sRGB space which makes it look as it's expected. This might sound complicated, but disabled color management is confused on it's own and it's only left there for compatibility issues. You're not actually supposed to use such a pipeline in modern environments. Thanks for the report, but it's just a specific of color management in blender..

Garrett commented

2014-01-28 03:04:42 +01:00

Thank you for explaining that and I apologize for the false bug report.

I have explained your solution on Blender Stack Exchange.

Thank you for explaining that and I apologize for the false bug report. I have [explained your solution ](http://blender.stackexchange.com/questions/6578/scene-clip-in-video-editor-affects-the-image-strip-above-it) on Blender Stack Exchange.

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Scene clip in VSE affecting the image strip above it #38344